Black6SpdTA

What's the AFPR to have? I'm ordering a Walbro 255 next week and was going to get an AFPR at the same time. I'm getting this stuff now so I can do the gear install and swap pumps at the same time because dropping the rear to change a pump must suck.

BTW, high or low pressure for the F/P?

aklim

I have an AFPR only because of the deal I got on it that made it better than the stock one. Currently I run stock pressure. Increasing the pressure just dumps fuel into the engine whether it needs it or not. Now, if you are trying to get better atomization and you are also changing the pulse width of the injectors, that is a different story.

Black6SpdTA

Whoa, I was under the impression they were one of the better mods. Sweet, less $

-Corey

Rice Killer87

i dont know about him,but when i had a close to stock TPI setup on my car,i had a Crane AFPR and it was great. u could definately feel a difference...especially in torque.

Black6SpdTA

I was thinking...I'm installing the gears/pump in a couple weeks. Would the pump be too much for the LO3? In which I'd need a regulator?

Superram 383 is going in this Summer.

aklim

You can wait on the pump till you have a problem. I changed the pump in my 91 last year because I was doing a tank. You can change gears without dropping the rear end, AFAIK.

Well, the AFPR will work if you can advance the timing to take advantage of it. However just upping the timing or cranking up the pressure will mean that it might be great at WOT but at some other point it might be too much.

If you do it thru the chip, you can adjust the fuel thru the pulse width and the timing advance curve and leave the at rest stock setting. My fuel pressure is stock pressure and timing is set at 6 deg. The advance and pulse width is set thru the EPROM. Otherwise, if you crank up the timing and fuel pressure, it will be great at WOT but may be too much when you are idling.

Black6SpdTA

I think so too. But we're putting the GTA rear in, it's a posi, so we're going to have to drop the rear anyway.

-Corey

dj haf

... my mechanic thinks i had too much fuel pressure (48 psi) and thats what caused me to loose compression in 5 cylinders... my plugs reeked of gas and were pretty much fouled up

aklim: if i were going to get a custom prom burnt, what psi would you suggest to keep the fuel pressure at? i have pretty much all the bolt ons... just need a larger tb and larger fuel injectors... i was planning on doing all the bolt ons, then get a new prom burnt for me, and then getting the MR, AFR heads and a big *** cam... then getting my chip re-burnt. have any suggestions on what i should do before i get my chip burnt? im pretty paranoid now on raising my fuel pressure to 48 again cuz i've got it in the back of my mind that that's probably the reason i screwed up my engine

aklim

DJ, I don't think so. That is unless youare running a carb. 45 psi is about where it should be. 48 is not going to be so rich that there will be tons of unburnt fuel washing down the cylinders.

I would start at 45 psi and then if the prom burners tell you to go higher then do so because they will have compensated for it. Fasterproms which is in your neighbourhood will be better able to guide you as to where it should be. Ask them for the diacom unit and or go to their place where they can take readings.

The larger TB and injectors will not help so why not wait till you are ready to do the entire intake and then go at it. I have a buddy with a stock L98 that went slower with the larger TB because the intake was still restrictive and causing some sort of air flow problem.

dj haf

my fuel injectors don't sound too good, thats why i was going to replace them... but your right, i should replace them later after im done with the h/c and intake since i'd be making more power. i think that my next mod is gonna be the prom, and then im going to start saving up for the intake, heads and cam - then go ahead and do a re-burn.

oo, btw. 2 things. 1) i actually think i had the fp at 49/50 psi for about a week, then the car died.... not 48. and 2) since my engine has to be rebuilt, im having my mechanic raise my cr to around 10:5:1... you think with that i should raise my fp to something higher than 45?

aklim

Don't know. When the engine is running then call Elieen Formato and have her tell you what to set it to since she is doint the EPROM. Like I said, I am running 10.8:1 and I am probably around 46. BTW, you are also going to the Ford injectors right? Those are 24 pph ones so they are larger than the stock 22 pphy ones so I would say that you can get away with it till the EPROM is finalised. How far are you from Tampa? If not too far you can run down and chat with them.

dj haf

bout 4 hours away... i think im down for a drive though, i need to take a lonngggg drive to break in the engine when the iroc gets back. do you think i should get larger injectors now, or when i get the MR, heads and cam? and what # injectors? thanks aklim

aklim

Well, if you do replace the injectors, your ECM might be able to compensate for a while till you get the intakes settled. How long till the other stuff gets on the car?

raul.garcia

Stock MFI 5.7L 350 fuel pressure is 40.5 to 47 with key on/engine off.
30.5 to 44 at idle. Mininum of 60 psi when return line is briefly pinched.

I'd do both the FP & AFPR, no doubt you're going to need them.

I have both from Holley.

aklim

Isn't the Holley one the same as the 255L Walbro or is that the Granatelli one? Well, I would change the FPR just because I am there and it might be getting old but that can wait till you do the injectors, whenever you are there.