fuel problems

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T

typesiracing

Senior Member
whats up everone.....just wanna pick some brains....this is my first post but you guys seem really helpfull...any way i have a 94 honda prelude si with crazy mods....i have a je pistons, crower rods the head is ported and polished with jg cams and a 3 angle valve job, the block is bored 40 over, crank is polished, dc 4-2-1 headers, a high flow cat, full custom exhaust, aem cold air intake, msd blaster coil, i also have a jet computer upgrade, well this should be enough info....i'm not trying to brag because the car doesn't even run right to be worth bragging about....i also have a fuel pressure regulator and to get to the point the car smoke black like crazy on accelleration....i tried to bump down the fuel pressure to the point it was below stock....my friend is a honda tech and he told me that the fpr will only change fuel pressure and not the amount of fuel being consumed....so i set it back to stock...i have an air fuel meter and it says i'm running slightly rich which really doesn't do justice to what i see coming out from my exhaust.....the spark plugs have some carbon on them but look kinda white...i'm getting frustrated here.....all the vacuum lines appear to be hooked up and the o2 sensor has just been replaced....i don't know what else to do...i'm thinking apexi afc....but i'm not sure if my mods warrant it and don't wanna waste the money if i don't have to......so maybe someone has had this problem or can help me out.......thanks for you help.
 
I dont know much about this, but it sounds like its either because its running rich or the bore. Most likely cuz its running rich though. Wait for someone elses response though cuz i'm still noob.
 
i'm not sure what you mean....maybe it's my fault for not being clear enough my problem is the car is running rich and i don't know why and i wanna stop it.
 
its the ECU
they are programed to run very rich
get a VAFC, hondata, or something else you can tune your AF with
or get rid of it all together
that will fix your problem
 
thanks for your thoughts but i believe the ecu made it worse but it was running rich before the chip.....any other thoughts
 
more air flow = more vacuum = more fuel will be sucked through the oem or aftermarket fpr.

i/h/e can make you run rich, simply because the motor sees much more air, even though its not really making much more power, and over compensates for it.

your problem here is that you have tons of parts, with nothing to tune them with.

get a vafc, or better yet, lose the jet chip, and get a hondata system. take it to a dyno. get it tuned with wideband 02 readings. you will not only get more power, your gas mileage will increase as well.
 
Tuning is key. If you're looking for something cheaper than a hondata and you are willing to use your brain instead of your wallet, there are several quality DIY solutions available.

Regardless of whether you go hondata or do something else, there probably isn't a ton you can do without converting over to a civic/integra ECU since hondata will not run on prelude computers. P06,PR4,P74,P75 will all work fine since unless I'm mistaken, the Prelude Si had H23 non-vtec in them. (If I'm wrong and you have a H22, use a p28)

HardLowrdRanger might be able to help you out with something for your Prelude ECU, but I can only help you once you're on civic electronics.
 
Well, lowering the fuel pressure will inject less fuel... Think of a water hose, when it's on it trickles out... Low pressure... When you put your thumb over the hole it SPRAYS... High pressure... Which do you think releases more fuel? High Pressure =) So for a temporary solution, lowering the fuel pressure would work or at least help out a little... Use the A/F gauge to get it into a better A/F ratio even though A/F gauges aren't perfectly accurate... It's a temporary solution to help limit that smoke...
What ECU do you have? What size injectors?

James
 
Originally posted by HardLowrdRanger@Jul 17 2003, 10:53 AM
Well, lowering the fuel pressure will inject less fuel... Think of a water hose, when it's on it trickles out... Low pressure... When you put your thumb over the hole it SPRAYS... High pressure... Which do you think releases more fuel? High Pressure =) So for a temporary solution, lowering the fuel pressure would work or at least help out a little... Use the A/F gauge to get it into a better A/F ratio even though A/F gauges aren't perfectly accurate... It's a temporary solution to help limit that smoke...
What ECU do you have? What size injectors?

James
Click to expand...

actually thats completely wrong. And a/f gauges are only accurate for one ratio, like 10:1 or something.


when you put your finger over a garden hose, it shoots a smaller amount of water out with a higher pressure.

bottom line is that if you want it fixed get the right fuel management.
 
Sorry, I'm with James on this one.

I have 450cc injectors in my LS powered CRX with one *hell* of a FPR (FP=24psi) and I'm able to run a stock ECU.

"But you have to have a hondata to run 450cc injectors"

Go cry your yourself a river and whine yourself a song while I have a car that runs nicely without "the right engine management."

Fuel delivery is *almost* directly proportional (i.e. LINEAR) to fuel pressure. I say almost because with too little or too much pressure, very bad nonlinearities develop. In other words, you have a lot of effective tuning that can be done with a fucking adjustable fuel pressure regulator.

'nuf said. use what you got before you blow cash on toys.
 
They're actually only accurate for ~14.7... And I think I clearly stated that the A/F gauges are not completely accurate... When the fuel pressure is increased before the injectors, when the injector opens more fuel gets through because the velocity is increased... The hose thing was a stupid little example, maybe not completely correct for this, but I was trying to prove the point that with increased pressure before the injectors you will inject more fuel... And that statement is correct... =P

James
 
and as for A/F guages, you are right about them being pieces of junk. They are tuned to the lambda of your O2 sensor, 14.7:1 A/F in most cases. You cannot trust them that "very rich" is twice as rich as "halfway between very rich and stoich" but they are generally accurate enough to give you an idea of whether you're swamped with fuel or have other issues.
 
arg. ok. Injectors feed off of a pressurized fuel rail. That fuel rail stays at a constant pressure, with excess fuel being sent back to the tank. When you increase the pressure in the fuel rail (ala an FPR or whatnot) all it does is make MORE fuel readily AVAILABLE to the injectors. It in no (or very little) way, affects how much fuel gets shot into the cylinder. That is the job of the injector.

as per my understanding. I could be wrong.

and as for saying your completely wrong, I was just talking about the garden hose example. thats wrong :p
 
you're completely wrong, sorry.

Actually, a second read, no you're not. "At a constant pressure" the fuel injector size and pulsewidth determines fueling. If you INCREASE or DECREASE pressure, you will affect volumetric flow characteristics.

If you don't believe me, explain how a rising rate FMU provides fuel in boost.

If you still don't believe me, go check out the effect of fuel pressure on injector sizing on RC's webpage.

Higher pressure means more fuel comes out of the injectors. plain and simple.
 
yea, because more fuel flies through the injector when it opens for it's normal duty. That is a complete hack way to manage fuel for an engine. It's abusing the injector, and going against the ECU. Just fucking get real engine management. I don't understand why thats so hard for everyone.
 
look dumbfuck, get your head out of your ass and quit eating the bullshit that has you fucked up in the head.

Running a 450cc injector designed to be run at 42psi at 30psi will LENGTHEN its lifespan if anything due tothe decreased forces on it.

HONDA *yes stock fucking honda* FPRs put out different amounts of fuel pressure. Ever do a Z6 swap into a obd0 car using an OBD0 ECU and not change the fuel pressure regulator to match the ECU?

OBVIOUSLY FUCKING NOT. QUIT SPREADING MISINFORMATION, QUIT BEING A TURD AND FUCK OFF IF YOU'RE GOING TO CONTINUE TO BE MISINFORMING KIDS TRYING TO GET THEIR CARS TO RUN RIGHT.

Actually, cancel that. I want some of what you're smoking because if it got you that fucked up, it must be wicked.
 
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