Gtx3071/3076

[steveboyslim]

Why did I think it was a Vaux engine,
You would need around a 1.5bar+ spring in wastegate and run the top port also this is the only way it will work correctly.

Mark

I also do GM XE/CLET/ZLET/LEH engines, I built Rick Drapers engine which you started to map.
Also do Renault, YB, Scooby, Mitsubishi, VAG, Lotus, Volvo Brigs & Stratton, Stihl, Makita, Mcculloch, Blackstone etc, but not for a living.

Steve

[steveboyslim]

Finally retested the engine, replaced the 3 inch inlet compressor housing, which turned out to be a non-factory machined GTX28 housing, this time used an original Garrett GT3071 4 inch ported shroud housing and back plate.
lapped the waste gate valve, replace the gate spring with a 20si 2 inch diameter version, re-piped the vacuum lines, both sides of the diaphragm to a 4 port MAC valve, engine did 530 BHP and 503 ft/lbs torque (or there about) at 28 psi, more than what was wanted, boosting from about 3400 rpm which is a 600rpm improvement over the previous non-baring turbo.
Also converted the obsolete throttle position sensor to a Variohm inductive type which involved modification to the throttle spindle, a vast improvement.
Will need a bit more adjustments in the car.

Steve

PS I only advised on the specification did not build it or map it