Compression Ratio Change vs. Oil Temp
 

Just curious if anyone has experience with this.

If you were to increase compression ratio only, would water and oil temperatures increase or decrease?

Chris Hill
Spec 125 Light

Chris, there are other factors involved such as how many points of compression is increased, cylinder head material and cooling system efficiency.

I realize the answer is not straight forward. I just didn't know if someone might have experienced this.

A fine example of my question would be chaning from a dish 305 to a flat top, or vice versa. I think they are the same except for dish volume, and thus compression ratio.



Chris Hill
Spec 125 Light

Chris,
An engine's inlet charge mixture is modeled as an ideal gas. If no other changes are made, increasing the compression ratio (compressing) will theoretically increase the inlet charge mixture temperature. It may be hard to see/measure the difference, but it will.

That said, the change doesn't have to increase other fluid temps as cooling system etc. modifications can be made to compensate.

D. Whitmore

Chris,
In your example the higher compression engine would have cooler chamber & most likely cooler ex temps if tuned correctly. It could also have cooler oil temps, but there are a bunch of things that can change oil temps. Esp. piston design.

Adger Smith