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Discussion Starter #1
Alright, so I finally get around to installing my walbro 255 hp fuel pump today along with my turbo timer and hacked down my short shifter... all thanks to Joel for helping me with everything. Now heres the confusing part. Before installing the pump my fuel pressure was at 50psi for idle and rose to 60psi at wide open throttle. Now since the addition of the new pump and unhooking the battery and rehooking it back up the fuel pressure works like this. -20 to 0 vac on the boost gauge it rises like normal 50 up to 60 psi at wot. Then as boost now starts to spool up for every psi of boost I'm building there is another psi of fuel being shown on my fuel pressure gauge. This never happened before I unhooked the battery or put in the new pump. Is this normal or is something not right? I'm running 4bar fuel pressure and a aeromotive fpr. Don't know whether to be worried because of the change or relieved because this was supposed to be happening all along and now it finally does. Thanks in advance. Sorry for sounding like a noob this just doesn't seem right as I'm pushing 72psi of fuel pressure at 12 psi of boost. Seems like a whole lot of fuel pressure to be running.

David
 

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Do you have an aftermarket fuel pressure regulator to control the extra fuel?

Ju§tin
 

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Discussion Starter #3
Yup, I have the aeromotive fpr. The thing I'm noticing is how the pressure goes from 50 up to 60 psi while the vac. decreases from -20 to 0. When it's at 0 my fuel pressure is 60psi when that used to be my max fuel pressure no matter what it wouldn't go any further no matter how many lbs. of boost I was pushing. Just all the sudden when i change the fuel pump it starts doing this. And of course this isn't helping my running rich problem I'm having right now either. Since I've changed the pump I can tell a definite change in performance for the better. No more leaning out up top. But an actual richness up top now too. 17psi at around 6000 rpms cuts loose and spins tires now in 3rd gear but also backfires like a machine gun so I don't like to do it. Not near as bad when in 12 psi. But this whole change has really got me confused. I thought that having a adjustable fpr where it is at a 1:1 ratio meant for every psi of boost I was building that I would build a psi of fuel pressure. Or thats how it was explained to me. In which case that makes sense. But also on the other hand why have the extra 50-60 psi change in fuel pressure before boost? Is that just from the 50 at to the 60 at full wot. Meaning all the vac. is taken out of the lines? Kinda like with my boost gauge how it sits at -20 vac and then rev the engine and it goes to 0 and stops there until I'm actually in gear and then when the cars starts moving and the tires rotate the boost builds? Does the fuel pressure build as boost builds on the 1:1 ratio after 60 psi being the fuel pressure with no vac. left in the lines? Sorry for so many questions but this has got me kinda confused.
 

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I know that the Walbro fuel pump increases the fuel pressure. So I would set my fuel pressure again. Are you sure you are setting the fuel presure the right way?
Just to recap - You're supposed to do it while the car is idling properly. Then you pull the vaccum line off the regulator and set the fuel pressure to 58psi. And then put back on the line that you disconnected.
I would try it and see if that helps.
 

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Discussion Starter #5
But see the thing is that it still idles at the right psi of fuel pressure. Still goes up to 58-59 psi like it's supposed to when I'm at 0 vac/boost. It's just that now when boost builds for every psi of boost I build, it increases the fuel pressure by that many psi. It's just making me scared to push 12 or even push the stock eight because of how much fuel pressure I'm using.
 

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thats exactly what is upposed to happen...1:1
 

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Discussion Starter #7
But the thing thats got me is... is it supposed to be 1:1 from the idle fuel pressure and the rise from 50 psi on a 1:1 ratio with the boost... or is it after I make it to the point of 58-59 psi of fuel pressure and there's no more vac. left in the lines does it rise on a 1:1 ratio then? That's what has got me scratching my head right now.
 

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Discussion Starter #8
1:1 ratio then meaning as I hit boost... it then starts to go beyond the 59 psi of fuel pressure that I was normally running at wot to for instance 71-72 psi of fuel pressure at 12psi of boost? Is this correct? Or am I just running way too much fuel like I thought?
 

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yes, just at boost. because before you get to boost your not getting any "extra" air from the turbo just more air because of the tb being opened more.
 

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jason did your swap right? do you know where he got your fittings for the fpr, i remember him saying he was having trouble finding the right ones.
 

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Discussion Starter #11
I found the fittings thanks to Brent (Coach) online at Summit. But the problem with the aeromotive fpr is that you need to also order their self seeping o-rings along with the fpr or the fittings won't work right and you'll have leaks and they don't fit tightly. The fitting for the fpr are -6AN fittings which are fairly common. The o-rings on the other hand... are not.
 

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Discussion Starter #12
All in all just go with the Nismo fpr. Much easier to use and from what i can tell... a much better unit all around too. Just doesn't look as flashy. I may switch to the Nismo soon just because of more knowledge of that fpr on the forum and also because of all the woes I had with this thing to begin with.
 

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can you give me part numbers for the fittings and for the o-rings
 

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Discussion Starter #14
I'll look for them today. I know I have them laying around someplace. You're using the JGY rail right? The o-rings you have to order from aeromotive because I haven't found any place that carries them around here. I'll make sure and look for the fitting part numbers for you today. I'll look through all the paper work and stuff I printed out.

But to recap this fpr thing... going to 59-60 psi from 50 psi at idle is fine before hitting boost? And then after I hit boost... I build another psi of fuel on top of the 60 psi for each psi of boost I'm pushing?
 

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yes
 

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Discussion Starter #16
Ok so good thing is finally the fuel pressure on this thing is working right. And I won't blow up due to lack of fuel. Bad side is I need to tune this baby badly on a dyno to get her running perfect and be the monster she's supposed to be instead of pulling 14.6 and such at the track. My car needs tuning bad. :(
 

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your car looks good, and i really like your exhaust...it's 3in right? I was down at jasons working for him when your car was down there.
P.S. how did you change the title under your name IE: Shift_17psi... Backfire!
 

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Discussion Starter #18
Yeah 3" from the turbo back. No cat, resonator or anything. Just the test pipe and piping back to a N1 muffler. Andreas made it for me a while back. It's a beautiful exhaust. had to get one of the flanges rewelded to make it fit right cause of clearance issues and all, but it's a real nice piece I know of atleast 2 or 3 other people I've seen with this exhaust and they've all got nothing but good things to say about it.
 

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Discussion Starter #19
You have to wait until you have like 150 posts or 200 or something like that. I didn't change mine till a little over 200 so I don't know. I think it's at 150 though. Then there's a new option in your profile to let you make your own little thing under your forum name.
 

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Discussion Starter #20
And man has this thread ever gotten off topic. lol. Ah well. Thanks again. I'm glad everythings cool with the fuel pressure on my car and can drive it instead of babying it because I was afraid something was wrong.

David
 
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