comp. ratio

[chillls]

can anyone give me a ball park on what my compression ratio would be

sea level

stock bore

stock stroke

19cc domes

with 170 psi

trying to figure out the minimum race fuel i will need to run

[BigRed350x]

can anyone give me a ball park on what my compression ratio would be

sea level

stock bore

stock stroke

19cc domes

with 170 psi

trying to figure out the minimum race fuel i will need to run

 

Some 110 or 112 will be fine for you. Anything above 155 you need race gas.

[RIPPEN]

On my bike with +4 timing and 170PSI, I run 110 and 91 mix.. I have been told its around 175 psi when you need to run straight race gas..

 

RIPPEN

[fastrthnu]

keep in mind with oil in the mixture your not going to run 93 with a 10.5:1 to 11:1 like with a straight gas motor. I think 150 will put you about 8:1, 160lbs @ about 8.8:1, 170lbs about 10:1. Depends on barometric preasure, altitude, ect as well. Thats a ballpark. either way what lbs you have is what you got, about a 100 or as they said above would work. Engine temps, component material, and weather temps can allow you to cheat a lower level. Hotter will increase the chance of detonation, so runnng a little higher octain would be safer in heat. Plus if your running a say for example 40:1 gas/oil mix over 20:1,. that helps lower the need for higher octain to a few points.

 

CR-PSI-RNGpsi

6.5 ---96-114 18

6.6 ---98-116 18

6.7 ---100-119 19

6.8 ---102-121 19

6.9 ---104-124 20

7.0 ---106-126 20

7.1 ---107-129 22

7.2--- 109-131 22

7.3 ---111-134 23

7.4 ---113-136 23

7.5 ---115-139 24

7.6 ---117-142 25

7.7 ---119-144 25

7.8 ---121-147 26

7.9 ---123-149 26

8.0 ---125-152 27