I have a 92 RS with stock computer and chip that I had a real basic crate 350 put in 2 months ago to replace my 305. I also still have the stock injectors in my TBI. I had it on the Dyno last weekend and at open throttle it is running 14.6 lean air/fuel. Which I was informed I should be at about 13.0. Also when I start the car you can here about 20 dry spark plug clicks form no fuel in the engine when it is first started. They said when I first start my car it is 18.1 air/fuel for a sec. I also had the flatest HP line anyone had ever seen. It had no arc at all. It ran a solid 150 HP thru the whole test. I have heard I should put a diffrent chip in and someone told me that I should check the fuel pump to see if it is taking a dump. Someone also said to put big block injectors in to get more fuel. I also checked out the Ultimate TBI in Tech info. What sould I do?

Thank you
David

 

Install a new fuel filter if you haven't recently.

Setup a fuel pressure gauge so you can read it as you drive at WOT. If the pressure drops as the RPMs climb, replace the fuel pump with a TPI model.

Get an adjustable FPR or make yours adjustable. Set it at 15psi and make another pass on the dyno. If its still lean, increase the pressure. Make sure that the fuel pressure isn't dropping.


Got a pic of the dyno graph you can post?

 

I've heard some horror stories about dropping larger injectors in an engine that doesnt need them, if you were to go w/ BBC injectors then go the full length and get the 2"bored manifold and TB to fit.

 

If you are running the stock 305 injector that is part of your problem. You need to use injectors for a 350, maybe even those for the Caprice 9C1. Same is true for your ECM - hope you upgraded your chip too.

 

yup. wont run with 305 injectors unless you max the FP or vafpr. and that is a poor way to substitute for tuning with properly sized injectors in place. fuel pump will most likely need an upgrade if stock. not sure what a stock FP for L03 flows? i think any file for a 350 v8 will get your started. looks like another candidate for tuning. start the learning curve..... now !!

 

Max the FP? Baloney. Raising the FP is an acceptable method of increasing fuel delivery. Especially when you only need to increase the pressure a small amount.

GM did just that when they offered the HT502 TBI kit. They took the BBC 17112560 injectors and added the VAFPR so they would have enough fuel for 340hp.

I wouldn't advocate running 35psi on 305 injectors when 350 injectors will work at lower pressures. However, there is no reason to buy 350 injectors if your 305 injectors will fuel your engine at 15-20psi.

 

As Ronny so nicely put it "that is a poor way to substitute for tuning with properly sized injectors in place. " That is not to say that increasing fuel pressure isn't a good method of squeezing a little more out of the engine, but I don't see how dumping 20 psi through a 45lb injector is going to fix your problem. Talk bout running rich at idle!

But hey you do what works for you. I would start with 350 injectors, a 350 chip, 350 knock sensor, and then start with the tuning from there.

Good luck!

 

Thanks for everything. I have my now Fuel Presure and air/fuel gauge comeing now so I have somewhere to start. make sure I am not dropping pressue and then do injectors and chip and knock sensor. Well see if that doesn't get me running better.

 

that vafpr is a marine application. it certainly will add more fuel as a function of map. only issue i see is that it was a marine application. somewhat linear on load engine sees. that works better with a marine engine i would think? only issue i see with vafpr is that often the need for fuel is not linear unless a 0-100 mpr drag or a moderate accelleration to 100mph. issue could be a slalom road racing course with full throttle blast, breaking for turn, back on the throttle again. most marine engine dont run like that. i think the ECU will have a hard time running engine management as the vafpr may not be in synch with ecu. stall? cough? stumble? now the 350 cid needs a certain amount of fuel at 5500 rpms assuming the engine runs max HP there. i think someone here knows of calculation. at 80% duty cycle a 65 lb(2) injector feeds about 210 HP and that is at 4500 rpms if i recall. 100% duty cycle a bit higher of course. i personally blew 2 accumulator gaskets with vafpr(one new). pressure was way too high. i think the stock 305 injectors are not up to the task possibly even with the vafpr..

 

http://www.paceparts.com/product.asp?3=40424

http://www.gmgoodwrench.com/perfpart...f/88890533.pdf

 

does that engine include the vafpr ???

 

I was hoping you would read the documents and discover the answer but...

As I already stated above, the HT502 kit uses the VAFPR #17113186.

Oh, and the HP numbers for the kit have varied from 320-338hp depending on which GM document you look at.

 

you are correct. i see that part # is the reg kit per gmpartsdirect.com. i assume it is the vafpr. that motor i further assume has 90 lb injectors, a mild cam, and spins at 4400 rpms. if we run the math i would expect the 90 lbs also to be underpowered to feed that beast at 4400 rpms or close to being marginal due to CID. I dont question GM engineeers choice to use the VAPPR however i think if a larger injector was available they would have gone that route rather that just up FP at mid/higher map with vafpr. another option would be to develop a 4 pod injector but that too would cost $$$$ to tool that up for limited production. i further note that they utilize a custom chip in that application that may have taken a while to optimize state of tune with the vafpr and remove any negative effects of fuel flow. they have resources we do not. I further assume they may use a second FPR to bleed off excessive FP if the VAFPR goes over the top. many of the members here may add the vafpr(as i did) and find it is not the answer to the problems they may be having with state of tune.