Charon wrote on 01/08/09 at 06:44:36:Back in September of 1996, when Suzuki reissued the Savage, Motorcycle Consumer News ran a test on it. I happen to have kept that issue, because of that test. In it they published their rear-wheel torque and horsepower curve. The torque curve looks rather "peaky" to me. Max torque was 30.5 lb. ft. at about 3700 rpm; max hp was 24.6 at 5000 (the high end of their published curve).
Reading from their graph:
2500 rpm (bottom); 13 lb-ft and 6 hp.
3000 rpm; 22 lb-ft and 12 hp.
3500 rpm; 30 lb-ft and 20 hp.
4000 rpm; 30 lb-ft and 23 hp.
4500 rpm; 28 lb-ft and 24 hp.
5000 rpm; 26 lb-ft and 24.6 hp.
Vehicle designers typically like to gear their vehicles so that, at what they consider to be cruise speed, the engine is turning just a bit over the torque peak. This makes the vehicle easier to operate, as whenever speed drops from some increase in load (up a hill) the engine "automatically" moves to a speed where it develops higher torque. The stock Savage seems to like cruising at 60 - 65 mph, which is just over the max torque speed. I'd have to say they did their homework. By the way, maximum torque speed is also the speed at which the engine is most efficient (least internal losses). One must bear in mind that torque curves are always generated at wide-open throttle, it always being possible to reduce torque by closing the throttle.
EDITED TO ADD:
Some time back, in another thread, I calculated that the Savage develops about 12 horsepower at 60 mph. From the owner's manual the Savage is turning about 4000 rpm at 60 mph. Using my old D-4 circular slide rule (Property of U. S. Army Air Forces) that comes to about 16 lb-ft of torque, roughly half the available torque at that speed. If we change the gearing to slow the engine while keeping the same road speed, we must increase the torque so the product of torque and speed (power) remains constant, or else the speed will change. Dropping the speed to 3500, the torque must increase to about 18 lb-ft, closer to two-thirds of the available torque. Dropping the speed to 3000, the required torque increases to about 21 lb-ft. But at 3000 the available torque is only about 22 lb-ft. Almost wide-open throttle would be required. In terms of pumping loss this is pretty efficient, but wide-open throttle results in pretty high cylinder pressures and temperatures. My guess is it might result in detonation and short engine life, but I'll happily defer to those with actual rather than theoretical knowledge for the definitive answer.
I sure would like to see your thinking on the chain conversion & the approximate 10% increase in gearing.
Would that be enough to put the engine at risk?
What about the jetting/exhaust changes? How do they impact the torque @RPM? Have to hit the dyno to know?
Its about 3 am, I am pooped & brain uis scrambled, so, if this is too disjointed to bother with, Ill try to ask again in a way thats decipherable.maybe.. Thanks./
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