questions about higher compression pistons


7 replies to this topic
  • Octanee

Posted April 19, 2012 - 12:42 PM

#1

im wondering about the higher compression pistons, i can get 91 or 94 octane, or i can also get av gas which is the 100LL, i have a 00 yz426f that it needs engine work, and will replace piston, i figure i may as well put ah igher comp piston in it, i might also rebuild my 06 yz450f, same thing, thinking higher compression piston.

so, my questions are, is will it give throughout all the range more power? im not 1 to rev way the hell up at like the rev limiter because there just aint no power there!, but of course guys do it any how...?, i do lots of trail riding, we have a kind of community maintained outdoor little track, its alright, but nothing much..... im looking for all around i guess more torque would be nice? i know my 06 450 with stock cams n crap, its got some good power all around and more so in the mid range, not so much higher up it really drops off, so would the higher compression piston add more power to the mid range and maybe bottom end?


i also know that higher compression = cant rev as high, But that dont matter to me because i dont go way up high in the rpm's i go where the power is and once im dropping out i shift,

what are the benefits and disadvantages in general to higher compression pistons in these 450's or 426,'s... AND what octane rating for each piston/compression ratio?

i the lowest elevation i ride is about 3,000 ft and max is probably 7,000 ft, Thanks again!

Edited by Octanee, April 19, 2012 - 03:13 PM.


  • grayracer513

Posted April 19, 2012 - 03:02 PM

#2

im wondering about the higher compression pistons, i see grayracer says stock 450's actually need only 86 or so octane fuel?


Let's start by having you go back and re-read that post. If you still think that's what I said, please link it here so we can discuss the matter.

  • Octanee

Posted April 19, 2012 - 03:09 PM

#3

Let's start by having you go back and re-read that post. If you still think that's what I said, please link it here so we can discuss the matter.


so many threads and posts, i could of read it wrong, i believe you had said bikes call for like 95 "ron" which is equivalent to about 86 octane, but i think i said it wrong, i just meant if in theory its 86 octane, then i would think theres room to improve the power? now i know octane is somewhat irrelevant to power, you stick too high octane in a bike not meant for that high octane and it wont run as well, ive learned lots about the snowmobiles end of stuff, i've done my own home made turbo kit for snowmobile of mine...but when it comes to these bikes thats another matter, + its a 4 stroke and not 2 stroke,

but like i said, im wondering on the higher compression pistons, ive searched the forum but havent come up with much at all other then the fact that it cant rev as high.... which i know, so im just trying to get some answers

Edited by Octanee, April 19, 2012 - 03:12 PM.


  • grayracer513

Posted April 19, 2012 - 03:34 PM

#4

What I said was, there are 3 major methods of measuring octane: Research (RON), Motor (MON), and the North American Anti-Knock Index (AKI). The oft quoted 95 octane requirement for your YZF is 95 RON which equates to about 86 MON, but you will not see either of those numbers on a gas pump near you. What you will find is the AKI, which is the average of those two numbers, so anything you see above 90.5 meets the 95 RON requirement.

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  • Octanee

Posted April 19, 2012 - 03:45 PM

#5

What I said was, there are 3 major methods of measuring octane: Research (RON), Motor (MON), and the North American Anti-Knock Index (AKI). The oft quoted 95 octane requirement for your YZF is 95 RON which equates to about 86 MON, but you will not see either of those numbers on a gas pump near you. What you will find is the AKI, which is the average of those two numbers, so anything you see above 90.5 meets the 95 RON requirement.


oh, i guess i miss read some of it,, my bad, but i understand what your saying now, so that said, 91 octane basically, i dont suppose a higher compression piston would work for 94 octane? or would the jump be to something like 100 octane fuel, and at 100 octane i'd get into using the Av gas for

  • grayracer513

Posted April 19, 2012 - 06:13 PM

#6

Try to avoid AvGas. It's the wrong fuel to use in a motorcycle regardless of what the folklore is. If you are riding at 3000 feet and higher, 13.5:1 should be OK on pump premium.

  • Octanee

Posted April 20, 2012 - 10:57 AM

#7

Try to avoid AvGas. It's the wrong fuel to use in a motorcycle regardless of what the folklore is. If you are riding at 3000 feet and higher, 13.5:1 should be OK on pump premium.


ok thanks, and av gas seems to be ok, but ive been running it in my snowmobile with the home made turbo kit, which is a 1000CC 2 stroke engine, runs good so far, but it can behave different in a motorcycle/4 stroke engine, none the less thanks again

Edited by Octanee, April 20, 2012 - 10:57 AM.


  • fastyz250

Posted April 22, 2012 - 01:42 PM

#8

Gray, why do you say to avoid av gas? i ran it in my 06 for a long time before the rebuild and never once had a problem it made the bike run much better. Just wondering what your thoughts were.





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