AnswerID: 390692 Submitted: Monday, Nov 09, 2009 at 22:03
Chaz
replied:
Thanks Malcolm, I don’t get on here as often as I'd like to.
Hi Blood,
If you block your EGR, you should by-pass the vacuum control solenoid. This will eliminate your boost fluctuations as a result of EGR.
The Dawes valve is set to control maximum boost but you should fit a needle valve to help control your low rpm boost or turbo spoolup. Then you can calibrate the turbo’s spooling through the rev ranges with the needle valve and boost limiting screw on the turbocharger. Ideally a setting of no more than 6psi at 1500rpm and 10psi at 2000rpm can be achieved. Above 2000rpm it should be safe to go to a maximum boost setting by the Dawes valve up to around 16psi at 3600rpm. This is ideal, but getting close to it would be good for engine and turbo life as well as lowering EGT’s.
Using a duel stage boost controller means fitting two Dawes valves and an additional solenoid valve to switch between the two stages. It simply gives you the ability to switch between two maximum limits, eg. 10psi for around town with low EGT’s and 15psi on the highway when EGT’s increase. These maximum boost limits are at moderate throttle inputs and can be exceeded at full throttle when rpm gets to maximum of around 4000rpm.
You do need a special controller such as the Dawes valve. It’s similar to a conventional controller, but doesn’t have the bleed hole to let pressure escape in order for the waste
gate to close. ZD30 VNT Garrett turbo’s are controlled by vacuum rather than pressure, so a different controller is needed.
Here are a couple of links that may help.
http://www.chaz.yellowfoot.org/zd30_engine_problems.htm
http://www.chaz.yellowfoot.org/Manual%20Boost%20Controller.htm
All the best,
Chaz
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