FE Power Forums
FE Power Forums => FE Technical Forum => Topic started by: turbohunter on June 22, 2017, 06:41:01 PM
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Im going to really show my ignorance here.
I'm curious, because Im thinking about this 24/7 these days.
Compression ratio
In choosing a CR for an EFI engine. How does the EFI relate? Do I have fiddle room for more compression with EFI? Why?
Cam choice.
Do I have more room for overlap? Do I choose what I would for a carb? Can I take advantage of EFI and go bigger and still get street able (qualified) manners? Do the basic adv/retard rules apply?
Porting
What does EFI like? Same as a carb?
Feel free to add what I should also be thinking about.
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Think about what they are getting away with in new cars. Higher compression, bigger cams, more power, etc. With EFI that includes sequential injection and timing control, you have more tunability across the entire range, you can compensate for variations in air temperature and coolant temperature, etc. etc. You are less likely to run too lean and get into detonation issues with a well tuned EFI system. So, your big cam that's a pain with a carb can be pretty manageable with EFI.
BUT, and this is a big but, none of us are automotive manufacturers that can spend countless hours dialing in the EFI system, with lots of instrumentation monitoring all aspects of the engine, and plenty of engines to burn up with mistakes before finally getting it right. My advice would be to build an EFI engine with the same compression as you would plan for a carbed engine, and maybe go a step bigger on the cam because you can tame the cam down at low speed pretty easily with EFI, in my experience. I don't think head porting enters into the EFI equation, at least not to a significant degree.
Hope that helps - Jay
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Im going to really show my ignorance here.
I've been doing that for years. One thread ain't gonna kill ya.
I'm curious, because I'm thinking about this 24/7 these days.
Yep, because sleep is so overrated. I mean, churning technical possibilities after a week of no sleep makes things so much clearer.
Compression ratio
In choosing a CR for an EFI engine. How does the EFI relate? Do I have fiddle room for more compression with EFI? Why?
Cam choice.
Do I have more room for overlap? Do I choose what I would for a carb? Can I take advantage of EFI and go bigger and still get street able (qualified) manners? Do the basic adv/retard rules apply?
Porting
What does EFI like? Same as a carb?
Do you lift your pinky when you say "streetable"? Run a double-pumper, weenie. Better yet, run dual double-pumpers. And, say no to ignition modules and run points. Man up. Don't be a snowflake.
Feel free to add what I should also be thinking about.
Well, for thinking 24/7, I suggest hookers and blow. The money you save on that EFI crap can pay for a fun weekend. If you're dealing with the hookers in my neighborhood, you're good to go for a month.
Hope this helps!
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I agree with all points but one.
Carbs are easy (qualified), we've all been doing them since we were kids.
Trying to do some learning and maybe shove the old heap down the road a little cleaner/faster/better.
And snowflake term is waaay out of place. I'm absolutely positive this "snowflake" could kick your ass. :)
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Im going to really show my ignorance here.
I'm curious, because Im thinking about this 24/7 these days.
Compression ratio
In choosing a CR for an EFI engine. How does the EFI relate? Do I have fiddle room for more compression with EFI? Why?
Cam choice.
Do I have more room for overlap? Do I choose what I would for a carb? Can I take advantage of EFI and go bigger and still get street able (qualified) manners? Do the basic adv/retard rules apply?
Porting
What does EFI like? Same as a carb?
Feel free to add what I should also be thinking about.
Marc,
First camshafts - You can do anything if the system is adjustable enough, more if you can make it NOT adjustable....more on that in a second.
The basic premise is, the engine doesn't know what is feeding it and for the most part, with the cam, power is power. However, remember, the engine is using the O2 sensor, along with the other sensors to adjust fuel. An O2 sensor doesn't know if it is rich from unburned fuel from a bad mixture or fuel being pulled out with a big overlap cam, so generally, on the street it is better to try to run less overlap. Cam choices stay the same, but you spread the centers to minimize overlap a bit to keep idle clean-ish. That being said, as a reference, my 10.7:1 489 runs a 286/294 cam (@.020) on 110 centers on 106, so you don't have to go crazy, I just wouldn't run a huge cam on tight centers.
I mentioned making it non-adjustable...thats the good thing about electronics. Let's say the idle is dumping fuel into the exhaust during overlap. If you decide you want to go "open loop" at idle and ignore the O2 sensor, you can. It uses whatever sensors you want and still does it's thing, but it doesn't adjust the fuel tables as much and doesn't use the O2 sensor to decide. So, very common technique is with a big cam, open loop at idle and make it sort of an electronic carb, then when the throttle cracks and vacuum comes up, it goes closed loop again.
Next thing is injector timing, I adjust my injector timing based on actual cam events. There are a couple schools of thought, and it really doesn't matter at high RPM as the injectors sort of just create a fog as they fire at 90+% duty cycle, but at low RPM it can be dramatic. You can spray a closed valve and keep it cool and continue as it opens, or you can time the injector to follow the valve movement. I do the latter. I really cleaned up idle that way and it just seems happier.
Next as far as far as compression and timing, think of electronic timing control as the thing we always wished we had. Can you run more compression? Sort of, usually, in the end you can go higher because you likely can control your timing curve is ways never before able. Load, temp, outside air temp, a/f mixture, throttle position, speed, all kinds of things. So, likely, you can run more compression, but the extra 1/2 point or so IMHO could be put into airflow and/or programming experimentation. However, total timing requirements are still based on what the combustion chamber is seeing, so the thought behind total timing isn't significantly different.
In terms of the timing curve to get there though, it's awesome. If the cam is a little big, you can crank at 0, 6, or 10 BTDC, whatever the starter can handle and immediately pop to 20 when it fires, you can pull timing out with boost, even with atmospheric pressure or coolant temp or air temp. My Mustang using 10 BTDC crank and +10 when it fires for 20 at idle. That can add or lower for load, temp, etc all the things I mentioned before, so drivability, especially when mixed with the injector timing can be dramatically different than a carb. In the end, basic rules still apply, but your curve becomes multi-dimensional adjustable based on your system and what you want it to do.
