Need help with fuel tuning with a turbo...

[Rick M.]

We are putting a turbo on a 2000 3.8 Camaro. we haven't got her finished yet...but we are wanting to go ahead and have everything ready to go when it is ready.

We got a 255lph Walbro fuel pump and we went ahead and got some 42lb. injectors because she will be getting a lot of work done in the future so she's going ahead and getting them (heads/cam/forged rods & pistons etc.). My question is how would I go about tuning with the maft+ and autotap? I guess I should be looking at what the O2's read and what the A/F ratio is? what would be the optimal O2 reading and A/F ratio for this setup? we plan on running about 10psi...maybe 14psi when we're at the track. Thanks.

[Tiago]

I don't think it will idle with 42 lb injectors unless you got a FAST DFI system to custom tune the fuel curve.

[fred slawson]

What about 29lb injectors Tiago?

[Rick M.]

whats the biggest injector we should go with Tiago? we trying to plan ahead because we'll probably be doing internals late this year/early next year so we want enough injector to possibly run 15-20psi...we will also be lowering compression...

[Tiago]

I have enough trouble with 24s on mine, I don't think going over a 30 would work on stock tune.

[slacker69]

You will be fine upto 50lbs injectors if you get your pcm custom programed the fuel curves www.intense-racing.com uses them and stock gtps come with 36lbs injectors so as long as you get your pcm done you will be fine.

[John_D.]

<blockquote>quote:</font><hr>Originally posted by Rick M.:
whats the biggest injector we should go with...<hr></blockquote>

Is that on a stock computer, or aftermarket system?

If you're looking at using the stock computer and a maft, then the range of adjustment on the maft is up to 35% lean. So theoretically you could run 32-33 lb injectors, setting the maft to max lean. (since taking 35% off 33lbs brings the rating back to about stock)

Not too sure how accurate the maf curve will be at that level though. I've run mine up to 20% lean before. Some people say adjusting the base setting on the maft throws the curve off. My experience has been that you have to let the pcm learn the new setting, takes about 30 miles of driving.

Running a V8 maf sensor will lean you out some too. In order of least to most lean: LT1 Impala, LT1 f-body, LS1 f-body. An LT1 Impala sensor on my car leans it out about 10%.

The pcm can also compensate, to a point. Somewhere around 10% or so.

Lets say you ran the max setting (35%), and an LT1 sensor (another 10%), and the pcm compensates 10%. "IF" all that worked together, you could almost run 40lb injectors...

Here's another thought for you. I went with 24lb injectors, and they supported up to about another 140hp over stock, with higher fuel pressure. (this was with nitrous, not a turbo, but fuel needs are very similar for a given hp output)

How much additional hp are you looking at? How high will you bump the fuel pressure?

[Rick M.]

so for injectors that big we're gonna have to do a pcm reprogram? we can't just use the Mini-AFC or anything like that?

[Arctc Wolf]

the car can re-learn to any injectors, it just needs time and it has to be done in steps. drive w/ injectors 2 lbs. bigger for about 200 miles, then go up another 2, and another 2 every 200 miles, and the computer will learn on it's own till u get to the injectors u wanna use. this will eat up ur pocketbook tho. if ur just looking for a little extra fuel that the car can handle at idle, then 2-3 lbs. bigger will be fine, but if u wanna go 42.5's or 50's, then a custom pcm should be used.

[nocutt]

Sorry guys the largest you can go is 29-33lb injectors...I used Grand national injectors 28.5 lb and used a MAF recalibrator...I was not impressed due to environmental changes...I would also get MAF (pukes) once in a while...IMHO I agree with a Custom PCM (aftermarket/ reprogrammed)that way you aren't skewing the MAF curve indirectly...

[ August 10, 2003: Message edited by: nocutt ]</p>

[Rick M.]

<blockquote>quote:</font><hr>Originally posted by John_D.:

How much additional hp are you looking at? How high will you bump the fuel pressure?<hr></blockquote>

based on what tiago and them have done with a 3.8 kit I'm thinking we'll be putting out about the same amount that they have, maybe a little more, because we'll be running the same turbo and about 10psi but have custom turbo headers. in the future she wants to rebuild with forged internals, lower the compression, and get the SSPP. Before that she'll probably get a moser 12 bolt with 4.10s (she already has 4.10s), suspension, and a stall though. It'll probably only be running about 10psi for quite some time. I was thinking maybe using some LS1 or SVO injectors? I'm kinda gettin' a crash course in this fuel tuning stuff from you guys...thanks for the help.

[Rick M.]

well I just got an email back from intense racing and told him my about my setup and they said they could change the fuel maps and everything to use the 42lb injectors, so now I get to talk to Sara and see if that's what she wants to do lol

they said it'd cost 400 bucks plus core charge...which I don't guess is too bad.

[Rick M.]

just another quick question...how much boost can we run safely on stock injectors/fuel pump? we're tryin' to get this thing ready by a local track day but we don't have enough to swing for pump, injectors, and a pcm reprogram...thanks guys.

[John_D.]

Fuel pump hit the limit at 120 additional hp for me. Beyond that, and it couldn't keep up with the demand at the top of each gear.

I had already upgraded fuel injectors before I got there, so I don't know exactly where they would have hit the limit. I would estimate somewhere in the 100-130 additional hp range. That was with the fuel pressure bumped to 65psi while spraying...