Cylinder head Squish?

[fatguy1]

Does anyone know what the least amount of squish a person can run on a rotax 800 before he has to run fuel higher than 100 octane?.... How about 92 octane?....

I have seen stockers run 0.065" on 92 with no problem. However the race book (05) says their MOD runs 0.055" but that's with race fuel.

Thanks in advance.

 

[triple7]

That is totally dependent on the shape of the cylinder head that you are running. Get the correct shape and you can run 25, with the stock skidoo shape you cant run anything like that. 50 thou if you are careful...maybe

 

[fatguy1]

That is totally dependent on the shape of the cylinder head that you are running. Get the correct shape and you can run 25, with the stock skidoo shape you cant run anything like that. 50 thou if you are careful...maybe

Yeah!, I know that it depends on the shape of the dome, and that the Squish is seperate from the C.R... The race books lists the 600RS as having a 16.9:1 C.R. and they run 0.046" squish. They must run C16 or something like that.

 

[HPJUNKIE]

Yeah!, I know that it depends on the shape of the dome, and that the Squish is seperate from the C.R... The race books lists the 600RS as having a 16.9:1 C.R. and they run 0.046" squish. They must run C16 or something like that.

I believe the 600 snowcross class has to use pump fuel now. (correct me if I'm wrong). If this is the case they must pull out massive timing in comparision to previous years to run @ 16.9:1

 

[SylvanLaker]

squish is important but not as critical as the uncorrected compression ratio. You need to ask yourself what is my corrected ratio? you can have very small squish numbers with a low compression and have no problem. but if the compression is high, watch out..

 

[gpr]

What is the stock squish suppose to be set at? I checked mine tonight and got .057" on the left and .058" on the right and this is on a stock motor.

 

[fatguy1]

What is the stock squish suppose to be set at? I checked mine tonight and got .057" on the left and .058" on the right and this is on a stock motor.

I have only checked 800 HO motors (two to be exact) and they were both about 0.063"-0.067", some where in there, at that I was told that the HO motors had 13.5:1 C.R. (not totally sure myself).

gpr, what kind of motor setup are you running?

 

[gpr]

That squish measurement was on a 2008 800r motor. I bought it used and as far as i know I believe it is completely stock.

 

[NoSecondChances]

What is the stock squish suppose to be set at? I checked mine tonight and got .057" on the left and .058" on the right and this is on a stock motor.

How did you measure the squish? less than 0.060 seems tight to me on a stock motor unless this is at the very edge of the cylinder. As stated above, the head shape will play a large role in the CR and what you can get away with on the squish at the edge versus in the middle.

 

[gpr]

How did you measure the squish? less than 0.060 seems tight to me on a stock motor unless this is at the very edge of the cylinder. As stated above, the head shape will play a large role in the CR and what you can get away with on the squish at the edge versus in the middle.

I check squish with thick solder wire and measure it at the edge of the cylinder. I always measure it out at the edge because this is the tightest area and seems to be more consistant way to measure, for me it is anyway. Not only will head shape play a part in how much compresison you can run but a big part of it is the squish band. Size, shape, width, angle etc... is a huge factor in the dome but all of that leads into a long conversation.

What is everyone else getting for squish? i liked the fact that it was almost identical on each cylinder for my motor

 

[fatguy1]

I check squish with thick solder wire and measure it at the edge of the cylinder. I always measure it out at the edge because this is the tightest area and seems to be more consistant way to measure, for me it is anyway. Not only will head shape play a part in how much compresison you can run but a big part of it is the squish band. Size, shape, width, angle etc... is a huge factor in the dome but all of that leads into a long conversation.

What is everyone else getting for squish? i liked the fact that it was almost identical on each cylinder for my motor

I measure the squish the same way and just assume that every one is looking for the measurement right next to the cylinder wall, I'm I out to lunch on this one?