Re: LT5 ECM Tuning thread
 

Jeff,

Maybe we should start a fund and see if we could pay someone who has the knowledge to create a def file for use by members of this registry.

Re: LT5 ECM Tuning thread
 

Maybe...

Re: LT5 ECM Tuning thread
 

Let me know when you want the money!

Re: LT5 ECM Tuning thread
 

Jeff and I will keep you posted.

Re: LT5 ECM Tuning thread
 

On another list there are people using advanced timing in the lower ranges to solve idle problems associated with cam overlap, that is what I was talking about. With a good datalog to see specific cells and a good wideband checked against the timing retard you might get the mixture to pass. You would have to go open loop all the time in the chip and customize it just to pass. If you went closed loop there is no way the calibration is going to let you get it right as it will try adjusting to 14.7 at all points. It may be that the motor needs cells at a different mixture range and spark point so it can interpolate between cells to get what he needs. IE you are starting the iginition early to get better combustion, since it is at lower speed should be able to monitor/adjust for any spark knock.

Todd comments?

Tyler

Re: LT5 ECM Tuning thread
 

You can take the Tunercat .tdf file and create a .xdf file. The early tunercat files had a problem in the VE tables that Todd found and we contacted them and they corrected it. So you need to make sure you have the later def files. I am not sure what you need beyond what is in the .tdf files for tuning as they are pretty thorough. I have the complete 90 commented GM calibration printout and it is over 1 in thick and 250 pages. Since it is a 90 the calibration has only sketches of where they were going in the egr area so it is only good to 92.

Todd has spent literaly 100s of hours learning what he knows, he and I am somewhat leary of handing out information before we know that the reciepent has a good understanding of just what is involved. I can tell you from bitter experience you can mess up big time if you do not have a good grasp on what is happening in a calibration.

The biggest problem is as you have described, a good way to log what is going on and be able to review the logs watching what happens as you make a change. My car has been off the road for 5 years so I have not had a platform to take advantage of the new software which is why I have not had much to contribute.

I believe Todd uses a FJO wideband and datalog setup, but I also know whatever he used it was the hours on the road that was most important. There are very few who really want to play with stuff and yes it is confusing to a newcomer but thats why you can count on one hand those who have the skill and knowledge to get results.

Tyler

Re: LT5 ECM Tuning thread
 

SA is likely not the issue. The condition you describe is precisely why you'd like to modify the O2 Window Terms. These will define the O2 sensor swing points that the ECM will try keeping the mixture at. And it can be varied on the basis of airflow. For those using cams with larger overlap, this helps tame idle surging and rich idle conditions. PID controls are helpful here too. These don't appear in the .tdfs and .xdfs generally available. There's nothing "hard-wired" in the cal for 14.7 being stoich. For those of us using gas with 10% ethanol, we benefit from changing stoich to 14.3:1 for greater tuning accuracy.



The .tdf is pretty basic. It lacks PID controls, IAC controls, O2 sensor etc. Quite a few missing parameters allow someone to really fine tune the motor particularly if significant mods have been made. For example, I found that swapping in an AL FW benefitted from changes to the VE tables but also to IAC and Proportional Gains.

That's true to an extent. But you can't learn about what various controls do unless you can play with them and see what the effect is. Some of us can't disassemble code, but we certainly can utilize the parameters, once revealed, to tune the calibration to our liking. What would you like to know about someone like myself that would make you feel comfortable that we know what we are doing and therefore share the commented hack? With the majority of ZR-1s being 90s, this would be very useful for the community.

As =Jeff= can attest, I've burned over 1000 bins using either proms or Ostrich/TunerPro RT combo. I use a ZT-2 WB for WOT tuning. Datalogging with EASE and http://www.dynamicefi.com/. I think you'll find that there is quite a large community of "tuners" out there pretty adept at making all kinds of engine combos run well. I need to give a great deal of credit for to people like Bruce Plecan ( generally acknowledged as the father of GM ECM tuning) and Rob Rauscher (RBob moderator on 3rd Gen) for freely sharing what they learned.
I don't think tuning an LT-5 would be any more difficult than some of the stuff you see on 3rd Gen. The fundamentals are the same, and as Todd has stated, much of the calibration is based off of the $8D code.

