Injectors/FPR/Fuel Questions

[Kevin 1G Drummer]

Actually, when it's bypassing the regulator you should be showing rich because the fuel is going around the diaphram into the vacuum line, then up into the manifold where it follows the air into the engine. Pressure might actually be a little low when that's happening.

[blackrosenova400]

If its going around the diaphragm, then the regulator is junk. My cavaliers regulator was bad, didn't know it. it was leaking fuel into the vacuum line and was flooding my motor. So badly the it clogged my catalytic converter and my engine wouldn't run, lol. figured it out by pulling the o2 sensor on the exhaust manifold to let it breathe.

Pretty sure the stock fpr return orifice is too small and will not flow enough to control a large amount of flow. And maybe if the regulator is old enough, it bursts the diaphragm or causes a leak. Either way there should never ever be fuel in the vacuum line.

I ran a 255 with the stock regulator the very first time I installed it to test it. Fuel pressure I think was 5-7 psi higher than it should have been. never saw fuel in the vacuum hose.

[4seasons69]

How can you tell him to keep the stock one?

The correct way to do it is to install a fuel pressure gauge, install the pump and watch fuel pressure at idle. If its too high the regulator has been overrun and will need an aftermarket regulator. Adjusting the global will set the tune correct at low loads until the injectors are opening enough fuel to the engine where flow is reduced and the regulator can finally keep up. when that happens, you are now running lean because the global is backed off. You can tune it out but it is just masking the problem.

cause brad is running 10's on the stock one that is how he can tell him to keep the stock one.

personally I say if you have the cash just get an afpr. it's just one less thing to worry about

[blackrosenova400]

Generally if someone is asking if they need to use a fpr, they are new to the world of tuning, and explaining to them the correct way of doing things is the best way. Brad is probably really experienced and can get way with it.

If the fpr is not up to the task of correctly regulating the fuel, get one in that can, pretty simple. Id hate to see someone wash there cylinders out with fuel because they weren't explained why they need an aftermarket fpr.



cause brad is running 10's on the stock one that is how he can tell him to keep the stock one.

personally I say if you have the cash just get an afpr. it's just one less thing to worry about

[4seasons69]

Generally if someone is asking if they need to use a fpr, they are new to the world of tuning, and explaining to them the correct way of doing things is the best way. Brad is probably really experienced and can get way with it.

If the fpr is not up to the task of correctly regulating the fuel, get one in that can, pretty simple. Id hate to see someone wash there cylinders out with fuel because they weren't explained why they need an aftermarket fpr.

I agree. I was just saying that's why he said keep the stock one

[Constant_Project21]

I know people using a cheap eBay fpr...does the same thing as the spendy ones. They haven't had problems with them, so why not spend $40 for an extra saftey net.

[desolate]

Many guys run fast on the stock regulator with an upgraded fuel pump, but that isn't to say you should do it if you still want the normal operation of the way the system was designed. It was designed to change fuel pressure according to vaccum & boost. The stock regulator's return hole is pretty small, so fuel pump upgrades usually overrun them.

How people run fast without fprs is because, the operation of fuel regulation always rises above the overran amount @ wot, so under boost the stock fpr will not affect performance. The running rich and the like happens typically under 15psi of boost because 255 walbros usually overrun fuel pressures to around 55psi @ idle.

That's pretty high, however, in the real world it's pretty common for the car to behave normally. You might see a dip in mpg, but things won't be terrible. One of the main reasons why the car usually shows no ill effects is because the ecu can adjust and compensate fuel delivery off boost and such is by using the fuel trims. However, overall it's usually best to have the car work the way it was designed by upgrading the fpr.

[Shane@DBPerformance]

You can tune around it easy. Yes, it is nice to have, but it isn't not a big deal nor hard to tune around, unless you you have a dual fuel pump setup or some massive single pump. A lot of people get an aftermarket FPR setup, but miss 10 other things that should have been fixed or upgraded instead of the FPR. There should be no drop in mpg or anything if some attention is given to the tuning.

I wouldn't call putting an ebay FPR on a car a safety net, I would call it a very dangerous potential failure point.

With the ability to tune the fuel injector size, latency times and MAF compensation in DSMLink or with a chip tune, overrun usually becomes a very minor issue. Most people have boost/vacuum leaks, idle motor problems, FIAV problems, etc that cause more trouble than some overrun. If you goto a speed density setup with DSMlink or AEM EMS, then overrun is a total non-issue.