So a larger compressor inducer (or small end, or intake side) flows more air than a smaller one, that's a given.

On Garrett's web site, they explain that a larger wheel trim flows more than a smaller one (see that here I’m talking about wheel trim, not wheel size).

But what about this example: given 2 exactly equal compressor wheels in all aspects but their exducer (or big end, or outlet side) sizes, in which one wheel has a larger exducer size than the other wheel, how each of these 2 compressor wheels will behave? What is the effect of a larger exducer size? Does it move more air given the same amount of turbine RPMs, hence making it more responsive? Does the larger exducer sized wheel ultimately flows less than the smaller one, since the one with the larger exducer will have a smaller trim number than the one with the smaller exducer?

Also, what are the effects of having more blades on a wheel? For example, most compressor wheels use 6 pair of blades (6 full blades and 6 half blades), but some use 7 pairs. Do the additional blades help it “suck” air easier, hence also making it more responsive or does the additional moment of inertia of this obviously heavier wheel cancel this improved response? Do they ultimately restrict maximum flow compared with a wheel exactly equal in all aspects but on the number of blades?

I have also read about compressor wheel dept (that is, the distance between the blade leading edges on the inducer side and the back of the compressor wheel, or the flat side which faces the turbine) affecting ultimate flow, in that a deeper wheel will have more flow capability than a shallower one. Shouldn’t ultimate flow be more affected by the aerodynamic design of the blades rather than its dept alone?

And then there is a whole bunch of variables on the compressor covers themselves, like A/Rs, backwall and cover sizes, etc.

Hope some more knowledgeable guys around here can help answer these questions, or even better, can help summon help from high above (turbo engineers, that is).

 

I had a 62-1, short exducer and it is my favorite street turbo- sick low end torque.
I put a t70, long exducer, on and it was more peaky. Also, a larger exducer seems
to make power longer- up to 4bar, whereas the graphs on the 62-1 show efficiency
falling off before 30psi. I know it is stupid to compare a 62-1 to a t70, but I think
the compressor graphs give you a good idea of response.

 

WOW, lots of questions. I'd like to post explanations, but I have to go shop right now and don't have the time . I've posted on this subject briefly at one point. Do a search.

~Mike...........

 

https://www.rx7club.com/single-turbo-rx-7s-23/question-re-comp-wheel-inducer-vs-major-dia-345518/

Found it for ya, I'll post more on it after the holidays.

~Mike.............