C5 With LS3 doesn't like to start.

[SydneyACE]

Hey guys!

Car is 2001 C5 Corvette
6-speed
LS3
Medium Cam
Vortech T-Trim
80lb injectors

Having difficulty getting her to start on her own.
It was ok with the factory flash...
I copied and pasted the parameters from a tune that I got from my supercharger supplier (C5 with a supercharger base tune).
The tune he supplied me with is almost spot-on for power enrichment (just a little fat, which is ideal for a new guy like me).
The drive-ability is also pretty decent right out of the gate... so I don't want to completely mess that stuff up if I can help it.

So the starting issue is this... I crank it without any throttle pedal and it fires for a second, then immediately dies.
If I try again right away, it's similar the initial fire is just a little weaker though.
It will start if I give it 30% throttle or more, then rev way up, and proceed to run after a coulpe of heavy surges.

Initially it wouldn't idle without my foot on the gas, and my wideband was pegged lean so I increased "Idle Air Flow" until it would idle.
When driving if I put it in neutral and coasted from a high-ish RPM, it would stall. I got that fixed by increasing "Idle Air Flow" some more. (I think I'm a total of 150% over where I started.)

Not sure if the issue is too lean, too rich, not enough throttle, or timing. It's hard to tell because my wideband takes 20 seconds or so to warm-up and restarts when I go to "crank". The O2s are reading in scanner, but I'm not sure how accurate those are during startup. I might wire the "ignition" wire on my wideband to constant power, so that it doesn't restart when cranking if necessary.

My other primary concern is that I had to lower the "Injector Flow Rates" about 20% to get it to idle better... which doesn't seem quite right because I think that tune is set up for 60lb injectors and mine are 80lbs. I may have inadvertently "scaled" my entire tune to make it run better.

So since I'm trying to learn, which parameters should I be looking at when adjusting start-up specifically?
Try to avoid acronyms if you can guys since I don't know them all yet.

I've attached my current tune as well as a couple logs where I simply cranked a couple times, then cranked with throttle pushed until it started.

Thanks in advance!!

[5FDP]

For sure you can't be touching injector data once it's in there. If you are running 80lb/hr injector at 58psi, the flow rate needs to say that. There is no reason to scale anything when those computers can handle over 200lb/hr injectors.

If the fueling was rich you could remove fuel from the MAF and VE tables. You can also lower the min fuel miligrams in the transient tab to help with idle fueling.

I tend to not do much with idle airflow tables and fueling until the MAF/VE are dialed in pretty close for the rest of the driving. You can be pulling your hair out if the fueling is off down low in both the MAF/VE. Try to setup your scanner with an AFR error against the commanded AFR with long term trims and short term trims disabled. Then pick the VE or MAF to start with first. You'll need a 2 bar MAP sensor to tune boost if you don't have one.

[SydneyACE]

For sure you can't be touching injector data once it's in there. If you are running 80lb/hr injector at 58psi, the flow rate needs to say that. There is no reason to scale anything when those computers can handle over 200lb/hr injectors.

If the fueling was rich you could remove fuel from the MAF and VE tables. You can also lower the min fuel miligrams in the transient tab to help with idle fueling.

I tend to not do much with idle airflow tables and fueling until the MAF/VE are dialed in pretty close for the rest of the driving. You can be pulling your hair out if the fueling is off down low in both the MAF/VE. Try to setup your scanner with an AFR error against the commanded AFR with long term trims and short term trims disabled. Then pick the VE or MAF to start with first. You'll need a 2 bar MAP sensor to tune boost if you don't have one.

I have a 3 bar (LS9) sensor in there now (you helped me with the settings for that in another thread). BTW on the MAP sensor, should that thing coincide with my boost/vac gauge? (IE 12"hg should show about 60kpa, or is that not a big deal?)

Sounds like I need to set the injector flow rates first because everything is based from that? That's kind of what I was afraid of... was hoping to get away with using the tune he supplied me with, then just tweaking the rough spots. Oh well, it will be a good learning experience for me.

I've noticed that injector flow rates seem to be a closely guarded secret around here... any idea what mine should look like with 850cc/[email protected] with a boost refrence fuel pressure regulator? Is it as simple as scaling 80lb @ 43.5psi up to 58psi?

[5FDP]

If they are name brand injectors they should have come with all the data required.

If they are something like deka's or whatever else, then finding the correct data is harder. I'm sure there are threads out there with helpful info but I'm not sure what you have or where to find those exact threads.

The other part is correct. If say they flowed 80lb/hr at 3 bar, you'd just scale it up to the 4 bar (58psi) setting. Which would be 92.6lb/hr. Depending on what fuel system this has it'll either be a solid number straight across or sloped from left to right.