Interesting read from the guys at Eclipse Turbos
@Eclipse . Reinforces that fact I don't care to much about boost pressure. I'm much more interested in monitoring EMP and getting the lowest EMP:IMP possible which goes hand in hand with optimal gate setup.
What they posted on Facebook below;
We ran some tests on this aftermarket Landcruiser turbocharger before removing and installing an Eclipse. From the attached graph, this is horrible!
High turbine back pressure is not good. No consideration in regards to turbine back pressure has gone into the design of this turbocharger. High pressure will restrict flow holding heat in the cylinders and given the right conditions, contributes to catastrophic failure due to excessive loads on the thrust bearing along with shaft over speed. If you want to know where the “choof choof” noise (compressor surge) comes from when lifting off the accelerator, this is the cause. During surge, the bearing experiences high hammering load effects even on deceleration surge. Exhaust valves will also be held open at these pressures, which is detrimental to both engine reliability and performance.
Ideally turbine backpressure of 1:1 is optimal, meaning the same pressure in the intake manifold as the exhaust manifold. But this is rarely seen. Industry standard threshold is a 1.4:1 ratio or less (42psi turbine/30psi compressor etc). Low turbine back pressure is just one of our criteria at Eclipse Turbo Systems when designing our range of turbochargers, but an important one. We design all wheels and volutes in house and test extensively before approval, and moving into the production stage. This Eclipse turbocharger recorded 1.25:1 EMP/IMP as compared to 2.7:1 EMP/IMP previously on the same vehicle.
We encourage customers to consider this important aspect before making a turbocharger purchase. If you’re not sure what your current turbocharger’s turbine back pressure is, ask the manufacturer or test it. If your turbocharger experiences “choofing” or “deceleration surge” there is a high probability it is experiencing the associated high turbine back pressure causing damage to the turbocharger.