boost referenced FPR?
boost referenced FPR? 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
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
Joined: Jun 2004
Posts: 1,501
Likes: 7
From: Ft. Irwin, California (But Virginia is home)
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
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
2. You want to put the FPR AFTER the rails and before the return. Run the retun back to the tank from the regulator.
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
http://store.summitracing.com/partde...5&autoview=sku
Joined: Jun 2004
Posts: 1,501
Likes: 7
From: Ft. Irwin, California (But Virginia is home)
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
http://store.summitracing.com/partde...5&autoview=sku
2. I have MotoTron 60lb/hr high impedence injectors.
3. The factory PCM uses high-impedence injectors.
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.
You'll want a return line with the regulator after the rails as said above.
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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
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
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Verdad Gallardo 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.
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.
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 
TECH Regular
Joined: Aug 2003
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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
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
Joined: Jun 2004
Posts: 1,501
Likes: 7
From: Ft. Irwin, California (But Virginia is home)
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
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
Ran the car like that for 2+ years w/ no issues. 
