sudden boost ,equals sudden fuel pressure, equals bad !

[shadowdude]

My fuel pressure is spiking right in synce with my boost with the RRR @ 4 to 1,so i am trying to figure a way to get a more smoother transition up to my max of 22psi .the grainger valve is giving hight to full boost @ half throttle ,when it does it throws my fuel pressure right up there to.This causes the car to get 75psi at half throttle ,that does not work very good,it spits and sputters and practicaly dies ,then if you play with the throttle and jam it then it takes off very hard and sorts itself out.so my question is ,does anybody have some ideas how to control this sudden increase of boost ?? I am still thinking it through but am also open to any thing you have to offer to .It would speed the fix up for sure. thanks ,The only thing i can think of is to two step the boost ,with a switch,run ,say, 14 psi one one end then when i hit WOT a micro switch will activate the 22 psi side.

[86Shelby]

I like the micro switch to stage the boost.

[puppet]

Say ... couldn't the fella stage the RRR? If 4-1 is what you need at WOT ... maybe a bleed could dial you in better at part throttle.

[shadowdude]

Yea a bleed to stage the RRR .I had kind of thought of that before ,I was thinking of bleeding the boost to the RRR to lower ,or regulate the ratio ,but with the bleed right in the line coming off the intake wouldn,t that cause boost drop though ?

[BARRON]

Hey Shadman!

..dosent a custom cal and larger injectors eliminate all this? I am just wondering because I want to be able to go this route instead of all this...fiddling?

[puppet]

Yea a bleed to stage the RRR .I had kind of thought of that before ,I was thinking of bleeding the boost to the RRR to lower ,or regulate the ratio ,but with the bleed right in the line coming off the intake wouldn,t that cause boost drop though ?

Guess you'd need to experiment as to how big a bleed you'd need to cut the ratio down to a decent level at part throttle. I can't imagine the hole being big enough to screw with your boost. The bleed would be by-passed at WOT anyway. Sort of like Gus's staged boost affair.

[iTurbo]

I have the same problem on my cars. It will sputter bad if the boost gets too high at part throttle. It may not be your fuel pressure, because my cars do it with +20s and stock fuel pressure regulator at stock base pressure, if the boost rises much past 15-16 psi at part throttle. The stock computers really don't like seeing too much boost at low TPS values. I think a WOT micro switch to engage a higher boost level would be optimal. Keep the part throttle max boost around 12 psi. Your engine will be a lot safer and you'll have better driveability.

[shadowdude]

Well ,i lowered the boost down to 14psi to test the car at lower boost levels ,with the idea that lower boost means lower fuel pressure @WOT with the RRR.then i did some charts and stuff and with a four to one rising rate @14psi witht the injectors and stuff i have will give 46psi @ WOT,just what i need low pressure around town .so i have a micro switch and am planning on adding the high boost side to the car as i type.As iTurbo siad ,the two stage is going to be the way to go from what i can tell.keeps you posted

[shadowdude]

OK ,well finally after A LOT of swearing i got the car to behave normal at 12 psi,went back through the RRR bleed and found it wasn,t bleeding enough even with the vale i was using.so anyways got that fixed ,BUT AS ALWAYS WITH THIS $*&^ CAR, i have yet another problem now .I have a map cut raiser installed ,it is black to ground and red to the green with red tracer.all connections are good ,tested it with an Fluke meter and it does work cause i can see the resistance of the pot in there going up and down as i turn it,but not matter how high or low it is turned ,it will not stop cutting out from over boost.the weird thing is this ,when i first start the car and go out for a run ,it doesn,t cut out and works well ,but after ,say 3 or four minutes of driving it starts cutting out every time,...stop the car shut it off wait for 5 -10 minutes and it doesn,t cut out again ,but drive for a bit and it does it again.any ideas ?? i am stumped??

[shadowdude]

DAMN IT !! blew my TII turbo,stupid me got greedy and ran it wide open,that was a stupid and exspensive mistake.

[cordes]

The 4:1 RRR is way too much. You would be better served with a custom cal. It would be much less work, and about the same price in the end.

[shadowdude]

I agree,but believe it or not I finally got the car figured out.i blead the line going to the RRR to "adjust" the Rate.it now runs (well i mean it did run ,when turbo was good)12psi around town smoothly and when i go full throttle the 22psi comes on and overall the car runs perfect now .but i still agree with you on the cal cause it sees 72psi of fuel pressure at WOT.To much and i dont want to start jamming loads of boost to tune it to the amount of fuel.275 WHP is all i want at a decent boost level.