Re: LT5 ECM Tuning thread
 

Dominic,
Tell you what, you guys give it a shot and post up here, or in a new thread, when you get stuck. I assure you if you get stuck along the way I will offer help. I couldn't disassemble code either when I started...heck, I have no training at all in this field.

Which calibration are you working with? AYBK? How far have you gotten into it?

Todd

Re: LT5 ECM Tuning thread
 

Todd,

I appreciate the offer of help. I have not started disassembling code. I have both the .tdf and .xdf editors. I have ported a .tdf over to an .ecu and .xdf file. (Pretty simple since both John and Mark built a function to do just that). I have previously created and modified .xdf items. I prefer working with TP but have used both as well as modifying calibrations directly in hex. I have modified .ads so as to output aldl items that were not supported in the scantool I was using. I've been able to introduce new output to the ALDL datastream (i.e. WB O2). Basically, if I have a hack, I can create the .xdf. What other tools do I need?
If you want to take people like myself, Shawn ZR-1 and =Jeff= through the steps, I'd do it as a learning experience. Not sure how that changes anything regarding my understanding and use of the parameters I'd like access to. But I'm willing to keep an open mind.

Re: LT5 ECM Tuning thread
 

I will offer some tips and questions to make sure you understand just what is being changes. The one that bit me first was something called.
'Secondary inj on fuel PW scaler.' Its in TC under a different heading, I used it on Rons car when Jim ran out of ideas, and TP, anyone know what it does and just how you can use it. I know Todd does but it is not to obvious and can have a dramatic difference.

Tyler

Re: LT5 ECM Tuning thread
 

Tyler,
It is a multiplier used to cut the fuel pulsewidth in half when the second set of injectors is active. For example, say you have an base pulsewidth of 10 milliseconds when the engine is running on only the 8 primary injectors. When the ECM commands the secondary throttles open, there is a very slight delay (0.3 sec) then the secondary injectors are energized, and the NEW pulsewidth is now 10ms x 0.51 = 5.1ms. Of course, since it is being delivered with twice the number of injectors, the overall fuel injected is the same as before the port throttles opened.

Increasing this multiplier would have the effect of adding fuel when the secondary injectors are energized. If it were, say, .75, then you would end up with 2 injectors x 10ms x .75 multiplier = 15ms total fuel delivered. This could be used as a band-aid to increase fueling if the injectors are too small or the VE table is not correct. However, I would think the transition would be terrible, and you'd end up with a surge due to the sudden enrichment.

just my $0.02.

Todd

Re: LT5 ECM Tuning thread
 

In my book your $0.02 is worth at least $1.00.

You are of course correct. When Jim Smith was trying to tune Ron Ks motor several years ago the car had a lean at this transission and he had the VE tables up to 100 and the car was still lean in transition. We took this to .56 or .57 and solved the problem and were able to back the VE table down some.

The above only applies if you are using secondary throttle plates.

Todd what did you with this when you change the calibration to have both injectors on all the time.

Tyler

Re: LT5 ECM Tuning thread
 

I left it alone. So basically had half pulsewidth provided by each injector all the time.

The base fuel calculation has no idea there are two injectors. In fact, the base calculation only knows the constant for 1 injector (.35 sec/gram). The pulsewidth is calculated using this. So, therefore, when you bring the second injectors online with the same calculated base pulsewidth, the scaler has to be used so that you don't deliver twice the required fuel.

Now, about that delay factor....who wants to discuss what effect that has?

Todd

Re: LT5 ECM Tuning thread
 

Todd,

Why don't we discuss Proportional Gain?

Re: LT5 ECM Tuning thread
 

wow todd really know his stuff. this is a good read . when i got a prom from mark haibeck he says he takes some of that out to give a better responce . is that what you mean. i just want to learn all i can . what are your thoughts on tunning is one takes the secondary throttle blades out . do they then run all the time ?

Re: LT5 ECM Tuning thread
 

OK. What do you want to know about it? It is pretty simple, and the first of three potential PID parameters to control pulsewidth based on feedback from the O2 sensor. There are primarily two tables at work...one is the base response to O2 error vs. airflow. There is a smaller proportional step at zero airflow (idle).

These steps are then multiplied by a factor, depending on how large the O2 error is. The bigger the error, the larger the multiplier. You end up with an adjustment "count" to modify the base pulsewidth. If the error is positive, fuel is removed and vice versa.

