johnc Posted September 15, 2011 Share Posted September 15, 2011 Call it 70 ft-lb/l, and your 3L should make about 210 ft-lb torque, and 7200 RPM works out to 288 hp (thats at the crank). I don't understand how you got 275 ft-lb at any RPM, but I'd like to learn. What I'm thinking is that a high-overlap cam has a sweet-spot in the RPM range where it combines with the manifold length to give a Veff > 1 and so generates a bump in the torque curve I made it a point to say that my engine was not a production engine. But even for production engines I think your rule of thumb is way low. For my particular racing 3L I had the builder optimize the engine for torque with as broad a torque curve as possible. Lots of head work including welding up and re-contouring the exhaust and intake ports so they all flowed the same. Development work on three different custom cam profiles, individual ignition timing for each cylinder through the Motec EMS, custom intake manifold, custom header, etc. It made 285 to 294 whp (depending on the chassis dyno used) and a consistent 325 horsepower on the engine dyno. There was a lot of tuning of intake runner length a taper, header primary size and collector merge, and a lot EMS programming to get the numbers my engine developed. The engine builder said it would have been a lot easier to build a horsepower engine. All the components were there to run the engine to 8,500 rpm but my imposed torque goal made that unnecessary. You should also search for a couple of Tony's posts regarding the L6 harmonics in the 7,000 to 8,000 rpm range. L6 engines are happy below and generally happy above that range. Within that range the harmonics require forged pistons, good rods, and outstanding balancing. For my engine the builder took 15 lbs. out of the crank, 25 lbs. out of the clutch and flywheel, and added a ATI Super Damper. Quote Link to comment Share on other sites More sharing options...
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