Model Engine Maker

Engines => Your Own Design => Topic started by: michelko on October 26, 2018, 10:57:30 AM

Title: Compression ratio for Model engines
Post by: michelko on October 26, 2018, 10:57:30 AM

Hi,
i am still Fighting with my Bugatti 8. Now that the summer is gone i will do some more work to get it starting and running reliable.

All the plugs i made went bad after a short time of running. The last set i made from macor is also crap so i thought About the compression Ratio for modelengines. I did some calculation and found that the Bugatti has ca. CR 6,47.
Can anybody say this is o.k. or to high or Maybe to low? All suggestions are welcome.

Regards Michael

Title: Re: Compression ratio for Model engines
Post by: Vixen on October 26, 2018, 11:58:24 AM

Hello  Michael
A compression ratio of 6.5:1 should be OK if you are burning petrol (gasoline). But if you are using methanol the CR would need to be higher circa 8.5:1
Sorry to hear the new micor plugs did not work

Mike

Title: Re: Compression ratio for Model engines
Post by: deltatango on October 26, 2018, 12:21:06 PM

Hi Michael,
My "Mastiff" is running on petrol, both what I put in our cars and what is sold in Australia as "Shellite" (lighter fluid, Coleman fuel?) with a calculated compression ratio of ~3.8:1 so 6.5:1 should be fine. My efforts at home-made spark plugs have also failed, the Rimfires I'm now using work well.
Regards, David

Title: Re: Compression ratio for Model engines
Post by: Roger B on October 26, 2018, 05:31:16 PM

Hi Michael, That ratio should be fine for Petrol/Gasoline or Alkylate (Coleman Fuel). My vertical single is around 9:1 but it uses a commercial spark plug. I have never tried making my own plugs.