Hey guys,

what are the signs that you should go with a return fuel system? From all the searching, people say with a supercharger and 650cc injectors its a nice to have but not necessary.

What logic goes behind that thinking? Like what hard #'s would you look at and say "ya, you need a RFS?"

also, is getting the billet fuel rails worth 450$ in price between the standard AAM kit and the CJM? At what point do the stock rails exceed capactiy? I wont be running the car over 420-450 hp on the stock block. If i was built, RFS no question.

My buddies say that a fuel pressure guage is kinda pointless since theres no way to actually regulate fuel on the stock system, but would this kinda gauge indicate problems if i didnt go with a RFS?

Thanks!

 

This is a very old debated question and if you search you would get many opinions. Some have went without them at those power levels. Remember that a RFS is a tuning tool. Bottom line, you want to do it right, get one.

I don't personally have one on my setup. I do have a fuel pressure gauge due to that. It pretty much runs at a steady 54-58 psi at all times.

 

I was told by 2 shops that fuel pressure monitoring on a stock setup is just as important as it is without it.

I would think replacing with a walbro pump would help indicate any faults in the system.

 

No one has done enough testing to tell you when you do or do not need line upgrades or rail upgrades and a return line, etc.

The rails themselves are very large inside, but the built in pipes that feed them are whats small which is the only reason to upgrade the rails.

can you be the first person to tell us if a fuel system is required at that type of power levels? heres how you do it. Remove the fuel pressure damper off the back of the driver side rail, and install a fuel pressure gauge sensor there. i will custom machine you the adapter to put a fuel pressure gauge sensor there if you promise to do the rest.

basically, if you see ANY fuel pressure drop at ALL thru the powerband with a 100% stock fuel system and only an upgraded pump, then we know that a RFS is needed for proper safetly. This is because that pressure drop at the very end of the system will cause uneven cylinder tuning which is terrible for your engine.

most people get the RFS to eliminate problems before they start. They are also very helpful for small adjustments in the tune. For example, the UTEC doesnt have any ambient air temp correction. So if its 40 degrees colder out than when you tuned, you car will run lean. You can just turn up the fuel pressure a psi or two and your covered.

 

Hmm, well a electronic fuel pressure gauge to match my other gauges and the AAM adaptor would run about 1/2 the price of the stage 1 AAM RFS.

I guess no one has done any testing bc if you are dropping $15+K, might as well spend the 500-1000$ on a RFS and not even risk it on the stock setup.

Phunk, sounds like a neat experiment. Would be pretty easy to do with a dyno i suppose. Just watch the fuel pressure as you accelerate and look for any drop.

 

you should have a fuel pressure gauge anyway, so i wouldnt compare it to the costs of getting a RFS. You wont need the AAM adapter because I am serious when I say I will machine you an adapter to put the fuel pressure gauge where it needs to be. The location of the AAM adapter is great for NA cars and what not, but when there is even a remote risk that you are running a fuel system on its edge, you want the pressure reading to be after the last injector so you can moniter pressure drop. Most of the restriction in the stock fuel system is after where that adapter goes, and of course you should have it after the last injector as well. This is why the NPT put on aftermarket regulators is typically the best place to check your fuel pressure... if you dont have one, such as if you stay stock fuel system, then on the back of the driver side rail is where you should put the gauge sensor if you want to get the most information out of it.

If you are willing to let us machine you the adapter I speak of and share with me the results of a few quick tests with it, I would get you a deal on a RFS if you decided to go that route or if the tests gave you the results that indicate that you should have one anyway. All I would need to know is which gauge you went with, so we could make the adapter have the same threads as your sensor, which would be either 1/8 NPT or 1/8 BSPT depending on the country of origin of the gauge sensor.

 

+! on the tuning and consisent capabilities. one main word is rising rate fpr. i know most know about it, but got skipped so far. if you don't raise the fp along with boost, your psi in boost will subtract from your psi of fuel in the rails. running 50psi fuel in the stock system, you theoretically (actual numbers will vary slightly) will only be running 36psi when the injector opens if you are running 14psi boost.
having it returnless stock is only to meet deq regulations, but definately not the best way to do your fuel system. on a side note, if it is tuned to compensate for the drop in fuel pressure, you will still be ok.
the stock rails do have good capacity on the inside, but the inlets have SERIOUS restrictions where it necks down.