Todd

Re: LT5 ECM Tuning thread
 

Isn't there a constant that defines the max airflow to be considered as IDLE? The 7747 code used a separate Prop Gain Bias constant for idle and the 2D table was pretty coarse.
EBL has 2 constants for Prop Gain at idle based on offset and duration and 4 tables.
So 1 Prop Gain table defining a gain based on Gms/sec which then gets further modified by a second table with factors based on O2 Error, right?
Which one do you usually modify and why?
If I change the gain up or down, what would I feel in the way the motor runs?
Why wouldn't I want to be able to modify this in the bin?

Thanks for this. Any more on the disassembly lesson?
Dominic

Re: LT5 ECM Tuning thread
 

No. Idle fueling is determined by TPS < 2% and vehicle speed <= 0. That combination sets the airflow term to zero.

There is a scaler term available to modify the Prop Steps, but it is not used (ie, = 1.00)

Todd

Re: LT5 ECM Tuning thread
 

Thanks Todd. Think I understand what's going on here now. :hello:

Re: LT5 ECM Tuning thread
 

The delay factor is there to let the air velocity catch up to the needed fuel. When you go from 1 to 2 runners in a cyl the increased airflow and pressure change has to be factored into the fueling equation and that is what the factor does.

I hadn't thought about that one in a while. On a removed secondary situation would you lower the delay or remove it alltogeather?

Tyler

Re: LT5 ECM Tuning thread
 

tyler thankyou so much for the insightfull info . guess i will send my prom to corey after i remove the secondaries

Re: LT5 ECM Tuning thread
 

If you do not include porting etc with pulling the secondaries it is a waste. If you do not go that far why not just have Corey change the calibration to allow dual injectors on all the time and force the secondaries open, Todd was the developer of this little trick and seems to work ok. Will B has this on his 90 and it works well.

Tyler

Re: LT5 ECM Tuning thread
 

From a calibration engineer:

Quote

Proportional gain is a method of controlling a signal of some sort generally idle speed control or EGR controller, etc; where a certain type of damping or control of a signal is required. It in it's self is not a
calibration parameter but exerts control over a device.
Generally the P part of a PID controller where I = integral and D = derivative. Any of these terms can be used in isolation but are generally used to fine control a feedback system of some kind. Look up PID controllers on the Internet for the full skinny! Should keep you amused for hours!!

Unquote

Tyler

Re: LT5 ECM Tuning thread
 

If you are interested in learning about the PID controls, have a read of the attached paper. Don't be surprised if it takes a few run thrus' to grasp what they do. Actually making the changes to the cal will solidify for you how these controls help in fine tuning the behavior of the motor. This paper was written for a TBI system but the operating principles and results are very applicable even to an LT5.

Re: LT5 ECM Tuning thread
 

Picking this thread back up, using a question asked on the list...

No idea about the cam timing. I have a Daytona 24hr calibration from Jan-93. I am sure it is not the same as the BW cars, because it was intended for racing, not passing 50-state smog.

The bin I have is based on a '90 (AUAH) calibration. Surprisingly, the changes are fairly minimal, compared to what one would suspect for a race engine. The SA table has few changes, mainly at WOT. About 28d total advance.

The VE tables are largely unchanged, except the high RPM table w/ SPT's open, no doubt where the car spent most of its lap. It is also clear that the race car had no Port throttles, O2 feedback, or knock feedback... not unlike the Snakeskinner calibration, in that regard.

Just trying to keep this thread alive ... ;)

Todd

Re: LT5 ECM Tuning thread
 

Just wanted to drop in and say this thread was still very informative some 16 years later. :D

Re: LT5 ECM Tuning thread
 

Yeah it was. I miss Tyler around here. RIP


Sent from my iPhone using ZR-1 Net Registry

Re: LT5 ECM Tuning thread
 

Tyler too? Man... I stepped away from this hobby for ~15 years and so much has changed. :( I also learned Grumpy from the DIY-Prom scene passed.

Re: LT5 ECM Tuning thread
 

Grumpy(aka Bruce Plecan) passed away quite a long time ago. We held a tuning symposium in his honor near his home in Ohio. He and RBob were the brains behind a great deal of the tuning knowledge we have today. Craig Moates still around we hope but out of the business. Mark Mansur for TPRT