Quote:
Originally Posted by Edelweiss
Dear Sirs,
yes right and there is a clear tendency of thinking bigger is better.
This is not the case - you can see the majority of exhaust tubing being oversized.
A lot of the people doing this systems are reasonable welders but far away of being exhaust experts or constructors.
The Porsche engines like relatively small tubes - as an example a 45x1 mm tube is good for 400 plus hp out of a full spec 3,5 l RSR style race engine with 50 mm flat slides.
Max power is at 8.600 rpm and shifting is at 8.800 to 9.000.
So a bigger tube is not automatically making more peak power - it can also mean loosing everywhere.
Same with the ports - work at the seat / bowl area but do not open it up too much.
Ports also tend being too big not being too small !
Best reg.
Dirk
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The configuration of Porsche's RSR track engine isn't necessarily a recipe for street-based engines, even uber-modified versions.
Not that PAG makes all the right calls, but one could take hints from the components they use (exhaust-wise specifically) in their production engines, some of which are pretty "uber". It appears the mods Fred made (displacement, compression increase, cams, etc.) would have provided a hefty boost to mid-range torque.
BTW, 45mm = ~1.77". Not sure if that dimension is tube ID or OD. If OD (as is typically used), the tube ID is typically 1-5/8" (41.27mm). By comparison, SSI tube OD/ID is 1.5"/1.375" respectively, not ideal for a 3.3 l engine according to "those in the know" and the more knowledgeable people here. I'm probably splitting hairs, but unless there are empirical test results, how does one know "my stuff" is not leaving untapped power on the table just because I can't feel the power loss?
Not to beat a dead horse, but unless there's a reference level, how does one feel a lack of e.g. +10-15 ft.lbs torque?
Sherwood