And...punch line...if you decide at times like WOT you don't want that, you go open loop to keep the computer from adjusting and the curve can be exactly like a standard distributor, but with no friction, rust or sticky weights, and when you come off WOT, it goes right back to adjusting for everything.
As far as porting, less of an EFI vs carb thing IMHO, but, I think i could tune some torque into a port that is a little too big using ignition timing and cam timing. As an example, who would think a ported Victor on a 489 with a 6400 shift point would chug around at 1400 rpm in 5th? (2.63 final drive when in OD)
Just remember, it takes two things:
1 - The ability to access and control the computer (system and it's interface)
2 - the time and willingness to learn to tune (your skill)
The first is generally a function of money spent, the second is generally trial and error and time.
I am not sure the end use of this car, but my opinion is for a street car.
- Use the most adjustable port injection you can afford and one you know has internet or a buddies with experience
- Lean more toward making power with good airflow and as much as you can without getting silly (heads, intake, exhaust) so you can run a little less cam
- Think cam timing as valve events and then build a cam that you want to match needs (likely not off the shelf)
- Practice, experiment, save your files, hit "undo" when you don't like it, and keep tuning until you love it
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Something else as a reference
With a 1000 Holley / ported RPM, at WOT, my car felt real strong It idled somewhere around 1200 rpm and was fussy cold, if I turned the steering wheel the PS could even stall the motor or at least require feathering, A/C required a electric solenoid to open the throttle, then I lost a clean idle circuit (a little anyway)
With a 1200 cfm, 45 lb injectors, ported Victor, I have a hot idle at 950. It fires immediately and I can back out of the driveway, turn the wheel, turn on the AC and it doesn't care hot or cold. I feel that I lost zero low end, maybe gained, but at WOT the big Victor really pulls hard.
Win win for me, only real downside is it aint cheap when you add dual electric fuel pumps in the tank, adding fuel lines, regulators, requirement for a good laptop, etc, but the TKO and the EFI were my favorite things on the car
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As far as compression ratios go, induced swirl due to highly developed combustion chambers, variable cam timing, knock sensors and computers that pull timing have more to do with getting by with the higher numbers than anything else.
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I just did a quick video review of the FiTech EFI on my 482 side oiler stroker:
https://www.youtube.com/watch?v=ZhSv4GffIiM
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Any idea how much an EFI system will increase engine longevity over a carb (i.e before the engine needs a rebuild)? I'm talking for a street car/truck. I like my quickfuel and ain't got the money for an EFI system anyway, but I'm curious if there's a rough idea.
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I x2 on what 427 said.I have spent the last year turning on my 477 fe.Have a fast sportsman unit in mine..So what i have learned is i am done with carbs .Once you get it you will never turn back.As 427 said if you can think of it you can do it. My cam is 240@248 @ 50 and it idles at 800rpm smooth... almost to smooth...Downside$$$$$$$$$$$$.
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And snowflake term is waaay out of place. I'm absolutely positive this "snowflake" could kick your ass. :)
Oh come on, we all know you California guys are snowflakes. It's on the news every day. Now that you're all riled up, slam on the carbs and points and come out here and kick my pussy butt. I'll be the guy on the demolition site sledgehammering down a 40-foot fence in the Severe Heat Warning we have going right now. Easy pickins for you. Meow.
I did notice that you included "hookers and blow" in the things you agree with. Maybe we should party before we fight. This is Arizona, after all!
https://s3media.247sports.com/Uploads/Assets/675/736/4736675.gif
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Oh come on, we all know you California guys are snowflakes.
IIRC you used to wuz a California boy. ::)
Now that you're all riled up
Nope, see the smiley face I used?
I did notice that you included "hookers and blow" in the things you agree with. Maybe we should party before we fight. This is Arizona, after all!
Ahh, the old days. I'm a few years past that now. But still trying to keep up.
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Thanks for the replies guys (even FElony)
As far as CR goes I think I'll shoot for 10.5 static. It's a 4x 4.180 bore. 1U crank offset to 4"
Gonna flow the heads (BBM) before deciding on a cam. Nothing off the shelf. Solid roller. Prolly won't stray to far off the norm.
Oiling through the pushrods to Harland Sharp (new) rockers.
351C RPM air gap through Jays adapter.
Should make a '66 scoot right along.
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TJ quote
Any idea how much an EFI system will increase engine longevity over a carb (i.e before the engine needs a rebuild)? I'm talking for a street car/truck. I like my quickfuel and ain't got the money for an EFI system anyway, but I'm curious if there's a rough idea.
I have read from different car manufacturer that reports same amount of cylinder wear with EFI around 200000miles vs, 125000 with carburetor because the fuel shutoff on throttle let go with EFI .
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Im going to really show my ignorance here.
I'm curious, because Im thinking about this 24/7 these days.
Compression ratio
In choosing a CR for an EFI engine. How does the EFI relate? Do I have fiddle room for more compression with EFI? Why?
Cam choice.
Do I have more room for overlap? Do I choose what I would for a carb? Can I take advantage of EFI and go bigger and still get street able (qualified) manners? Do the basic adv/retard rules apply?
Porting
What does EFI like? Same as a carb?
Feel free to add what I should also be thinking about.
Jay pretty much wrapped it up. I am not familiar with the Sportsman or any other aftermarket EFI units but if you had one where you could preset a constant AFR that would provide some ease when playing with ignition and injector timing. A direct injection DOHC FE head with dual VVT would be interesting.
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Thanks for the replies guys (even FElony)
As far as CR goes I think I'll shoot for 10.5 static. It's a 4x 4.180 bore. 1U crank offset to 4"
Gonna flow the heads (BBM) before deciding on a cam. Nothing off the shelf. Solid roller. Prolly won't stray to far off the norm.
