Transient Fueling Tune issues

[DRTWRK]

I have been experimenting with Transient Fueling for some time now and found varying and inconsistent results. I can alter either or both Evaporation Factor and Transient Fuel Mass Gain/Impact Factor and initially find expected results and can verify by logging IDC and obtain satisfactory fueling on immediate throttle transition into boost. What I can not understand is why the expected results will only work through 1 or 2 key/start cycles. For whatever reason the IDC reverts back to percentage of change comparable to stock setting.

Is there some kind of adaptive or learning feature in the computer that we don't have access to? The values in the cells reflect just as I input.

I can Log on first start up after changing settings and see my IDC increase 10 to 90% or higher depending on what value I input and will repeat those values every time I hit the throttle during the first startup cycle. I can hit throttle 10 times and I will see IDC shoot up 10 times and be very consistent.

I then turn ignition off and restart engine. Start scanner and while logging find IDC reverts back to values just like I never made any changes.

Can anyone explain?

[10_SS]

There was another post very similar to this, IdriveAG8 or however you say that complained of it, and did I since I think I was the OP, and I ended up just slowing down the Throttle Opening rate a bit, but to do that you have to take it down to say 5 from 100. to stop all that built up boost from creating a lean condition between shifts.

I believe Chris or Bill wanted data at the time, but it was hard to capture so nothing ever happened with it. If you have definite clear data to prove this, I would ask them for help directly since we got nowhere.

[DRTWRK]

I can probably offer some screen shots or logs showing how the IDC really escalates due to values I input in tables and show the next log after restarting engine.
Its like I never changed anything. I do believe I can eliminate or at the very least minimize my problem area if I could figure out the reason for the inconsistency. I have an A6 so I do not get a lean spot after shifting. It is just immediately (.20 to .40 seconds) following WOT in any gear.
I have worked around the problem somewhat by adjusting my Knock Retard Decay in the problem areas to return timing sooner. But I don't think this is the correct way to do things.

There was another post very similar to this, IdriveAG8 or however you say that complained of it, and did I since I think I was the OP, and I ended up just slowing down the Throttle Opening rate a bit, but to do that you have to take it down to say 5 from 100. to stop all that built up boost from creating a lean condition between shifts.

I believe Chris or Bill wanted data at the time, but it was hard to capture so nothing ever happened with it. If you have definite clear data to prove this, I would ask them for help directly since we got nowhere.

[DRTWRK]

Here is a log after I made some pretty radical changes and the corresponding IDC spikes because of the settings.
Go the frame 9914, 11681,12378 and 14888.
After I turned engine off and restarted and made another log WITHOUT any tune changes the IDC did not spike at all. There was no evidence of transient fueling changes

[mourat]

Transient fueling does make a substantial difference, for me turning it off made the world a much better place

[DRTWRK]

Transient fueling does make a substantial difference, for me turning it off made the world a much better place

From what I have experienced with adjusting Transient fueling I believe it will offer enough of a result that I can live with it. But I can not obtain consistent repeatable readings after a key on/off cycle for whatever reason. By the way, I do have the Custom OS and tuned speed density.

The fuel delivery delay maybe a mechanical issue. I have a LPE duel pump return LESS system now. I have some recommend a return system while others tell me it is the computer not being able to respond quick enough and no real fix. I really do not desire to throw additional money on a new system (possibly a Squash setup) especially if I don't know if will fix the problem.

[10_SS]

I would think the IDC spike difference before and after a key on/off cycle would be all they would really need... you could try to email them or contact Bill and bring this up again, maybe looking at it this way, quick and clean, we may at least get an answer as to why the spike changes over time? I think SD mode never really worked how people remember older ECU's acting though... to some it seems like it's a limp home mode... it seemed that way to me anyway since I get crazy burst knock retard no matter what I did in SD mode... I wonder how this IDC would react with the same test in MAF mode.

[mourat]

I went vacuum / boost referenced FPR and found no need for transient fueling anymore, I run a 3.4 pulley and there is no stumble, car runs cleaner and decels much nicer with it completely off and my LTFT's dead on

[DRTWRK]

I would think the IDC spike difference before and after a key on/off cycle would be all they would really need... you could try to email them or contact Bill and bring this up again, maybe looking at it this way, quick and clean, we may at least get an answer as to why the spike changes over time? I think SD mode never really worked how people remember older ECU's acting though... to some it seems like it's a limp home mode... it seemed that way to me anyway since I get crazy burst knock retard no matter what I did in SD mode... I wonder how this IDC would react with the same test in MAF mode.

I had the same problem with MAF only. One of the reasons that I went with a Custom OS. Custom OS offers traditional VE table that was to help with throttle transitions over that of MAF only. I have fudged on the VE table and created a "bubble" in the effected cell areas where the problem occurs but still no real fix.

