Hey there,

Im trying to train my tuning skills on TunerProRt. I want to change my cold start fueling on my 1988 305 tpi cause its running lean in two spots (20°C and 32°C). You can see that in the table shown below. Right in this situation my car has a harder time to start, I can see that on my AFR gauge. Its showing nearly 16:1 AFR at cold start. Also the open loop AFR is not nice, its just better as it gets into closed loop.
Whats the deal of the change from 50 at 8°C to 12.11 at 20°C? Thats a big step leaner. Cant get beyond that.

And if I want to change just that, my car idles high and stays high until I get it stopped at 0mph (warm) then it slowly goes back to target 780rpm idle. What´s that???
I tried to change the values to like 32 or something like that between 50 and 12.11 to find more easy startup AFR..

Could someone help me? Im using the APYM 89 bin file and $6E xdf and 1227165_6E.adx

 

As you are stating it, the deal is that you seem to be comingling 3 things:
1) Startup enrichment which does affect OL AFR, but only until it's decayed out
2) OL AFR after startup enrichment is decayed out
3) High idle
Need to address one thing at a time.

1)
Changing the values in the table you posted should not affect idle RPM, only AFR. The "drop" you describe appears to be because GM tests showed that less fuel was needed as startup temp approached 68*F(20*C) from 46*F(8*C). If your starting problem is truly due to these values, increasing them will provide more cranking fuel (lower AFR).

2)
I believe you'll find that OL AFR is determined primarily by these tables. Change as necessary:


3)
Need specific details to address this.

 

84Elky

 

First off, if your car is stock, the tune is not the problem. You have mechanical or electrical issues.

Sequence of events on cold start:

1) Cranking fuel delivery
2) Start-up Enrichment AFR
3) Start-up Enrichment AFR decay delay
4) Start-up Enrichment AFR decay
5) Open loop AFR
6) Close loop AFR

There are multiple tables involved in this sequence that deals with MAT, CT, MAP, MAF, TPS, DRP and INJPW

When, during that sequence, is it showing lean? Are you stationary no throttle, stationary with throttle, moving no throttle or moving with throttle? You need to know when during the sequence, as it points to specific tables for correction.

If it has a "harder time to start" at certain CT, it has nothing to do with the table you posted.

 

Thanks for answering guys.

Im pretty sure I JUST changed the table values shown above. So cold start enrichment. If Im doing so it will start more easier and nearly dont drop the rmp (like hesitation).
And then the idle wont come down. I didn´t change OL AFR.

It is showing lean so long until it enters closed loop. This will happen at ~40°C (?). So after ~3 minutes of driving. While driving it will not response as good as warm when giving some throttle. But the main problem is the AFR I know for sure. The car otherwise runs very good and has no problems at all. Fuel pressure is correct, no vacuum leaks, great maintained ignition system etc. The car has no mechanical fault. Of ourse its not "stock", but the changes are very mild:
Heads were milled over, (more CR) 1.6 roller tip rockers, better flowing y pipe from Magnaflow 3", straight through muffler & catback, ported factory exhaust manifolds, cold air intake, A.I.R. delete, smog pump delete, coolant bypass mod and some standard plenum porting work.

I thought this problem maybe comes from my 9th injector and to test so I unplugged the connector to it and load a stock $6E bin file on it to test. It will also idle bad (stumbling for 2 sec and searching idle like having a big cam in it 500-550 rpm) and AFR showing more than 15:1 AFR, sometimes even more when dropping into gear (load).

Than I started to change cold start fueling. It will start good then and nearly stays at a beautiful idle speed BUT stays in high idle. And again, I just changed startup enrichment, not decay, not delay. Just the amount. Was it wrong?

Is it maybe helpful to upload a datalog that you cann view it?

Greetings,

Chris

 

Chris ---

The quote above is the first statement in your first post. Then you tell us about 3 different issues.

I'm going to apologize up front for being the one to say this, but it needs to be said. People here want to help, That's what this site is all about. But in order to be helped, two things for sure, are critically important:
1) Concise problem statement with as much data as possible to define/support the problem, and
2) Consistency in discussion

With all respect, you're not doing that. Here's an example in your latest post:Among other things, you just said that you did not change OL AFR (when you were provided what would allow changing it); and that until it goes into CL, the engine is lean. Hmmm.

Let's start over. What exactly is the issue or are the issues you need help with?

