Created 1/5/2001

Giving some thought to the new M-Roadster engine based on specs found here.

"251 lb-ft. (vs. 262) @ 4900 rpm. "

Hummm... expanding upon my responses to this post.

The old 3.2l US engine had 236 lb-ft at 3800 rpm.

When I tested Ron's M-Coupe I found that at 3800 rpm the volumetric efficency difference between a stock airbox and Jim C's intake was roughly 5.8%. If we assume that 5.8% increase in airflow equals roughly the same percentage increase in torque we find that...

236*1.058 =249.688 ft-lbs. Extremely similiar to the new engines torque at 4900 rpm.

OK, but how would Ron's engine breathe at 4900 rpm? Ve is actually about a tenth of a percent higher at 4900. The torque should be similiar, at least from looking at the breathing capacity of the engine.

Now if we calculate that torque at 7400 rpm (the new engines peak HP) we get 350hp. But the engine is rated at 315hp. We can calculate that the engine is producing about 224 ft-lbs of torque at 7400... or about 10% less then at 4900. If nothing else changes (which wouldn't be the case as internal friction losses will increase with RPM) in theory we should expect to see about a 10% decrease in Ve comparing 4900 and 7400rpm on this engine. The Ve of the current 3.2l is about 24% down at 6900 rpm as compared against 4900. IOW, those lovely multiple throttle body intakes, cool new head and everything else really only improve upon the current engines setup at elevated RPM.

When somebody gets one of these near me you gotta take me for a drive so I can test airflow!

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