FE Power Forums
FE Power Forums => FE Technical Forum => Topic started by: Pentroof on June 14, 2018, 07:04:40 AM
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I recently put a 390 together for the F100 I built for my daughter. A bit of a budget build, in that I used a rotating assembly I had on hand: 390 GT stuff that results in 10.5 CR.
Motor has Edelbrock heads, Sniper EFI controlling timing and this juice roller:
(https://cache.nebula.phx3.secureserver.net/obj/MUNCMDlCQTZFQTAxRjkzQzk0Q0U6MmY4ZmE0ZmUyOWExNzU3ZDBmZDNlNDZhMTE1MzI1ODc=?uid=cefdf548-a411-4d77-a96e-af1adcb7caf7)
Initial timing is 16, total set at 36 and cam was installed at 110 ICL. Transmission is a C6.
I was very happy with the combo's initial results. Runs great, sounds great (for a truck) and had no pinging whatsoever. Running best pump gas I can get.
Recently, the temps and humidity have risen and I'm getting pinging under load. It's very controllable, meaning it's fine if I keep my foot out of it. However, I'd prefer to be a little further from this edge. I do plan on buying the full Holley software package to add some detail to my curve, but I'm looking for some thoughts on cam and ignition timing.
I'm considering retarding the cam, lowering the total timing, or both. Any thoughts?
I'm also hoping I can modify total timing based on temperature, but not yet sure I can do that with the Sniper, even with the full software package.
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Jim, I'd pull 2 degrees total out of it and see how it likes that.
I wouldn't move the cam timing unless it's a very last resort. Retarding it further will take some of the low-end snap away from it.
Did you calculate the actual compression ratio, or is that a guess based on parts?
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Jim, I'd pull 2 degrees total out of it and see how it likes that.
I wouldn't move the cam timing unless it's a very last resort. Retarding it further will take some of the low-end snap away from it.
Did you calculate the actual compression ratio, or is that a guess based on parts?
+1 Do not retard the cam. Reduce total timing or at least initial timing as Brent suggests or mess with the vacuum advance. Retarding cam timing will make things worse for sure. "To me" 36* is more total advance than you need with that head.
Randy
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Brent and Randy have much more experience than I have. I can only back up their suggestions, by saying I have an SDS computer from Western Motorsports, I find that pulling 2 degrees out of the total works wonders. All we have here is 91 octane. I run 34 degrees total, it's hot and humid, but pulling out just 2 degrees worked.
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Echo. I'd dial total back to 32 and see how it does. If you run a curve you want to keep as much initial as it can stand.
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Jim, did you use factory pistons?
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Echo. I'd dial total back to 32 and see how it does. If you run a curve you want to keep as much initial as it can stand.
+1 always limit the total . Initial is your friend.
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Randy/Brent, wouldn't it be easier and better to just install a stiffer spring and slow the advance curve down?
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Randy/Brent, wouldn't it be easier and better to just install a stiffer spring and slow the advance curve down?
That would be an option depending on what the curve is like right now. Could have a slow curve in it already.
There's several variables here and I'm kinda reluctant to give a firm answer one way or the other until we get some answers. The quick answer is if he's wanting a quick reprieve, he can pull a couple degrees total out.
I'm curious about the rotating assembly and I'm waiting to hear what pistons are in it.
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Thanks for discussion so far....
No vacuum advance or springs involved: timing is mapped and controlled by the ECU for the EFI. I entered initial and total and Holley translates that to a curve. I'll be able to tweak that if necessary once I get the PC software, otherwise it's pretty linear. Watching timing on the handheld display, the timing jumps to total VERY quickly.
Yes, pistons are stock style and compression was not directly calculated, just estimated based on the GT specs as publicized by Ford.
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Jim,
Edelbrock's 72cc heads usually come out closer to 74cc. However, if we were to use the 72cc number, a .040" gasket, and put the pistons at zero deck, it would take a 2cc valve relief to get to 10.5:1 SCR. Most factory 390 pistons were around the 9-10cc mark. Even if we used an 8cc valve relief volume, you'd be at 9.8:1.
