2003 Corvette, 408, Centri, E85

[JamesTheriot]

Small backstory car has been running great before my recent adventures.

Engine is a 408, PRC heads, ~11.25:1 compression, high ram intake, NW 103 throttle body and ran well before on 93 octane

2 months ago I broke the differential at the track. Swapped in a C6Z drivetrain with 4.10 gears, while building the diff I found a deal on an A&A Centri kit.

since then added a secondary fuel system, return style, and 1500cc injectors and the car will be solely on E85

I have it running now but I have to throttle it a little to get it to start and once its idling the pedal response is almost not there. The throttle opens, vacuum drops, KR goes up sometimes and if the engine revs at all its way too late.

I figure I must have missed for Fudged something when I scaled the tune.

This is my first time scaling a Gen3 ECU for boost, and my first time with E85 on a Gen 3.

I have a wideband but its hit and miss when it will report to the scanner.


Current tune and Log
JAMES C5 V057 STARTUP AIRFLOW.hpt
E85 Idle log, no throttle response.hpl

Previous tune before blower and E85
JAMES C5 V0051 32 deg.hpt

[blindsquirrel]

You cannot have the MAF codes set to No Error with the MAF failed. For speed density to work it has to set a P0102/P0103.

[gtstorey]

Injector data? You need real good injector data when going that big on injectors.

[blindsquirrel]

Your injector data is also wrong, Offset table is set up as if it's returnless.

Why did it need to be airflow-scaled? Which imaginary problem are you hoping to avoid, hitting the airflow limit or the spark table limit?

[JamesTheriot]

I've been told that you have to scale it because the spark table stops at 1.20 cylinder air mass.

I was very tempted to just put in my injector data and run it but I was told it wouldn't work.

[blindsquirrel]

It will work just fine. Spark doesn't stop past 1.20, it just continues with whatever's in the last row. Are you expecting to be at part throttle and above 1.20g/s? Because that is the only situation where you would need fine control of spark timing, for WOT you can give it one single number for the entire table and it will rip just fine. (look up 'locked-out distributor', a thing from Ye Olden Days)

[JamesTheriot]

Thats how I thought it would work too. Thanks. Ill check back.

[JamesTheriot]

1000X better!!

Back to fine tuning. Thanks.

[blindsquirrel]

The other thing about airflow scaling is, you trade away resolution where it's actually needed (down low, part throttle cruise and stuff) in exchange for the top end stuff, where it isn't needed and will mostly end up with close to the same numbers in all the cells anyhow. It's a bad deal and should be the last resort when there's no other options to solve a very specific issue, it should never be done 'just in case'. It's also annoying AF to deal with.

[edcmat-l1]

^^^ Yes to all that. There's no need to scale it if it doesn't go into REP. You can typically make 8-10 psi of boost in a C5 without having to scale it.

[abc]

I have two C5's under my command. One is at 14psi of boost and the other at 16psi. Both are on 2 bar OS and neither one has found a limit that I know of. Both shift near 6500 rpm. One of them does intermittently suffer from the REP issue but it happens just as the engine is started and has never happened at WOT.

[gametech]

I have two C5's under my command. One is at 14psi of boost and the other at 16psi. Both are on 2 bar OS and neither one has found a limit that I know of. Both shift near 6500 rpm. One of them does intermittently suffer from the REP issue but it happens just as the engine is started and has never happened at WOT.

You would have to be hitting the spark table limit on both of those, but on blower cars it really should not matter since you are not changing max boost levels. Scaling for the spark limit is pretty much a turbo thing, since you can run vastly different max boost levels at the flip of a switch. Nobody wants a 5psi setting to have the reduced spark of a 15psi setting, or turn up the boost on the higher spark of a lower boost setting.

[Alvin]

You would have to be hitting the spark table limit on both of those, but on blower cars it really should not matter since you are not changing max boost levels. Scaling for the spark limit is pretty much a turbo thing, since you can run vastly different max boost levels at the flip of a switch. Nobody wants a 5psi setting to have the reduced spark of a 15psi setting, or turn up the boost on the higher spark of a lower boost setting.

kind of a old trick but you can set PE richer in that 15 psi setting with a corresponding negative number in the PE spark adder table.

This only works with 2-3 bar OS's.

[gametech]

kind of a old trick but you can set PE richer in that 15 psi setting with a corresponding negative number in the PE spark adder table.

This only works with 2-3 bar OS's.

I have seen reports of the boost enrich table not immediately re-engaging after pedaling the car, as if it is not referenced at the same speed as the regular PE table. This would not be a big issue for fueling, but could be a big issue if used for spark control. Rather than running a series of tests to see if this is the case on my computer I decided not to risk going that route, and just scaled my tune 75%. I still max out the spark table, but only in high boost, and by only scaling 75% I have not needlessly lost too much resolution.

[Alvin]

I've never heard of such of thing happening.

Very very early.. talking like 15 years ago they had a issue with some of the COS not using BE at all. But that has been fixed.

[abc]

Well... I did it now, had to open my big mouth. Mine went into REP at WOT this morning. I was not logging and I think this is not a HPT or tuning issue unless you guys can school me on it and if you think I should open a new thread just say so.
Scenario, traction control on, rapidly increase throttle angle to 100%, wheel speed rapidly increases and blows through the traction control, REP shuts the power down to basically an idle. It does present C5 vette code P01515.
My question is: (because I know very little about scaling) Do I assume I attack the diagnostic for the 1515 code first or is this a air mass scaling issue?
Is it possible the air mass was significantly higher than a WOT pull that takes more time to develop RPM unlike a rapid RPM increase as when you loose all traction? (the road is very cold right now)

Here is a version of the .HPT that is close enough to view the basics.

mischief 146 TCC change o2 timing change .hpt

[edcmat-l1]

If your P1514 tables are maxed at 4.1 you'll have to scale it.

[Alvin]

Well... I did it now, had to open my big mouth. Mine went into REP at WOT this morning. I was not logging and I think this is not a HPT or tuning issue unless you guys can school me on it and if you think I should open a new thread just say so.
Scenario, traction control on, rapidly increase throttle angle to 100%, wheel speed rapidly increases and blows through the traction control, REP shuts the power down to basically an idle. It does present C5 vette code P01515.
My question is: (because I know very little about scaling) Do I assume I attack the diagnostic for the 1515 code first or is this a air mass scaling issue?
Is it possible the air mass was significantly higher than a WOT pull that takes more time to develop RPM unlike a rapid RPM increase as when you loose all traction? (the road is very cold right now)

Here is a version of the .HPT that is close enough to view the basics.

mischief 146 TCC change o2 timing change .hpt

What throttle body is on this? This isn't a tune issue.

That 1514 table shouldn't be maxed out.. It can cause some to go into REP right away. 3 g/cyc is plenty high enough.

[edcmat-l1]

What throttle body is on this? This isn't a tune issue.

That 1514 table shouldn't be maxed out.. It can cause some to go into REP right away. 3 g/cyc is plenty high enough.

That's interesting. I've never seen one do that. I max them on all FI applications I do.

[Alvin]

Yeah, I had to drive 30 min to a customer to fix a start up tune I did for them. It would go into REP right away.

EFiL makes a big deal about not maxing out stuff. This is one of the few times I've seen something go wrong.. Same thing if you max the speed limitor on a manual chevy SS