And like the above, in order to tune successfully, most everyone here will tell you that you must:
- deal with only one thing at a time,
- take detailed notes of changes made, and
- record the results
Rinse and repeat.

 

The main problem is I´m not native speaking english, and to tell you about the problems in detail its better for speaking in my mother tongue. Sorry, I understand that you need detailed information and want to give you that. I just did change the Startup enrichment so only one thing at a time and just the block values from 20 and 32°F. Today I changed the OL AFR and it also went in high idle (Open loop change vs coolant temperature).

The core is its running lean and I know that. Its mechanically in good condition and my changes works but create a high idle!
And I just wanted to know, whether this is a common problem and what do you guys change if its going lean in cold start and cold open loop?
Maybe I can try some more things then and keep you updated.

Chris

 

Understand Chris and thanks for the elaboration. So I'll ask some questions just dealing with starting the engine to begin with:
1) Please describe the problem you are having starting the engine. Don't care how it runs right now. We'll deal with how it runs later.
2) What is your altitude and what is the outside temperature when you having difficulty starting the engine?

 

Appreciate your patience with me. So how it behaves:

Im going key on, let the fuel pump priming and start the engine. It doesnt take long cranking time to start, maybe 1 or 2 seconds at most. Then the idle is up on point at maybe 1100rpm for ~ 3 seconds, then it starts to drop in rpm very quickly, fall down to 550-650 rpm (dont count it on the gauge) and is hunting idle like having a big cam. This stays for maybe 3 seconds. During that seconds my O2 Sensor starts working and the gauge will show up lean AFR (as you know). After all maybe 7 seconds the engine will recover and go to normal idle like its recovering (~1100rpm) and hold it steady. The AFR gets better in idle (into the 15:1 direction) but if I drop into gear, the AFR will go leaner again to nearly 16:1. The engine wont jack off, it still runs. During this problem the car is not as responsive in taking throttle as it warms up (already clear with that AFR). Every minute it gets better and better, I think the ECM goes through the OL AFR tables. And after ~3 minutes its away cause it gets into closed loop.

Altitude 34-70m over normal zero (we say in germany). So pretty normal, not very high. Between 34 or 70m there is no difference in starting behaviour as long as its the same temperature outside. I could swear if its colder outside it will working properly as I can remember. But not tested this year, good wheather car only. Cold starts were done just between 15 and 30°C. And of course in really hot wheather situation it will also start better...

I hope it makes things a little bit clearer.
I can post videos or datalogs if needed.

 

Your issue is not engine startup. 1-2 seconds to start is good. Should temperature drop and starting becomes a problem, increase the values in the table you posted in Post #1. This WILL NOT affect OL AFR!

Why idle hunts for a a few seconds after startup, I do not know. Maybe someone else here knows. 1100 RPM immediately after start may be normal but depends on what/s in your commanded idle table. 15-16 AFR is not causing lack of responsiveness until it warms up. Something else is causing that.

Please post your BIN and XDF for review.
Also, please describe car, condition, engine age, injector types and flow rate, ignition type, etc.

And, yes, videos and datalogs (exported .csv file) always helpful. More is better.

 

To 84Elky: It seems that all his mods made the engine leaner. Would be interesting to see a data log of his BLM (should be lean). I'd say before he does anything, he should look at his BLM. If they are lean, he needs to tune his MAF table first and see what it will do for OL. If he tunes OL and then he has to increase his MAF values, OL will become rich (chasing his tail!). Make sense? Like you said, need some data. Maybe his BLM are rich and it causes a lean restart with Stay Alive Memory (SAM). Who knows?

"Why idle hunts for a a few seconds after startup, I do not know. Maybe someone else here knows."
Could be being too lean/rich. I had that problem with new 383: hard start-up (up to 6s of cranking), immediately after start-up idle would go up, then down, chasing and stalling. Cranking was too lean and start-up enrichment was too rich. After adjusting both, it starts and runs very smooth. No more chasing idle. Now in his case, could be ok at cranking and leaning out immediately after start-up.

"1100 RPM immediately after start may be normal but depends on what/s in your commanded idle table"
Yep sounds normal.

"15-16 AFR is not causing lack of responsiveness until it warms up. Something else is causing that".
Mine was leaning out while accelerating in OL and it caused lack of responsiveness. It was hitting 16-17 on AFR gauge.

 

sb: Yes, makes sense. Without logs and an understanding of engine age, condition, etc., analysis is impossible.