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Old 05-25-2016, 08:42 AM   #2
j.fro
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Join Date: Feb 2005
Location: Virginia
Posts: 1,369
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Hey Stu,
Here's a chart I put together of the M96 & M97 engines and the 996 GT3 engine:
Car Litres HP TQ Bore Stroke Hp/Litre Compression
986 2.5 201 176 85.5 72 80.4 11 to 1
986 3.2 250 225 93 78 78.125 11 to 1
996 3.4 300 258 96 78 88.2352 11.3 to 1
996 3.6 320 273 96 82.8 88.88 11.3 to 1
997 3.6 321 273 96 82.8 89.167 11.3 to 1
997 3.8 355 295 99 82.8 93.4 11.8 to 1
GT3 3.6 380 284 100 76.4 105.55 11.7 to 1

To get just 986/3.2 power from the 2.5, you'd need to be making 10hp/litre. I don't think it's possible with just bolt-ons. Except for GT3 engines, Porsche didn't get there until they introduced DFI. Even if you could get to 250HP, the weight of the car is an issue. with 250hp in a 2855# car, you're still at 11.42lbs/hp. To achieve what (I think) you're looking for, you need to break the 10hp/lb mark...meaning a target of around 300HP. The 996 3.4 will get you there, but I bet the cost is about the same as swapping in a 400HP LS engine. And I think the LS engine is a bit lighter.
You coming to RPM next month??
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Last edited by j.fro; 05-25-2016 at 08:46 AM.
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