Let have a technical discussion on optimum performance tuning for a N/A FE.

[69Cobra]

Hey Guys,
 With having my first Stocker motor on the horizon I've been wondering about getting such an engine to perform at its optimum level leaving nothing on the table. So I would like to discuss tuning methods based on A/F ratio, ignition timing, individual cylinder tuning as well as ignition timing curves for each gear. I've been beating my brain on the best way to attack this once its off the dyno. Knowing that a dyno will get me close but its just a tool and not the same as the 1/4 mile. Do I just take a simplistic / commonsense approach. Find where the engine is about perfect as far as plug readings, timeslip, vacuum, etc... and just go with that? I bought a RacePak V300SD that's going to be the back bone of my data logging to help me with this and I'm going to go with MSD's new Power Grid System which will let me tune the timing in each cylinder as well as timing curves for each gear but how much info can I take from the dyno?

Ok, So first off I'm wondering if the A/F ratio's from the dyno will be a good starting point in the car even if the DA between the two locations are vastly different? For an example if you dyno at a location that is at sea level and you make the best power at 12.8:1 A/F and 40* of timing. Then you go home and you are at 3000' DA what's the best way to get your 12.8 back? De-jetting the main fuel jets? Jetting up the air bleeds? Add more timing to lean it back down? Or do you not get hung up on that number and just start making passes? Tune until you get the most MPH and then see what the 02 sensor is reading at that time? But again how do you get there? Main jetting? Air Bleeds? Timing? Remember we are not using the same sensors so there could be a difference between them and the 12.8 from the dyno could be 13.2 on my 02 sensor.

Ok, what about timing... To me the correct amount of timing is whatever number of degrees of timing will allow the fuel in a given combustion chamber to burn for the most degrees of crankshaft rotation with the greatest pressure without detonation. But how do we get there and when do we know we are there? There are so many things that I would think effects ignition timing? Burn rate of the fuel being used, Combustion Chamber efficiency, Piston dwell, Timing of the Valve events, engine load verses crankshaft acceleration, Heat, Quench, Plug location, Detonation, etc.... Now no mater how efficient the engine is or is not you need enough time to completely burn the intake charge. Now you have faster burning fuels and slower burning fuels. Speaking in the FE world only I don't consider the CJ combustion chamber to be the most efficient design out there so with a CJ combustion chamber would you benefit from a slower burning fuel or a faster burning fuel?

Next. Individual cylinder tuning. My engine specifically will have a C7-F PI cast aluminum intake on it. Which is the same as the CJ iron intake just aluminum. Does anyone have any experiences with individual cylinder tuning with these intakes? Do that have a tendency to run a specific cylinder leaner than others? If you don't have a dyno with 8 02 sensors the only two things I know to go by is plug readings and header tube readings. I would love to hear personal experiences on this.

Last but not least. Ignition timing curves. Back in the old days they would flip a switch to kill one set of points to richen the engine up if I remember correctly. Then they went to an actually retard device to pull 2, 4, 6* of timing all at the hit of a switch. Now you can graph to the tenths of a degree every 50 RPMs. So its obvious that you can make that as hard or as simple as you want it to be but what is goal here. Keeping the A/F ratio in the optimal range throughout that gear? That would be my guess. Like above I would love to hear personal experiences with this as well.

Alright guys lets hear it.

[jayb]

Well, that's a pretty full set of questions LOL!  I will take a stab on at least some of the answers, especially the dyno related ones:

- It has been my experience that there is never enough time to really wring the combination out on the dyno.  Even with a dyno in my own shop, schedules to get the engine in the car or get to the track generally cut the time short.  This is much worse for most people, who are at the dyno for only 4-8 hours.  You just don't have time to try all the different combinations.  So you will probably have to figure on getting individual cylinder timing, stagger jetting, and other more advanced tuning work done at the track.

- You are correct that the dyno will get you close, but that you will have to optimize in the car.  However, my experience has been that the dyno will generally get you really close, especially with a naturally aspirated engine, so there is nothing at all wrong with running the same settings that you got on the dyno first time at the track (if it is close to the same altitude; see more on that below).  On the dyno remember to jet for horsepower!  The A/F numbers are a guide, and will get you in the ballpark, but some engines want to run leaner than 12.5:1 - 13:1, and some want to run richer.  If you are dialed in right in that range, don't be afraid to go up or down in jetting and come out of that range in the search for more power; your engine may want that.

