I checked my pressure yesterday and came up with these numbers:

With the vaccum line to the AFPR connected:
44psi...with just the pump running...39-40 at idle

With the vaccum line off:
46...with just the pump running...49 at idle

Which reading more accurately represents my actual fuel pressure?

I'd like to have it around 48 lbs.

 

line on is your idle pressure and I believe your line off is your WOT pressure... Im not 100% about that, but I am sure that those numbers look pretty healthy to me, assuming you have a stock setup.

 

With motor running only..

Your fuel pressure at idle is your base pressure with vacume.
wich you said was 40 psi. normal and ok

When you disconnect your vacume line to the regulator its the same as having your motor at WOT because no vacume is present at WOT. It should jump 10 psi with out vacume to 50 psi in most cases it will bounce around between 45 to 50 psi depending on how strong your fuel pump is.

IF it falls below 40 with out vacume you might have a flow problem or need a new fuel pump. If you want to play with your fuel pressure install a fuel pressure regulator.

 

ok cool..so when people adjust there fuel pressure, which figure are they basing it on?...WOT with no vaccum?

 

People??? Hmmmm
depends on who the people are...
IF the people are talking to people who know fuel injection motors it is assumed that if you talk about an idle pressure you can already make the assumption that 10 psi more would be the answer for WOT wide open throttle and a WOT pressure being 10 less than the idle pressure.

 

This is rich!

Guy knows he needs to set his fuel pressure to 48psi (where did that number come from?), but doesnt know if he should set WOT or idle pressure.. hah

-- Joe

 

Yo smartass...when I purchased my car it came with an adjustable regulator. I asked a mechanic friend to set it at 48 psi for me(based on what I'd read about optimum fuel pressure for my mods..THATS WHERE THE NUMBER CAME FROM). Last year a speed shop I went to turned it down without me asking and now it feels a little down on power. SOOO..I went out and bought a gauge and figured I'd try to set it back to 48 myself. But being a little unclear on which readings were accurate, I figured I'd do a little research here. Now, is that OK with you or do you find it amusing to bash someone who poses a legitimate question?

 

tpiterror, i had the same question when i first started modding my iroc. i myself found setting at idle worked better for me. i too have mine set at 48 psi, anything lower and you can feel a power loss.
anesthes, nice to see how people like you are still around. you know, have nothing better to do in life but bash someone who doesn't know something! i'm sure if you could answer it yourself, you wouldn't, just because your ignorant.

 

I'm one of the people "still around" that do writeups, research and post data here, hoping folks will read it and learn.

This site is full of archives of information by all of us. Learn to use the search feature. Do you seriously thing fuel pressure has not been covered before!!? I absolutely will not answer this. Infact, I recently did a followup post on experimenting with fuel pressures.

 

There is no optimal setting for your mods. Myth, pure and simple.

Fuel pressure effects atomization, and puddling in the runner floor. I, and others have done a lot of experimenting with various fuel pressures. You can use the search feature to find others results.

Anyone who blindly increases their fuel pressure without scanning, then making changes in the prom is just plain <B>S T U P I D</B>. End of story.. Fuel pressure is for automization, compensating for injector angle or depth, etc. NOT for "tuning AFRs".

-- Smartass

 

Yeah, ummmm..anyway. If you read my post, you'd see that I had it at 48psi and the car ran beautifully. So its not some figure I chose "blindly". I also did a search and didnt come up with an answer. All I was really asking, was which figure from my above readings to adjust my pressure by.

But, please continue your pompous rant. automization? injector angle? whatever.

 

See. Thats why I don't bother answering questions anymore.

-- Joe

 

Thanks for simply responding without all the bs! So you're saying with the vacuum line off, adjust it at idle? If so, mine is at 49, right?

 

Fear not..you answered nothing.

 

https://www.thirdgen.org/techbb2/sho...l+AND+pressure

https://www.thirdgen.org/techbb2/sho...l+AND+pressure

https://www.thirdgen.org/techbb2/sho...l+AND+pressure

 

holy this site is starting too sound like [fbody.com ] or as i see it f everybody .com...why is everyone so hostile. ..p.s.youre supposed to set with vacuum dissconected.

 

[QUOTE]Originally posted by anesthes
[B]There is no optimal setting for your mods. Myth, pure and simple.

Fuel pressure effects atomization, and puddling in the runner floor. I, and others have done a lot of experimenting with various fuel pressures. You can use the search feature to find others results.

Anyone who blindly increases their fuel pressure without scanning, then making changes in the prom is just plain <B>S T U P I D</B>. End of story.. Fuel pressure is for automization, compensating for injector angle or depth, etc. NOT for "tuning AFRs".

well then i guess TPIS has it all wrong then. there's a company that has been experimenting with the tpi system since it came out on the market. and they noticed power differences with boosted fuel pressure. you have to "tune" the afpr to get the fuel pressure, that of which allows the proper atomization, so what the hell are you talking about. why don't you look up TPIS and tell them your "theory," i'm sure they could use a good laugh. oh yeah, i forget to mention Holley, Lingenfelter, and GM itself. All of which manufacture the afpr's.
i agree that tpiterror should have done a search, but would it have been so hard to tell him that instead of make an *** out of him?

 

[QUOTE]Originally posted by mjustdie
[B]We all figured out TPIS was a joke years ago.. Start reading, searching newbie.

TPIS also told me about 5 years ago to not try messing with my prom, instead fax them my specs and they would make me one. Else I would blow up my engine.. Uh huh.. right guys.

I also didnt say increased fuel pressure didnt help. I said we covered this a million times. And there is no "set" pressure. Don't be dumb!


