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alright need a little info got everything for boost 72mm turbo. 10.2 cr cc503, forged pistons and rods with steel crank. crank is stronger then stock. anyway i built the engine for N/a but like the turbo to much lol. turbo is a 72mm turbonetics. i know cc503 not best for boost and 10.2 not best either but listen. i want to fab the manifolds and get everything put on and run hopefully 7psi on intercooled 91 octane for the time being. i will be switching to a 62cc head and a actual boost cam, hopefully to get 14psi out of it. my question is will i beable to get 7psi on 91 octane without KR? 3800ft 98*
 

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had a odd conversation today. will a bigger turbo make more power with less boost then a smaller one. like 7psi on 76mm 600rwhp and 7 psi on 70mm 500rwhp. i know with the bigger turbo the lag will be more but the boost will come on in less of a spike. my question is will the knock count be diffrent between the two at 7 psi or will it be the same?
 

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You won't know until you start tuning and find out; is the definitive answer.

If you keep the timing safe, and could run a higher octane that would help. I can say with some confidence that if you installed a good meth injection kit that you would be fine.

As for the boost vs power question; at a given pressure, only so much air can be moved through a given size tube. The problem is maintaining that pressure as engine RPM's increase. While turbo charger's ability to perform is not linear, they do have a volume that they peak at. This is seen in flow charting for a given compressor. However a larger turbo charger has more resistance to movement due to the rotating mass of the turbine and impeller so they are less responsive. But they have a larger capacity. This larger capacity is needed to deal with higher engine RPM's and boost levels that can be obtained.
You want to stay with the smallest turbo that will produce the amount of air needed to produce the boost pressure you want. Other factors to consider are size of the tubing used, including the inter-cooler. The bigger the tube the longer the spin up time. Also the longer the run, the longer the spin up time. If you are using 1 1/5 inch tubes and inter-cooler, then you can get by with a smaller turbo charger. But if you go to 2 1/2 inch tubing size a bigger turbo might be needed, but the end result will be much the same at top end however the car with the smaller turbo and inter-cooler tubing will be quicker getting to the desired boost level.
 
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