Fuel Pressure Drop? Numbes Included
 

Hi guys,

I finally got my fuel gauge hooked up and did some pulls.

At idle my fuel pressure sits at a 50-52PSI, under a 4th gear WOT run it drops as far down as 36PSI. Under lighter loads the fuel pressure sits anywhere between 40-50PSI.

Just curious if that is to low? I have the supplied fuel pump from Boosted Performances Kit 340lph pump. I have also ran larger gauge wire (both power and ground) to the pump.

I am just looking to see if high 30's is ok or if thats starting to get dangerous.

Thanks!

Mitch

it all depends on your afr's if it sniffs good your fine. your really cant control it unless you put in a return line. the tune will be set to run larger pulsewidths to make up for the drop in pressure so as long as you don't run out of pulsewidth to adjust the afr you are fine. With a return system and boost referenced regulator you can get more power out of the injectors, but if what you have works there is no need to change until you want to go bigger.

Here's a link to a handy calculator for checking values as an FYI, but everything 1slow said is spot on.

RC Fuel Injection

It does sniff good, down into the 10's under load.

Thanks 1slow, It just seemed like a big drop in pressure to me. But I am coming from the diesel world where if you lose 30% of your fuel pressure its just not going to perform like it should.

Thanks for the link Jordo!

:tiphat:

Do you have a fuel regulator and return system, you not suppose to loose that amount of pressure, your pressure should be solid, I have a boosted car and had a lot of problems with pressure and I fix by getting a walbro 485 and 10G wire, I deleted VVEL and set a pressure to a solid 53, tuned and car got a solid 53 even close to 7500rpm.

Its ok; BUT its not the ideal pressures. Pressures should be steady at all RPM's
It depends on AFR, injector duty, and heat. The stock pressure regulator is not the best for pressure control on a FI system. Fluctuating fuel pressures affect AFR ratios and can cause a lean condition if pressure drops to low. A good tune will compensate for that by keeping the injectors open longer.

Having experienced low fuel pressure at full boost and almost losing a motor,
(I guessed the stock regulator either stuck open or the fuel line was too small) I firmly believe all FI systems should have a full return system with a larger fuel inlet supply line. The stock one is less than 1/4" and is too small and if anything, increase the fuel line size to 3/8"

My plugged nickel opinion as I've been there; seen it

Also remember our regulator is at the tank so by the time your getting to the rails it's even lower. Even if ur a/f is on point could still be maxing out injectors and pump. And running something at max constantly (imo) is never a good thing


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