When I grind cams for others, I usually am pretty conservative on the numbers that affect the octane requirements.
My guess is that you're sitting at around 9.7:1 SCR with around 7.8:1 DCR. It should run perfectly fine on 90-91 with those numbers, even with a heavier truck and a higher rearend gear ratio.
You may want to double check your ECU settings and make sure that it's not an issue with the timing curve. I do assume that you degreed the camshaft and installed it on the 110° ICL.
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Thanks.
Yes, installed at 110 ICL, as I noted above. I may still have my notes to verify. I do remember there were no surprises, meaning I think the sprockets ended up installed without any adjustments.
Head gaskets are FelPro 1020 and pistons are stock, 4 reliefs.
Also for the record, and before it gets asked, cooling is not a problem.
I should probably verify that when the LCD is telling me 36 that it's not actually 40 or something. I did have to slightly adjust the IAC to get the initial timing up to the 16 that I wanted. At that time, the setup has you also verify that general timing movement and total timing at the balancer jives with what was typed in. I remember thinking it was fine, but I should make sure. Balancer is marked up to 45, so there should be no questions.
So, are you saying 36 degrees should not be an issue, given what you now know? If so, I'll keep digging with the ECU and put a hustle on getting the software in hand.
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No sir, I don’t think 36 should be a problem.
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More info:
I've found that there are 3 timing inputs, not just the 2 initially input during the setup configuration:
Idle
Cruise
WOT
From these, the software blends the curve (unless you define the map using the software). Currently, my cruise and WOT settings are both 36. I'm thinking I should be increasing the cruise (as would a vacuum advance) and retarding the WOT.
It would make more sense to me if I could see the map with manifold pressure (vacuum). Maybe the software will let me do that.
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Is it a factory balancer or a new one?
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Is it a factory balancer or a new one?
New balancer and verified with TDC
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The Sniper uses a delay versus an advance. Generally, they have you set it up to a 45 degree reference angle, then adjust the rotor.
This essentially has your engine at rest at 45 degrees advance +/- a degree or so for tolerance stack. The system then calculates the amount of delay needed for initial and total, and the entire curve along the way for all conditions. The extra amount is used for high vacuum conditions, like vacuum advance.
So, if you are right on the edge of pinging, you can a few things, turn the distributor a degree or two, it will shift the whole curve down, but it's really not the clean way to do it. You could lower initial and total by 2 degrees, which would also shift the whole curve down. Or you could change initial to a lower value, which will make the curve less steep, but the change will be less dramatic. Remember, the EFI will adjust your idle so no worries there.
Personally, I'd try setting the initial at 12 first leave the 36 total, and see what it drives like, then try 14 and see if the ping comes back.
Your engine certainly doesn't sound like it has an issue and I would hate to retard that cam more for that use
ON EDIT: Two other points
1 - Just my opinion but my guess is that your parts are under 10:1 not 10.5, Brent's info was right on. You'd need to measure to be sure, but if really 390GT with Edel heads and 1020 gasket, it could even be closer to 9.75:1
2 - As far as the 16-36, using the Sniper, are reference numbers not actual numbers in my opinion and totally based on how precise the distributor setup was. 16-36 could easily be 18-38 or even more depending on distributor location or rotor correction, both are variables as is the balancer marking if . I would not worry about what the number is, as much as trying changes and writing settings and evaluating behavior.
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Ross, that makes no sense to me. The timing is at 36 when I'm experiencing the pinging. Are you suggesting the cruise advance will drop by reducing the initial?
I understand the reference angle thing and how the system arrives at timing for a given point in the "map". What I don't understand is the generation of the curve. For example, my timing is never above 36. So, there apparently isn't any higher vacuum, low load timing advance built in. If I'm cruising, the timing is at 36. I add load and there is no timing change.
With this engine, where would you expect the timing to be at cruise with a correctly set distributor? I'd say well North of 40.
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2 - As far as the 16-36, using the Sniper, are reference numbers not actual numbers in my opinion and totally based on how precise the distributor setup was. 16-36 could easily be 18-38 or even more depending on distributor location or rotor correction, both are variables as is the balancer marking if . I would not worry about what the number is, as much as trying changes and writing settings and evaluating behavior.
