durty

iTrader: (3)

im putting a 4.8 into my 93 fox body, the 4.8 has TEA stage 1 241s, and a custom comp grind, .563/.571, 113+4 i believe. going with a MPt70 .68 exhaust side

anyway, i was looking at running 42lb injectors with a boost referenced FPR, but after searching ive found that people are just upping the fuel pressure, and not running the boost referenced FPR, wouldnt that make it run fat on the bottom?...i figure with the 42lbers and a 1:1 FPR it would idle decent and still provide the fuel i need, planning on referencing before the t/b blade, so it wont see vacuum

am i gonna run into problems doing it this way?..im not really shooting for a certain hp number, as i dont care how much power it makes, just what number it runs, looking to go deep into the 10s if possible

also will i be able to run returnless fuel rails with an external return style FPR? running one of the outlets off the the FPR to the rails and the return back to the tank?

before anyone goes off on the 4.8, only reason i have the 4.8 is cause i got it dirt cheap, so once it blows or i scrounge up some funds ill pick up a 6.0 shortblock and a second t70

Schantin

iTrader: (6)

1. I still run an Aeromotive A1000 regulator. Referenced it before the throttle body in the intake track like you stated. Worked fine when I was boosted (I capped the reference line now that I'm NA). Makes tuning easier cause you only need to tune for the "boost compensation" and not the wide swing in pressure between light crise vacuum and full boost.

2. You want to put the FPR AFTER the rails and before the return. Run the retun back to the tank from the regulator.

03 snake

iTrader: (28)

What he said.. A1000 here too.

durty

iTrader: (3)

so i will need return style rails?...the returnless rails only have the single inlet, this the regulator you running? what injectors where you running?...the factory computers are setup for high-impedance injectors right?

http://store.summitracing.com/partde...5&autoview=sku

Schantin

iTrader: (6)

1. I run SpeedInc aftermarket rails.
2. I have MotoTron 60lb/hr high impedence injectors.
3. The factory PCM uses high-impedence injectors.

durty

iTrader: (3)

aeromotive 13101?....

thanks ALOT for your help, really appreciate it

calongo_SS

iTrader: (7)

Why would you not want a boost referenced regulator to see vacuum? It should see both boost and vacuum, that's kind of the point of it. You want the fuel pressure to remain constant relative to manifold pressure.
You'll want a return line with the regulator after the rails as said above.

durty

iTrader: (3)

if the FPR sees vacuum it will pull fuel pressure, from what i have read on here 20 inHg equals close to 10psi fuel pressure, id rather not have the fuel pressure swing from 48psi at idle to whatever it ends up being(58psi fuel pressure+10-15lbs), i ran a blow thru carb on my old 302 coupe, and i had to reference it at the carb hat so it wouldnt see vacuum

if it sees boost only then it should retain the correct fuel pressure at idle but only add fuel when needed

please correct me if im wrong but thats how i thought it needs to be

calongo_SS

iTrader: (7)

No, I'd think that will give you tuning problems.
You set your base FP @ atmosphere (say 50 psi) when you are pulling 20 inHg of vacuum your FP gauge will show ~40 psi, 10 psi of boost 60 psi FP. But the FP at the injector relative to manifold pressure will remain constant. That's a big benefit of a BR FPR. You can set your IFR constant all the way across the board because the pressure in the rails will remain constant relative to manifold pressure.

Having less FP at idle and part throttle helps tuning with large injectors also b/c sometimes it can be difficult to get them to stop dumping so much fuel, lower pressure = less fuel dumped per pulse.

durty

iTrader: (3)

so reference after the blade then?...im guessing the need to reference before the carb on a blow thru setup is due to the low base pressure, 5psi base pressure - 5-10fuel pressure would not be good

Vetal

iTrader: (3)

What inexpensive boost-referenced FPR can I buy?

T6Rocket

To the OP: you have to run a boost referenced FP on a boosted car. That info you read on the internet is BS.

If you set your base fuel pressure to 40 psi with a boost referenced FP regulator, you will ALWAYS have the equivalent of 40 psi when the car is running, regardless if you are in vacuum or boost.

If you are running 20 psi of boost, the fuel pressure rises to 60 psi, BUT the effective FP is still 40 psi because the 20 psi of boost is overcoming 20 psi of fuel pressure.

Same thing when under vacuum, the fuel pressure appears to drop to 30 psi, but the engine vacuum pulls the effective FP back to 40 psi, or at least uses the same amount of fuel.

Turbo FI cars come from the factory with the FP seeing vacuum and boost. Sure, you could tap the line in front of the throttle body so it doesnt see vacuum, and it should give you the same FP, but why make something simple complicated!

Al

Schantin

iTrader: (6)

Nothing complicated about it at all. I found that trying to calculate the FPR for all vacuum conditions a bigger PITA (cause the stock injector tables do NOT work in the above described manner, though it is logical). I set the values as if NA and then reduced the pulse-widths in the low RPM cells so the bigger injectors didn't over-fuel. Guess you could call this more more complicated, but it seemed easy to me when I did it Ran the car like that for 2+ years w/ no issues.

BLWN1

iTrader: (6)

what I was lookin for.....