After taking my '90 'Vette with a newly installed :cheers: ProCharger twin intercooled P600B and 10 psi boost to the Dyno, I found it is running way too lean. :sad: The only mods I have are Flowmaster mufflers and an adjustable fuel pressure regulator.

The Air/Fuel ratio starts at about 13:1 @ 3000RPM and ends up at almost 16:1 at 5500 RPM.
The '90 Vettes use a MAP not a MAF sensor so I am wondering how does the computer know that it needs to get more fuel through? The MAP only measures vacuum to no vacuum, not boost or air flow under boost. I am dealing with ATI but they think you can just ram in more fuel with pressure.:skep:

I upped the adjustable fuel pressure regulator and removed the restrictor in the FMU like the ATI guy said and pressure went from 80 to 90+ but I get injector lockup and absolutely no change in air/fuel ratio.

I think the computer needs to think there is more air coming through. More fuel pressure is going to have a very limited effect on the amount of fuel going throught the injectors. I think I need about 30% more fuel.

I suspect that the ATI guys aren't directly experienced with this application. :banghead: They say I sould be able to make it work without new injectors. Any ideas out there? :confused:


[Modified by gstreak, 4:40 AM 10/14/2003]

 

What size injectors??? If you change to larger inj. then they will flow more....Of course then you need to burn a chip for inj. constant etc to keep your part throttle blms about 128.

 

Depending on the RPMs your going to be running, really dictates the injectors needed.

I just did a tune with a guy this weekend as a matter of fact on a 355 blown vette. We had no problems with Duty Cycle with 50psi on 24# injectors.

The car ran great after I was done with the tune. I suspect Jojo to be posting some reports on the forum about the experience.

But 13.2 AFR is about as lean as I would suggest going. 14-16 is way out there :eek:

Make sure your FMU is working properly, and you have a good solid pump. :cheers:

Most likely a new tune is in order also. :thumbs:

 

The injectors are stock (22#?) and the FMU works more than fine. It goes to 82 psi at 5500 rpm. When I up the adjustable fuel pressure regulator from 42 to 47 psi at idle, the pressure goes to 95 psi at 4700 and the injectors lock up. The air/fuel runs look identical, regardless of presure in that range which tells me we are not going to get any more signifficant fuel flow with more frickin' pressure. :nonod:


[Modified by gstreak, 11:09 AM 10/17/2003]

 

The longer you program the injectors to stay open the higher the duty cycle and the bigger the chance of over heating them, and eventually cause failure.
Fuel failure of any type is extremely dangerous on boosted applications.


Some injectors use a pintle for the spray pattern, others use a disc. The disc type is has a built in feature in that they self clean better, but will lock up under high pressure. You need to study the power your planning on making and then select the proper size injector. My guess is at least 36lbs if your gona be in the 10 psi level with an inter cooler on a 350 ci.

Programming can get expensive, so you want to avoid doing it multiple times. I highly recommend you start off with the right injector size to begin with.

 

There's no necessity to run that high of PSI on 24's to get the fuel delivery you need. In fact, I've been told never to go above 60 psi on pintle style injectors or suffer the consequences of a lean out and ruined injectors.

Now...Please tell me that you're not running a stock fuel pump with the AUX POS inline....If you are, before you do ANYTHING ditch both of the fuel pumps and go with the http://www.racetronix.com kit. It only takes about an hour to install. Start out there, and then play around with your AFPR and FMU.

Get a chip burned too. ski_dwn_it above did my chip and it runs great!

From what you're telling me it sounds like the lock up is what's causing the lean condition considering you have such a high pressure. But I would still ditch those fuel pumps regardless.

 

VVV90-
I agree that I shouldn't need that much fuel pressure. The injector lockup is occuring at about 90 psi. The car has 23K miles on it so the injectors should be in good shape. The lean condition starts at the beginning of the run at about 2300 rpm where it is 13:1.

What I really want to know is how is my car with a MAP sensor is going to know the difference between 4000 rpm and 3/4 throttle and 4000 rpm and WOT? It will need more fuel at WOT but 0 pounds of boost and 6 pounds of boost probably look the same to the MAP! If it is set up at 12:1 for WOT it seems like it would be rich at 3/4 throttle when the intake pressure is close to 0.

Also the in-line POS may be exactly that, but it is not the problem since we agree that I have more than enough pressure at the fuel rail (60-90 psi).

I appreciate this input guys. Keep it comming. :chevy

 

MAP sensors are available with different bar readings.

 

Well this is my 2 pennies and i have a 1991 vette with 11psi and this has been my problem all along...ok i think it is not a Fuel pressure issue... you are getting the fuel you need BUT the weak point is the injectors and the cpu!

