Building a hybrid turbo

[sen2two]

I'm building a hybrid turbo with the stock S5 turbo. 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.

[classicauto]

I don't have much info on making a hybrid turbo. I've tried it once using some ebizzle "TO4-ES" a friend bought and putting it on a stock turbo, and it actually worked not bad. All I did was bolt the backing plate on and install the seals and comp wheel. Didn't last long though, about 12,000kms.

What I can offer advice on, is staying away from an oil cooled center. I used to think it wasn't a problem, until I tore down a turbo (oil cooled) I ran very breifly before tossing an apex seal through it. The shaft was blue'd completely all the way up until about 3/4" behind the comp. nut. The turbo shop who rebuilt it told me if I wanted anything with decent life on a rotary to *never* use oil only - its just plain too hot to cope long term.

Whether or not you do is up to you - but that's my two cents

[sen2two]

I have since decided to stick with the stock TII CHRA and just rebuild it. But i'm still unsure about the compressor choice.

From the research I have done, I came up with a 3rd choice. Which i think might be better than the two choices i had prior. I found a 56.5/76 compressor blade with a .50 ar cover. Its basically a cheaper version of a GT30. It's not Garrett, but it's not China garbage either.

This looks like the way i'll be going.

[JustJeff]

Please keep us posted on this one. I've got a S5 turbo that needs to be rebuilt and I'd love to learn from your experience

[rotaryracer]

Also interested in hybrids. keep us posted. thank you.