I have been hearing a lot about this on the Skyline forums. Supposedly we need a regulator upgrade if we go with a larger fuel pump (which I have... walbro 255l/hr high pressure) and/or larger injectors.
This has been an unclear issue for me... and I was hoping someone here could clear it up. If we do need one can we use some of the american units from some of the supercharger companies (I have never heard of any from the Japanese companies)?
Thanks,Sig
Fuel regulator upgrade
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rbsileighty
- Posts: 1694
- Joined: Sun Feb 09, 2003 8:10 am
- Car: 92 S13 Hatch w/ RB20 & 05 Audi S4 Avant 6MT
You should only need an aftermarket fuel pressure regulator if the Walbro pump moves enough fuel at idle to overrun the stock fuel pressure regulator. In other words, at idle, the amount of fuel used by the engine + the amount of fuel that the reg can return < the amount that the pump pumps at that fuel pressure.
What happens is, the pressure goes up until the amount of fuel used by the engine + the amount of fuel that the reg can return = the amount that the pump pumps at that fuel pressure (and since when pressure goes up, flow goes down, this balances out at a higher pressure).
But from the most reliable sources I have, the Walbro pump doesn't pump enough to cause a problem like this on KAs or SRs, and I am pretty sure the RB reg is internally the same, so it shouldn't be a problem.
Now, a lot of people upgrade to a Z32 TT pump, which moves more fuel than even the largest Walbro, and does cause this problem on KAs, SRs, etc.
You should be fine with the Walbro pump. Regardless, it'll only be a problem of running rich at idle, not everywhere else (since as you get off idle, fuel pressure goes up anyways, as does fuel consumption by the engine).
Dennis
What happens is, the pressure goes up until the amount of fuel used by the engine + the amount of fuel that the reg can return = the amount that the pump pumps at that fuel pressure (and since when pressure goes up, flow goes down, this balances out at a higher pressure).
But from the most reliable sources I have, the Walbro pump doesn't pump enough to cause a problem like this on KAs or SRs, and I am pretty sure the RB reg is internally the same, so it shouldn't be a problem.
Now, a lot of people upgrade to a Z32 TT pump, which moves more fuel than even the largest Walbro, and does cause this problem on KAs, SRs, etc.
You should be fine with the Walbro pump. Regardless, it'll only be a problem of running rich at idle, not everywhere else (since as you get off idle, fuel pressure goes up anyways, as does fuel consumption by the engine).
Dennis
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rbsileighty
- Posts: 1694
- Joined: Sun Feb 09, 2003 8:10 am
- Car: 92 S13 Hatch w/ RB20 & 05 Audi S4 Avant 6MT
-
rbsileighty
- Posts: 1694
- Joined: Sun Feb 09, 2003 8:10 am
- Car: 92 S13 Hatch w/ RB20 & 05 Audi S4 Avant 6MT