Oiling through the pushrods to Harland Sharp (new) rockers.
351C RPM air gap through Jays adapter.
Should make a '66 scoot right along.
Marc, cam and compression should be selected together. Don't order the pistons until you know which cam you will be using - Jay
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Short answer is "EFI don't care". You build the motor, then you'll have to tune the fuel system and timing to make it live. That's it. Either can cost you time on the dyno or a lot of passes on the strip to get dialed in. EFI just costs more up front. IMHO it can actually be more work than a carb - same feed back required using a wide band sensor - except you have to get your hands dirty taking the carb apart to change jets as needed. For a street car, once you do get EFI dialed in with the fuel curves and timing - if it's a closed loop system it'll tend to take care of it's self. If its for bracket racing, I'd stick with a good carb. If using EFI for brackets, I'd choose open loop. Don't need to be changing fuel calibrations as the day goes on.
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Yeah Jay I'll get all the info first.
Chris it's definitely more work and money for efi but I've committed to it in order to learn. I know next to nothing about injectors and modern gear.
I'm actually going to follow Jay's idea with his efi thread and fire the engine on carb while having the gear in place to go efi then switch it over. That way I'll have a baseline in my head about the engine and where it should be.
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The only thing I'll reiterate is that overlap does matter to EFI, the lower the RPM and more often the engine will operate there, the more you want to limit overlap.
It doesn't have to be dramatic, you can run a decent cam, but as overlap increases, at lower RPM the O2 sensor will not "see the truth" and report to the ECM that the engine is rich when it's really not, that goes away somewhat with RPM.
My opinion, with a good system you can tune for almost anything, but to uncomplicate things, limiting overlap to mid 70's will help you on the street
What does that mean in numbers? Along with proper cam choice in general, with a 300 degree hyd roller, I'd spread to 112-114 and pick whatever ICL you want to match compression and use (earlier usually better on the street IMHO) For a 290 degree or less SFT, I'd go as tight as 110. The less lobe you have (and more lash), the tighter you could go because overlap is reduced
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I know it might be counter intuitive for the street, but I am toying with the idea of solid roller.
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I am not a solid roller fan, but admittedly haven't used one since good pin oiled lifters came out (I know, get with the program, it's only been 15 years LOL)
However, typical solid rollers and solid flat tappet advertised duration is at .020 rise, hydraulics are at .006. Not as huge of a difference as you'd think comparing the two because of lash make up .006 ratings are within guessing distance of a lashed .020 duration, but the shape of a solid lobe usually minimizes overlap a bit so it shouldn't hurt.
What's the planned gear ratio / tranny / street use plan when complete?
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TKO 600 with the .68 5th gear to 4.10s (Truetrac) in the rear end.
I went with the taller 5th gear because I plan to do some freeway driving up to PCH and a few great roads.
Figured I wanted a 4 speed around town with a nice over drive for gitten where I gotta go.
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That's a great combo, I love the tall 5th TKO in mine with 4.10s and 275/60s
Is it a stroker FE?
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Good point on the overlap. I do know that a lot of the farther out builds tend to use F.A.S.T units. Most of the street friendly/DIY friendly units might not be able to handle very radical cams and such. Even with a carb, that really screw up low speed metering.
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I would like to qualify Ross's statement about overlap. If you have a self-tuning EFI system that relies on the O2 sensor to determine the fuel required then yes, a big cam will tend to fool the sensor and make the EFI system not work properly. However, Marc is going with a REAL fuel injection system, not one of the tunes itself versions. In that case any cam can be set up properly. After screwing around with these systems for several years I can say with confidence that any cam can be used with a fully tunable EFI system. The trick is to tune while driving the car, and use the O2 sensor as a guide only, not in closed-loop mode.
My Galaxie is a good example of how this can be done. Back in 2008 with the EFI system first installed, the engine was making 935 HP and had 286@0.050" cam lobes on the intake, if I recall correctly. After tuning on the dyno at wide open throttle and at idle, I got the engine in the car and hooked up the computer. My son the computer geek rode along, tapping the keys. We went to a straight stretch of road and I held a constant speed (constant RPM and vacuum, or MAP) so that the indicator on the VE table (fuel table) was stable in one spot. Again, this was open loop mode, so the O2 sensor was not doing anything to change the fuel delivery. While reading the O2 sensor I told my son to lean out the map until we were at about 14.7. The engine was sputtering badly long before we got there, it was so lean. Clearly, the O2 sensor was being fooled by the cam events. Next we went the other way, richening that spot on the map until the engine started sputtering with too much fuel. Now we had a range. I figured it was probably an A/F of 10:1 on the rich side, and 16:1 on the lean side, so we went most of the way back to lean, so that the engine was still running nicely. The O2 sensor was reading about 11.2:1! No way was that the real A/F ratio, I'll bet we were close to perfect stoich at that point. We tuned by listening to what the engine wanted. And it was easy.
We repeated this procedure for several more points on the VE map, different engine speeds and vacuum readings, and when finished I extrapolated between these points to fill in the rest of the map. I made further adjustments later, but the car was perfectly drivable under all conditions at that point. No feedback control from the O2 sensor was ever used because as stated earlier, a big cam will fool the O2 sensor, to say nothing of what would happen to the car if the O2 sensor went out of calibration or failed completely.
It was really fun to tune the car like this, by the way. You get an instant reaction from your inputs. You can save all your tunes as files, so that if you screw something up you can go back to the previous version. Close to unlimited flexibility, makes tuning the engine a blast.
Marc, on another note I am glad to hear that you are thinking about a solid roller cam. Go for it!
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Jay, you are 100% correct and that is what I tried to convey early in this, that you can do anything if willing to manage sensor input in open or closed loop when appropriate if the system allows. However it is not just a cheap system that can trick an O2, it is ALL systems if you use that sensor in a closed loop option, the question is, does the system have the ability to allow you to tune around it and will the vehicle behave the way you want it to when you do?
