Thread: Suitability of this turbo?

Originally Posted by Dougal

the wastegate allows more exhaust flow and lower exhaust pressure once enough boost has been developed. Letting the engine rev more readily and produce more power.

With a shut wastegate unless you have the fuel to match the boost keeps climbing, the exhaust pressure keeps climbing and power is lost to pumping loss.

With no intercooler my egt is the same at 20 and 24psi boost. But with the wastegate shut for 24psi the engine hits a power wall around 2500rpm.

For years Ive had a valve setup to vent pressure before the wastegate actuator (activates about 9 or 10psi) which deactivated the actuator keeping the wastegate shut. This improved the 4BD1 performance IMO and resulted in lowered EGTs. My theory was not enough air was being pushed into the motor because the turbo wasn't working to full capacity due to too much exhaust bypassing.

Tonight I acted on Dougal's post and adjusted the valve so it vents less and theoretically let some pressure to the actuator, causing the waste gate to open to some extent. This improved the performance again IMO and again lowered EGTs in the higher rev range. The engine seemed to rev easier and run a little quieter.

My Auberins boost gauge is not set properly so I don't know for sure what boost I'm running. It reads 5 or 6 psi at idle which isn't right and reaches about 26psi. Maybe its boosting to 20psi.

Maybe Im imagining the whole thing. At least the lower EGTs are a measurable improvement. Is there a wastegate actuator that's set to 20psi.

Originally Posted by rar110

For years Ive had a valve setup to vent pressure before the wastegate actuator (activates about 9 or 10psi) which deactivated the actuator keeping the wastegate shut. This improved the 4BD1 performance IMO and resulted in lowered EGTs. My theory was not enough air was being pushed into the motor because the turbo wasn't working to full capacity due to too much exhaust bypassing.

Tonight I acted on Dougal's post and adjusted the valve so it vents less and theoretically let some pressure to the actuator, causing the waste gate to open to some extent. This improved the performance again IMO and again lowered EGTs in the higher rev range. The engine seemed to rev easier and run a little quieter.

My Auberins boost gauge is not set properly so I don't know for sure what boost I'm running. It reads 5 or 6 psi at idle which isn't right and reaches about 26psi. Maybe its boosting to 20psi.

Maybe Im imagining the whole thing. At least the lower EGTs are a measurable improvement. Is there a wastegate actuator that's set to 20psi.

And your T28 is larger than most of the turbos people are using. So your improvement is smaller than most would get.

I bought a 22psi actuator off Ebay and currently running it. I had to run a lot of preload and it's holding boost at 20psi on my T25.
Without the wastegate I had boost climbing to 24psi but less power (exhaust was being choked and would hit a wall around 2,500rpm) and the same EGT. With the functioning wastegate I can rev out to the governor.