Agreed. After phasing the rotor, I went to great detail to set the initial, and verify actual with the ECU. Holley also has you verify stability of timing control and allows an adjustment for this with their static timing check and inductive delay offset. Testing proved I didn't need any offset with my setup.
That said, I'll spend some time this weekend to understand this more. I'm still interested in your train of thought regarding lowering the initial timing. I really don't want to increase temperature without need either. It will definitely build more heat at idle at 12 degrees advance.
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So some of this is educated guess, some WAG, some deduction, I haven't seen what the curve is on a Sniper, but did some reading and applied it to some others I have seen, so no doubt I think we can get you there, but take the specifics with a grain of salt
So, first, if you indeed are at full advance when you are cruising and it doesn't fall out at all when accelerating (assuming you are watching it) AND that is why it's pinging, then I would just drop total and see what happens. You are right on the edge, so this is tweaking, not a problem with the vehicle, and certainly not a cam timing/DCR issue.
Second, I didn't assume you were there, I assumed this was happening when you were not at full advance or it was in the period of time you were running on cruise advance (vacuum like) just before it fell out. So in that case, lowing initial changes the whole curve right up until total. You can draw two lines one from 10 - 36 and another from 16 to 36 and see what I mean, the whole curve is lower until the end.
Third, I would not say heat WILL increase if you drop to 12. 12 is still plenty of initial for a mild cam. FWIW, a similar cam to that in 1969 in a CJ would be running 6 degrees BTDC and have a much slower curve. I would try it and see, remember, this thing won't vapor lock now
Fourth, I would expect that if the Sniper has a vacuum advance that kicks in during cruise, it would indeed be over 40. In fact, it seems to me that setting the reference angle at 45 degrees as I read in their instructions, would tell me that's the max it puts out. However, I wonder if there is a field there somewhere that allows or disallows that from happening.
Finally, how does the Sniper pick the a/f ratio? I have been seeing more people look for 14.5:1 stoich, and with the wide range of fuels out there, it's likely safer to run a little richer. In fact, I doubt there is any fuel in any commercial tank that has a fuel with those characteristics anymore. Do you have the opportunity to adjust? Slightly richer, even ever so slightly, will help, especially if targeted to a time when it's just a little too lean
Again, if I understand the problem, you got a little bit of controllable pinging, the easiest way, like Brent said way back, pull a couple degrees out and evaluate
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So I did a little research after I posted. Some additional questions, but I won't be back until late night....
BTW, no priority order, just generating options, but I would do only one at a time
1 - I see that there is an idle, cruise, WOT, and acceleration enrichment - I am unclear of exactly when yours is acting funky and how much learning time you gave it, but my hunch is cruise and WOT richened by just a little bit may help
2 - I also see that there are three options for timing, idle, cruise and WOT. I would look and see how they correspond, and depending on how it behaves, adjust cruise or WOT
3 - The system under advanced tuning uses load based enrichment, that is "power valve" to me. Look close at that, if this is a pinging under a load, a slight enrichment there may be all you need
4 - AE TPS vs CTS - Another one you could look at, it changes when the "power valve" kicks in
A combination of those 4 things should fix what you are complaining about. Recommend you change one at a time, run it for a while and make a decision. FWIW, many of us disable learning and get things as close as we can without the computer "helping" and then when it's running well, you turn it on. Just a technique, but if you want to dive right in, that's how many do it
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Thanks Ross, we're on the same page. My plans are to investigate exactly those elements of the system, but in the order of 2,3,1,4.
I posted above on the initial, cruise and WOT timing and how my cruise and WOT settings are currently both set at 36 (?). To me, this is fundamentally wrong and therefore the first place to look. The System setup process only asks for idle and max timing, so....perhaps it's not done learning? Only a couple hundred miles on this so far.
Before changing them, I want to understand the I/O relationships and download the full software package. Plan is to do that tonight.
The next couple days will be warm and not that humid. However, just behind that, we're expecting temps approaching 100 and very high dew points. Should be good for testing.
