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voitureltd voitureltd is offline
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Join Date: Feb 2008
Location: Bayside Wi
Posts: 2,537
Originally Posted by copbait73 View Post
Ok, I'll admit it, these threads about Kremer and RUF cars and Porsche porn made me hit the books published in the 70-80s. From my research I'm questioning accepted wisdom regarding desireable intake and exhaust port and valve sizes on these 30 plus year old engines.
1) Yes, the street TURBO uses X and Y sizes but these were driven by emissions, fuel ecomony, part throttle response and CIS system AT a specific (low 260-300HP) horsepower level.
2) Factory racing TURBO engines have larger intake ports and valves BUT more importantly they have huge exhaust valves and ports. Before you say they would have no response on the street reread Bruce Anderson's book. Several 962s were adapted to the street in the late 80s. They were responsive and VERY powerful.
3) I stopped by a local P-car engine builder, 36 years at it. He has flow bench, fixed dyno and has been porting and flow benching for years. He says he's porting 930s and getting 75HP for the effort. He didn't elaborate (obvious, he wants to get paid for his work) but mentioned EXHAUST.
Ok, what do you guys know based on actual back to back testing. What has been done, this looks like uncharted territory.
This has an point, I have a Superflow 110 flow bench and I'd like to start doing some testing.
We measured the ports on a current rebuild with twin plugged heads It has been increased by 4mm intake and 6mm exhaust with correspondingly larger valves with titanium hardware. The builder with many years of porsche engine expierence ( recently did a factory 935 ) said with the cam profile we are using, it should have more torque than HP.These guys do not elaborate much. I think some of the 962 heads had even larger valves and exhaust ports at 41mm. I live in WI so let me know what you are doing with your equipment.
Old 02-17-2008, 11:48 AM
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