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911st 911st is offline
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Join Date: Jan 2004
Location: Sacramento
Posts: 7,269
On a NA motor with SC/Carrera cams above 200whp one starts to benefit with a change to 1 5/8's primary tubes.

Is there a way to find out where a turbo will benefit in a jump up from 1.5" primaries?

Any third party expert info on this or rules of thumb?

If not, can we calculate it some way from the NA info above?

My gut tells me that if at 1 bar if we are pushing up to twice the NA air through the intake it might be about about 2 times or 400whp +/- but this may be far from, far from true.

If it is true and a 1 5/8's is about 20% larger that might take us up to about 480whp.

And if 1 3/4 is about 40% larger than 1 1/2 that might be good up to about 560rwhp.

This dose not mean we can not make much more hp, only that there might be some HP to be gained on the top end if there is not something else limiting.

Again, this could be far from true.

Anyone have any data points on primary tube sizes?
Old 01-16-2010, 07:50 PM
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