Anyone who tunes seriously uses the open loop regularly when needed, but it is limiting the function of the system by design, and to be honest, using a purely open loop speed density system will run great, but is limited in it's ability to adapt if you have an engine that doesn't need to run open loop.
Let me qualify what you said too, because I actually run a more "real" system than a FAST SD by running a MAF system with both WBO2 and NBO2 and left and right bank inputs. The modified OEM system I use is more adaptable than any speed density system because it additionally measures intake airflow, something a speed density system cannot do. The system is also modified to only adjust a/f tables using WBO2 in those times that I allow to and uses NB for normal operations. That NBO2 is limiting in itself in its narrow range of responsiveness, and I may actually dump them now with a recent upgrade to the software, but having the input for both styles and the combination of logs that can be combined with load, speed, airflow, ambient temp and pressure, etc, really works well.
In the end though, open loop is not as responsive by design as closed loop and depending on the use of the car, may not be as happy as yours have proven to be for your use. It is essentially creating a map or table for a given range as you discuss, if you want a multi-dimensional map and want the system to adapt it, that O2 sensor is a very good thing (until you have a characteristic of the engine or environment that you cannot do it, but on a pure streeter, IMHO the goal should be to get back to closed loop if/when you can)
I do agree with you completely though, when you have a system, and that system has the ability to be manipulated for your use, and you learn how to work it, it becomes very usable.
I am also not a cammer guy, but I am interested in what your equiv overlap at the valve is with a 286@.050 SOHC cam and how they are installed compared to a wedge, my hunch is a quite a bit less duration at the valve with the low rocker ratio so therefore less overlap. (Although I bet the overlap on a hemi does have more authority) Not that it matters with the way you use your system, but if i remember correctly, you mentioned that the cam has to make up rocker losses. Regardless, I cannot see a a 286@.050 being the right cam choice for an EFI wedge with a 2.63 final drive, so hard for me to recommend open loop operation for a 600-ish hp wedge.
For the crowd, you are seeing the most common EFI argument on the net unfold between experienced guys though :) technique vs technique. I try to avoid open loop and get into closed loop as often as I can because of the rpm range and power levels I am tuning. Jay is building for MUCH more power and RPM, needs those tools and is experienced to tune to it. Who is right? The answer is yes LOL but bottom line, neither could do what we are doing with a handheld controller
I also need to echo Jay's tuning fun comment, file save, reload, try something new again, sometimes even in a parking lot on the way home, undo and go back to last Thursday's load, all in the course of a ride across town without getting dirty. It's cool as cool can be
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On the SOHC, rocker ratio won't enter into the overlap value because overlap is in degrees. For that cam I mentioned above, overlap was 87 degrees. The SOHC lobes are large compared to a normal FE wedge lobe in order to make the valve follow the same profile as a normal engine, even with the low rocker ratio. So what the valve sees is essentially the same as what a wedge engine valve would see with an equivalent cam. And you are right about the sensitivity to overlap with the SOHC Ross, pretty easy for that intake charge to go out the exhaust during overlap with the canted valves and hemi chamber.
I think one major reason I don't like to run in closed loop is I have seen sooooo many of the wideband O2 sensors go bad, either not working completely or being significantly off, and not able to be calibrated. I'll bet I've tossed out 20 or 30 of those Bosch wideband O2 sensors over the years, and a few NTKs also. Funny how some of them seem to last a long time, and some don't. This is mostly in dyno situations so one could argue that they are being abused, but it still seems excessive to me.
The only reason I think I would run in closed loop was if I was worried about variations in the fuel. On my cars I normally use a single table, with the top of the fuel table (e.g.wide open throttle) tuned for race fuel and the rest of the table tuned for pump premium. If there were significant variations in the pump gas I was using, the closed loop system would have an advantage. But since I only drive my cars in the good weather months, I don't worry about that too much.
Also, I would strongly disagree with your statement that open loop is not as responsive by design. That's just not true, IMO; in either case the engine is operating somewhere on the fuel map and will respond the same in either case. Can you provide an example of why a closed loop system would be more responsive, to back up your argument?
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On the SOHC, rocker ratio won't enter into the overlap value because overlap is in degrees. For that cam I mentioned above, overlap was 87 degrees. The SOHC lobes are large compared to a normal FE wedge lobe in order to make the valve follow the same profile as a normal engine, even with the low rocker ratio. So what the valve sees is essentially the same as what a wedge engine valve would see with an equivalent cam. And you are right about the sensitivity to overlap with the SOHC Ross, pretty easy for that intake charge to go out the exhaust during overlap with the canted valves and hemi chamber.
I think one major reason I don't like to run in closed loop is I have seen sooooo many of the wideband O2 sensors go bad, either not working completely or being significantly off, and not able to be calibrated. I'll bet I've tossed out 20 or 30 of those Bosch wideband O2 sensors over the years, and a few NTKs also. Funny how some of them seem to last a long time, and some don't. This is mostly in dyno situations so one could argue that they are being abused, but it still seems excessive to me.
The only reason I think I would run in closed loop was if I was worried about variations in the fuel. On my cars I normally use a single table, with the top of the fuel table (e.g.wide open throttle) tuned for race fuel and the rest of the table tuned for pump premium. If there were significant variations in the pump gas I was using, the closed loop system would have an advantage. But since I only drive my cars in the good weather months, I don't worry about that too much.
Also, I would strongly disagree with your statement that open loop is not as responsive by design. That's just not true, IMO; in either case the engine is operating somewhere on the fuel map and will respond the same in either case. Can you provide an example of why a closed loop system would be more responsive, to back up your argument?
