Re: Displacement/engine speed/HP

Posted by Thanks for opening this line of discussion. on September 03, 2000 at 21:13:54 from (207.177.47.176):

In Reply to: Displacement/engine speed/HP posted by John Hallman on August 30, 2000 at 06:56:00:

John & All- Thank you for opening this line of discussion. It involves numerous technical points I've had trouble with for many years.

Torque is brute twisting power applied to a shaft. Horsepower is a meaasure of work and calculations involve time, distance, and mass. They're two different issues.

Long ago, in a tech tng class, I asked a Chrysler tng rep why the short stroke and elevated RPM. Answer came back as "lowered emissions". Bravo sierra!

Do some calculator work on cylinder bore vs crankshaft stroke. It is almost a no-brainer! The long stroke hemi-head engine wins every time. Their smog problems were from the long overlap camshaft grind and the slovenly carburetion needed to make their powerful hemi work.

Look back thru the 70's & early 80's Japanese engine specs and you'll see a bunch of long stroke vs bore hemi head engines in the high MPG and low emissions category.

Very interesting is that the short stroke design has a higher "cold wall quench" ratio and theoretically higher exhaust emissions problem.

What needs to be addressed is that engine power boils down to how much fuel and air can be burned in a unit of time. Run up the RPM and the BTU's used go up accordingly. But, efficiency goes to pot and exhaust emissions go up. A wonderful opportunity to add on lots of "value added" smog equipment...

Modern computer control technology has made it possible to do miracles with the spark ignition IC engine. But, in 1980 I was doing carefully controlled 2 way road test runs with a 1920 Model T Ford and getting 28 - 32 MPG and extremely low exhaust emissions.

Looking forward to more discussion on all this. "Three pedals and a lever", IHank

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