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Old 10-26-2000, 10:15 AM   #1
DaveK
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Join Date: Sep 2000
Location: Colorado
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1988 323 GTX
black

Question Rrfpr

I'm planning on buying a turbo kit in the next year. I saw that JC Sports recommends the RRFPR for their kits. I'm also trying to spread out purchases by buying some things the kit doesn't include...
Is the RRFPR necessary with an upgraded fuel pump?
Is this something that will give me any HP gains while the car is N/A?
Will it help to eliminate the flat spot at about 4000?
Or will it just hurt my gas mileage and make the engine run rich?

Engine Mods: AMSOIL air filter
Unorthodox Racing Pulley
straight thru muffler

Thanks for any suggestions
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Old 10-26-2000, 11:32 AM   #2
Tim Prudence
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The whole point of a rrfpr is that it raises fuel pressure when it senses boost, so, it would do nothing for a N/A vehicle.
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Old 10-26-2000, 03:51 PM   #3
Tim Prudence
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DUDE! Like I said previously, a rising rate fuel pressure regulator increases fuel pressure when it senses boost. A 5:1 rrfpr will increase fuel pressure by 5 psi for every 1 psi of boost. If you are running 5 psi of boost, then you will get an additional 25 psi of fuel pressure.

Note - the stock fpr and aftermarket adjustable fprs will increase fuel pressure with boost at a 1:1 ratio. The only reason you would need a rising rate fpr is because under boost (with stock injectors at least) you may need a lot more fuel pressure (depending on how much boost you are running).

Adjustable fprs are just that, adjustable. The stock car comes with the fuel pressure set at about 30 psi at idle. If you have a high flowing fuel pump, the tiny stock fpr will become overworked and feul pressure will rise up to 40 psi at idle. If you have an adjustable fpr then you can lower it back down to normal. The only way you can gain power from an adjustable fpr (like weaponR) is if you are running lean at the top end, you can crank up fuel pressure and regain the power you lost because of the lean condition. However, this has the adverse side effect of raising fuel pressure everywhere in the power band (including at idle) and you will most likely have to deal with a rich idle. Something like an AFC gives you more control over where extra fuel is added.
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Old 10-26-2000, 04:45 PM   #4
DaveK
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I tried doing some searches on the RRFPR, and didn't come up with much, so I asked the question.
Your second explination makes alot of sense to me now that I understand generally how/what the device is doing.

Thanks for clearing that up
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Old 10-26-2000, 09:42 PM   #5
ImprezaRS dot com
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Talking

I am using a plain fuel pressure regulator borrowed from JC Sports until I get my RRFPR instaled with my turbo kit. This is similar to the weapon-r regulator.

I find what Tim says is right on - If I increase fuel pressure to 45-55, the turbo loves it, but the car stumbles driving off from idle and is too rich at low rpm. If I drop fuel pressure to 35-40, then it is fine to about 5,000 rpm.

Imprezer had a write up on his car in Tuning Concepts Magazine a while back, with intake and exhaust (no turbo) and he was using a weapon-r fuel pressure regulator to bump to the low 40's and improve power.

I plan to run my Bell 20007 RRFPR at 35-40 psi idle, and it will climb to 85 psi at 7 lbs boost. We will then tune the fine points with my APEXi S-AFC if needed.

Larry www.ImprezaRS.com
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Old 10-27-2000, 12:16 AM   #6
DaveK
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Weapon R makes a fuel pressure riser that they claim is good for 5-10 (???) HP. So what is the difference between this and a RRFPR?
Is it that the RRFPR only increases fuel pressure if it senses that there is an increase in fuel demand on the engine?
Would you need this if you have a higher flowing fuel pump?
Thanks again for the replies.
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Old 10-27-2000, 09:21 AM   #7
DaveK
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Larry,

I thought I came across a post on here that said you would be at JC Sports on Saturday?
If this is correct would you mind if I showed up to check out your setup?
Thanks
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Old 10-27-2000, 01:45 PM   #8
DaveK
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Cool

Sounds good. I will try to show up around 10 or so. Hope all goes well
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Old 10-28-2000, 12:27 AM   #9
ImprezaRS dot com
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Saturday 28th - I will be at JC Sports for these things in the order of importance (#1-3 are mandatory) - feel free to visit as long as you don't try to talk to John and slow him down

1) ACT clutch (I'm passing on the 12lb flywheel though - my wife won't like it)
2) RRFPR (maybe a fuel pressure gauge to mess with it myself)
3) Redesigned downpipe that doesn't scrape my wierd steep driveway with my lowered car
4) Blitz turbo timer (I picked up locally)
5) Intercooler water sprayer
6) Pizza and finish turbo kit install instructions.

Larry www.ImprezaRS.com
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Old 10-28-2000, 01:06 PM   #10
Kwez
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quick note: if you DO have a stronger fuel pump (again not needed when n/a), then a adjustable fpr is very good idea so that you can adjust the base idle fuel pressure back to something closer to stock. (We fixed a prob w. my s/c install that way)
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