Sure, I do not mean responsive to your foot, I mean responsive to conditions, sorry for the confusion. Certainly no intention to say that it doesn't respond to foot pressure. I also do not mean that open loop cannot work well with tuning, because it does and I run open loop myself when required, but if you could map for all situations, there wouldn't be need closed loop and WBO2 sensors on modern vehicles needed because a/f mixtures would be where you want them to be and remain in a narrow range. Remember, just like you, I am talking for a type of build and use that I build, so I am not saying you are wrong in any way, I am just saying that you can make good street power in closed loop, and that the WBO2 dilution isn't just a cheap EFI problem it is a problem with too much overlap even on adjustable systems that let you tune around it.
As far as no change in duration with rocker ratio, if I have 286 degrees at .050 lobe lift with a 1.5 rocker, at that lift point I have .075 of lift at the valve, with the same .050 lobe lift and a 1.76 ratio, you'd be at .088 at the valve. If you measured rotation at the valve from .075 to .075, you'd get more duration from the wedge. So essentially the wedge rocker creates duration at the valve, which increases overlap on both lobes. Inversely, at the valve, the time that a valve is open for a given lobe duration is less on a SOHC. Heck I thought I read that in your book, either that or I read it in the older magazine article with the Coon parts :)
Again, please do not let me sound like I am saying you are incorrect in using your equipment the way you do. It is a standard and proven tuning method, especially for the power you are making. I just wanted to point out some rules of thumb and point out the fact that at some healthy levels you can run closed loop without incident, and that my original point wasn't far off, sometimes you need open loop, however my technique is to return to closed loop too
I do like the way you tune though, especially the idea of changing parameters in portions of the curve for fuel. Just don't go WOT with cheap gas right?
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Very much enjoying your discussion guys. Thank you.
All you guys.
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Ross, I'm still not clear how you are coming to the conclusion that closed loop is more responsive to conditions, unless you are assuming that the fuel map and the temperature corrections are not right. Seems to me both would be equally responsive to changes in conditions. Can you provide a concrete example of what you are saying? I'm not trying to be argumentative, I'd just like to know your rationale.
Also, you are correct on the fact that more duration @0.050" is required for an SOHC with the lower rocker ratio, than would be required for a wedge. Probably about 12 degrees more. However, overlap is generally given in degrees from intake seat opening to exhaust seat closing. The duration at 0.050" given in your example doesn't enter into it. And the point at which the seat opens is not dictated by rocker ratio. So, for the cams I use the advertised duration is given at 0.020" valve lift, which is the lash value, and is calculated the same as it would be for a wedge.
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Jay, I know you aren't argumentative, you never are, in fact I continue to hope that you know it's the same for me. I love to think about how things work as much as you, so it makes me think harder, but the rocker ratio thing I really think we need to kill first
First advertised duration on all the cams I buy or have ground is based on lobe lift, not sure if the SOHC is different, I am always open minded and I hate absolutes, but I have not seen an advertised duration on any cam take lash into consideration or be measured at the valve, its a hard measurement from .006, .020, or .050 tappet lift in everything I have seen.
With your cam, and knowing you are smarter than the average bear and pick your own stuff, I suppose it very well could be, but typically advertised for a hyd cam is rated at .006 lobe (tappet) lift and solids are at .020 lobe lift. With a 1.76 rocker and .024 for lash, not accounting for loss, advertised actually would relate closer to .011 valve lift, and tighter the lash, the closer a solid looks a lot like a hyd .006 rating when measured at the valve.
Assuming the SOHC is the same, and runs a 1.3 or so rocker ratio, .020 tappet lift is .026 at the valve, and when you subtract lash it's closer to zero at the valve. So rocker ratio, unless somehow you have purposely ground it different, does matter for effective duration at the valve.
If you don't believe me, measure a 1.5 rocker in a wedge and then a 1.73 for degrees of crank rotation from .006 to .006 at the valve. The 1.73 rocker will start earlier and end later at the valve, (just like a bigger cam) that will change both DCR (by changing exhaust valve closing point, and also effective overlap at the valve because EVC is later and IVC is slightly sooner. It doesn't change the lobe, but it changes what the engine sees in operation which accomplishes the same thing.
This is one reason why lash adjustment is a tuning tool, the .002 or .005 is miniscule in lift, but by opening the valve sooner on the ramp and closing it later, you increase duration and increase overlap when measured at the valve.
As far as concrete evidence on system responsiveness, I cannot give you calculation time or measured response off the top of my head any more than I can determine which processor is faster, a FAST system or a CBAZA Ford with a QH rider chip, but here are a few calculations that I can control, not limited to these three, just a few I pulled off Binary Editor related to closed loop HEGO and fuel control, some examples:
1 - HEGO bias - My system allows me to tune and then adaptively control the weight of O2 sensor input based on differences from mixture on that bank. I can build fuel tables, injector slope, timing and duration, and either let it run and adjust to the full range of control or limit it to adjust bias from that table to tune each bank. That bias can be tracked and see how it changes. From the definition: HEGO bias - used in open loop as a fixed value and a scalar in closed loop. These learning correction values are used in closed loop as a function of engine RPM and torque to manage power rate output and final a/f
2 - Fuel scaling for load - closed loop only - these values will adjust based on calculated load adjusts HEGO exhaust pulse delay, provides input to HEGO bias and amplitude to account for abnormally high or load loads as calculated by air/sea load inferred by BAP live calculation
3 - MinADP - Sets fuel adaptive learn minimum, requires active HEGO as controlled by affected multipliers in open loop or scalars in closed loop
I couldn't cut and paste and had to retype all of this so i just posted a few to show you what it was looking at but it does adjust and allows what it sees to tailor fuel based on load. It is very similar when it tweaks spark and injector timing based on all sensor input. The question is, is the word responsive incorrect? you make that call, but the more variables that can be compensated for real time, the more responsive I call the system. Responsive to variables, i.e "pays attention to more stuff and acts on it"
Keep in mind, OEM Ford has not used a Speed Density system since the mid 90s in pickups, and even then, those ran in closed loop. That is not a 900 hp race car of course, but even in those 200 hp 302s, an EFI based on tables could not maintain an a/f mixture that met emissions standards in later years. Now you are not doing this for emissions, but it took WBO2 sensors and closed loop for Detroit to make significant things happen under the hood of new cars. I would think that Ford would not have went to such lengths if it just took a good tuner to build tables
What I will try to do is see if I can figure out exactly what changes based on O2 sensor output, the reason I say try is guys spend years inside these OEM computers and continue to find more. When i get a solid list of O2 sensor controlled adaptive learning variables, I will build a log to track how much they change, and we can see changes based on O2 sensor and how often it happens on a long ride or some throttle horsing. To be honest I have never had to log that kind of detail, but logging based on parameters like the bins above should show what it is doing and what is driving whatever it does
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On the SOHC, all I can say is that when I set the lash at 0.020" and measure the seat to seat duration, I get exactly what's on the cam card. So, I'm sticking to my guns on that one.
