Rb26 Power Issues - Boost Leak?

[R31 Gagz]

Hi Everyone,

Since my last tune at Racepace, I have had an ever present problem with the GTR. I was led to believe at first that it was a boost leak but I'm not so certain anymore.

The problem is that you start feeding on the power and can hear the boost building but you don't go anywhere. It is usually really bad when the cars only been running for 10min after having been off for a while, once she's warmed up properly I slowly feed on the boost in 3rd or 4th gear where the leak (supposed leak ) manages to stay closed and I can built boost with good power...after doing that then I pretty much can floor it in 1st gear and it will hold good boost and make good power, taking off through all gears. Sometimes the "leak" will come back a little bit and I have to ease it on with 3rd or 4th gear again. Sounds weird but that's the best I can explain it. I'm pushing 320awkw so I know when its not making power and when it is , its really annoying not knowing whether its going to be there or not, I loose confidence with the car in what its going to do and also loose the enjoyment of the power on tap.

I have double checked most of my intercooler piping that I can get to, the ones I can't haven't been touched for a long time and from what I can see shouldn't have any leak issues, we've also gone around with an alcohol/meth solution spraying all vac lines and such to try and see if it bubbles or changes the engine note to look for leaks, that didn't turn anything up.

So any suggestions on what it could be, things to try would be very much appreciated. Currently I don't have the money to take it to a workshop otherwise I would consider doing that so I can get on with enjoying me car

Thanks,

Craig

[Moodles2]

Could possibly be the fuel pump if it's the standard one.

[R31 Gagz]

Could possibly be the fuel pump if it's the standard one.

What's your reasoning behind that? Why would it not work then work fine after my method to get the power back? Plus it has worked flawlessly for 4 years on this power level. Not saying your not right but would like to know your reasoning, what makes you think it could be the fuel pump?

Cheers!

Craig

[payback21]

Boost controller, vacum lines to boost controller and wastegate, or prob with waste gate? sitcking and isnt fully shut to get boost?

Just taking a stab out of the dark here. Anything is possible.

[CGB_R32]

Am experiencing somewhat of the same issues with the hearing the boost building but not really going anywhere however after this i get like a stuttering effect....and after changing gears (any for that matter) it seems to disappear and come back intermittently ive replaced my plugs, and wacked in some spitfires i thought it may have been a spark issue however this hasn't fixed the problem im a little bit new to the gtr after coming from a gtst so im still a little uncertain with my assumptions however a new fuel pump will be going in this week as i thought it may have been a fuel issue and the stock item is on the way out so I will keep you posted. My other though is a dodgey AFM but seeing as you've had a tune i'd imagine this wouldnt be the case (especially if your not running AFM's)

[R31 Gagz]

- Actually still running the two standard AFMS, never had a prob with them.

- Boost controller is just a bleed valve set statically to 20psi.

- Checked the blow off valves, they seem to be holding vacuum fine.

- Not sure how to check the wastegates, anyone please??

CGB_R32, if you could let me know how you go with the fuel pump and whether it fixes the problem that would be great

Cheers!

Craig

[Moodles2]

What's your reasoning behind that? Why would it not work then work fine after my method to get the power back? Plus it has worked flawlessly for 4 years on this power level. Not saying your not right but would like to know your reasoning, what makes you think it could be the fuel pump?

Cheers!

Craig

No mods, or supporting mods were mentioned, just assumed you had a stock pump. I'd be checking for error codes/sensor failures. AFMs dry solder might have deteriorated on one of them.

Should be able to disconnect the bleed valve, and hook up a air compressor in it's place (wastegate source).. Even with all the intake piping in the way should be able to get a view of both wastegate actuator rods moving at whatever PSI the actuators are set to.

Do you have HKS style split dumps? The wastegate flap could be fouling on it if so.

[R31 Gagz]

No mods, or supporting mods were mentioned, just assumed you had a stock pump. I'd be checking for error codes/sensor failures. AFMs dry solder might have deteriorated on one of them.

Should be able to disconnect the bleed valve, and hook up a air compressor in it's place (wastegate source).. Even with all the intake piping in the way should be able to get a view of both wastegate actuator rods moving at whatever PSI the actuators are set to.

Do you have HKS style split dumps? The wastegate flap could be fouling on it if so.

It could be the stock pump...never checked...the whole car was rebuilt ground up around 5 years back so it most likely had a new one installed if not an aftermarket one to support the HP they installed the other supporting mods for (sard 800cc injectors) but its pretty quiet so I assumed its a stock one. Would you expect

Thanks for the tips on checking the wastegates, will do that ASAP...checking for error codes though will require me getting a hand controller for the apexi power fc which won't be happening for a while ...or do they still have little LEDs on the outside and a screw to turn it into diagnostic mode?

Cheers!

Craig

[CGB_R32]

Just got the car back from the workshop, they tested the fuel and it turned out to be perfect so it wasnt a fuel issue, ended up being a faulty AFM that was causing the stuttering and lack of power, so if you can try and grab a hold of another AFM and test them out. Theres a few floating around the for sale section. Michael