big time fuel problems - Zilvia.net Forums | Nissan 240SX (Silvia) and Z (Fairlady) Car Forum

gsracer · 10-07-2009, 10:17 AM

Keep in mind that this is on a supercharged V8, with 8 injectors lol

Ok, guys heres the skinny.

Im out of fuel.

I replaced my fuel pump with a brand spanking new walbro 255hp. The car doesnt drop fuel pressure anymore and doesnt go crazy lean anymore but i am officially out of injector.

Data logs show

at 5800rpm 87% injector duty cycle and 12.3 afr wot
and by only 6600rpm
99% duty cycle 12.1 afr wot.

Clearly im out of injector, now heres some ideas
Band-aid idea
i can run the injectors @ 4br 59psi rail pressure and give me a new flow of about 430cc per minute, and i should see 88-90 percent duty cycles by redline. Only problem is that with that rail pressure the walbro 255 will only flow enough fuel to support 440cc injectors. So ill be maxing out the pump yet again!!!! My only solution to this is to run either a second walbro intank, or an external pump such as an aeromotive.

The right idea.
Grab some deatscworks 550cc injectors and run them around 74 percent duty cycle by redline, but once again not enough for the walbro as at standard rail pressure it will only flow enough for 480cc. So im in the same boat.

My main problem is $$$ i have officially run the project fund dry here, i cant afford to do both the pump and the injectors, so do you guys think that runnning the stock injectors at 4 bar and 88-90% duty cyclle is a bad idea? Obviously i would imagine that 99 percent is much worse, but im really concerned about the 12.1 afr as i would like it to be a tad lower in the 11.7-8 range.

10-07-2009, 11:17 AM

on an inexpensive note

which is less complicated

what type of wiring is your pump setup with? be sure to use a high quality relayed harness (thick gauge) to provide your pump with as much current as possible. there is a big shift in fuel pump performance based on current.

also, why are you running a walbro? its been discussed time after time that these pumps are wishy washy. out the box ive seen them have problems.

i picked up a used MKIV supra fuel pump (denso) for 30 bucks. stick with something quality. if thats not enough, add an additional external pump or double pumps, splitting between the two banks of injectors

gsracer · 10-07-2009, 11:34 AM

Well, ive never had bad experiences with walbros and ive had quite a few on different cars with no problems, this is really the first i hear about them being wishy washy.

I have the walbro relayed from the battery (trunk mounted) to the pump with 8ga wire + and -. I see 13.8 volts at the pump. The single denso pump i dont think flows that much more than the walbro.

And for the first question, i think running a second walbro and bumping the fuel pressure to 60lbs is by far the easiest option, im just worried about running the injectors at 90% duty cycle for extended periods of time.

10-07-2009, 03:48 PM

interesting reading here:
Stealth 316 - Fuel Pump Upgrade Guide

sounds like you'll need bigger injectors, but the twin fuel pump shouldnt be a bad thing

you've got a ballerific supercharged v8, dont talk about being conservative about money if you've got a setup like that. park it until its properly usable, but dont cut corners.

juiced305diesel · 10-25-2009, 11:13 PM

Jerry just buy the injectors and a another pump and do twin in tanks. You can also try and run a twin secondary rails with factory injectors but I dont know if you have space or if your strand alone would be able to tune it.

steve shadows · 10-26-2009, 01:48 AM

Quote:

Originally Posted by gsracer

Keep in mind that this is on a supercharged V8, with 8 injectors lol

Ok, guys heres the skinny.

Im out of fuel.

I replaced my fuel pump with a brand spanking new walbro 255hp. The car doesnt drop fuel pressure anymore and doesnt go crazy lean anymore but i am officially out of injector.

Data logs show

at 5800rpm 87% injector duty cycle and 12.3 afr wot
and by only 6600rpm
99% duty cycle 12.1 afr wot.

Clearly im out of injector, now heres some ideas
Band-aid idea
i can run the injectors @ 4br 59psi rail pressure and give me a new flow of about 430cc per minute, and i should see 88-90 percent duty cycles by redline. Only problem is that with that rail pressure the walbro 255 will only flow enough fuel to support 440cc injectors. So ill be maxing out the pump yet again!!!! My only solution to this is to run either a second walbro intank, or an external pump such as an aeromotive.

The right idea.
Grab some deatscworks 550cc injectors and run them around 74 percent duty cycle by redline, but once again not enough for the walbro as at standard rail pressure it will only flow enough for 480cc. So im in the same boat.

My main problem is $$$ i have officially run the project fund dry here, i cant afford to do both the pump and the injectors, so do you guys think that runnning the stock injectors at 4 bar and 88-90% duty cyclle is a bad idea? Obviously i would imagine that 99 percent is much worse, but im really concerned about the 12.1 afr as i would like it to be a tad lower in the 11.7-8 range.

you can go all the way up to 12.5:1 afr on 91 or 93 Octane man.

DUH!

