FPR question: auto FP boost when less vacuum?
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From: MA
Car: 93 GM300 platforms
Engine: LO3, LO5
Transmission: MD8 x2
FPR question: auto FP boost when less vacuum?
Forgive me in advance if this is a stupid question:
Does anyone make, or has anyone made their own, fuel pressure regulator (FPR) that has both a manual static pressure adjustment as well as a load-sensitive (via vacuum connection) automatic adjustment that will slightly boost the fuel pressure as WOT is applied (and manifold vacuum drops to zero)?
example: the static FP is set to 12 psi and it stays at 12 psi during normal driving. During a moderate throttle opening, the vacuum in the intake drops from 17 in-Hg to 9 in-Hg, and a vacuum signal through an orifice delay then causes the FPR to increase the FP to the TBI from 12 psi to 13.5 psi.
a second example: like the above, 12 psi during normal driving. At WOT, the intake manifold vacuum goes to 0 and the FPR increases ramplike from 12 to 15 psi in no more than a second.
I'm asking this because it occurs to me that, short of doing a proper ECM recal for various engine mods, a cheap shortcut would be to have a vacuum sensitive FPR that would automatically increase the fuel pressure to the TBI injectors (thereby providing more fuel) but only under severe load (no vacuum), and with some transition zone in between.
The vacuum signal is damped via a small orifice plug in the vacuum line from the manifold to the FPR. The delay might be needed to prevent vacuum signal oscillations to the FPR as well as to let the FP to the TBI to ramp up, assuming that the motor couldn't instantly use the extra fuel anyway.
The benefit would be a crude but effective way to get the extra power from moderate TBI mods without an ECM rework... and the normal part throttle driveability, fuel economy, and emissions should be mostly unchanged. Motor mods to ECM controlled cars don't respond well because there isn't any extra fuel being supplied to match the extra air the mods provide... unless the ECM is reprogrammed. And just bumping up the FP for all conditions might make the WOT results good, but the part throttle driving will be too rich, the motor will be a slug, and the fuel economy will suffer.
I suppose there would be no reason why this couldn't apply as well to a TPI car so long as the manifold vacuum were taken in the plenum and not near the runners.
Lastly, you woundn't need to do this on a carb because carbs self-regulate the fuel supplied, and the fuel pressure to feed a carb is only needed to keep the carb's fuel bowl(s) fed.
TIA and sorry if this one has been answered before. - Ken
Does anyone make, or has anyone made their own, fuel pressure regulator (FPR) that has both a manual static pressure adjustment as well as a load-sensitive (via vacuum connection) automatic adjustment that will slightly boost the fuel pressure as WOT is applied (and manifold vacuum drops to zero)?
example: the static FP is set to 12 psi and it stays at 12 psi during normal driving. During a moderate throttle opening, the vacuum in the intake drops from 17 in-Hg to 9 in-Hg, and a vacuum signal through an orifice delay then causes the FPR to increase the FP to the TBI from 12 psi to 13.5 psi.
a second example: like the above, 12 psi during normal driving. At WOT, the intake manifold vacuum goes to 0 and the FPR increases ramplike from 12 to 15 psi in no more than a second.
I'm asking this because it occurs to me that, short of doing a proper ECM recal for various engine mods, a cheap shortcut would be to have a vacuum sensitive FPR that would automatically increase the fuel pressure to the TBI injectors (thereby providing more fuel) but only under severe load (no vacuum), and with some transition zone in between.
The vacuum signal is damped via a small orifice plug in the vacuum line from the manifold to the FPR. The delay might be needed to prevent vacuum signal oscillations to the FPR as well as to let the FP to the TBI to ramp up, assuming that the motor couldn't instantly use the extra fuel anyway.
The benefit would be a crude but effective way to get the extra power from moderate TBI mods without an ECM rework... and the normal part throttle driveability, fuel economy, and emissions should be mostly unchanged. Motor mods to ECM controlled cars don't respond well because there isn't any extra fuel being supplied to match the extra air the mods provide... unless the ECM is reprogrammed. And just bumping up the FP for all conditions might make the WOT results good, but the part throttle driving will be too rich, the motor will be a slug, and the fuel economy will suffer.
I suppose there would be no reason why this couldn't apply as well to a TPI car so long as the manifold vacuum were taken in the plenum and not near the runners.
Lastly, you woundn't need to do this on a carb because carbs self-regulate the fuel supplied, and the fuel pressure to feed a carb is only needed to keep the carb's fuel bowl(s) fed.
TIA and sorry if this one has been answered before. - Ken
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