-- Joe

 

why not try constructive critisism if you feel some need to be better then everyone anesthes. when you attack people just asking a question "just plain S T U P I D, I absolutely will not answer this and Don't be dumb!" all you do is make yourself look ignorant. further more, when you do this you give the vibe that you probably don't know what you are talking about when you answer other questions and your credit for trust worthy info goes down the drain.

 

I'm not really too concerned. I do enough writeups, and help people who have moved themself far enough along.

I get really angry when the same question gets asked every 3 days. For example, 3 posts under this was the same exact question. Come on, give me a break.

 

well said 1992rs/ss!! anesthes, let me get this straight. you are always on here, you do all kinds of research on the thirdgens, and you know all so well you can degrade other members. hmmm, sounds like its time to move out of mom and dad's basement and get a job. if you know so much about these cars and how specifically they run, why don't you have a job with GM. or better yet, why don't you get a job, sounds to me like you have too much time on your hands. as for newbie, maybe to this site, but i've been toying with 3rd gens for 7 years. being dumb? man, grow up! now you're starting to sound like my 4 year old!!!
tpiterror, this topic has gone off topic. you're better off doing a search like ******** said you should have and go with what works for you.

 

haha

Ok. I see how it is.. Now we have to have this contest right? Ok. I'll play.

Lets see. You have a 4 year old child. And I have 2 cats.

You have been toying with 3rd gens for 7 years, and my family owned a dealership for nearly 20.

After that, I owned (and still have) a shop, until getting into law enforcement.

Why don't I have a job with GM? Because i'm not interested in one? Sure, I burn my own proms, write code, I made my own EFI setup (manifold, etc), I build every aspect of my car myself, including machine work. But what makes you think i'd want to work for GM?

Now the basement and job thing. I just don't get. Now, I havn't made detective yet, but I can't figure out why you'd assume I lived in my parents basement?

And while we're attacking employment status, what do you do for a living?

 

glad to hear you have such an interesting life. a cop, heh, now i can see where you have all the time in the world. and if your attitude is like this to the public, i can see why you haven't made detective. i'm not playing a game, i'm just sticking up for a fellow member that asked a question that you just had to insult him for. as for my employment status, i'm a welder/fabricator. i work for a company that constructs various large scale buildings per customer order. might not be as intriguing as getting the ability to have a badge and using it to sink fear into the common citizen, but it pays well and it's a trade i enjoy. I also have a small bus. on the side working on cars when i have the time, usually just on the weekends. The whole basement thing, just to **** you off. the job, well we covered that. i'm not having an internet fight/war whatever in the hell you want to call, with you. just go about harassing others as you seem so well at doing. i'm sure there are others that have told you how rude you are and i'm sure there will be more to come.

 

Wow
Is this a typical thread? Is it normal for you guys to bust each others *****, kick each other around and not help in the problem solving process??? I have been looking around this site for a couple of hours and man, Bad attitudes!!! Just an idea, if the question is beneath you, why not move on and not post a smart B.S. responce....just an idea.

 

The real joke of this is, I clicked those links above that anesthes listed(which I've come across myself) and only the first one halfway answers my question. Anybody who has been on these boards as long as I have, knows that often getting a definitive answer from a search is like playing multiple choice. Many times a direct question ends up going off on a tangent or turning into some halfass battle of wits. Sound farmiliar?

So that DO A SEARCH cop-out crap is even more annoying than a "repetative" question if you ask me.

And believe me, I dont feel like the *** here. If thats what anesthes was attempting...it backfired.

Anyway, I'm sorry this got ugly. I just was trying to narrow down my findings so I wouldnt screw up my car.

SO, just to be clear...the psi I base my adjustments on is with the car idling and the vaccum line removed, right? So based on that, I'm at 49psi..so i guess i can leave it alone.

 

Its not as simple as that. Its like asking what the stock fuel pressure is on a TPI car. Who knows? I wanted you to search so you'd understand the whole thing. If anything backfired, than that was it. But I don't see it as <b>MY</b> loss..

The reason you set the fuel pressure with the vac line disconnected, is because your setting it relitive to the atmosphere. So in your case, 49psi at atmospheric pressure of wherever you live. (14.7psi if you lived on the ocean).

If your motor could achive 100% VE at WOT, you'd see this on the gauge at WOT.

When your car is idling, the pressure is lower inside the motor that the atmosphere, so it creates vacume. The diaphram on the regulator pulls back pressure to compensate for the lower atmosphere inside the engine. On hard decel, you have more vacuum (lower kpa), and on accel you have less vacuum (higher kpa, nearing 100kpa or 14.7psi at sea level).

The purpose for this variable regulator, is to maintain the same pressure RATIO at all times. Wether or not its WOT, or DECEL you get the same ratio of fuel pressure.

So when your setting fuel pressure, you always set it with vac line disconnected, because your setting it at 1 atmosphere.

I've experimented quite a bit with different fuel pressures when I ran my TPI setup, and with my singleplane EFI setup. I've found that higher pressures (50-55 psi vac disconnected) do infact create a better idle, and more power. Not because the car is getting more fuel, but because it creates better atomization of the fuel and air, and reduces the puddling effect on the bottom of the runner. I don't just adjust fuel pressure and drive car. I adjust it, then tune my VE, AE, and PE tables to achive the same BLM and 02 readings as with the prievious pressure. I record in my little brown notebook, until i've found the best combination.

Currently, my car idles around 50psi. At WOT, i'm around 55psi at 100kpa (1 atmosphere). Under full boost, I see a little over 60psi
on the gauge.


I know <B>I</B> covered this a month or so ago, so a search should have brought it up. But whatever.
-- Joe

 

Now that was a better reply, that makes lots a sense to me and I bet everyone else got it too! Thanks Joe

 

No prob.. Hopefully it will be found in future searches.

-- Joe