16G Set-up Questions

^
With my stock fpr and a fuel pressure gauge at the filter, it's showing stock base fuel pressure. And for the record nobody is "knocking" the people that use one but its just not "super duper, one of you first mods have to do" necessary. I want to be like one of those people that runs 10's with a 14b. I want to run 10's on a stock fpr. /ubbthreads/images/graemlins/rofl.gif Not really and in fact its probably been done multiple times.

 

[belize1334]

^^ +1. Even on my rewired EvoIX fuel pump, which doesn't flow nearly as much as a Walbro 255hp at idle, I get 45psi on my fuel pressure gauge at idle. If I go back to stock wiring it drops down to 40psi which is decently close to OEM pressure and totally manageable. This is compared to my old vr4 pump which was a rock solid 37psi regardless of how much power I gave it. Arguing about whether over-run is a deal breaker is one thing. Arguing about whether it exists is just pointless. It exists. It's well documented. Get over it.

 

[turbowop]

Quoting crankwalk:
^ And for the record nobody is "knocking" the people that use one but its just not "super duper, one of you first mods have to do" necessary. I want to be like one of those people that runs 10's with a 14b. I want to run 10's on a stock fpr. /ubbthreads/images/graemlins/rofl.gif Not really and in fact its probably been done multiple times.



This is what I mean by "knocking":

Quoting CutlassJim:
Kind of like adjustable fuel pressure regulators. Let me get one and set it at stock fuel pressure, I'm so cool! That and my adjustable cam gears set at 0. Might as well put a shocker sticker on your car while your at it.






I never said it was a good candidate as a first mod. I only suggest using one for easier tuning when running a high flow fuel pump. For most people running 14b/16g turbos a 190lph fuel pump is good enough and I never had an issue with overrun on mine when I had it. I ran mid 12's with a small 16g and a 190/550's back in '02 on my full weight car. I know it isn't required. Sheesh.

 

[CutlassJim]

Quoting turbowop:
Quoting CutlassJim:



And I'm assuming you have logs of fuel pressure vs rpm and or load to back up this "overrun" that people like to throw around. Cause it would be the first one I will have seen.



/ubbthreads/images/graemlins/confused.gif Who needs logs? You can see the higher flow fuel pumps overrun the stock FPR with a simple fuel pressure gauge mounted at the filter if need be. If it's higher than stock base fuel pressure, it's overrun. It's also overrunning the stock FPR at anything in vacuum since it can't even bleed off enough pressure at zero boost/vac.




You should have included the next line of my post where I say I get no overrun with my stock FPR. 37.5 at idle (no vacuum to FPR) with a stock wired 255.

Maybe it's much more prevalent on a rewired pump and on a 2G FPR?

Also it's never really bothered me because the only downfall I see of "overrun" is running slightly rich at idle. The second you apply throttle I would guess that the injectors start flowing enough where so much doesn't need to be bypassed that it could even occur. Then you could just turn down the 1000 rpm slider/knob on whatever you use to tune.

 

[turbowop]

Well it doesn't work like that on my cars stock FPR's, hence why I use an AFPR on the one with the 255HP.

 

hugs

 

[turbowop]

Quoting CutlassJim:


Also it's never really bothered me because the only downfall I see of "overrun" is running slightly rich at idle. The second you apply throttle I would guess that the injectors start flowing enough where so much doesn't need to be bypassed that it could even occur. Then you could just turn down the 1000 rpm slider/knob on whatever you use to tune.



I would actually think it gets worse the farther into vacuum you go, with idle being the worst. If overrun is prevalent with the vacuum line removed (meaning that the FPR can't even bleed off enough pressure at zero boost/vac to keep a steady base fuel pressure) then as soon as vacuum is connected, where fuel pressure is even less, the problem worsens. Since the ecu or chip is set to fire injectors based on a certain base fuel pressure, you now get to tune around that overrun issue whenever the motor is in vacuum. Only when the motor enters boost, is when more fuel pressure is needed and overrun becomes a non-issue.

On paper, it sounds worse than it is. In practice, I find it easier to tune with a nice linear fuel curve and AFPR setups aren't that expensive.

 

Quoting turbowop:
I find it easier to tune with a nice linear fuel curve and AFPR setups aren't that expensive.



Agreed. From my own personal experience, running a rewired 255 on a 1g without an AFPR translated into being rich at idle, hella rich between shifts, and my fuel curve was sloppy and unreliable - I would have to make frequent adjustments on a more than regular basis.

 

^Jeez, what are you using to tune with?