Re: Displacement/engine speed/HP

Posted by Ken McWilliams-THINK ABOUT THIS, FELLAS on August 31, 2000 at 18:51:35 from (172.153.51.244):

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

John and others think about this.

Most tractors with gasoline engines in the 30 - 50 HP range operate at about 2200 to 2600 rpm and run about 6.5 to 7.5:1 compression.

The flame travel is so fast at these low RPM's that that pre-detonation is not uncommon. One of my several tractors is a John Deere 1020. When I plow or heavily load it, I get the ping from it. When I know I'm going to lug it hard for a long duration I'll use premium gas or throw in a few mothballs (mothballs are made from a close cousin of the benzene and toluene family (unsaturated hexagonal ringed hydrocarbon) which is a component in Turbo Blue Racing Gas) that I keep in the garage to raise the octane.

Automobiles usually are rated at about 4000 - 5000 RPM for the advertised horsepower.

If you would turn up the governors on the tractors to allow the HP to be generated at higher RPM's as was described in the Farmall H story, you could get more power from them. This would be limited somewhat by the intake and exhaust passages and the shape on the camshaft lobes. These will be signifcant restrictions if someone wanted to increase HP more than 50% or so.

The reason that tractor engines endure so well is because the more massive construction of the block, crankshaft and rods. The flip side is that these engines probably wouldn't hold together long at a doubled RPM due to insufficent balancing and low pressure oiling. Due to the high circumferential speed of the bearings at higher RPM's, high pressure oiling is needed to maintain a film of lubricant between the sliding surfaces.

I've seen race engines get trashed in a few seconds after losing oil pressure. Spun bearings is the least, seized engines and thrown rods are the worst.

Chevy small blocks have endured over the years running at high RPM's because they comparitively run smaller rod and main journal diameters which minimizes the circumferential speed between the bearings and the crankshaft journal surfaces.

One of the main ingredients of race engines is a high pressure/high volume oil pump to provide a film of oil to float the bearings on.

Ken McWilliams
Dayton, OH

Follow Ups:

• Re: Re: Displacement/engine speed/HP John H. 06:16:39 09/01/00 (1)
  • Re: Re: Re: Displacement/engine speed/HP Ken McWilliams 17:29:01 09/01/00 (0)

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