JUST CURIOUS ABOUT COMPRESSION RATIOS FOR GASOLINE TRACTORS

Posted by Ken McWilliams on December 02, 2000 at 18:30:14 from (64.12.105.49):

Most gasoline tractors that I'm familiar with have had compression ratios ranging from 6.5 to 7.5. Are there any popular tractors that had compression ratios significantly higher than 7.5?

These tractors make advertised horsepower usually around 2000 to 2800 RPM, and are designed more for torque and lugging, more so than an automobile engine that usually makes advertised horsepower at 4000+ RPM and higher compression closer to 9 to 1.

I've noticed over the years that even though the several gasoline tractors that I've plowed with had somewhere in the 7 to 1 compression, they will develop a pre-ignition ping or rattle when pulling very hard. In recent years when I know I'm going to plow I'll use higher octane gasoline to eliminate the pre-ignition rattle.

Has anyone else had a similar experience?

Knowing a little about flame spread rates of gasoline, it seems to be a compromise of compression ratio and the relatively low RPM's of the tractor engines. It would seem if the compression was much higher than the 7.5 at these low RPM's (2000 - 2500), that the tractor engines would really have some trouble with pre-ignition rattle with the flame travel rate of gasoline.

Thus, my question: are there any popular gasoline tractors that had much more than a 7.5 to 1 compression ratio? If so, I'd like to find out how it was accomplished ( via spark timing, , higher RPM, compression chamber design, cam timing, etc.).

Yes, I know that LP gas tractors have higher compression, but the LP gas has much higher octane than 87 octane regular gasoline.

Ken McWilliams
Dayton, OH

Follow Ups:

• Re: JUST CURIOUS ABOUT COMPRESSION RATIOS FOR GASOLINE TRACTORS Aaron 19:33:17 12/02/00 (0)

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