Now i have noticed i am running 24# injectors and i when i did my dyno run when he was driving it was around 13.5 a/f driving around the punched it ...dropped to 11.5 till about 4000rpm then it started leaning out really fast
4000rpm 11.8 a/f
4500rpm 13:1 a/f
5000rpm 15:1 a/f
5500rpm 15:1 a/f
5800rpm 14:8 a/f
that was my first run here is the second run
3000rpm 13.0 a/f driving not WOT
3500rpm 11.5 a/f punched AT WOT
4000rpm 11.5 a/f
4500rpm 12:1 a/f
5000rpm 13:1 a/f
5500rpm 14:5 a/f
5800rpm 14:8 a/f


So the only think i can think it is both injectors dont keeping up and cpu tuning and yes speed density really sucks for some reason when tuning under boost?

So get some 42# injectors w/cpu tuning! i would say that would fix your problem?

 

This is because at WOT the computer does not use input from the MAP sensor to adjust fuel trim. The WOT sensor triggers the computer to go into Open Loop mode, which means the CPU then looks at programmed tables to decide how much fuel to run. This is where the FMU comes into play. Essentially it is the device that senses boost, ups the fuel pressure, (I think the ATI one is 4:1 ratio, but since you're at 90PSI :eek: it's probably more like 10:1) This ideally gives you the fuel you need. However, that is not the most efficient way to handle it especially if you're not going to dyno tune with the FMU. The only option you have right now is to have a reputable tuner burn your chip, and do the other mods I suggested (Fuel pump and AFPR) That way you can have your Fuel pressure at a constant, and predicable level and the computer will set the injector pulse to be optimal. You should run a scan program along with your wideband readings so that the tuner will be able to see how much fuel to add at whatever cell or RPM.

Exactly, but I wouldn't trust that setup. If one of those pumps fail you'll have a very serious lean condition with consequences.[/QUOTE]

:cheers:

 

vvv90-

"This is because at WOT the computer does not use input from the MAP sensor to adjust fuel trim."

This is the information that I was looking for. This tells me that under normal driving conditions, the CPU can run "standard" settings. The CPU can be reprogrammed for the deficiency in WOT condition and the inability of the MAP to measure boost doesn't matter. This also tells me that I don't need a 2 bar MAP, just a reprogram of the chip. :yesnod:

If I get 36 or 42# injectors and a new chip now, will a new fuel pump later cause a problem with the new program? Is the fuel pump that you recommended quieter than the in-line POS? :confused:

 

Depending on the injectors you go with. I have SVO 30# injectors which are equal to Chevy (Lucas I think) injectors rated at 33#. 30# injectors can support 500HP so I think they should be enough for you. You don't want to overcompensate, then you'll be running really rich at part throttle which will rob HP in the lower RPM's. Besides, I don't think the computer can adjust for Stoichiomatic 14.7:1 at idle and cruise either with those bigger injectors, but I could be wrong.

The Walbro pump from http://www.racetronix.com is what most of us are running. It's a completely stock, in-tank replacement that is just as quiet as the stock one. The new fuel pump will IMMEDIATELY up your fuel pressure to like 80 at idle. That's why you'll need an AFPR.

If you want to just run the dual pumps that you have now, at least run the AFPR and tune appropriately. That way you can set your fuel pressure the same when you swap the pumps.

Also, a 2-3-4 bar MAP will never work with our stock computers. It doesn't have a provision to adjust fuel based on the voltage from the sensor. Only aftermarket DFI, FAST, or CPU conversions like the sy-ty chips can do this. However, if you get your car properly dyno tuned you can program the computer for the correct BLM's or AF ratios. (Still a good idea to have an EGT and Wideband O2 sensor just to keep a watchful eye over everything)

 

so vvv90 you are saying...
when you get a chance if wanted dump the stock fuel pump and aux pump (in time)
then get 36# injectors (pintel or disc)
then get cpu tuned...
if you still have problems???? then who knows! :(

 

The tune will be affected by the injectors more than anything. If you plan on changing those, do those first, then get a burn. Once you have the new FP and AFPR that can be adjusted accordingly. Basically, your tuner should know what your Fuel pressure should be set at for the program.

 

mmmm makes sense! yeah i need to have ski_down do my chip i wonder if he has a payment plan! :lol: god i am broke!

still need injectors....
still need DFI
still need Intercooler!
still need 502 BB
gosh i think a second job is looking bright here in my future!

 

You could....ah....sell the WS6 :thumbs: :lolg:

 

OUCH!!!! yeah the ws6 is the back up car incase the vette breaks down and if the ws6 breaks down i have the Toyota Celica :leaving:

 

Does anybody else have air/fuel dyno results for a '90 or '91 with a Procharger.

 

I am home from the hospital now. I have a broken pelvis and lower spine. The CHP is still investigating but I think I was run off the road. I have no memory of it. I totalled the 'Vette. I thought I would close out this thread.

I got a chip burned by ski_dwn_it that solved the problem. At WOT it was a constant about 13:1. 347rwhp and 407rwft-lb. I also made a tensioner assist spring that took care of belt slip.

I will be parting out the car, since I don't have collision insurance. I am not sure what I will be getting next but I think a newer vette, naturally aspirated, with a little more power will do it. Please email me your suggestions.

 

:eek: :eek: :eek: :eek:

Holy Schnikies! Glad to hear you're alright. Hope you get another vette :thumbs: