kevyn_rx7

iTrader: (9)

ok so i posted a thread a few weeks ago about how my car was bogging out around 4k rpms after my friend installed a boost gauge onto the fuel pressure regulator. another friend pulled the boost gauge lines and we discovered that a vac. line was missing that ran to the fpr. we are quite puzzled.

when we installed the boost gauge, the car was down for about a month because the same friend who did the boost gauge install messed up the water pump and we had to pull that from the block (you'd think i'd learn from my mistakes and not let him work on the car anymore...) in that time we also pulled off the emissions stuff and i installed block off plates/vac line caps where necessary.

i ran a vac line from a nipple under the bac to the fuel pressure regulator/boost sensor... still bogs out.

the reason i ran a line from the nipple under the bac to the fpr is because we were all of the sudden missing a vac line to the fpr... is it possible that hidden somewhere under the uim i have a vac line that is just open and causing the car to bog?

note: the car only bogs out when you punch the gas. if you bring up the rpm's slowly it does fine (i only bring it up to 5-5.5 k rpms)

any advice? should i pull the uim and go vac leak hunting?
thanks

RotaryRocket88

iTrader: (7)

The nipple you used is a vacuum source, so it's fine to have the boost sensor and FPR connected there. But if you had a nipple uncovered somewhere it would not create major problems. All it would do is make your idle a little unstable.

The problem you're having sounds like fuel cut fuel due to overboosting. If your exhaust or intake are modified, this is very common on the stock wastegate. S5 turbos run 7.5psi max, and fuel cut will happen at 8.6psi. 4k RPM is the prime location for boost creep to happen. Your options will be adding some restriction back into the exhaust/intake or porting the wastegate. If you're unable to port the wastegate, and option like the Rtek 1.5 chip (www.pocketlogger.com) will remove the fuel cut, but the downside is you will have to be very careful in making sure boost does not spike beyond about 9psi on stock fuel. Uncontrolled boost creep can easily destroy an engine if it is bad enough.

kevyn_rx7

iTrader: (9)

that makes perfect sense because i did have a full 3' exhaust and i did a custom TID also.
but i have a fuel cut controller on the car, would that still not prevent this problem?

thanks for all the help since i've been on the forums. i really appreciate it.

kevyn_rx7

iTrader: (9)

would an option be upgraded/ported waste gate?
i may just buy a new one

RotaryRocket88

iTrader: (7)

An FCD would prevent fuel cut, so if that's connected, it's going to be something else. It fit the description though. Start pulling codes and testing components like the boost sensor, AFM & TPS. The FSM has info on this.

Side note: you can't just buy a different wastegate. The stock turbo uses an internal wastegate design, so you would need to port it. http://www.fc3spro.com/TECH/HOWTO/KWG/kwg.html