Riffraff FRX
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Senior User
Joined: Jun 2012
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Riffraff FRX
Just placed my order with clay for the FRX for my '99. While I wait for it to show up thought I'd post a couple questions on it to the diesel gods lol. First I notice it comes with 3 springs for different fuel pressure levels, how do I know which one I want? I only have basic mods on my truck like cold air intake, 4" catback exhaust & an edge evolution programmer. Also is this something that kind of replaces the hutch mod in a way? Just as far as eliminating air in the system due to faulty fittings or coming from the tank? I am planning on doing the hutch mod still but figured this was a good first step. Thanks for any input guys!
Postmaster
Joined: Jul 2006
Posts: 4,993
Likes: 2
From: Bend, OR
Its a poor mans regulated return (a great product, just the easiest way to explain it)... It does not fix the fuel tank issues the hutch mod's do.
Without a fuel pressure gauge there is no way to know what pressure or spring to run.
You should have 65-70 psi most of the time.
Without a fuel pressure gauge there is no way to know what pressure or spring to run.
You should have 65-70 psi most of the time.
Postmaster
Joined: Jan 2012
Posts: 2,693
Likes: 3
From: West of Chicago
The instructions will tell you what spring to use I believe its the gold spring. I have the FRx and the Hutch mod done and it feels like a whole new truck. You might not notice a difference at first at least I didn't until I did the hutch mod. Those plugs are a bit of a pain a 7mm box wrench works the best for the plugs. you could try an 11/32 wrench but If they start to slip go with the 7mm!
9 ECHO 1
Joined: Aug 2009
Posts: 12,467
Likes: 58
From: Missouri
I recommend checking the fuel pressure before and after installing the FRx. In addition to having a before/after benchmark, you can verify the proper fuel pressure is being provided.
The FRx is on my list too. Poor man's regulated return is a good way to describe it. In my case it is the CA resident's regulated return. Still not smog legal, but a lot easier to fake.
The FRx is on my list too. Poor man's regulated return is a good way to describe it. In my case it is the CA resident's regulated return. Still not smog legal, but a lot easier to fake.
Postmaster
Joined: Apr 2012
Posts: 2,613
Likes: 8
From: North Georgia
I used the black spring because i lost the gold one under my hpop.
Hutch mod by itself cured the below 1/4 tank issues and quieted down the motor a lttle bit.
Frx quieted motor down a lot more and i saw improved throttle response. Ill say it again.
Shiznit-o-bam... snip snap salad.
Hutch mod by itself cured the below 1/4 tank issues and quieted down the motor a lttle bit.
Frx quieted motor down a lot more and i saw improved throttle response. Ill say it again.
Shiznit-o-bam... snip snap salad.
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Cargo Master
Joined: May 2010
Posts: 3,047
Likes: 10
From: Snohomish, WA
The stock pump is more than capable of the pressure. The FPR regulates it to 60-65. With the FRx springs you can tweak it by swapping springs.
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Postmaster
Joined: Jul 2006
Posts: 4,993
Likes: 2
From: Bend, OR
NO.
Higher fuel pressure does not mean more performance. Anywhere between 55 to 75psi will always be the same. Adjusting pressure is one of those things that you do to supply your injectors as much fuel as they need at 100% throttle.
Example... I dynoed 502hp with 62psi fuel pressure...
Higher fuel pressure does not mean more performance. Anywhere between 55 to 75psi will always be the same. Adjusting pressure is one of those things that you do to supply your injectors as much fuel as they need at 100% throttle.
Example... I dynoed 502hp with 62psi fuel pressure...
</O
Tuned
Joined: Oct 2009
Posts: 292
Likes: 0
From: Raleigh
I recommend checking the fuel pressure before and after installing the FRx. In addition to having a before/after benchmark, you can verify the proper fuel pressure is being provided.
The FRx is on my list too. Poor man's regulated return is a good way to describe it. In my case it is the CA resident's regulated return. Still not smog legal, but a lot easier to fake.
The FRx is on my list too. Poor man's regulated return is a good way to describe it. In my case it is the CA resident's regulated return. Still not smog legal, but a lot easier to fake.
Postmaster
Joined: Jul 2006
Posts: 4,993
Likes: 2
From: Bend, OR
No. There is no way for the PCM to know what the fuel pressure is. Need a gauge.
An air pressure or water pressure gauge can be used in a pinch for short term, off the drain valve.
