Hey guys I need a little help. Would a O trim turbine with a large A/R flow
as well as a P trim with a small A/R.

Example O trim-90 to 100ish A/R compared to P trim 58 A/R. Would the two spool at simuler rpm's?

Thanks for the help!
Steve

 

The trim will not effect the spool up time as significantly as the exhaust housing. With compressor trim you have to take into account the rotating inertia (additional spinning mass of larger compressor) as well as the way the compressor "compresses" the air. On aggressive compressors, lag time is enduced from compressor blades that "cut" the air and trap more volume in between each blade. The more volume the blade has to more multiplied by its rpm, will give you the total torque the compressor is trying to overcome.

With exhaust housing size the flow of the exhaust gas is processed in different manners. With a smaller housing the exhaust gas will hit the peak rpm of the compressor shaft sooner, but will become a restriction to the overall flow with increasing engine speeds. The larger housing acts in the opposite manner. You really have to consider the turbine wheel trim in the same manner as the compressor trim.