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post #1 of Old 07-16-2019, 11:36 PM Thread Starter
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NGM reflash issue, suggestions needed. Long.

It's been awhile, but I dusted off the ole Tib and looking to do a little track time this summer. I've had a persistent tuning issue with my current setup and figured it couldn't hurt to ask for suggestions. This will be long.

Relevant mods are: fully built 8.8 lower end, NGM Assassin, 460cc injectors, AEM alcohol injection, AEM wideband, Walbro 255 lph pump, and that intake set NGM sold that included a 90mm TB, 4 inch fenderwell intake and MAF, and matched ECU reflash. The car has an AFC Neo and J&S Safeguard Vampire. I have the same mods and the same blower speed as the test car (3.2 upper and stock lower). The test car made 340 whp, and mine feels pretty close to that. I'm making about 17 psi at 7,000 rpm.

The issue I'm having is an unstable fuel curve. It dumps fuel around 2,000 rpm as soon as I tip into it between about 20 to 60%, to the point where it bucks and pegs my wideband rich. It straightens out at higher throttle positions and higher rpm. But past around 5800, it leans out, ending up at low 13s at redline. I'm spraying a lot of alcohol, so there's no detonation, but I don't want to run it that way for long. I did mod the fuel sender and install 3/8 fuel line all the way to the fuel rail, thinking it could be a fuel starvation issue, but there was no change.

I have messed around with the tune a little. I was able to kind of get the AFR toward where I wanted it by cranking up the FP, but then I was cutting a ton of part throttle fuel with the AFC which I didn't like. Adding fuel up top with the AFC doesn't change much, but it does push MAF voltage out of range. I know the reflashes (and the GK ECUs themselves) are very quirky, and tuning them can make them unpredictable.

My first thought was to try to get my tune fixed, but I'm not sure that's cost effective. I'm near Minneapolis, and I think I'd have to get the car to the east coast for tuning. Also, I'd like to be able to make changes when I want to.

I have also thought about going to a local tuner, and having them attempt to dial it in with fuel pressure and the AFC that's on the car. I am concerned that I'd just end up blowing a bunch of money on dyno time, and still not get where I want to be.

Ideally, the car should have a full standalone, but that's going to set me back another 2k easily, and the car will be mothballed yet another year while I save up for one and sort it out. I was really hoping to get out to play this year yet.

I see the F/IC is now working on the V6 cars (this wasn't the case when I last tried one), and I wonder if that wouldn't be an option for my setup?

Anyway, just wondering if any of you had any ideas on this? Thanks in advance.
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