1996 Vette LT1 - 388 CID; EAGLE Forged Crank and 6" Rods, SRP Forged Pistons, XFI 230/236 Cam, Scorpion 1.7s, AFR 190s Ported to 212ccs, Ported LT1 Intake, HUGHES 3000 Stall, ATI Super Damper, GM Opti, PCMFORLESS Tune, etc.

I put this up on the Corvette Forum, but I figured folks here could benefit from it too, so here goes:

A couple of days ago I decided to check my stock FPR. I attached a pressure gauge and fired up the engine and let it idle. Well, I forgot to check the pressure with the vacuum hose disconnected, so yesterday I did that.

To my surprise, when I clamped off the vacuum hose, the pressure reading, with the engine at idle, didn't increase a single psi. So then I knew I had a FPR problem.

Engine gave no sign that the FPR wasn't functioning properly, no code, etc.

So I went to O'Reilly's and ordered a Borg and Warner ADJUSTABLE FPR, part # 23064, $99.xx It installs just like the stock one - slick as goose greese. LOL

I just finished installing it and I did the same test over again.

With the engine idling, pressure was the same as it had been with the stock FPR. When I clamped the vacuum hose pressure increased. BINGO!

Moral to this story: Even though you think your FPR is working fine, it's a good idea to check.

Hope this helps.

Jake

 

41-47 psi is the range for stock injectors with the hose off the regulator. Stock injectors are rated at 43.5 psi for proper operation. Increasing the pressure over stock is not needed and can even cause short term mis-fueling. There is no need to be running 57 psi of pressure with stock injectors.

 

I'm not running stock injectors.

Jake

 

Nowhere in your post was that indicated. Your advice should be specificed as to the situation. A guy with stock injectors would not benefit from 57 psi of pressure.

 

You're missing the point of my post. If you zero in on the fuel pressure number you're missing my intent. I'm not asking for different opinions on what fuel pressure I should run.

I posted so that others would know that checking my FPR showed me that it was malfunctioning and that others should check theirs also.

That's it.

Jake

 

It just seemed like you were also advocating higher than normal pressure was a good thing without there being any information to qualify that point. I was trying to make sure people with stock fuel systems did not misunderstand (and go out and buy an AFPR, then be mad that they were misled).

 

not to mention the fact that even with my 30# svo's and a tune if i adjusted the pressure that high it would throw things off

 

JESUS! Seems like reading comprehension isn't working today. What words can I use to make you guys understand??

Let me try again: Don't be concerned about what my fuel pressure setting is, or what my spark plug gap is or tire pressure, etc. None of that is relevant.

I'm only suggesting you check your fuel pressure regulator to be sure it's operating properly.

I'm NOT advocating or soliciting tuning advice. I'm only suggesting you check your fuel pressure regulator - There I said it again.

BTW, while I was at it, I also checked the adjustable fuel pressure regulator bolted to the MiniRam II on my 415 and it works fine, just as it should. I won't post any numbers because numbers seem to confuse this issue.

Bottom line: If you want to KNOW that your fuel pressure regulator is working as it should, don't just assume that it is, test it.

Jake

 

why is your fuel pressure so high? That's rediculous, did you also not bother to think maybe that fuel setting was part of your "tune" and now that you added the Adjustable you have now thrown the tune off?

 

This is becoming very tiresome.

What part of "Don't be concerned about what my fuel pressure setting is. . ." don't you understand? I didn't, and DON'T want tuning advice. If and when I do want advice I know how to specifically ask for it.

Fuel pressure on our engines should not be static and should not remain at a constant pressure no matter what the throttle position is. The pressure should rise and fall based on the vacuum the regulator sees. My intent was to share the results of my test, that my pressure was static at all times, indicating something was amiss with my regulator.

Further, that I changed regulators and the problem was solved. My fuel pressure then became responsive to the rise and fall of engine vacuum. That's all I was trying to do.

I didn't, and DON'T want tuning advice. When I want advice I know how to specifically ask for it.

It doesn't matter what my pressure setting is, the regulator should respond to the absence or lessening of vaccum by increasing the pressure. The upper pressure is limited by the maximum capability of the fuel pump.

