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Turbo Garrett g25 550 or 660

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What effect will a larger compressor wheel have on engine response and low end torque for a street/ track day car application. I have decide on a garrett g25 550 with 0.72 turbine housing... what I find confusing is according to Garrett boost advisors the g25 660 also meets my requirements... essentially they the same only the 660 has a bigger compressor wheel..

What would the negative be going the bigger 660hp capable turbo compared to the smaller 550hp

I'm targeting 350whp so I think the g25 550 is the correct option but our local agent advised me to take the 660 because he recon s there no negatives.

The larger compressor will be slighlty slower to respond, it will also be more likely to surge at low speed.

I have the same dilemma. 2.0 modern DI engine (718 cayman), the purpose of the car is the same (track day), and not sure should I go 660 or 550.

Have you decided? What are results?

The smaller will potentially offer better response and better lower range torque - both of which will be more beneficial that pure top-end power.


On a 2.0l 4cyl the spool difference is about 200rpm give or take 50rpm, that's on a 9.5:1 engine(vw/audi/porsche). The 660 is soo sooooo good, and the LITTC hybrid 660 is pretty sweet. With the cayman having 10.5:1 iirc and modern DI engines also being higher in comp...it will be so much better(3k for roughly 20psi)

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