I am putting a TPI from a 305 on a 350. Since the injectors are only 19 lbs/hr instead of 22 lbs/hr, I was told I can increase the fuel pressure. Where can I get an adjustable fuel pressure regulator from? What should I adjust it to? I'm thinking somewhere between 42 and 50psi. Has anyone done this before?

 

Read my reply to a similar question on this link https://www.thirdgen.org/messgboard/...ML/001203.html

This contains your answer (and saves me from typing the same reply twice).

 

Thanks. What I'm worried about is encountering a lean condition. The 350 I'm putting it on has basically stock heads, and comp cams tpi cam (low lift, around .428). The block was completely rebuilt, bored .30 over, and fully balanced. I just want to know if my 19lb/hr injectors will keep up with it. The motor is really nothing radical, but I would hate to starve it for fuel and damage it under full throttle conditions. I plan on putting a new PROM in it. I don't have the hardware to burn my own, I do plan on purchasing it sometime. For the time being, are there any respectable programmers? I heard Hypertech and all the big name programmers are crap? Thanks again.

 

#19 pounders won't damage or hurt the engine in any way. The engine will still gets plenty of fuel especially at part throtle where the ECM can somewhat compensate for it. At WOT the engine won't perform at its full potentia, maybe it'll be a couple tenths slower, but nothing to the point where it can get damaged. BUT if you install an AFPR and increase the pressure a little, it might just give it as much fuel as #22s. Either way, you'll be just fine with 19s until you can get the #22s.

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92 Z28 L98 350
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Well, if you install 19# injectors and crank up the fuel pressure, it should flow enough to handle a mild 350 @ WOT, which is you major concern. At low load (idle and part throttle) you will be in closed loop, so the ecm will compensate. But if you "drop" into open loop (like when you first start, idle for a long time or go down a hill for a period of time), the engine will be lean.

The only way to compensate for all this is to burn your own eprom. "Off-the-shelf" eproms will do nothing to fix this. You can get a custom eprom writer like Ed Wright to burn you one, but now you will be getting damn near the cost (if not more) of the equipment (without a scan tool...which is a recommend item IMO...you'll save money in the long run by being able to diagnose problems in the future and fix it yourself).

If all you want is to get the eprom right and NEVER plan to change your car, then get custom eprom from one of those professional writer that create "formula" eproms. They will work reasonably well, but won't be as good as if you made one yourself. Every engine is different due to factors like "wear and tear and overall condition". You and I could have identical cars, with identical mods and identical fuel pressure, and even though my eprom will probably work very well in your car, it won't be perfect.

The difference between a perfect eprom and a close eprom is increased driveability, increased smoothness, increased gas mileage, possibly lower emissions (haven't tested that one though I might) and generally better performance. The increase in performance is really more noticeable on seriously modded engines than basically stock engines. On a basically stock engine, you might be talking 5-10 HP between a perfect eprom and a close eprom. On something "out-of-whack", like you may face, the HP difference can be a lot more significant.

Just one guy's opinion.

 

BTW, I just saw your other thread about wanting a larger cam. That will severely affect your decision of what to do.

My suggestion is to determine EXACTLY what you want to do (get a plan) and then make a decision based on the plan. Otherwise, you will end up buying a couple of different eproms, possibly a couple of different injectors and spend more money that you had to.

If you are serious about modifying your engine, go learn to burn your own eprom. It is acutally one of the simpler (and cleaner) parts of the car to work on. A basically stock car is a perfect place to begin, because you can slowly make changes, won't terribly ruin anything (unless you go lean) and by the time you are ready to modify your motor, you'll know exactly what to do in getting a "starter" eprom to basically getting the engine running and how to tune it.

The guys that wait until they've seriously modded their engine and then decide to learn about burning their own eprom face a tough challenge. They don't know where to begin in just getting the engine to run half decent, let alone optimally. Right now, you at least have your car running half decent.

Perfect time to start.

Go here: https://www.thirdgen.org/newdesign/tech/promintro.shtml

 

Glenn, you're trying to get everyone into PROM burning arent you! hehehe :P

[This message has been edited by Blade (edited February 01, 2001).]

 

Thanks for your help. If I do run into a lean condition at WOT how can tell?

 

Blade, you say if I increase the pressure a little, it should help. How much is a little? Where do you recommend I start out. By the way Glenn, you've convinced me on burning my own proms. I'm lookin into it now.

 

Blade, what ever makes you think that?

I initially went into it partly out of curiosity and partly because I could tell I had a rich condition, even after lowering my fuel pressure as much as I could. I knew that the solution was to shorten the pulse width, but I couldn't stand the thought of spending good money on a custom eprom, only to have to replace it again, when I change my intake (and again when I do the heads and again when I do the cam).

Plus, if my Miniram deal does not pan out for some reason, then I will go RamJet/Fastburn and there is no eprom for that.

But the biggest thing I want to make people aware is that, other than the initial learning curve and investment of about 10-20 hours (sooner if you have all the equipment, it makes even more sense), almost anyone can do it. Its the tuning that is the tougher part, and that comes with time and patience.

I just wish that this knowledge existed back in 1991 when I got my car. It would have put me on the "right track" a lot sooner and it really develops a good understanding of EFI. Exposes a lot of the myths and facts.