Dyno Tuning and Tweaking

[Blown1993Z28]

I was wondering how long the ECU takes to re-map the fuel air tables and timing after you disconnect the battery. The issue is I want to do some dyno runs while varying the boost and I know varying the boost will invalidate my current fuel air tables. I have a scanner that can read all my sensors, timing adjustment, and the fuel air tables but honestly I don't know what I'm looking at.:help:

Timing presents the same challenge. I have an aftermarket PROM chip which propably has a bit more agressive timing curve than I need but my LTCC LS1 ignition controller has a dial in retard switch. How do I know what timing is best? Just guessing, whatever dyno pull makes the best power without setting off the knock sensor? The Speed Shop says I get a half a day for $350 so I will need to limit my tweaks by whatever learn time the ECU will need. Are there any other tweaks I should be trying?

[95z28onjuice]

well does your table read out the a/f ratio on a graph? you want it 12.1 ratio all the way threw the rpm. It takes any where from 5-10 minutes to relaern the adaptive memory for the ecm. so when your at the dyno there not tuning it for you or your just renting the dynonot the tuner?

[Tony]

I was wondering how long the ECU takes to re-map the fuel air tables and timing after you disconnect the battery.

It doesn't work like that. You can leave the battery unhooked and it won't mess with your tables. I'm not sure how long it takes to flash a PROM, but on the newer cars, the entire upload takes about 5 minutes. and for $350 for 4 hours on the dyno, that's a pretty good deal.

[Blown1993Z28]

It doesn't work like that. You can leave the battery unhooked and it won't mess with your tables. I'm not sure how long it takes to flash a PROM, but on the newer cars, the entire upload takes about 5 minutes. and for $350 for 4 hours on the dyno, that's a pretty good deal.

The fuel air tables I am talking about are volatile (memory gets lost when power is disconnected). They are also "learned" by the PCM itself through the O2 sensors (and TPS,MAP etc.) If you ever noticed the engine idleing really crappy right after a power disconnect it's actually the PCM reading sensors and "trimming" the Fuel:Air tables. Thats the definition of closed loop. This is according to the GM Service Manual. What the Manual doesn't say is how long this takes. Juice got this one. 5-10 min at varying throttle positions AND under load sounds right. The only better way I can think of to tell for sure when its done initial trimming is to keep doing data captures until they stop changing (or keep doing Dyno pulls until the HP and Tq graphs settle). I am pretty sure the factory target F:A is set a little on the rich side. The aftermarket guys change it to where it should be for best performance so thats what I'm going to verifly by swapping out EEPROMS (I got 1 stock and two different aftermarkets). So I got timing and F:A to play with. Any other tweaks I should be trying?

[FANTA-Z]

Actually you should be targeting the A/F ratio at WOT in the 12.8 to 13.2 range. Its a known fact that the LT1 runs best around these numbers. As for the learning curve of the PCM........well thats constant so its not something like a 5 minute deal. The longer the car runs the better it learns itself and the better it runs. Speed Density is very easy to tune so you shouldnt have any issues actually. Tuning with the VE tables help out a lot, and even though there is always an argument about if the VE tables do anything on a MAF car (I know yours is not a MAF car just throwing this out there) they do. If you throw a MAF car into SD mode and tune it first and getting the PCM as close to perfect as you can get, and then switch it back over to MAF mode it helps the PCM tremendously in learning and correcting. It doesnt have to travel near as far with corrections and just makes everything much easier to deal with.

[Blown1993Z28]

Actually you should be targeting the A/F ratio at WOT in the 12.8 to 13.2 range. Its a known fact that the LT1 runs best around these numbers. As for the learning curve of the PCM........well thats constant so its not something like a 5 minute deal. The longer the car runs the better it learns itself and the better it runs. Speed Density is very easy to tune so you shouldnt have any issues actually. Tuning with the VE tables help out a lot, and even though there is always an argument about if the VE tables do anything on a MAF car (I know yours is not a MAF car just throwing this out there) they do. If you throw a MAF car into SD mode and tune it first and getting the PCM as close to perfect as you can get, and then switch it back over to MAF mode it helps the PCM tremendously in learning and correcting. It doesnt have to travel near as far with corrections and just makes everything much easier to deal with.

