hi,
can someone tell me what size the dawes device needs to be drilled out to on a ukMY99 to prevent boost spikes?
cheers

 

I believe they should be pre-drilled to 1.5mm

 

Can confirm 1.5mm

 

dito.

 

...although my GBE MkIIa has 1mm as standard, and I haven't had any problems thus far *crosses fingers*

 

cheers guys,
gonna have a blonde moment here when you say pre drill 1.5 mm are you meaning they come pre drilled to 1.5mm or need drilling prior to fitting?
ta

 

I think STi meant re-drilled

 

sorted that then! wasn't having a pop sti, just making sure i don't **** it up!
cheers

 

I'd suggest around 1-1.1mm for stock turbo, bit bigger (1.5) for vf23 and td05.

Richard

 

I meant Pre-Drilled. I was always under the impression that the Dawes bought from JW Racing for the MY99/00 cars already had a 1.5mm hole. If it's for an earlier car it may be different. They may have also changed this since I bought mine over a year ago.

 

1.5mm is a bit too big to start with, I'd suggest 1.0mm at first.
drilling out to 1.5 may cause a loss of boost,as dont forget, the larger the hole, the faster the boost is detected by the control solenoid. it does NOT work the other way round.
Smaller means more boost, larger [the hole] is less boost.

 

1-1.5 is good. If you want it smooth, go for 1.5, if you want it a bit more aggressive go for 1.

If you start with 1 you could do some increments in between. Note that when you get to 2mm it is almost a pure bleed valve.

I prefer 0.5 on a larger turbo like a TD05.

The main reason for the larger hole on the small turbos is that they have highest ability to get high boost on part throttle at low RPM where the car is likely to go lean.

Generally the OEM DV will protect you from much compressor surge with a Dawes, driveability and part throttle fuelling are the main concerns.