Celica Forums General Discussion Exterior fuel pressure regulator

I read in a magazine that when you put an intake, exhaust, and headers you also have to add a fuel pressure regulator or the car is going to be lean in the air/fuel mixture which could result in damage to the engine is this true?

If I'm correct, the factory fuel settings are rich so that when you add I/H/E, your a/f ratio's may be off, but not to the point where it may harm your engine.

Anyone want to shed some light on this?

Yup, you are correct. FPR is only needed when you need to suppliment the fuel to a point at which the stock system cannot compensate anymore. Your stock fuel system will note the added flow into the engine (through the maf sensor) and enrich the fuel through the stock system, the exhaust mods only allow spent combution gasses to flow out of your motor more smoothly and with less restriction, which has noting to do with fuel pressure at all, rather, it has to do with backpressure. Less backpressure gives more HP because it allows your motor to "breate" easier, but too little backpressure will result in a loss of torque. Therefore, the only mod that relies on the fuel system to work is your intake, and that can be handled by the stock fuel system.

*for example, the Celica GTS comes from the factory equipped with 310cc "saturated" injectors, I've done the math, and figured out that these injectors can flow more fuel than the stock 2zz setup requires for optimum operation. If this paragraph sounds like greek to you, Check out the July 2003 issue of Import Tuner magazine, and read the article, "Injection Perfection" for more info.

If you go forced induction, or do some serious internal engine mods, a FPR can help raise fuel pressure at the fuel rail to compensate for a lean condition.

However, using an aftermarket FPR can help maximize the effect of an intake, header and exhaust combo, used in conjunction with a dyno & some form of fuel management (like an Apexi AFC, or their new SAFCII, which looks to be even better) you can tune your configuration on a dyno, eliminating lean & rich spots in the powerband. doing this, you can squeeze a few extra HP out of your existing mods.

Of course, there can be problems. Most of the newer engines you see these days can't accept an aftermarket FPR because of how the fuel system is set up from the factory (like the I-Vtec motors that lack a fuel return line), this has led manufacturers to find alternate ways to suppliment fuel delivery, either with new computers, injectors and fuel pumps. While I believe the GTS and GT fuel rails can accept an aftermarket FPR, odds are, it will have to be an imported part, as I know of no domestic source for an FPR for our cars, Try Blitz or XS engineering for a hookup on a FPR, if they don't have them, they probably know where to get one.
You WILL need access to a dyno to dial it in, or at least a G-TECH, and you will need to know how to dial it in. otherwise, it's just a lump of metal under the hood that takes up space and adds weight.

This is on my list of future mods, I'll do a write-up on the install when I get around to it.
-Rave669

nice post..

thanks rave669 i really appreciate all your information

No Problem, Glad I could assist where I could

The best money you can spend right now would be on an air/fuel ratio gague and a decent o2 sensor to drive it. that way, you can see if the motor is leaning out, or going rich. you can make notes on where in the RPM range you go lean/rich, and when the time comes, you can add a FPR or new injectors, and use the info you collected to help dial it in. I already have a nice Sunpro A/F gague, and plan to install it in the near future. it also helps to diagnose problems such as failing injectors, stuck valves and failing sensors.

BTW, an easy fix to a lean condition in the motor (by adding minor mods such as intake & exhaust) is to simply increase the octane in your fuel a few points by adding an octane booster, or blending racing gas with 92-93 octane pump gas.

A while back, I created a octane blending chart for just this purpose, if you want to read it, I have it posted on my server at the following link:

http://homepage.interaccess.com/~wcsi/octane.html

-Rave669