- I'd suggest you get the A/F in the right ballpark, then run dyno pulls to optimize timing.  Most CJ head engines will want 38 to 40 degrees total; make sure when you check the timing you are doing it at an RPM where all the mechanical advance has come in; that's where most of the dyno pull will be taking place.  Run some good race gas at the dyno so if you go to far with the timing, you won't hurt the motor; make sure it is the same gas you are planning on running at the track.  Start at 36 and go in increments of 2 degrees until you see the peak power start to fall off.  Go back a degree at a time to really dial it in.  Usually I've found that there is a 2-3 degree band where the engine makes the same peak power, so if you find that set the timing to the low end of that band.  After you have the timing set, then start moving the A/F around with the main jets to see if you can pick up power going leaner or richer.

- If the altitude of the dyno shop is dramatically different than the altitude where you are running the car, then you may need to adjust the jetting somewhat from the dyno settings before you run at the track.  If you are going up in altitude at the track, you'll be rich compared to the dyno jetting.  I think I'd run a pass with the dyno jetting anyway, because it will be rich and you won't have a chance of hurting the engine.  Look at the wideband O2 sensor and adjust from there.  If you are going the other way, meaning the dyno is at a significantly higher altitude than the track, you will need to jet up to be safe.  Just as a guess, I'd say one jet size for every 1000 feet of altitude difference.  Again make sure you are running good race gas so you've got some margin for error.  Also, main jet size will have a much bigger impact than the air bleeds, so I'd be working with the main jets at first.

- On individual cylinder timing, most of the systems I'm familiar with retard timing in the various cylinders.  So, if you start messing around with this, you will need to retard the timing on some cylinders and then advance the timing overall to compensate.  Regarding exhaust temps, I have found them to be a poor indicator of mixture and timing, because every cylinder has a little bit different flow path and this affects the exhaust temps.  A/F numbers are much better.  You don't need 8 O2 sensors, just 8 bungs; do the cylinders one at a time.  You will be surprised at how much variation there is from cylinder to cylinder, especially with stock heads and a stock intake.  If you adjust the timing on one cylinder and the A/F numbers change, obviously timing will have an effect on that cylinder.  But jetting will generally have a bigger effect than timing.

- On my favorite subject (intake manifolds), the PI intake is definitely not the same as the CJ intake, although they are pretty close in power production.  The CJ intake usually makes more low end torque than the PI.  Neither of these intakes has particularly good distribution, compared to a single plane intake, so stagger jetting may buy you something.  I've never experimented with that though, so I can't really say what will work there.

- Finally, there has always been talk of ET to be had by pulling timing out of the engine at the top end of the track.  I know some folks who have tried it, and it has never worked for them.  But some people say it works.  I would say it is combination specific, and maybe worth a try, but not until you get some of the other stuff dialed in.

[afret]

I'm not much help since we do it the very old fashioned way.      We just go to a T+T session and hook up the A-F ratio gauge,  look at plugs, and mess with the timing to see where it runs the best.   It's a big help to have old timers like Alex D and Tony D there and to be able to compare notes with Richie P and Don K if they're around.  These guys have flogged this combo for so long, that they've tried just about everything to see what works.  It's a great way to cut corners.  LOL

I'm sure what you're going to do with your computer will be the way to get optimal results.  That complicated stuff gives me a headache.  Sucks to be a lazy old fart.     Maybe someday after we kind of get our new combo dialed in we'll give that new stuff a try.

It would be interesting to see what difference the PI intake makes.  Nice to get rid of the weight in the front.  Will need wheelie bars for sure.  Richie is supposed to be using a PI and his car is running great at Pomona.

Here's a friend that runs a Chevy stocker having a Motrin moment with his laptop hooked to his MSD.

[fe66comet]

I knew that was a camaro LOL, honestly I have always gotten my best results street, strip, or off road by actual purpose testing. The old advance till you get some ping then back up a few degrees, read the plugs has been my best indicator. Even on fuel injection the computer will send you to some dark corner of the universe until you get a baseline to work from. Sometimes over complicating the wheel just gives a bumpy ride.

