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  Forum  General  Technical  compression ratio?
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New Post 18/06/2010 13:12
  amartipz
25 posts
No Ranking


compression ratio? 

loved to know what the latest thinking is on the best compression ratio to run, the 7:1 ratio mentioned in the MZ tuning guide seems to require a very small head volume compared to the standard head and i'm starting to have a few doubts. i usually run a 20:1 castor based mix. Squish band,on my engine, is still the same width at present....cheers

 
New Post 18/06/2010 17:22
  pmb5
85 posts
No Ranking


Re: compression ratio? 

 I quit mid 2008, but this is where i was making huge leaps forwards in the power-out of my MZ, working with Brian Rogers.  I doubt this is the sort of info that would be easily given away.

I cant remember what i ended up with, i gave all the paperwork/ research info with my bike but my compression ended up being quite low, with a narrow-ish squish band.  I'm afraid i cant remember the % of the squish with but i think it was only around 20%, maybe 14mm wide and my compression ratio was about 12.5:1 (maybe 22cc?).  I cant even remember the bore size of an MZ (i know my CBR 600 is 67mm :)

Basically I was making my squish band narrower and the compression lower. My aim was always to make my bike rev as high as possible and run shorter gearing, then figure i could make the rest up coming off the corners faster.  Then Deano/Tony H popped along with a bike (and a lot less gut on him which obviously helped) that would destroy mine off the corners and was quick enough top end to hold that gain till the next corner (unless the straights were really long like at the old Silverstone).  I understand they all made another leap forward in 2009 with motor specs (and ridding skill), so most of this info is probably useless now.

 
New Post 18/06/2010 18:05
  Deano
158 posts
10th Level Poster


Re: compression ratio? 

those were the days i remember the race phill, you overtook both me a chris at once , sure it wasnt the motor it was the double slip stream , and im sure i wasnt skill although i remember you boasting that you used all your skill and talent to take us in a straight line lol

 
New Post 18/06/2010 18:12
  pmb5
85 posts
No Ranking


Re: compression ratio? 

Hey! It does take skill to go fast in a straight line, Scott Jerome didn't always manage it without falling off.... its the only place i didn't fall off.

P.s. It was You, Chris, and Matt Baldwin.... i have the whole thing in pictures....So i can say: "look, I used to beat Dean Stimpson" when you're in moto2 :)

 
New Post 21/06/2010 20:29
  amartipz
25 posts
No Ranking


Re: compression ratio? 

Thanks phil for dusting off the cobwebs,  i've gone for a 6.5:1 effective compression ratio, with a reduction of 50% of the squish band, i'll use this as a base to work from, Im assuming with a lot of guys using flat top pistons even this might be a little on the high side.......cheers

 
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