Won't boost over 0.5 bar in parallell mode - wastegate problem?

[halllon]

Hi guys,

 

We are running a VVTi 2JZ on a custom Autronic map and thus running the stock VVTi J-spec turbos in parallell mode (having removed all the stock sequential system valves).

 

We have installed a manual boost controller and set it to peak at 1.4 bar in the mid range and drop to about 1.2 bar approaching redline. We know this is pushing the stock ceramic turbos a bit far. Power is 455whp at this pressure, so the turbos are maxed out.

 

During a race last weekend the engine started loosing boost and it's now peaking at 0.7/0.8 bar before rapidly dropping to 0.5 bar where it stays throughout the redline. What is causing this?

 

1. Both turbos look perfectly fine, with the correct axle play and both exhaust wheels are intact.

2. There are absolutely no boost leaks at the pressure side.

3. There is some oil in the intercooler which we believe is perfectly normal given the performance of the engine (the car is driven hard in drifting coompetitions)

4. The engine is fuelled on E85 (85% ethanol, 15% gasoline)

5. The wastegate actators "feel" perfectly fine and we have compared them to other ones.

6. There is no difference in boost characteristics if we unplug the boost controller and vent the wastegate actuator connectors to open air.

 

We are now swapping out the actuators with ones from another twin turbo set to check whether this solves the problem.

 

Are there any other points we should address? Have any of you experienced the same issue, e.g. not getting the engine to boost properly, where it has not been caused by a knackered turbo/boost leak, but rather a wastegate problem, etc?

 

All answers appreciated! We are in a hurry and need to solve this asap.

 

Cheers in advance!

 

Freddie

Edited July 7, 2009 by halllon (see edit history)