[fe66comet]

Check this out you can be on Twitter, Facebook, Texting, while tuning your car on your android phone. Now why would you want to do that I am not exactly sure?

http://m.summitracing.com/parts/src-518650

[69Cobra]

Well, that's a pretty full set of questions LOL!

LOL Yeah that's just a little glimpse of whats running around inside my head.

- I'd suggest you get the A/F in the right ballpark, then run dyno pulls to optimize timing. Most CJ head engines will want 38 to 40 degrees total; make sure when you check the timing you are doing it at an RPM where all the mechanical advance has come in; that's where most of the dyno pull will be taking place.  Run some good race gas at the dyno so if you go to far with the timing, you won't hurt the motor; make sure it is the same gas you are planning on running at the track.  Start at 36 and go in increments of 2 degrees until you see the peak power start to fall off.  Go back a degree at a time to really dial it in.  Usually I've found that there is a 2-3 degree band where the engine makes the same peak power, so if you find that set the timing to the low end of that band.  After you have the timing set, then start moving the A/F around with the main jets to see if you can pick up power going leaner or richer.

Ok. So you get the A/F in the ballpark then go after the timing, then back to the A/F to optimize that particular degree of timing. But that brings me back to what effects timing. If we look at timing as "whatever number of degrees of timing will allow the fuel in a given combustion chamber to burn for the most degrees of crankshaft rotation with the greatest pressure without detonation". What outside conditions effect that number? Altitude? Humidity? Fuel burn rate? Heat?. As long as I stay with the same fuel the burn rate will not change and I can control to some degree the temperature of the engine. So that leaves altitude and humidity. Then what about engine load vs crankshaft acceleration? If changing the rear gear to a higher / taller gear adds load to the engine but slow down the crankshaft acceleration how does that effect timing, if at all?

- On my favorite subject (intake manifolds), the PI intake is definitely not the same as the CJ intake, although they are pretty close in power production.  The CJ intake usually makes more low end torque than the PI.  Neither of these intakes has particularly good distribution, compared to a single plane intake, so stagger jetting may buy you something.  I've never experimented with that though, so I can't really say what will work there.

Well I've been over here in Afghanistan for a couple years now and I think your book came out somewhere in the time frame of me trying to get my stuff together to come over here so I never did read your book. Do you know if I can buy that digitally so I can down load it? I would like to get a hard copy as well for home. Anyways without having an intake in front of me can you tell which cylinders would be fed by which jets on the carb? Also, if you don't mind could you post the dyno results of your findings between the CJ and the PI? If the CJ made better low end did the PI make a little more up top?

I hope this discussion keeps going as I think everyone could learn a little on this topic if you go deep enough.

[69Cobra]

I'm not much help since we do it the very old fashioned way.      We just go to a T+T session and hook up the A-F ratio gauge,  look at plugs, and mess with the timing to see where it runs the best.   It's a big help to have old timers like Alex D and Tony D there and to be able to compare notes with Richie P and Don K if they're around.  These guys have flogged this combo for so long, that they've tried just about everything to see what works.  It's a great way to cut corners.  LOL

Absolutely, Old timers are good. I plan on leaning on my Dad who's tuned a few fast cars in his time. I'm just trying to look at this from a Pro Stock point of view. Those guys don't miss a tune very often and they have basically the same over all set up. N/A carburetor induction with probably the same MSD ignition. Now I know they spend millions of dollars in R&D work but they still have to turn for optimum performance at the track pass after pass with changing weather conditions. So what all do they give credit to, to stay on top of it?

I'm sure what you're going to do with your computer will be the way to get optimal results.

Well unfortunately a computer is now part of the tools in the tool box. I've been recording my runs for about 10 years to tune my clutch and without a computer I would not know half the stuff I do about clutches. Not that I know anything much but I can get by.

It would be interesting to see what difference the PI intake makes.  Nice to get rid of the weight in the front.  Will need wheelie bars for sure.  Richie is supposed to be using a PI and his car is running great at Pomona.

Yes I seen that. He's running very well. I wonder if it helped him any? Yes removing the weight is definitely a plus. I know I'm very happy to get rid of that weight up there especially with a 117" wb. I know that if you looked at the difference between the stocker motor my Dad raced back in the 70's and 80's vs what my new one. It would be like comparing a 70's stocker to a 70's super stocker so I'm very optimistic to see how it runs.

Here's a friend that runs a Chevy stocker having a Motrin moment with his laptop hooked to his MSD.

