First start up, New build 355

[steveo]

??? Are you saying that my throttle plates should not be completely closed?? (risk of sticking??)

i think i said that before.. just closed enough where they dont stick in the bores.

if you were playing with the throttle screw with it running, that explains it, but makes the log a bit invalid.

fyi you never use that screw to set idle speed on a fuel injected car. it is computer controlled with the iac. set it and leave it, and tune idle in your bin. spcifically on an lt1, you set it nice and low to achieve a healthy range of iac operation and get as much air through the iac as possible (and not past the throttle plates)

you need to at least turn the key off and on again after playing with that screw (i actually reset the ecm at this point), so it can re-learn what 0% tps is; it remembers the lowest value it's ever seen as '0%=closed', and you changed that mid-log, so the ecm just assumed you were holding the pedal down a bit, and stopped trying to achieve the idle target.

[terpngator]

i think i said that before.. just closed enough where they dont stick in the bores.

if you were playing with the throttle screw with it running, that explains it, but makes the log a bit invalid.

fyi you never use that screw to set idle speed on a fuel injected car. it is computer controlled with the iac. set it and leave it, and tune idle in your bin. spcifically on an lt1, you set it nice and low to achieve a healthy range of iac operation and get as much air through the iac as possible (and not past the throttle plates)

you need to at least turn the key off and on again after playing with that screw (i actually reset the ecm at this point), so it can re-learn what 0% tps is; it remembers the lowest value it's ever seen as '0%=closed', and you changed that mid-log, so the ecm just assumed you were holding the pedal down a bit, and stopped trying to achieve the idle target.

AHHHH- That makes sense. I set the throttle screw so the plates are just barely off their seat and left it there.

So--I thought I had an exhaust leak on the right, though I couldn't see where it was, I could hear it. I pulled the header off (brand new) and the center tube was split where all 4 tubes come together, just before it goes into the collector. Pulled the tubes apart and welded it up. Put everything back together, made the changes you suggested and pulled another log. I forgot to re-connect the right 02 until late in the log, but when I did, the BLM split came very close. I'll pull a better one tomorrow. Here is the log and the new bin. Please make sure that I made the changes you suggested correctly. Thanks so much Steve.

[steveo]

im glad you found it. it's looking much better. now you can tune it properly, and it should stop dumping crazy amounts of fuel.

those changes were just a shot-in-the-dark attempt, and since it was a mechanical problem not a tune problem...i'd reccommend changing the integrator delay and corrcl to back how they were before; and work from there.

right now closed loop looks 'lazy', it could be finding its trims much faster with the delay set lower.

[Fast355]

i think i said that before.. just closed enough where they dont stick in the bores.

if you were playing with the throttle screw with it running, that explains it, but makes the log a bit invalid.

fyi you never use that screw to set idle speed on a fuel injected car. it is computer controlled with the iac. set it and leave it, and tune idle in your bin. spcifically on an lt1, you set it nice and low to achieve a healthy range of iac operation and get as much air through the iac as possible (and not past the throttle plates)

you need to at least turn the key off and on again after playing with that screw (i actually reset the ecm at this point), so it can re-learn what 0% tps is; it remembers the lowest value it's ever seen as '0%=closed', and you changed that mid-log, so the ecm just assumed you were holding the pedal down a bit, and stopped trying to achieve the idle target.

The LT1 engine is the ONLY GM engine I have messed with that I like the IAC actually having a decent number of counts. The TBI, TPI, and Vortec engines run best with the least number of IAC counts possible (most of the air through the throttle plate(s), is desireable.)

[terpngator]

im glad you found it. it's looking much better. now you can tune it properly, and it should stop dumping crazy amounts of fuel.

those changes were just a shot-in-the-dark attempt, and since it was a mechanical problem not a tune problem...i'd reccommend changing the integrator delay and corrcl to back how they were before; and work from there.

right now closed loop looks 'lazy', it could be finding its trims much faster with the delay set lower.

Great, I'll reload the old tune and pull another log tomorrow.

The LT1 engine is the ONLY GM engine I have messed with that I like the IAC actually having a decent number of counts. The TBI, TPI, and Vortec engines run best with the least number of IAC counts possible (most of the air through the throttle plate(s), is desireable.)

Reminds me of a question that I had. I've seen the term "counts" used for several settings in the tune. Can you explain what is meant by "counts"? Is that a measurements of time or what?

[Fast355]

Great, I'll reload the old tune and pull another log tomorrow.



Reminds me of a question that I had. I've seen the term "counts" used for several settings in the tune. Can you explain what is meant by "counts"? Is that a measurements of time or what?

The IAC valve is controlled by a stepper motor that is moved in or out by pulses of electricity. The ECM or PCM depending on the year operates the IAC on a scale from 0-255 or 0-310 steps or counts. It will increase counts to increase the valve opening and increase engine speed and vice versa.

[terpngator]

Very clear now. Thanks

[terpngator]

OK, loaded the original bin file with the exception that I changed Target Idle Speed to 900 rpm. After starting I reved the engine a bit because, even set at 900 rpm, it was still stumbling. Could be I need to replace the plugs again. The rest of the log, the engine was idling and stumbling pretty bad. I've run larger cams than this one without this much stumble. Course, that was with carburetion, not FI.

[steveo]

i'd be tempted to pull the plugs i guess, you did beat that thing up pretty good with that leaky header!

i'll look at your log in a bit

[terpngator]

i'd be tempted to pull the plugs i guess, you did beat that thing up pretty good with that leaky header!

i'll look at your log in a bit

Thanks Steve. Yeah, I picked up a new set of plugs last evening. I also pulled my 02s out last night an left them to soak in TECHRON. What would be considered a "normal" count for the IAC during, both, open and closed loop?

[ony]

does your file have a stall saver inable,disable rpm like 7747's have?

[terpngator]

Sorry, unless your talking about DFCO, not sure what that is. I'm sure Steve can explain.

[steveo]

the lt1 doesnt seem to have stall saver code.

cold idle the iac should be over 60.

hot idle open or closed loop I'd like to see over 40

when driving, iac steps depend mostly on vehicle speed

[terpngator]

i'd be tempted to pull the plugs i guess, you did beat that thing up pretty good with that leaky header!

i'll look at your log in a bit

OK, I replaced the plugs and also put a knock sensor for a 95 PCM on it. Here is the log. After running the log, I pulled the plugs and they look really good. Whatcha think?? Why does it take so long to get into CLOSED loop? What conditions have to be met, in the tune, before it gets to closed loop? Also, how can I tell if the PCM performed a knock limit test, or whatever it's called when the PCM advances the timing till it gets a knock? OR do we have that turned off right now?

[steveo]

coolant temperature (also influenced by intake temperature), time, and o2 preparedness (via voltage) thresholds all have to be met. since you're running this thing idling, warmup takes a long time.

the knock test should be turned on. im not sure what the thresholds for it are, and i've never had a car fail it...

but screw that, just test the knock sensor with a hammer, whack your motor with the logger running and see if it registers knock counts.

the knock sensor wont actually retard timing under certain MAP values, or under a certain coolant temperature value, but the counts will still increase. those tables are fairly clear in the xdf, im sure you can figure 'em out.

will look at the log when i get home, glad it's going better for you