Injectors/FPR/Fuel Questions
 

I've recently decided to bump my injectors from FIC 650's to PTE 850's, and was wondering if I "need" an FPR to regulate the additional fuel, as the current tune is compensated for the 650's. I have DSMLink as well.

I really want to know if I want to go to MAP to retune the car, if they can just adjust the fuel via DSMLink, and everything will be fine, or if I need an FPR for the increase in fuel and an adjustment in my DSMLink tune.

Thanks in advance for your advice.

- Stephen

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Re: Injectors/FPR/Fuel Questions
 

an aftermarket FPR is not needed for bigger injectors, it is needed if you get a larger fuel pump, bigger than 190, to prevent the fuel pump from over running the stock fpr.

so all you need to do is adjust your injector deadtime, and global fuel in dsmlink to run the larger injectors

Re: Injectors/FPR/Fuel Questions
 

Alright! Thanks!

I think my Supra pump is less than 190LPH. I hope...

Re: Injectors/FPR/Fuel Questions
 

i think the supra pump is over 190 but under 255, and it seems that for the 255 the AFR is recommended, but i think you should be fine with the supra pump

Re: Injectors/FPR/Fuel Questions
 

Actually if you look here at the flow chart, the supra pump flows more than the Walbro 255 (GSS341).

Re: Injectors/FPR/Fuel Questions
 

AFR would be recommended then?

Re: Injectors/FPR/Fuel Questions
 

Yes you must get one or you will run very rich.

Re: Injectors/FPR/Fuel Questions
 

Adjust the global & deadtimes, and go!

Re: Injectors/FPR/Fuel Questions
 

Keep the stock one.

Re: Injectors/FPR/Fuel Questions
 

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.

Re: Injectors/FPR/Fuel Questions
 

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.

Re: Injectors/FPR/Fuel Questions
 

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.

Re: Injectors/FPR/Fuel Questions
 

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

Re: Injectors/FPR/Fuel Questions
 

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.

Re: Injectors/FPR/Fuel Questions
 

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

Re: Injectors/FPR/Fuel Questions
 

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.

Re: Injectors/FPR/Fuel Questions
 

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.

Re: Injectors/FPR/Fuel Questions
 

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.