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Discussion Starter · #1 ·
does anyone know what the compression ratio is on a sy moto??
 

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I believe it was posted before the hack that they have a 10:1 SCR. But I don't think it was specified as to what motor. A compression check shows a cylinder pressure of 120psi on my bike (the unbranded motor). And you really can't convert that into a static compression ratio because of the intake and port timing (because I don't know what it is).


So it's safe to assume it's 10:1. Just high enough to run 91/93 octane and do well but not high enough to run full out 110 and get the full potential.
 

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Ooops, let me restate that last comment.

Edit - Just high enough to run 91/93 octane and do well but not high enough to require the use of full out 110.
 

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Discussion Starter · #4 ·
thanks for the info
 

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Would this be correct?

0psig = 14.7 psia
120 psig = 134.7 psia
cr = 134.7/14.7 = 9.16

what is the higest cr to safely run 93 octane pump gas at?
 

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I dont know, but my car was running 11:1 on stock management running 92 and it ran perfect, no pinging or anything like that ever.
 

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detonation,. or pre igniton, is realley bad if you can here it.
on a scale of 0 to 10, 0 being not bad at all, and 10 being if your engine runs another 30 seconds its a mericle, if you can actually hear the detonation of a engine it is rated around 7.5 to 8 on that scale.


they measure the gas # by squeezing it , at what ever preassure it spontaniously burst to flames is its octane rating. 87 octane sucks, it will ignite it self at lower compression ratings than 93 octane. back in the day they used to alter the fuel with this stuff called tetracol led, it would make crappy grades of gas hold a higher rating of preassure before spontaniously igniting. so led gas was like 87octane with the lead crap made that gas act like 99octane.

then it became illegal cause it was bad for the ozone. but thats a whole nother story.
what were we talking about again?
 

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I know they are not cars but gas is gas and can only handle certain levels of compression, no matter where it is compressed. and I know there could be some detonation you cant hear but it just ran SO smooth and never stumbled on itself ever or stuttered anywhere in the rev range at any throttle position. I know I was pushing it though.
 

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I have read somewhere that some of the Polini or Blata engines were running 13:1. I don't know if that's Static Compression Ratio or Dynamic Compression Ratio. More than likely it is SCR whereas the DCR would be quite different. I believe they still run 93 octane pump gas. I could be wrong.

SCR is only part of the equation though. The DCR is what constitutes what kind of octane you'll need to run in your motor. Example: You can create an engine with 12:1 SCR but put a large enough cam in it to lower the DCR to pump level octane requirements. Of course it would not make for a perfect engine combination. Anyway, if you could find out what the intake and exhaust porting timing was you should be able to figure out what the DCR is.

DCR dictates what octane range your engine will need.
 
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