LOL I've been there.

[jayb]

Sorry for the delay in my response on this, I've been pretty busy.  Regarding timing, or any other engine parameter, there are probably a variety of factors that will influence it.  My opinion is that timing is influenced primarily by fuel quality (burn rate) and temperature of the air/fuel mix in the chamber.  So, as the air temperature goes up, you will want less timing, and as the air temperature goes down, you will want more.  Assuming you are operating at about the same temperature most of the time, and that you are using the same fuel at the track all the time, you should be able to optimize timing and have it stay pretty close to optimum even if conditions like humidity change.  Also, I don't think that engine load, at least within the normal parameters of a race car, will change timing requirements.  A long time ago I ran an experiment on the dyno to optimize timing at different acceleration rates (300 RPM/sec, 600 RPM/sec, and 1000 RPM/sec), which is essentially varying the load that the dyno puts on the engine.  I did not see any difference in where the ideal timing was.

My book is not available for download or on CD, just the print version.  Give me a couple of days and I will try to get those dyno charts you asked about posted, and look to see which jets feed which cylinders.

[69Cobra]

Sorry for the delay in my response on this, I've been pretty busy.  Regarding timing, or any other engine parameter, there are probably a variety of factors that will influence it.  My opinion is that timing is influenced primarily by fuel quality (burn rate) and temperature of the air/fuel mix in the chamber.  So, as the air temperature goes up, you will want less timing, and as the air temperature goes down, you will want more.  Assuming you are operating at about the same temperature most of the time, and that you are using the same fuel at the track all the time, you should be able to optimize timing and have it stay pretty close to optimum even if conditions like humidity change.  Also, I don't think that engine load, at least within the normal parameters of a race car, will change timing requirements.  A long time ago I ran an experiment on the dyno to optimize timing at different acceleration rates (300 RPM/sec, 600 RPM/sec, and 1000 RPM/sec), which is essentially varying the load that the dyno puts on the engine.  I did not see any difference in where the ideal timing was.

My book is not available for download or on CD, just the print version.  Give me a couple of days and I will try to get those dyno charts you asked about posted, and look to see which jets feed which cylinders.

Can you explain your reasoning on the temperature changes with the timing adjustments you mentioned? I would think it would be opposite of that. For example if the temp goes up your tune up would automatically get richer and if you take some timing out its going to richen it up more right?

Also very good info on the acceleration rate I guess that doesn't effect timing after all.

BTW I did order a couple book so thanks for your time and effort that you dedicate to the FE world.

[jayb]

Hmmm, I don't think taking timing out will have any effect on the mixture.  I'll explain my reasoning on the timing, and this is based on my own observations rather than what anybody else told me, or any dyno data.  Back when I was first playing around with performance cars in the 1980s, if the water temperature creeped up to 210 degrees, they would tend to knock a little bit on acceleration.  On the other hand, they ran beautifully if I had a good enough radiator and fan system to keep them at the thermostat setting of 160 degrees.  What I think was happening there was that the air/fuel mixture was heating up in the intake and heads and coming into the chamber at a much higher temperature, so the combustion process occurred faster, and peak cylinder pressure occurred to early.  Ideally you would like to reach peak cylinder pressure just after top dead center, like around 7 degrees after top dead center.  When you optimize timing on the dyno, you keep advancing the timing until you start to lose power; what you are doing is dialing in that peak cylinder pressure so that it happens around 7 degrees after top dead center.  Once you have that dialed in, if you raise the temperature of the incoming air/fuel mixture, the combustion process will happen faster because it doesn't take as long for the A/F mixture to reach combustion temperature after the plug fires.  So, peak cylinder pressure will occur sooner.  If it occurs too soon you will get knocking, and up to that point you will be losing power from your original setting.

The thing about this is that with the air temperature variation you normally see, this would be a pretty small effect.  If I recall correctly combustion temperatures are around 1300 degrees.  Assuming you have a good fresh air package on the car and you are keeping the coolant temperature down, if the air temperature goes up from 70 degrees to 85 degrees, you are only seeing a change in temperature between the air and combustion temperature of 1230 to 1215 degrees.  You might not even notice any difference in the timing requirements of the engine at that point.

Again, just my opinion on this, and I've been wrong before    For what it's worth, I almost never adjust timing at the track; I focus on A/F adjustments and suspension adjustments.

