99 Ultra, 95" Screaming Eagle upgrade, 203 cams, CNC machined heads, flat pistons. Do I have 9:1 compression ratio or...?

 

You can damn near use kerosene! Only kidding!
At that compression I'd say that 87 octane would be absoluetly fine.
Scott

 

Thanks. What is compression ratio? Is that stock compression? 9:1? Are flat pistons higher compression pistons?

 

Bud of mine has a 02 SE 95'' and he runs 87 all the time without issues. Mind you , I don't know what cam it has and sometimes this could have a play on what works too. Basically if it pings, then no.
Ron

 

Ran 87 octane in my bike with 205ccp this summer....ran fine and didnt even ping...suprizingly. That said i usually run 93 here as many places have it.

 

One atmosphere is about 15 lbs per sq inch. This number varies with altitude and temperature.

The way I figure this, and I may not be completely right, is whatever number you get, less 15, divided by 15. Round about.

so you do have about 9-1 compression.

 

An interesting side note.

Where I worked awhile back we had a BIG old air compressor that was single stroke for some reason. Used for a particular job.

Most this size are two or three stage with intercoolers but this one wasn't.

It pumped 115 discharge. Or about 6.5-7 compression ratio.

The temperture before the cooler was 450 Degrees. Always though about that.

So if you have 10-1 might be 650-750 degrees before the spark.

Don't need much