Thanx! That 12.8 - 13.2 Target A:F is what I was looking for. I'm guessing the 12.1:1 Juice mentioned is the stock (rich) target. I agree with you about the trimming never being "done" it keeps trimming whenever its in closed loop. The part that I still don't understand is the WOT tuning. To my understanding Open Loop stops reading the sensors altogether and just goes on the F:A learned values from previous partial throttles. I'm basing this on the GM Service Manual's instruction to NOT run at WOT immediately after power disconnect and to "[drive] at part throttle, with moderate acceleration and idle conditions until normal performance returns" The last four words is why I posted this. I would like to think I know the car pretty well, just not good enough to accurately know when it's done initial trim. Hopefully it wont be "normal performance" that returns but increased performance:dizzy: I didn't want to have to annoy Bob Bailey (THE MAN for EFI Tuning) but I may shoot him an email about timing tuning with his LTCC box.

[FANTA-Z]

You are correct that PE (Power Enrichment mode) goes on a percentage and if your computer is constantly trying to get the car running the best it can then your PE should change as well until you get to a certain point.

[theguywhoknows]

i wouldn't run anywhere close to 13:1 A/F in a boosted application, especially with the crappy stock hypereutectic pistons these motors have in them. I'd run more like 11.8:1.

[Blown1993Z28]

i wouldn't run anywhere close to 13:1 A/F in a boosted application, especially with the crappy stock hypereutectic pistons these motors have in them. I'd run more like 11.8:1.

The Manual for my scanner says the optimal A:F should be 14.3 : 1. It is not specific for the LT1 (or boosted LT1s) so I can't really rely on the book for my setup. Putting together a good package is pretty complex (and expensive). So I got Boost Pressure, Fuel Pressure, Air : Fuel, Timing, and Methanol Injection jets to play with. Not always, but I have seen cases where tweaking one thing throws out a previously tuned item. Anyone know what order I should go on to minimize that?:confused:

[Tony]

14.3, holy crap!!! I wouldn't run a motor that lean. You are just asking for trouble if you do that.

[FANTA-Z]

The 14.3:1 is Stoich which is basically what your wanting for cruising around town and such. Just like the LT1 is 14.7:1 if I recall correctly but this is not what your wanting at WOT. As said I would shoot for being fat at first because you dont want to be lean and blow your motor right quick.

As far as your tuning I would stick with the 4.5 boost, fuel pressure should be set at a constant and left alone and then deal with your tuning. Yes you will be able to run more boost safely with the Meth but I would get everything lined out perfect before moving on to the Meth and adjusting for it.

[Blown1993Z28]

The 14.3:1 is Stoich which is basically what your wanting for cruising around town and such. Just like the LT1 is 14.7:1 if I recall correctly but this is not what your wanting at WOT. As said I would shoot for being fat at first because you dont want to be lean and blow your motor right quick.

As far as your tuning I would stick with the 4.5 boost, fuel pressure should be set at a constant and left alone and then deal with your tuning. Yes you will be able to run more boost safely with the Meth but I would get everything lined out perfect before moving on to the Meth and adjusting for it.

Yeah, I double checked and it was actually 14.7:1. The scanner is made by Auto X Ray. If I'm reading you correct I need a good baseline BEFORE tweaking. That might be a problem, I got the stupid EEPROM (3 of them)but the scanner does read it. I'll see what data was burned onto each and post it so y'all can tell me what one will make that good baseline. Fuel is going to be an even worse problem. The S/C came with a FMU (Vacuum Adjustable Fuel Management Unit) that pinches the Fuel Line return hose to get higher Fuel Rail Pressures proportional to RPM/Engine Load. I left that part off and just got the right size injectors (30#). The PCM thinks I have 22# injectors and I am pretty sure I need to burn a new custom chip just to fix that one problem. If my real time monitoring of the A:F showed it running lean I had planned on using that FMU with the 30# Injectors. Last problem is a sucky one. I installed Bosch Platinum 4 prong spark plugs and went for their O2s to match. Can I tell if they are OK or just ditch them for the AC Delcos?