I hope this discussion helps others as well, and doesn't deter from EFI acceptance for the old schoolers. This is great learning and just as simple as understanding how to properly setup a carb and distributor.
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I am in the same boat, Omaha in the upper 90s. I have a 428 to disassemble and I don't feel like sweating LOL
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Before one know the timing curve from idle and up and what happens att different load att different rpm WOT, CRUISE, and between that(part throttle) and exactly load and RPM when it pings, its just a guesswork. Yes one can pull out a couple degrees from total and "see what happens"
You have to take total control of your timing including MAP sensor to have it all POWER and MILEAGE and without detonation.
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Just a quick note, as I did some minor testing on the way to and from Home Cheapo yesterday. Since the temp was in the low 80s in the early evening and humidity was low, I was surprised that a stomp on the throttle still produced pinging. This was previously not the case, as I remembered.
Since the Sniper is so easy to change, I made 2 successive changes to WOT timing. First, I dropped it from 36 to 34, then down to 32. Detonation is STILL present.
I got home and walked myself through the setup and build to understand what changed. Then it hit me...there was a significant change that could be causing this detonation: I addd a CD box with multiple sparks.
I first installed the Sniper using the "coil driver" that comes with the kit. This is a very small (pack of gum small) unit that is used to drive the coil, instead of a CD box. This is how the system was configured when I remembered being able to hammer it without it pinging.
I had initially wired the Pertronix Digital HP box and forgot to remove the factory 12+ from the coil, resulting in a fried box. To get the motor up and running while waiting for another box from Pertronix, I used the Holley coil driver.
A couple weeks later, Pertronix sent me a new box (seriously, at no cost or shipping) and I wired it in. The trigger configurations allow for power level selection between 187mJ and 145mJ and multi-spark ON or OFF. The EFI is still controlling timing, but the CD box is supplying the power.
I configured it at the lower power level with multi-spark. This is probably more than this motor needs, but I really wanted it for potentially better idle and crisp starting. It will take me about 5 minutes to change the configuration to single spark and test it.
Stay tuned....(see what I did there?)
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For the record, this is a standard small cap Duraspark.
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Well, that wasn't it. Changed to a single spark and still have pinging under WOT acceleration, even with reduced timing settings.
So, back to original plan. I have downloaded the full Holley PC software and will begin understanding what I actually have before continuing with any changes.
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What rpm is it att when you stomp it. Then check what the timing is att that rpm.
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RPM can be anywhere. Not correlated to RPM. Using the Sniper LCD, I have a defined set of gauges that show RPM, timing, AFR! and coolant temp simultaneously.
I can see when the ECU interprets a shift to WOT and drops the timing to whatever I have set for WOT timing. The AFR never really goes lean before dropping from enrichment.
I really need to view my tables to understand where I am before moving forward, IMO.
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Good thinking
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Software has been downloaded (didn't know it was free) and the $50 USB cable arrived (making the software not so free).
I'll be diving into the tables this weekend.
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UPDATE
Before changing the base timing table or any parameters that could modify the timing, I decided to throw a timing light on it to verify nothing has changed. I couldn't find my newer, adjustable timing light, so I grabbed my trusty chrome Sears Penske old school light.
lol and behold...timing at idle was like 26!
Once I find my other timing light, I'll do a comparative test, but I don't know how I could have had any dial back into it. Of course, I can't be that bright because I can't even find the damn thing and I just used it recently!
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That would sure change things, but remember, depending on setup, the Sniper could add advance as soon as it sees vacuum.
How does 26 degrees compare to the table now that you can read it?
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The ECU was telling me in real time that the timing was at 26, while the light was observing 16 on the dampener.
I think I'm going to start from scratch and set up everything with the laptop instead of the little LCD. Shouldn't matter, but some things are easier with the software. I need to turn off "idle control" so no other influences are present and then set and verify static timing. During that check, rpms are brought up to verify timing stays at the static number. This verifies the inductive delay setting. If timing increases or decreases (as witnessed with a timing light) with increased rpm during the static test, the inductive delay is adjusted. This ensures the ECU is giving you the timing you think you're getting.
I don't know how it changed, or if I just had the timing light dialed back. ???