And I still don't see how you can say that closed loop is more responsive than open loop. You are talking in some cases about have two O2 sensors, and making bank to bank variations. I've tuned with eight O2 sensors, one in each header primary, and used eight different trim maps in the EFI software to adjust the values in the main fuel table. And of course when you have MAP, you have engine load, and that is also tunable with an open loop system.
I guess we will have to agree to disagree ;)
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Understanding how it works in the automotive field in OEM settings but not having a clue about the aftermarket I was thinking starting 12:1 afr, tuning the rest and then trimming fuel as needed. Is it that simple?
For my use I would run a closed loop. 5v reference 12v heater? Do you have to use dedicated O2 sensor with the system or can you solder in any sensor you want?
Jay,
When I think of an open loop and a barometer I think of multi port injection. I believe Ross is talking about climatic changes and how quickly the closed loop system with a MAS adapts. For what your doing with an open loop it sounds like the technology has improved from what I am familiar with. Do the open loop systems respond to temperature and humidity as well? I am guessing there is an air charge temperature sensor in there somewhere?
Been thinking about it but not convinced in all the car show hype. Would like to know it runs in the FE community.
Thanks
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I guess we will have to agree to disagree ;)
Fair enough on the EFI LOL
As far as the cam...I am not sure why you are getting the same seat to seat as lobe lift unless the design/geometry of your rockers are losing lift somewhere or you measure lash on the cam of the rocker on a SOHC
You should be gaining duration at the valve, it's a simple lever. I'd be interested in what you see if you put your cam in v blocks or chucked it up in a lathe to see if it was 286 @ .050. If it is, then either an OHC cam is measured differently or you have 1:1 rockers (unlikely)
Regardless, your shit runs and stays running, my shit runs and stays running, and neither of us are burning pistons. 8) 8) 8)
One last comment, in years of OEM stuff fixing cars, trucks etc since the 80s, and quite a few cheapo and expensive EFI conversions I have replaced ZERO O2 sensors due to electronic issues. Physical damage yes, but true failures, none.
Does your system shut power off to the O2 sensor when it is in open loop? The only failures I have heard about are damage due to fouling or saturation when the heated part of the "HEGO" is shut down and the sensor cannot stay clean.
The other potential option is that you have it sitting in the exhaust flame at WOT and it is overheating, I don't have that issue with mine, but the option there is to move it back further, usually requiring a longer collector pipe if you run open headers, which for you may not be what you want to do either
To the crowd, Jay and I aren't agreeing on some details, but in no way am I saying the modern aftermarket tunable systems are not good, I am also not saying he is wrong, or you need a MAF/dedicated closed loop tune all the time. (Although he may be saying I am wrong LOL)
His stuff works the way it is designed, for those people who are considering EFI, realize how deep we can get into adjusting and tuning with either of our systems and how different each are, those techniques are why we don't agree on the small stuff in this post
We both said the exact same thing on two points:
1 - Adjustable systems can be manipulated to do just about everything on any combo
2 - The hand held controller stuff are not that adjustable.
However if you are not far from normal, I am not sure the TB systems NEED to be as adjustable, but I sure wish there were, because it would be pretty slick
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I don't have much input on the EFI stuff, but I will say that camshaft duration is measured at the lobe. It has to be that way, or else you would be chasing yourself around in circles while degreeing a camshaft, using checking springs, actual valve springs, different rocker arm ratios, etc. It should be assumed that you first check the camshaft lobe geometry against the cam card to make sure it's right, then you spend the rest of your time minimizing losses in valve motion.
I would also assume that it's the same for a SOHC engine. How would you ever know if the camshaft lobe was ground correctly if your rocker arm ratio was off?
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You guys are right about cam duration being measured at the lobe, but perhaps they spec the SOHC duration differently. Rocker ratio on the SOHC varies somewhat due to geometry but it is around 1.3:1. Back to the original point, 87 degrees is the seat to seat overlap on that cam, for sure.
On the wideband O2 sensors they are sensitive to race fuel, and I have heard estimates that they will go bad as soon as 50 hours of continuous exposure to race fuel. But I've replaced a lot of them far sooner than that. I always power up the O2 sensors when the ignition is on because I log the data. You can damage an O2 sensor by running it in the exhaust without powering the heater circuit in the sensor, so on my dyno and in the cars they are turned on with ignition. Usually I put them in the collector, just after the merge in a merge collector setup, or somewhere in the middle if its not a merge collector. I do have bungs in the primaries on my race car, just so I can do the eight O2 sensor tuning on the dyno, but haven't used them much that way, just for a few dyno pulls.
Ross, how do you know your O2 sensors are still good? What is your reference? On the dyno, I have an O2 sensor on each side, plus the fuel and air turbines that monitor the fuel the engine is using and the air the engine is using, to give a direct A/F readout from those measurements. So, I have three A/F measurements going at once. When everything is working right, all three are in good agreement. Right at the moment I've got one Bosch O2 sensor that is going bad. It used to read the same as the other one, and the dyno A/F number, but now it is reading about a point rich. I've done all kinds of tests in the past to sort this out, for example swapping the sensors from side to side when there's a discrepancy. The outlying data always follows the sensor. It may still look like its working, but its no longer accurate. It calibrates fine in free air, but the data is off when compared to other standards. I would suggest that you may have had bad O2 sensors in the past, but not known it because you don't have a good reference. As I mentioned earlier, lack of confidence in a good, consistent wideband O2 sensor over time is a major reason why I prefer to run open loop.