P.S. DAMN IT!!!:growl: Spark Plug Gap. Another variable to tune for

[theguywhoknows]

soichiometric A/F depends on the fuel used, gasoline is about 14.7:1. alright dude i'll help ya out a bit. first off tune for the new injectors. then ditch those bosch plugs for some br6ef ngk plugs, those are the correct heat range for you and not projected tip. gap those plugs at .030. when tuning, first make sure your a/f ratio is SAFE, like 11.5:1. then you need to adjust spark advance to make the most hp and tq verify this value by looking at the timing mark on a few spark plugs. after spark advance is set, then tune your VE and PE tables for maximum hp and torque. Remember that there is a line between safe, and maximum power on pump fuel. You need to keep boost pressure, and fuel pressure constant. once your timing is set, keep that constant and focus on a/f.

[theguywhoknows]

are you planning on tuning the entire car by yourself? i hope not, you do NOT have near the knowledge required to tune a N/A car, yet alone a high compression boosed car on pump gas... hire a professional is my final bit of advice.

[Tony]

Went ahead and moved this thread into the tuning section.

[Blown1993Z28]

are you planning on tuning the entire car by yourself? i hope not, you do NOT have near the knowledge required to tune a N/A car, yet alone a high compression boosed car on pump gas... hire a professional is my final bit of advice.

I think you've lived up to your handle, and I have to agree with you on this. I have years of experience tuning RF Electronic Circuits (Spectrum Analyzers, Vector Network Analyzers, Noise Figure Meters, etc.) and thought tuning Fuel Injection would be similar. It obviously isn't plug and play or anything close. I'm really against a "mail order tune" but that might be my best option. I still want to learn how to tune EFI, just not at the cost of leaning out my motor and melting pistons. I kinda hate this but the young Asian "Tuner" crowd might be able to teach me some secrets. (Here in NYC American Sports Cars are not popular, rice burners are:growl: AND NO I am NOT getting a Honda Civic!!!)

P.S. Tony, thanks for putting my post here, I didn't know there was a Tuning section. I thought you said OBD 1 was easy to tune?:no:

[theguywhoknows]

Honestly I've never tuned a 93, but I DO know how to tune. But knowing that you have to deal with chips, I wouldn't touch it unless i knew all about them, which i don't. talk to alvin at pcmforless, he's the resident PROM tuner there. I'm sure he could guide you in the right direction, and also provide a mail order tune for your car.

[Blown1993Z28]

Honestly I've never tuned a 93, but I DO know how to tune. But knowing that you have to deal with chips, I wouldn't touch it unless i knew all about them, which i don't. talk to alvin at pcmforless, he's the resident PROM tuner there. I'm sure he could guide you in the right direction, and also provide a mail order tune for your car.

I have a little experience with the EEPROMS, my 85 Monte SS had one and a buddy of mine in the NJ Air National Guard used to burn them but that was an Electronic Carburetor (STUPID IDEA!) I think the only difference between the EEPROM and the flash style is the soft memory. You can write to the flash one but not the EEPROM, so you gotta plug in an adaptor chip (piggybacked to the programmer) in place of the EEPROM while tuning, so it will act just like the newer flashable PCMs and then burn your best results onto your EEPROM. I did a little research on the plugs you suggested and the temperature ranges. NGK says you can sort of tell lean/rich just by inspecting the plugs. I'll give that a try. I'm running 8 LS2 coils right now and they spark better than the Opti so I'm going to have to play around with different plugs and gaps and the dial in retard feature on my ignition. Paulster told me the Bosch O2 sensors are quirkey and to ditch them. I thought at least my 4 prong Platinum Bosch spark plugs at least were good, I guess not. Thanx for the tips*z28rocks*