Compound turbos?

R

Rich V

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Dec 25, 2008
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I've been thinking of doing a twins setup down the road to allow me to make decent power and still tow a 19k trailer. I got to thinking, at what point does a small top turbo become a restriction for the bottom turbo?

Solving the problem of drive pressure should be easy with a large enough external waste gate; but what about the compressor? When does too small of a compressor begin to hurt the performance of the bottom turbo?

Say for example I wanted to design a twin setup that would spool FASTER than stock and still make 600-650 rwhp by using a smaller than stock turbo using an external waste gate combined with a decently sized bottom turbo; it certainly seems feasible. If the top and bottom turbo were sized well and you were not looking to make any record breaking power, what is to stop this from happening?

Any input or discussion is appreciated. I'm trying to learn as much as I can about compound turbocharging.
 
Rich V said:
make decent power and still tow a 19k trailer.

When does too small of a compressor begin to hurt the performance of the bottom turbo?

spool FASTER than stock

make 600-650 rwhp by using a smaller than stock turbo

decently sized bottom turbo

If the top and bottom turbo were sized well
Click to expand...

at 650 hp your truck will spool a 62 or maybe even a 64mm wheel as quickly as it spooled the 54mm when it was stock

put a 62 over a 75 and be done with it

that is what was suggested to me for that power level
 
s300g over a k31 would be my first choice. 62/65/12 over s475 would be my second.
 
IMO I do not think the top turbo will limit HP as long as the turbine has sufficient wastegating.

Look at Reb B's twin setup, a 62/71 S300 over a S500 that did over 1k on fuel (IIRC). And even the BD R700 twins still use a 57mm S300g on top.
 
My garrett twins spooled considerably faster than stock and supported over 700hp... no external gate needed
 
soulezoo said:
My garrett twins spooled considerably faster than stock and supported over 700hp... no external gate needed
Click to expand...

What Garretts did you use? A nice set of ball bearing turbos would be great but they might be a little spendy. Care to tell us how much they cost you?
 
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