boost problem

[red91tsiawd]

at full boost, the car has jerks of on/off power like its hitting the rev limiter but i know its not because its doing it from 4500 rpm on up, and when i don't get that, i get a holling noise????? any clues to why its doing this would help me lots, thanks

 

[red91tsiawd]

o and when i just slowly rev up to near the rev limiter, it goes right up there just fine without boost

 

[larryd]

its called fuel cut man.. turn down the boost

 

[red91tsiawd]

hmmmm, i have 550cc injectors, a 3000gtvr4 fuel pump, and the boost is set at 1.15 bar

 

[DamionGST]

Yeah it's probably because of colder weather (fuel cut) but you can get around it by getting an S-AFC and some bigger injectors (550cc). (Assuming you are not just running to much boost)

 

[red91tsiawd]

and by the way, SWEET car, i want it

 

[red91tsiawd]

and wuts the howling noise when its set at a low boost?

 

[larryd]

interesting.. so you have larger injectors, larger fuel pump, afc and your still hitting what appears to be fuel cut.. that aint right.. what are your AFC settings?

 

[red91tsiawd]

the afc isn't installed yet but it should be on monday (tomorrow), but the a/f is REALLY rich, as rich as it can be. wut should the afc be set at as a starting point?(is RRE's a good startingpoint?)

 

[larryd]

yes.. id base it off of RREs settings as a basepoint.

 

[Bohrn]

just a shot in the dark, but maybe he has a boost leak?? It pressures up and looses a bit, then the leak closes, and it pressures up again, and keeps going thru this cycle until he lifts. At partial throttle it doesn't build the boost high enough to make it leak.

Just a guess

 

[red91tsiawd]

now how do i stop the leak and where do i start looking for it?

 

[jw]

Either running too rich will bog or boost leak.
You can make your intake leak tester for < $10. Go to Home depot, pick up a plastic end cap (the size that will fit your turbo inlet). Get a tire valve stem from Hi Lo, drill a hole on the end cap that fit the size of the valve stem, put the valve stem in and JB weld the thing. Voila, you have an intake leak tester.

You can use either air compressor or air pump to do the job.

1) Use a coupler to mount the tester to the turbo inlet.
2) Setting the motor to TDC
- Remove the upper timing belt cover.
- Using a 1/2" extension from the driver side wheel well, crank (clockwise only) until the dowel pins on the cam gears are pointing at 12am and aligned the markings on the gears to face one another.
- If you look at the crank pulley marking, you should also see it pointing at TDC on the lower timing cover mark.
3) Remove MBC and cap off the nipple.
4) Start pumping with someone watching the boost gauge. Listen and fix all leaks.