Just my opinions of course, and I agree with Marc that this is a valuable discussion...
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Jay, what is the marker that tells you an O2 sensor is going bad initially.
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Ross, how do you know your O2 sensors are still good? What is your reference? On the dyno, I have an O2 sensor on each side, plus the fuel and air turbines that monitor the fuel the engine is using and the air the engine is using, to give a direct A/F readout from those measurements. So, I have three A/F measurements going at once. When everything is working right, all three are in good agreement. Right at the moment I've got one Bosch O2 sensor that is going bad. It used to read the same as the other one, and the dyno A/F number, but now it is reading about a point rich. I've done all kinds of tests in the past to sort this out, for example swapping the sensors from side to side when there's a discrepancy. The outlying data always follows the sensor. It may still look like its working, but its no longer accurate. It calibrates fine in free air, but the data is off when compared to other standards. I would suggest that you may have had bad O2 sensors in the past, but not known it because you don't have a good reference. As I mentioned earlier, lack of confidence in a good, consistent wideband O2 sensor over time is a major reason why I prefer to run open loop.
Just my opinions of course, and I agree with Marc that this is a valuable discussion...
I have 2 narrowband and one wideband and the system has calibration tests I can do on the NB as well as being able to see the bank reference. I have no reason to ever look at logs for a bad one if I don't see a check engine light or code, but I do periodically run my self tests when I am bored, easy to do with a scanner on the OEM NB sensors. As far as the WB, I just haven't seen them log anything funky
I'd also ask, how often do you change them in your truck or wife's car? I can't compare the performance you are asking your race car to parallel mama's grocery getter, or vice versa, but I just don't see O2 sensors fail in OEM either.
I do not run race gas though, I in fact, I run pump 89-91 most of the time with no knock sensor (hard to get to work properly with a noisy solid lifter motor) Mine is of course only 10.7:1 and a 286/294 @ .020 lobe, I run lashed at .014 instead of manufacturers spec of .028
On edit - Something that just occurred to me, do you have a stable reference voltage, good grounds and clean power? One thing I have done on most EFI installs is replace electromechanical voltage regulators, ensure there are very stable grounds and overall very careful with wiring. Dirty power and EMI can be real funky, maybe the dyno has something happening there?
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I'd also ask, how often do you change them in your truck or wife's car? I can't compare the performance you are asking your race car to parallel mama's grocery getter, or vice versa, but I just don't see O2 sensors fail in OEM either.
I do, but then I work on this stuff for a living. I've replaced 3 in the last year alone, among the 32 FI vehicles that I take care of.
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You can check for a bad O2 by putting a little water in the air intake. 1v means it is able to go to it's max range but I do not know if that would work in a race gas senerio. If it has lead like aircraft fuel it would build up on the sensor and not make it read right.
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Jay, what is the marker that tells you an O2 sensor is going bad initially.
That's the problem, Marc, there really isn't one. Unless you have two, and one starts to drift with respect to the other.
Ross, I am a fanatic about clean power, because I had that problem with my first EFI system. Big caps on the power supplies, heavy gauge wire, etc.
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Jay, what is the marker that tells you an O2 sensor is going bad initially.
That's the problem, Marc, there really isn't one. Unless you have two, and one starts to drift with respect to the other.
Funny you posted that under open ended the answer.
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Chris, per your previous question all the systems I'm familiar with are capable of running in closed loop. But once they are tuned, you can run them open loop without any trouble, and avoid any questions re the O2 sensor. They all have compensation for air and water temp, altitude via the MAP sensor, etc., whether running in closed loop with the O2 sensor, or open loop where the O2 sensor does not provide A/F feedback to the system.
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Chris, per your previous question all the systems I'm familiar with are capable of running in closed loop. But once they are tuned, you can run them open loop without any trouble, and avoid any questions re the O2 sensor. They all have compensation for air and water temp, altitude via the MAP sensor, etc., whether running in closed loop with the O2 sensor, or open loop where the O2 sensor does not provide A/F feedback to the system.
Jay, I know yours has a great ability to respond to conditions, and how much a system needs to compensate depends on the varying environmental conditions and range of use, but a couple points. This one is long, and generally I don't hang onto anything, but I just feel that there is more to be said about the EFI.
First one is goofy and I am not part of the word police, but just HAVE to say it as a career aviator...your MAP adjusts for elevation by allowing inputs to calculate air mass. You are fast, but altitude is where your ALL wheels don't touch, I am very impressed with you hanging the hoops, but it's not altitude LOL That being said, all over the net they say MAPs adjust for altitude, but until you call "gear up" it's elevation :)
Seriously though a MAP measures manifold pressure, and also true, a MAP and BAP are often the same sensor, one with a vacuum source, one sensing atmospheric pressure, but they are quite a bit different in the gonkulation. A MAP, usually combined with an air charge temp sensor (ACT) is used as an input to calculate air mass that is going into the engine in lieu of a combination of measuring it with a MAF (Mass Airflow meter) and a BAP (barometric sensor). You know how yours works, as you said it in your last post
Now, knowing that cylinder fill is a function of relative pressure of an evacuated cylinder, those forces acting upon emptying it more, and those restricting filling it, versus atmospheric pressure trying to push it in, a MAP does technically account for it mathematically and it is pretty good at sensing engine load differences, but the function is very different than a BAP, and honestly I do not think either MAP or BAP sensors measure very precisely.
