I swapped my 3.125 pulley to a 2.70 reichard racing anti-slip pulley. I am still on the stock internal engine except for the cams, so I know I am pushing it.

Fuel system:
JWT ecu with 100 octane timing program
Z32 MAF
deatschwerks 550cc injectors
Walbro gss342 fuel pump
coolingmist water/meth injection
SAFCII for small fuel corrections
adjustable fpr set at stock 3.5 fuel pressure

I was out doing some test runs today and ran into a big fuel problem. I think I know what it is, but thought I would post to get some opinions from some other experts. This was a 3rd gear run. 1st and 2nd gear feel fine, but its hard to tell due to the massive wheelspin.

Here is the log from my PDA showing the A/F ratio.


Here is the boost pressure. (Its a GM 2 bar Map sensor, 4.5 volts = 12psi)


You can see, around 6400rpm I was around 11.80 A/F and 12 psi of boost, and then right after that the A/F pegs out the wideband lean and then I got out of it quickly. Most of the run the A/F was around 11.1-11.2, but at 6000 rpm it started creeping up and was at 11.80 at 6400, and then wham!

1st of all, hopefully I didn't do any damage to the engine. It still runs fine but I will check for blow-by and make sure I didn't burn a piston.
2nd of all, does this look similar to the fuel pump problem that meximax had? I think I will get a boost-a-pump, but I wanted to make sure that it is the problem. I was going to dyno today but I will wait and make sure I get the fuel corrected before I do. I would guess I am around a similar hp number to meximax when his fuel pump ran out of steam.

 

Looks very similar to my problem with the JWT ECU and 550s. I am pretty certain that its your fuel delivery associated with the Walbro. Do you have a AFPR with a 1:1 rise rate? Are you monitoring your fuel pressure? You could start by hard wiring the fuel pump and see if that help any. Otherwise, a boost-a-pump will probaby get you over the hump (mine did the trick at 16V). An alternative solution would be an in-line T-rex fuel pump.

BTW, I think that you will be making more power than me. We have basically the same setup, except I am running lower compression, and a heavier flywheel and transmission. Best of luck on your tune, can't wait for you numbers



.

 

When you hardwire the pump:

1. Do you keep the fuel pump control module and dropping resistor and use a relay with the stock wiring and new larger wiring directly to the battery?
2. Do away with the dropping resistor so the fuel pump receives full battery/alt voltage all the time through the stock wiring?

I saw where people talk about both ways.


Also, if I end up with a boost a pump, should I use the boost input to turn it on, or just hard wire it so it keeps the pump on all the time?

I see where people do that both ways also. The BAP installation instructions say its okay to do it either way.

 

On the pump hard wiring....I went with option 1 and kept the fuel pump control module to close the circuit on the relay and then feeding the fuel pump a straight thick 12 ga. wire from the battery which is in the trunk of my car. That kept the pump running a bit stronger and more consistent, but still not enough to feed the demand.

For the BAP....I don't have it running all the time just because I wanted to preserve the life of the fuel pump and also because a constant high voltage means a higher fuel flow which tends to warm up the fuel. I now have the BAP on the 12 ga. wire between the batter and the fuel pump. I T'd a vacuum line to the BAP from my console (going to my J&S) so that it would only activate under boost above 4psi (I think).

 

96sleeper, I bypassed my fuel pumps drop resistor, by cutting the ground (under the rear seat) which leads into the pump, that ground on the pump side i grounded it directly to the body, this provides the full battery/alty voltage. iv had it like that for more than 6 months, no issue. Ofcourse my problem wasnt because the pump was giving up (not putting near close power as u guys), but i wanted to have a more constant higher voltage.

Meximax, let me ask u a questions, so basically "boost a pump" is a voltage booster that you have activated at 4psi so that it provides higher voltage to the pump at that certain boost?

 

I'm not Meximax, but I can answer you..yes..that's exactly what it is. YOu can adjust it to feed a certain amount of voltage when the boost kicks in. THe boost a pump is by kenne bell, but there are 1-2 others out there. I think AEM has one. It's definitely a good option if a high pressure Walbro doesn't supply enough fuel even when hard wired.

 

hardwiring the pump and grounding it out so it runs all the time seems to have fixed the problem...for now.

 

I'm running into a similiar problem as 96sleeper. I don't have an FMU in and I'm running 440's. I have my FPR set to 51psi. I'm going to be putting an FMU in, but I was wondering if it was worth doing what you did?

Do you suggest I go about the method you did and dead the ground going to the pump and re-ground it to the body? B/C they mentioned running a hardwire to the battery, but you method sounds easier. Thanks.

 

I just grounded it directly to the body, didnt need to hardwire the pump's positive or anything (in my case).

 

Sorry for the noob question, but just so I am 100% clear, you cut the ground wire leading to pump, grounded the actual pump to the body, and took end of the ground you cut, and also grounded it to the body? Thanks man.


96sleeper, what was your final A/F?

My uego reads 10.0-10.3 until top of third (5kish), then it just pins "----" not sure if it's too rich or just spiking out lean. Regardless I let off quickly.

 

I have not tweaked the A/F yet with the SAFC, but the log showed 11.2-11.6 for a 3rd gear pull after I hardwired the pump.

 

Glad to hear that the fuel pump hard-wiring solved your issues.


I pushed my stock VQ35 to the OEM 6500rpm limit with my 2.62" pulley. I can only imagine that gush of power you are making on that stock compression cammed VQ35 with that 2.7" anti-slip pulley

I have been lonely on this maxima VQ35 SC world. Hurry up and dyno

 

lol no you haven't. We just don't have the time to post. Soon tho

 

Excuses excuses... post it up...

 

lol...if you only knew...



ROUND 1


EU - 1 Me - 0


ROUND 2

Tommorow >=)


But cars all together, just need EU and tune. and IM DONE!!!! ....for now.

 

the ground that comes from the drop resisitor is just tapped off and not connected to anything, the pump is infact grounded to the body yes

 

Steve do you need help with the EU...? PM me if you need to...

 

I checked with a probe and the black wire seems to be the ground that Streetz is referring to. Can anyone else confirm? I'm penned in to get my EU installed, and a FULL tune on saturday so I wanted to get this done before then. Thanks in advance.

 

What I ended up doing was eliminating the drop resistor by grounding the pump directly to the body. Then I ran a relay and a 10 gauge power wire directly from the battery to the pump. I used the factory wiring to turn on the relay, which feeds 10 gauge power directly from the battery to the pump. I also used 10 gauge for the ground wire to the pump.

If you use a meter, the power wire to the pump and ground to the body should read 12 volts, the power wire to the pump and the ground from the pump will read around 7-8 volts at idle I believe, thats the drop resistor in action.

 

Do you remember which one it was off hand? I located 2 grounds one black and one black/green. I just want to make sure I'm groudning off the right wire. I PM'd streetz, but he hasn't gotten back to me yet. Thanks again man.

 

seems like on my car the two wires to the pump were green/red for ground from dropping resistor, and black/yellow for power. It might be different on different years. The only was to be sure is with a meter.

 

I just did the pump hardwire, and i recommend it to anyone with the larger than stock pump with higher than stock fuel pressure. I am tuning my 99 with V2 3.125 pulley, 3.5" CAI, 450cc deatschwerks, EU. Once i got up in the revs and around 10psi i could tell from the injector map(i have no gauge)that i was losing fuel pressure as my duty cycle was 95%, i just hardwired the pump and once i'm tuned to where i want to be i bet i won't be over 80%.