Just need ideas kicked around - tuning problem?
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From: Ashland, KY
Just need ideas kicked around - tuning problem? I'm not comfortable with my car and neither is my tuner. Let me say now it's not making a lot of power, but that's an issue of heads and cam, and I am making what I expected to since it's still my stock cubed top end. So let's not even worry about addressing the power issue. That's a separate issue and it's not what I am trying to address. If I can't get my problem fixed first, I certainly won't be putting better parts on it, of course!
That being said, here's my problem:
My car wants no fuel!
What I mean is we tune it and somehow, even at 12.8:1 air:fuel ratio, it is only using approximately 22lbs of injector to make 425rwhp and 400ft-lbs. At least, that's what the tune equals out to. Which is so ridiculously efficient that we just can't believe it's possible. But the car reads as having a safe AFR on 2 correlating widebands at the same time (probe in cutout + O2 bung wideband), and at WOT on the street it blows an appropriate amount of fuel smoke. So even my tuner - one of the most knowledgable tuners you'll EVER meet - has no idea what we have going on.
Anybody have any ideas?
That being said, here's my problem:
My car wants no fuel!
What I mean is we tune it and somehow, even at 12.8:1 air:fuel ratio, it is only using approximately 22lbs of injector to make 425rwhp and 400ft-lbs. At least, that's what the tune equals out to. Which is so ridiculously efficient that we just can't believe it's possible. But the car reads as having a safe AFR on 2 correlating widebands at the same time (probe in cutout + O2 bung wideband), and at WOT on the street it blows an appropriate amount of fuel smoke. So even my tuner - one of the most knowledgable tuners you'll EVER meet - has no idea what we have going on.
Anybody have any ideas?
I'd look first at the thing you're fixating on, the injector
"pounds". Like whether you're considering the mfr's or the
"effective" delivery rating, at LS1 rail pressures and so
on. And do you know the rail pressure to any accuracy?
You might want to look at the injector duty cycle rather
than pounds/hr or whatever. That you look at it this way,
makes me think the tuner is messing the IFR table around
to get fueling right, rather than looking to airflow errors.
Injector delivery is one of the few things you can get
fairly right, just by measurement (rail pressure), ratings
(mfr mass delivery @ rating pressure) and arithmetic.
So it's not a good thing to use for faking-in AFR instead.
If you fake the fuel side then the air side is guaranteed
to be at least as bogus, if not more.
"pounds". Like whether you're considering the mfr's or the
"effective" delivery rating, at LS1 rail pressures and so
on. And do you know the rail pressure to any accuracy?
You might want to look at the injector duty cycle rather
than pounds/hr or whatever. That you look at it this way,
makes me think the tuner is messing the IFR table around
to get fueling right, rather than looking to airflow errors.
Injector delivery is one of the few things you can get
fairly right, just by measurement (rail pressure), ratings
(mfr mass delivery @ rating pressure) and arithmetic.
So it's not a good thing to use for faking-in AFR instead.
If you fake the fuel side then the air side is guaranteed
to be at least as bogus, if not more.
How high are you revving it? You need much larger injectors if you want to rev the crap out of it ( assumption based on numbers, I'm guessing 6000-6500 max?) since you have a shorter time to inject the fuel.
What is the actual problem your having?
What is your fuel rail pressure? and do you have it vac referenced?
Ryan
What is the actual problem your having?
What is your fuel rail pressure? and do you have it vac referenced?
Ryan
Thread Starter
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From: Ashland, KY
I'll give my tuner - Bluecat - this link to see if he can answer any of the questions. I don't believe we've checked the fuel pressure as best I can remember. You think maybe my pressure is sky high from my little Walbro 255, causing it to actually squirt more fuel per pulse than intended?
Thread Starter
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Joined: Apr 2006
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From: Ashland, KY
Nevermind. Ended up that my nitrous arming switch was fried. I had no bottle in the car, so when I went WOT, I was spraying fuel so rich that it was pegging the wideband rich.