[DRTWRK]

Is there any thing in the injector settings that will set a limit or affect Transient fuel tables? It seems like after I flash the new tune (transient settings) and during that initial key cycle everything works as expected. As soon as I turn engine off, (cycle key) and restart there seems to be some kind of "Check" or diagnostic sequence that is canceling out the previous settings that were input in the transient tables prior to the re-start cycle. The values in the transient tables remain as I input but the logs reflect the IDC no longer responds to the values as before the key cycle.

Again this is on a 2011 Camaro with E38 and Custom OS

[mourat]

When you key off and let it sit for a bit, your IAT's will rise, when that happens your fueling changes accordingly, you may need to add fuel as IAT's rise, look at your IAT's before key off (all good) condition and then let it sit for a while and start again and check, I"m thinking thats what the phenomenon is for you.

What are your fuel trims like before and after on the second ignition cycle?

[ttz06vette]

When you key off and let it sit for a bit, your IAT's will rise, when that happens your fueling changes accordingly, you may need to add fuel as IAT's rise, look at your IAT's before key off (all good) condition and then let it sit for a while and start again and check, I"m thinking thats what the phenomenon is for you.

What are your fuel trims like before and after on the second ignition cycle?

Also check once you start driving again and IAT's return to normal see if your transient changes are reflected once again. I also have modified transient impact and fuel wall to eliminate lean spot, but my meth injection allows me to keep any IAT changes from occurring. Only time I see them high are when car is turned off after running awhile and I get heat soak. As soon as I get moving they rerun to normal. You may need to modify your IAT tables.

[DRTWRK]

Also check once you start driving again and IAT's return to normal see if your transient changes are reflected once again. I also have modified transient impact and fuel wall to eliminate lean spot, but my meth injection allows me to keep any IAT changes from occurring. Only time I see them high are when car is turned off after running awhile and I get heat soak. As soon as I get moving they rerun to normal. You may need to modify your IAT tables.

IAT's tables have been modified but I don't think this is the issue. After key cycle IAT's can be the very same or even less and not be within any cells/range affected by values that would pull timing. I log and monitor IAT. MAT and IVT close

[topher455]

Im glad I found this! I have a bolt on G8 that is tuned maf only and I have an off idle sag like you guys are describing and I have modified the impact gas table as well in the lower kpa cells where the stumble occurs. It did the same thing. Seemed to work for a few days maybe less but then seemed to revert back. It is very odd..

[Maxwell Power]

have you logged timing during your tip in stumbles? I've found that in cars with the worst stumbles, the timing dips to less than 5 degrees.

[DRTWRK]

Im glad I found this! I have a bolt on G8 that is tuned maf only and I have an off idle sag like you guys are describing and I have modified the impact gas table as well in the lower kpa cells where the stumble occurs. It did the same thing. Seemed to work for a few days maybe less but then seemed to revert back. It is very odd..

I found you need to play close attention the IVT's when modifying the tables. Too much increase at lower IVT temps and you will definitely get a "stumble" sensation. Log IDC and you could see 100+ % (static) for a split second causing the "stumble". At least these were some of my findings after much experimentation. I have logged IDC readings that indicated 172%-264% resulting in engine response resembling total shut down. I don't think that is physically possible but that is what scanner readings reflected.
I guess what I am saying is just alter values within your engines normal operating Intake Valve Temperature range. I made very slight adjustments within the table maybe as low as 277* and more aggressive changes at 306*-334*
My problem was not in lower MAP regions but within the first 0.2- 0.4 seconds immediately following WOT

[ttz06vette]

I found you need to play close attention the IVT's when modifying the tables. Too much increase at lower IVT temps and you will definitely get a "stumble" sensation. Log IDC and you could see 100+ % (static) for a split second causing the "stumble". At least these were some of my findings after much experimentation. I have logged IDC readings that indicated 172%-264% resulting in engine response resembling total shut down. I don't think that is physically possible but that is what scanner readings reflected.
I guess what I am saying is just alter values within your engines normal operating Intake Valve Temperature range. I made very slight adjustments within the table maybe as low as 277* and more aggressive changes at 306*-334*
My problem was not in lower MAP regions but within the first 0.2- 0.4 seconds immediately following WOT

Are you seeing IVT ranges that high?

[DRTWRK]

Are you seeing IVT ranges that high?

Motor at normal operating temps, ambient air 90* Cruise approx. 55-70 mph, 5th gear 1500 to 1900 RPM,s = IVT's approx. 303* to 318*
Varies with load, RPM, (How much time you stay in lower gears @ higher RPM,s = higher IVT) Apply throttle for any length, fuel cools valve = lower IVT. Run in low gear at low load high RPM,s = higher IVT

[MikeOD]

I think we're missing access an intake manifold/plenum volume constant that could be cause this for some guys...especially with ported heads, FAST manifolds, or positive displacement blowers. I'm e-mailing support now.

...I think my intake "system" is roughly 35% larger than stock between the throttle plate and intake valves...and if the PCM does math the way I think it needs to during a transient situation, then I think this is a fairly important constant.