lcheater

Hi,

Since getting my RB5 back from having the gearbox replaced it hasn't been boosting properly. It boosts but I can hear what sounds like pressure escaping from somewhere in a chattering fashion and the boost feels like it is fluctuating / flattening off a bit at the same time.

Now, before people start blaming a loose hose etc, the gearbox was replaced by a good friend of mine at his own garage. He took the car back in after i reported this problem to him and he took the TMIC back off, inspected the hoses and re-fitted it. That was the only thing he removed to get to the gearbox. We then thought the actuator was not holding pressure so we replaced the vacuum hoses going from the turbo to the T-piece and from the T-piece to the actuator, tested the actuator using a pressure / vacuum tester and it was all OK. However, in replacing those hoses, we didn't realise that we had done away with the restrictor pill (it wasn't until i googled it, i realised what it was for)! So we refitted the bit of hose that the pill was in and it all seemed to be OK. However, it wasn't long before it was back to losing boost again! I cant think what is leaking, unless something is telling the car to back off and the leaking that i can hear is through the waste gate...

Sometimes during full boost, the car will cut off completely for a split second, i.e it feels like a very shocking sudden power loss - im guessing that is the car thinking it is overboosting and cutting the power? I hate it when it does this because it feels horrible and cant be doing the engine any good!

I have read this thread: https://www.scoobynet.com/scoobynet-...-weak-bov.html and some of what people said in there does sound like my symptoms, and i am running a VF35 too. The thing is though, is that i wasn't experiencing the problem in the 4 days i owned the car leading to it having the gearbox replaced...?

The car is running a simtek ECU mapped by Bob Rawles, large downpipe back exhaust with single sports cat, K&N cone filter, HKS TMIC and turbosmart Dump Valve. Bob Rawles guesses it is running at 330ish bhp.

I have read about 2 and 3 port boost solenoids and wondered if i could have a faulty solenoid? I have a 2 port, see pic below.



Any help in sorting this out would be appreciated.

Big 'D'

VF35 turbos are very prone to boost creep especially when running a full decat, do you have a boost gauge fitted to your car?

Cheers Iain

lcheater

Hi, no I don't but it's something I will be buying and fitting soon! Any idea on how to stop the boost creep you mention?

Joe will

iTrader: (9)

replyed on rb5oc bud.

Big 'D'

To stop the boost creep you will need to port the wastegate, to test to see if you have boost creep you will need to first get your boost gauge, then connect a hose directly between the turbo outlet nipple and the actuator so you are running on wastegate pressure only. Then go for a drive in 3rd and 4th gear from about 2500rpm, if the turbo holds approx 0.5 bar then you have no creep, if the boost continues to rise well beyond 0.5 bar to over 1.0 bar then you have boost creep, it is not something that can be mapped out or mechanically tuned out it is simply that the wastegate port itself is too small to allow enough exhaust gas to bypass the turbine to ensure correct control of the turbo.

Cheers Iain