9.7:1 Ls7 supercharged startup airflow, timing and hot start issues

[Pierrel]

Hi Guys,

Been asked by a friend to get his car running after modifications to seat the new piston rings and cam etc.
Just want to verify a few things, and hopefully help out my issues.

Ls7, 427 cu with 9.7:1 CR
221/243 116 LSA 0 overlap Camshaft
A&A supercharger
ID1050x injectors
Fast 102 intake and stock 92mm TB
Centerforce clutch with slightly lightened flywheel i think

Set it up to run pure MAF as a starting point.

Set idle timing at 17 degrees and had to raise Min airflow to 16.7 at idle 900 rpm to get it to run. Been out doing MAF Cal using Cringers new tool, what i great thing!

Idles alright i think and returns to idle without over/undershooting. Clutch in during coasting will bring RPMs upp a bit. But numbers seem high, according to most of the guides out there i should only have needed to add about 3-4 g/s to the stock tables?

But hot starts are absolutely horrendous. Car will not fire up first try, but take 3-4 tries after having my friend pedal the throttle.
Ive increased the idle startup airflow by a lot at higher operating temperatures but havent really helped much.
What am i missing out on?

Attached is the final tune made yesterday, a driving log with idle in the beginning, and a short no start log.
Appreciate any input or guidance, thanks!

[edcmat-l1]

Few things here.

1, You need to get the MAF dialed in better. Turn off the long terms and rough it in using the short terms.
2, You have way too much startup airflow in it. If you get too far out of its normal range it'll actually close the throttle blade. That's probably what it's doing now. As you're adjusting and trying to dial in the startup, you need to pay attention to the throttle blade %. Once you get to a certain point it just won't open any more and it'll actually go back the other way. You shouldn't need any more than about 50% increase in startup airflow. Definitely don't need 6x the amount.
3, If you need to crack the throttle for it to start, there's too much fuel. Take out some cranking fuel.
4, Put a 2 bar MAP in it so you know how much boost it's making.
5, Straighten out the timing tables. They shouldn't look like rolling hills. And if it's a stock piston LS7 you'll want to start out with much lower WOT timing. Need to understand where you're operating in the timing table at WOT.

[Pierrel]

Few things here.

1, You need to get the MAF dialed in better. Turn off the long terms and rough it in using the short terms.
2, You have way too much startup airflow in it. If you get too far out of its normal range it'll actually close the throttle blade. That's probably what it's doing now. As you're adjusting and trying to dial in the startup, you need to pay attention to the throttle blade %. Once you get to a certain point it just won't open any more and it'll actually go back the other way. You shouldn't need any more than about 50% increase in startup airflow. Definitely don't need 6x the amount.
3, If you need to crack the throttle for it to start, there's too much fuel. Take out some cranking fuel.
4, Put a 2 bar MAP in it so you know how much boost it's making.
5, Straighten out the timing tables. They shouldn't look like rolling hills. And if it's a stock piston LS7 you'll want to start out with much lower WOT timing. Need to understand where you're operating in the timing table at WOT.

Thank you for taking the time and effort into helping out!
I will follow your guidance and will have a go at this in a few days. I will check out the MAF adjustments and try to get them much closer to 0% error, at idle and above.

Also , a 3 bar map from a ZR1 is going to be installed, thanks!
Pistons has been changed to forged, but I agree to stay cautious .

[Alvin]

Heads up.

In the injector section there is a table for Offset vs Injector TIP temperature.

The ECM calculates the tip temperature via math models. This model gets messed up for 15 minutes after a reflash. During that time the car will run much richer especially at lower loads/throttle. This is especially bad with larger injectors like you have. I'd suggest zeroing it out.

Also for your idle issues. There are idle speed start up tables that still have the stock idle RPM. They are right underneath the Base idle RPM table that you've already modified.

There are some other things but this should help get you going in the right direction. Getting it done right in speed density is going to make a big difference in driveablity.

[Pierrel]

Heads up.

In the injector section there is a table for Offset vs Injector TIP temperature.

The ECM calculates the tip temperature via math models. This model gets messed up for 15 minutes after a reflash. During that time the car will run much richer especially at lower loads/throttle. This is especially bad with larger injectors like you have. I'd suggest zeroing it out.

Also for your idle issues. There are idle speed start up tables that still have the stock idle RPM. They are right underneath the Base idle RPM table that you've already modified.

There are some other things but this should help get you going in the right direction. Getting it done right in speed density is going to make a big difference in driveablity.

Thanks Alvin!
I've read about the rich after reflash, and have been monitoring/filtering out the first part of the runs. Like you say, it takes about 15 min of driving before reaching normal Temps again.
Zeroing this table, will it completely remove the issue, or just lessen it?

Will have a look at those idle speed tables. Bumping them about the same as the idle table?
Driveability on Maf only wasn't that bad to be honest. But who knows, with some time in it we might try a SD tune.

[Alvin]

It will completely go away.. the rich after reflash issue. With large injectors that rich after reflash issue is enough to cause harm IMHO. They will be pig rich at idle and could easily dirty up a plug and foul up the oil.

Yes move all the tables up by the same amount.

[Pierrel]

Alright, so.

Ive followed the advice given by you guys.
Ended up removing some more fuel from cranking and adding a bit more startup airflow. Now the car starts decent when hot/heat soaked. Does not flare and starts on first try like 95% of the time.

Happy life i thought. Well, this morning he told me that after starting the car cold, and just touching the throttle to take off, the throttle hangs at around 2000 rpms until the engine reaches higher temperatures. It hangs as soon as he touches the throttle pedal even standning still.

Must be too high base running airflow when cold? Or some fueling issue with Open loop fueling until reaching higher temps? Or is it my MAF /VE table thats incorrect and causing this situation when cold? Noticed my MAF frequency from 1000 - 2350 hz is way lower than a stock file.

Sorry, dont have a log since he was alone in the car. Ill attach the tune thats in the car at the moment, and a short drive log prior to finding this issue.

Thanks!