Some regulators are designed to be 1:1, meaning for every 1" less vacuum fuel pressure should increase 1 psi. Others, like stock ones and those based on the stock design, such as the Borg-Warner I just bought, are 2:1 - for every 2" less vacuum fuel pressure increases 1 psi. These are close, design approximations.

Assuming an engine has 14" of vacuum at idle and you're engine would pull ZERO vacuum at WOT (not too likely though), fuel pressure, at WOT should increase 7 psi using the stock-type regulator and a full 14 psi using some of the aftermarket regulators.

Hasn't anyone ever posted about the rise and fall of fuel pressure before or is this virgin territory? Maybe that's why I'm receiving so many responses which completely ignore the core issue and are only interested in my pressure numbers.

I'm trying not to sound too agitated but this is fast becoming ridiculous.

Jake

 

I believe the problem was Jake, that there are alot of "novice" people on the forum and might have read your 57psi as being normal for a stock engine.... I think that what Shoebox was refering to.....

But, I do see you went back and posted your engine info, which shows its not stock.....

As far as Heatmaker, looks like to me he is asking why a high pressure for your setup???????? You might know something we dont know?????

 

"Tell ya what I'm gonna do": (sic). I'm going to go back and edit the original post and delete all the pressure numbers. Maybe that'll clear the air for the benefit of any future reader.

For those who have already read the original, well I can't do anything about that.

Jake

 

How's that?

Jake

 

I keep hoping this "tuning" part will go away, but it doesn't seem like it's going to happen. So this is my last response to the tuning questions.

Let me give all a little background.

I'm 62 years old and have been screwing on Chevy engines since I was in my 20s. I use to build BB quarter mile engines - all ran 8s with a single carb, NA, - for several teams in the Chicago area.

I use to race a mid 8 second, 170+mph roadster and when entered into the 8.90 second index, I had to slow it down a tad. I had to try to find which was best, to slow down the leave, the mid-range or the top end charge. I adjusted in order to give me the most consistent times as close to the index as possible.

Over the years, I've learned to let the engine tell me what it wants/needs and what it doesn't. When building one, I begin with the recommended settings; those that the manufacturer recommends. To me those are generic settings.

From that point on I tweak, letting the performance change tell me which way I should go. These tweaks cover every part of the setup. Say for example I'm dealing with a new camshaft. I degree (I use the Lobe Centerline Method) it in according to the specs on the cam card. We then run the car and see how that works out. I then advance or retard the cam depending on what results we received and what the goal is.

Same thing applies to valve lash/lifter preload, ignition timing, carb jetting, tire pressure, on and on.

I do the same thing with the engines in my Vettes (86 with a 415 and 96 as above). Although not as easily tweaked as older model engines, there are certain things that still can be done.

The fuel pressures shown in my FSMs and the tuning I've received from PCMFORLESS, to me, are merely starting points. From there I tweak letting engine tell me what it likes and what it doesn't.

So don't think, for example, that just because I may use two full turns of lifter preload that it'll work for your setup. By the same token, when I read posts from guys using 1/8-1/4 turn of preload, I don't jump in and say "That's wrong, blah, blah, blah". If they ask what is the recommended preload setting, if I respond, I'll simply post the "generic" setting; what the manufacturer recommends.

Also, I don't let others determine for me what I should and shouldn't do, there are just far too many opinions out there. Just take injector size recommendations as an example. "I'm running 30s"; "Well I'm running 36s"; "So and so said 42s"; "Look at so and so's chart and they say you need (fill in the blank)"; "Here's the formula for determining the correct injector size"; "No those formulas don't mean jack, they don't work", etc.

See what I mean. I let my engine's performance do the telling.

My thinking is that once I decide to modify my engine, all bets are off. The factory settings then are only a starting point.

Anyway, that's just me; follow your own path.

Hope this helps.

Jake

 

I played with my FP one day on the dyno...ended up finding about 25 h.p. Of course this is nowhere near a stock combo or streeteble......


But checking and tweaking all the small stuff is what puts you out front in the long run.

The guy makes a good point....just simply to check things and see they are functioning as they should be. Alot of people need to check alot of things with some of the numbers a see posted with the parts and engines they have......its the small stuff that counts, So check it