13.5:1 is NA V8 target AFR, and Boosted is 12.0:1 target AFR.

you're fine!

Ali 556 · 10-26-2009, 02:34 AM

Duel MKIV Supra In tank FP,

2 x -6 Merge Into -10 --> FPR --> Rail(s)

a single MKIV pump will support up to 550Whp On Supra's (they have 550 cc inj)

IIRC you are in the 41x whp right?

10-07-2009, 10:17 AM	#1
gsracer Zilvia FREAK! Join Date: Mar 2003 Location: Miami Age: 41 Posts: 1,590 Trader Rating: (7) Feedback Score: 7 reviews	big time fuel problems Keep in mind that this is on a supercharged V8, with 8 injectors lol Ok, guys heres the skinny. Im out of fuel. I replaced my fuel pump with a brand spanking new walbro 255hp. The car doesnt drop fuel pressure anymore and doesnt go crazy lean anymore but i am officially out of injector. Data logs show at 5800rpm 87% injector duty cycle and 12.3 afr wot and by only 6600rpm 99% duty cycle 12.1 afr wot. Clearly im out of injector, now heres some ideas Band-aid idea i can run the injectors @ 4br 59psi rail pressure and give me a new flow of about 430cc per minute, and i should see 88-90 percent duty cycles by redline. Only problem is that with that rail pressure the walbro 255 will only flow enough fuel to support 440cc injectors. So ill be maxing out the pump yet again!!!! My only solution to this is to run either a second walbro intank, or an external pump such as an aeromotive. The right idea. Grab some deatscworks 550cc injectors and run them around 74 percent duty cycle by redline, but once again not enough for the walbro as at standard rail pressure it will only flow enough for 480cc. So im in the same boat. My main problem is $$$ i have officially run the project fund dry here, i cant afford to do both the pump and the injectors, so do you guys think that runnning the stock injectors at 4 bar and 88-90% duty cyclle is a bad idea? Obviously i would imagine that 99 percent is much worse, but im really concerned about the 12.1 afr as i would like it to be a tad lower in the 11.7-8 range. __________________ ANTI-STRETCH NAZI Vortech Supercharged Vh45de S14 V8nissans.com

10-07-2009, 11:34 AM	#3
gsracer Zilvia FREAK! Join Date: Mar 2003 Location: Miami Age: 41 Posts: 1,590 Trader Rating: (7) Feedback Score: 7 reviews	Well, ive never had bad experiences with walbros and ive had quite a few on different cars with no problems, this is really the first i hear about them being wishy washy. I have the walbro relayed from the battery (trunk mounted) to the pump with 8ga wire + and -. I see 13.8 volts at the pump. The single denso pump i dont think flows that much more than the walbro. And for the first question, i think running a second walbro and bumping the fuel pressure to 60lbs is by far the easiest option, im just worried about running the injectors at 90% duty cycle for extended periods of time. __________________ ANTI-STRETCH NAZI Vortech Supercharged Vh45de S14 V8nissans.com

10-25-2009, 11:13 PM	#5
juiced305diesel Zilvia Junkie Join Date: May 2007 Location: Dade County Age: 40 Posts: 595 Trader Rating: (11) Feedback Score: 11 reviews	Jerry just buy the injectors and a another pump and do twin in tanks. You can also try and run a twin secondary rails with factory injectors but I dont know if you have space or if your strand alone would be able to tune it. __________________ "Being a SSR wheel nude model is NOT easy, I just make it look like it is!"

10-26-2009, 02:34 AM	#7
Ali 556 Zilvia Junkie Join Date: Sep 2006 Location: Far Far Away...... Posts: 359 Trader Rating: (0) Feedback Score: 0 reviews	Duel MKIV Supra In tank FP, 2 x -6 Merge Into -10 --> FPR --> Rail(s) a single MKIV pump will support up to 550Whp On Supra's (they have 550 cc inj) IIRC you are in the 41x whp right? __________________ '95 S14 Se With HKS's - BREMBO's - ES/SPL.

10-07-2009, 11:17 AM	#2
ixfxi Guest Posts: n/a	on an inexpensive note which is less complicated what type of wiring is your pump setup with? be sure to use a high quality relayed harness (thick gauge) to provide your pump with as much current as possible. there is a big shift in fuel pump performance based on current. also, why are you running a walbro? its been discussed time after time that these pumps are wishy washy. out the box ive seen them have problems. i picked up a used MKIV supra fuel pump (denso) for 30 bucks. stick with something quality. if thats not enough, add an additional external pump or double pumps, splitting between the two banks of injectors

10-07-2009, 03:48 PM	#4
ixfxi Guest Posts: n/a	interesting reading here: Stealth 316 - Fuel Pump Upgrade Guide sounds like you'll need bigger injectors, but the twin fuel pump shouldnt be a bad thing you've got a ballerific supercharged v8, dont talk about being conservative about money if you've got a setup like that. park it until its properly usable, but dont cut corners.