max compression on pump gas for a 660?

[ThisGuyAlex]

11:1 piston and deck the head or just 12:1 and leave the head alone? i wanna stay pump gas

[Colorado700R]

11:1 piston and deck the head or just 12:1 and leave the head alone? i wanna stay pump gas

At your altitude, I'd run 11:1 for pump gas.  Your deck height will determine your final compression.

Aaron

[ThisGuyAlex]

i know this....but i was wantin to push it as close to 12:1 as i could get away with on pump gas there's a whole formula for calculating using combustion chamber volume, head gasket thickness, deck height, and piston dome size

[1FST690]

Whats your elevation?

[ThisGuyAlex]

i dunno illinois flatlands

[Sandeater]

Haha where I used to live!!  Oh wait....IL is just a flatland lol nah not really but central IL is!

I would say you could probably run a 12:1 with 93 and be just fine.  I ride at 5k or above and run 87 with an 11:1

I guess ask guys where you live what compression they are running and what octane.  I was just told a lot of us run a higher octane than we really need and we are actually loosing power because of it.

[Peelz]

Haha where I used to live!!  Oh wait....IL is just a flatland lol nah not really but central IL is!

I would say you could probably run a 12:1 with 93 and be just fine.  I ride at 5k or above and run 87 with an 11:1

I guess ask guys where you live what compression they are running and what octane.  I was just told a lot of us run a higher octane than we really need and we are actually loosing power because of it.

I have a friend that rides a banshee that won't shutup about 100 avgas. He mixes his 50/50 with 100 and 91 before oil mixing. I always turn him down. I did finally get to explain the whole compression thing to him, that raptors are built lower for longevity. The extra octane is a waste of money unless you are 12:1 piston or better.

[1FST690]

Octane requirement is a direct reflection of compression, altitude, and cam profile. The higher you are in elevation, the bigger the cam profile, the higher you can go on compression and still run a lower octane fuel.

[kyledvor61]

Haha where I used to live!!  Oh wait....IL is just a flatland lol nah not really but central IL is!

I would say you could probably run a 12:1 with 93 and be just fine.  I ride at 5k or above and run 87 with an 11:1

I guess ask guys where you live what compression they are running and what octane.  I was just told a lot of us run a higher octane than we really need and we are actually loosing power because of it.

I have a friend that rides a banshee that won't shutup about 100 avgas. He mixes his 50/50 with 100 and 91 before oil mixing. I always turn him down. I did finally get to explain the whole compression thing to him, that raptors are built lower for longevity. The extra octane is a waste of money unless you are 12:1 piston or better.

did he have some warriors before hand?

[ThisGuyAlex]

what does the warrior thing have to do with it?

[Peelz]

what does the warrior thing have to do with it?

umm, yeah, warriors?

[ThisGuyAlex]

the higher octane than you need does in fact cause power loss.....higher octane fuel is harder to burn.....so you don't get a complete burn = loss of power....

[Peelz]

the higher octane than you need does in fact cause power loss.....higher octane fuel is harder to burn.....so you don't get a complete burn = loss of power....

unless you have more compression, ie more pressurized air to help with the burn. That is the easiest to understand explanation for that I've seen so far, Alex.

[ThisGuyAlex]

i know...it's pretty simple if you take out the 14 syllable big words huh.....

[racinjason68]

So since I live at 1000ASL  I can get away with running 11:1 with Stage 2 hotcam and still use 87?   

     I was thinking I would have to run 91.....  But with the good cooling of the rappy and alum head I guess it can get rid of heat pretty easy....

I am the same way I wanna go to the point where I can still run 87.  For now.