Re: Shift points for the highest torque?

Posted by rhudson on October 05, 2003 at 06:05:30 from (65.161.23.254):

In Reply to: Shift points for the highest torque? posted by Cliff on October 04, 2003 at 23:30:45:

Hi Cliff,

truck and tractor engines have "fairly" flat torque curves. as opposed to a highly tuned and modified 2 cycle engine like a motorcycle. the curve goes up sharply, peaks and goes down sharply all within a few hundred rpms.theory would be to accelerate to just a few rpms past the peak, then shift hoping not to fall back down the curve diring the shift to loose torque. in my old scca days most transmissions/flywheel/clutch/gear combinations would loose about 400 rmp on a shift. so you would run the engine rpm past the peak of the curve by about 300 rpm. shift and if all went well you were just about 100 rpm on the "left" or start of the peak. on most engines (not all) the red line has little to do with peak torque. it depends on what rpm the peak is tuned. that has to with the whole engine dynamics (carb bore and distance to the inlet valves, exhaust bore and distance to outlet nozzle, valve size/location/lift/and duration. red line has to do with the weakest sections of the engines starting to vibrate at critical frequences. you can tune a peak curve with what you've got. to raise a red line of an engine,,,well you've got to redesign components of the engine..big money. and finding the peak? you are right seat of your pants,,kinda. the engine should be dymonitored to find peaks on graph paper, but then it boils down to spending some "quality time" with the engine/drivetrain/atmospheric conditions/track conditions. been out of the game for some time. there are probably computer systems that allow you to monitor and make decisions on all the stuff we use to do by scientific trial and error. these days i'm not looking for max accleration, i'm looking for max fuel ecomony. thats on another curve by the way.

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