Iskwezm

why do you have a boost referenced regulator?

Norm Peterson

If you don't reference the fuel pressure to manifold boost, it'll run lean as the boost comes up. Manifold pressure still represents a resistance to fuel discharge, and if you could somehow achieve the silly case where boost = regulated fuel line pressure, you wouldn't get any fuel out at all.

If the car isn't FI yet, there may be plans to do so.


Norm

ic237

I gotta tell you I absolutly love your car!

Iskwezm

thanks norm for a answer i already knew.

I was asking becasue there is no reason to have a boost referenced regulator with no forced induction, unless i missed a hidden blower or turbo

Iskwezm

Thanks!

rsusmark

Hi Guys...the discussion about reference is correct....sort of in this instance. It's true that if you don't reference the BOOSTED manifold pressure, your fuel could be shut down but that is not why FAST put this on. (my car does not have a blower) The regulator you see on my car is the fuel pressure regulator and they reference the maniforld pressure so that the pressure to the injectors remains proportionate to not only the manifold pressure but atmospheric as well. Basically they are making sure that the A/F ratio does not change do to external changes. These injectors have the capability to feed a much large engine so they want to keep the fuel flow "in the box" by making sure the pressure delivered to the four injectors in the throttle body are the same, no matter what the loose nut behind the wheel does with the throttle or where he points the nose of the car...Pikes peak or the Mariana Trench. BTW, you guys can download the ENTIRE installation manual for this set up from FAST...makes interesting reading before you buy! Reid

Iskwezm

Thanks, i wasnt want aware of that.I went with a different brand, but still might put on on my boat that is a N/A 514 BB

ozarks06

As far as I know, return-style regulators normally reference manifold vacuum or boost. For boost, it raises the pressure to overcome the boost (39 psi + 10# boost requires 49 psi for the same fuel flow). For vacuum, it reduces the pressure to correct for that. Without correcting for vacuum, the injectors would spray too much fuel since the injector flow is calibrated for a given pressure drop (not absolute pressure at the injector). To set the base pressure, you check with the engine off since it will drop with vacuum (mine is set for 39 psi but at idle it's about 28 psi).

67 evil eleanor

Very good explanation. Norm is correct as usual.