I'm building a hybrid turbo with the stock S5 turbo (2nd gen). So the turbine will be factory (un-clipped) which is: inducer 63.75mm/exducer 54.61mm. I will do some porting, smoothing, and machining to the turbine housing to optimize flow. But not all that much. I will also be using a Garrett to4b CHRA. Which is almost the exact same thing as the stock S5 one, but is only oil cooled. No water cooling passages.


I'm stuck choosing between two different compressors for this hybrid. For reference, stock measurements of the compressor are: inducer 43.68mm/exducer 63mm (48 trim)

The two choice's I have are:

1st choice - .60 ar Compressor (57 trim)
Compressor Wheel 54.28 /71.32

This has a good sized compressor wheel and the compressor housing AR should help me to make power down low. But I'm unsure if it will make it to the 350whp range. I'm guessing this turbo will peak out to early.




2nd choice - .50 ar compressor (62 trim)
Compressor Wheel 66.72 /84.25

This one has a lower .AR, making its low end not as good as the other choice, but top end should be better. Larger .AR housings are better for low boost applications, and smaller .AR are used for high boost applications. I'm guessing that with the overly large compressor wheel for this size turbo, that it should make up the loss of low end.


I'm looking to make in the 350whp area on stock ports (s5 TII) with minimal boost as possible. I'm trying to keep it in the 15psi area. I could not find a compressor MAP for either of the two, so I'm going of the rest of the numbers I have for them. I'm not as concerned with the target number, as much as I'm concerned about lag. I would much rather have a nice average HP number with a strong power band all the way through. Than to only have my power at the last few thousand RPM.

 

You want the biggest front cover A/R you can get ideally 0.6 or 0.7. I personally think you want the highest trim compressor possible so I would chose either 54mm/70mm v-trim or 57mm/70mm H trim. A 13B should get close to your goals around 15psi of boost. I chose the v-trim myself because I can't see there being any difference beside more wheel to spin up if using the H-trim and the stock turbine is smaller than both. My next engine I am going to build something with a small as possible stock ports The goal will be a late open early close primary plate (12AT) with normal open early close secondary plates (anything 4port pre FC/GSL-se) and use early 13B housings which open later and shut earlier than any standard mazda turbo engine.

 

^ The V trim and H trim wheels are used in the BNR stage 1 and 2 respectively. Unless the OP really wants to build his own hybrid turbo, he might as well just send it off to Bryan.

 

Do you know the specs of those wheels?

 

Do you know the specs of those wheels?

 

up at the top of this page howard coleman posted a list of turbos by wheel AREA. (and how to compute that).

there are two things i noticed, the "ideal" rotary turbo has a compressor and turbine that are almost the same size (vs a piston that takes a huge compressor/small turbine)

two that the V trim wheel is about equal in area to the stock exhaust wheel.

three the japanese, and BNR use the v trim too.

go take a look at people's BNR dyno sheets, real basic cars are putting down really good power numbers.