Hi guys,

My GP Tjet is fluctuating and sometimes not boosting as hard as it should; coming off boost and reapplying the accelerator will 99% of the time make for correct boost pressure.

I believe it could be the boost solenoid down by the radiator. Can anyone point me in the right direction of replacing this please?

Nick

The car was designed to have some overboost... what you feel when releasing and pressing the accelerator... after that the boost will fall off.
Overboost will also be less obvious if you are slowly revving the engine.. or if you are in a wrong gear

aurick86 said:

The car was designed to have some overboost... what you feel when releasing and pressing the accelerator... after that the boost will fall off.
Overboost will also be less obvious if you are slowly revving the engine.. or if you are in a wrong gear

Click to expand...

No, this issue I am experiencing is not normal. The car loses boost, but only sometimes. Sometimes I will go to accelerate and it will pull hard, other times it will barely pull at all, and to make it pull, I have to stop accelerating and accelerate again. I am changing the spark plugs and oil soon just as part of a service, and some people have said the same issue has been caused by a dodgy plug, but I'm not convinced. Others have said it's the N75 Valve / Boost controller. I need to know where to get a replacement so I can rule it out.

Also, the car is going into limp mode when I push it quite hard and it sits at high revs if I accelerate to a high speed.

What non standard tuning bits have you got on it?

Have you checked for codes with mes?


Cheers

You need to do actual diagnostics.
-it's tuned
-does it have any errors?
-are you running a bov?

You need to to a lot of diagnostics with MES in Graph mode, parameters that should be selected:
-rpm
-car speeed from CAN %
-accelerator %
-throttle %
-manifold pressure -mbar
-expected manifold pressure -mbar
-boost pressure -mbar
-boost solenoid %

Graph should be made in 2nd, 3rd and 4th gears, steadily accelerating from ~1200 rpm to 4500 rpm
You posted before with strange problems, to me it seems that it wasn't done right, and the ecu is cutting boost because it's not receiving what it's expecting.

Ecu can cut boost in multiple ways:
-boost solenoid,
-recirculating valve
-throttle valve
-spark timing
-injector cut-off

I've heard before about tunes that prevent the ecu from throwing /deleting error.

Okay mate. I think I'll take it in soon to be diagnosed on a dyno run. Thanks a lot.