[69Cobra]

Interesting and I can see your point but in the scenario where you were developing a knock or preignition what do you think would've happened if you would've just added fuel and left the timing alone?   

In the past at the race track with no 02 sensor I had a suspicion that the car was a little rich. With not clicking it off at the traps and driving the car back through the pits I didn't put much faith in the plug readings. So I was just going to pull some jet out of it as see what happened. Dad said here let me put some timing in it and see what that does. Went from 37* to 39* and it pick the car up about .08. So that's whats got me thinking, if we were already rich and added timing to give it more time to burn the amount of fuel in the charge which in my thinking leaned it out a little. I don't know. Ok let me think about this. If the amount of hp an engine makes is directly proportional to the amount of fuel it can burn wouldn't more fuel + more timing make the most hp?

Anybody else what to chime in with there experience?

[jayb]

Maybe my situation would have improved with more fuel; I never tried that.  And maybe your car just wanted more timing, rather than less fuel.  When Blair Patrick was here dynoing his 352 stocker engine, we ran the timing all the way up to 42 degrees at one point; seems to me we settled around 40 degrees for best power on that engine.  So at 37 degrees and a stock chamber, I'm thinking you were a little undertimed with that engine.

Also, for what it's worth all the formulas I've seen regarding peak horsepower production look at the amount of air the engine can pump, not the amount of fuel it can burn.  Can't have one without the other, of course, but the engineering formulas for horsepower production that I've seen rely on air volume, not fuel volume.  Here's a related "quiz" to get you thinking along these lines:

- I have an 8' X 10' room, with an 8' ceiling.  The room is at sea level, and 68 degrees Fahrenheit.  How much horsepower can I make with the air in the room in one minute?

I'll bet Bill Conley will get this one, if he's watching...

[69Cobra]

Hummm Interesting... I'm curious about the formulas and how your 8x10x8 room works out there. I'm curious how much compression that room has and how many times a second you can exchange that air lol.

[billballinger]

I would use the T&T and the LM on both banks  to dial the engine in to the highest MPH you can do on the track.  Then work on the suspension, tire pressure, slick compound, and mental focus on off the line ritual to shorten your 60 ft times, when you have that where you know from experience you are within the range check that you are still on the mph and you LM shows no fat spots. Try a degree of timing up and down, and see if your 60' improves while staying on the MPH and vice versa.  You can log these for the weather, and basic off the trailer starting points.  Most places you find a lot more, within a small range that you can't dial it.  Also try T&T in the heat, and as the sun goes down and when its cool as it is in the later rounds.  You can make your changes as you run rounds if you know the track gets slick as it cools, pull a degree of timing out to knock off some torque and adjust your dial accordingly. 

I used to do that without the LM, but if it had been around back then I would have snapshotted my data stream for various conditions, and folks would have swore i was a Morman walking around with a Bible of about every combination I could collect. 

Your best tuning tool? Ritualistic discipline driving the car, and keep your changes to small adjust able things on the car, and keeping a log with every condition that you can.  It is almost infinite, but you would be surprised at how few setups there are that will cover ranges of conditions, and slight changes on your dial  can do the rest.  But you don't know if you don't baseline it and keep track of what to do as the rounds go by.   Remember, you are racing yourself, what you do gives you predictable results, and you won't get spooked when a guy goes by and has to pedal it at the end.  You will 9.5 times out of 10 hit your dial and that is all that counts.       

[Joe-jdc]

Recently I had an opportunity to help on a couple of dyno test sessions, and found out a few concepts on timing.  First, is the combustion chamber effeciency, compression ratio, camshaft overlap, and rod ratio--yes, rod ratio.  A short rod will require more lead time because it accelerates quicker just before TDC and BDC in each cycle.  The longer the rod the more dwell time at or near TDC, thus less lead on the timing necessary.  It may only be a couple of degrees different, but it will be different.  I agree with Jay in that once the timing has been established as optimal, set and forget, but verify occasionaly that the distributor has not developed a mechanical problem.  Also, my cars always went faster when they were lean enough to start a temperature rise due to less fuel/air ratio.  EGT rise, water temperature, oil temperature all need to be watched along with the atmospheric conditions to find the optimal carb tweaks at the track.  Joe-JDC.