Again, how precise is needed? It depends, however, OEM applications do not use MAPs and Speed Density calculations anymore (that I know of), they use MAF and BAP or MAP because they give more exquisite data than the one sensor alone. One reason is the sensors are dedicated to measure one thing (although a lot of new MAFs also measure air temp too, older ones like mine use a separate air charge temp sensor), another reason that EOM shifted from MAP in many applications, is that MAPs are fed by a relatively violent source (think Kaase's clear intake manifold test).
Now, that doesn't mean MAPs are bad or obsolete, they are still used with MAF, the line to the BAP will of course dampen the signal and the BAP itself has some mechanical damping and the ECM has smoothing in the program, but it is by no means a precise sensor IMHO. One thing the MAP does do better than a BAP is measure actually changes in load though, especially when compared against the TPS data with changes in throttle, however, it is used with the temp sensors to calculate changes in air mass where a MAF measures changes in airflow and compares to air temp and baro to come up with the data.
I have seen guys add a BAP to a SD system, so it measures baro and still uses intake pressure from the MAP to have a more precise air density calculation, but I would be surprised if it changes in use much other than adding difficulty to the programming and tuning. It's an attempt to be more reactive though when calculating adjustments.
You and I may never agree, but looking at our complete systems:
My MAF, BAP, and ACT measure all the characteristics of the air coming in, the ECT adds engine temp info, the TPS translates what the guy behind the wheel is doing, then O2 senses what is coming out. All of those provide near-real-time info to adjust well calibrated tables and adjust them within the limits the guy tuning it (or the ECM) allows.
In a SD system like yours, you have a MAP and ACT that provide input to calculate air density, the ECT provides engine temp, and the TPS translates what the guy behind the wheel is doing, all of that is compared to well calibrated and well thought out tables (as you pointed out) but in open loop, you only adjust for changes in inputs, you don't measure output when you exclude the O2 sensor info. To me, that is cheating the decision maker by not providing the whole story (stay with me though, because I actually think for you, it is a smart choice)
I cannot explain your O2 sensor calibration changes and failures, FYI, Brent says he sees some similar things on the dyno, and I cannot say for your application and your environment that your system does not compensate enough, because it clearly DOES for you and many other guys. You are essentially taking a very precise program and still allowing it to compensate it for many things that a carburetor would have to use physical airflow and fluid/aerosol management (bleeds, boosters, orifice sizes, throttle blades, venturi designs etc) to manage. Your stuff is WAY more adjustable than that, likely significantly more responsive to environmental changes than a carb, and way cool as you know
However, measuring both sides of a process and providing information by design allows more information, and if the sensors on both sides of the process measure more and rely on less calculation, there are less chances for errors. That is true in any human or non-human decision making process, including the ones you ask an ECM to make
It comes down to is where I started, I am not saying open loop is wrong, as a metaphor...how much information do you need to order a pizza vs a big investment decision?
Although there is no way I can ever agree that an EFI without an output loop has as much data and therefore as much ability to respond as one with one, I am not asking or recommending you change yours, because it clearly is responsive enough for your conditions. How do we know? You are measuring output using your eyeballs on plugs, your O2 sensor during testing and are not burning up pistons.
Additionally, another reason I wouldn't recommend you go closed loop at WOT (even with a very narrow learning factor) is because your environmental conditions change less than the risk you are seeing with a bad O2 sensor. If the O2 sensor fails at WOT you could hurt your car, if it fails cruising around town at drag week, probably not, but my position is, in my tuning, I go open loop at WOT in many tunes, just not in all conditions
Therefore I cannot argue with your technique, I think it is SMART. However, I just have to stand by my guns that you have chosen to limit the information to your ECM (for good reason) and therefore our academic discussion about ability to respond I still hold my position. You have good reason, but you took an output sensor out of the loop.
Similarly, I think that the setup I have, for the use of my car and a bunch of street cars out there, is clearly proven by my experiences and the way modern cars have evolved for precise emissions (read: a/f and timing) control, but again, we use our vehicles very differently and I do not think that the wide range of fuels, elevation, driving conditions, part throttle load, etc, that open loop would provide an ECM used like mine enough data.
One last comment to everyone, Speed Density systems have come a VERY long way, and I think the modern versions like Jay uses, as opposed to 90's OEM, are very good for street use, and I am very happy with the TB systems I have installed using Speed Density (aside from a lack of good interface on most) In fact, SD solves some packaging issues that MAF systems have, and MAF systems are very tough to build, but I generally tune both MAF and SD systems for closed loop where I can, and open loop only when the engine or risk won't let me ( so far...only idle with too much cam/not enough vacuum or WOT).
Again, there is a gradient on how adjustable and then how responsive a system needs to be, and it is a combination of risk/reward and environmental conditions that determine that. Like I said, I do not need a financial prospectus to order a pizza, or even to go out for a night on the town, but as the environment gets more complicated, mo' info is mo' better to be able to respond to varying environmental, load, and fuel changes IMHO and I want that O2 sensor to provide that data at the times I want it to
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Chris, per your previous question all the systems I'm familiar with are capable of running in closed loop. But once they are tuned, you can run them open loop without any trouble, and avoid any questions re the O2 sensor. They all have compensation for air and water temp, altitude via the MAP sensor, etc., whether running in closed loop with the O2 sensor, or open loop where the O2 sensor does not provide A/F feedback to the system.
I see, when you go open loop it is basically like a limp mode but instead with your preset fuel timing and trims.
The last comment was referring to testing a bad O2 by slowly introducing some water in the intake. This should work on any with any EFI system:
At 2000 rpm adding water increase will show a steady voltage increase on the O2 until it reaches 1v. A flat spot, no change or inability to max out means a bad sensor. Anything I am familiar with has a long term fuel trim that is too slow to lean out the engine to a dangerous low.
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Jay,
I gave an answer on O2 testing with no acknowledgement. I usually say thanks when someone gives me free advice. Instead below that you posted there is really is not way to test an O2. Is that a coincidence or are you trying to tell me something?