What is ideal compression??
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Road Captain
Joined: Apr 2010
Posts: 513
Likes: 3
From: Charlottetown, Prince Edward Island
What is ideal compression??
Hi all,
I recently upgraded my 96" with an S&S 106", TW-555's, etc... I'm really happy with the results although I don't have dyno access so I don't have any numbers to speak of. I settled on this kit as compression was 10:1:1, I see most kits go with 10:5:1 but I thought this would suit my riding style better. Anways I recently bought a set of heads worked by Hillside and now in the midst of getting them installed. My mechanic called me with "concerns" the other day, turns out the heads have been milled as well which may raise my compression over 10:5:1 - after weighing the pros and cons I decided to go ahead and install them. I realize these will add quite a few horses to my ride but is there anything else to be concerned about other than the obvious? Just wanting to hear from someone who has a similar setup.
I recently upgraded my 96" with an S&S 106", TW-555's, etc... I'm really happy with the results although I don't have dyno access so I don't have any numbers to speak of. I settled on this kit as compression was 10:1:1, I see most kits go with 10:5:1 but I thought this would suit my riding style better. Anways I recently bought a set of heads worked by Hillside and now in the midst of getting them installed. My mechanic called me with "concerns" the other day, turns out the heads have been milled as well which may raise my compression over 10:5:1 - after weighing the pros and cons I decided to go ahead and install them. I realize these will add quite a few horses to my ride but is there anything else to be concerned about other than the obvious? Just wanting to hear from someone who has a similar setup.
Thread Starter
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Road Captain
Joined: Apr 2010
Posts: 513
Likes: 3
From: Charlottetown, Prince Edward Island
best case scenario is the compression comes in at 10:5:1 and no higher. He did mention octane boost in the fuel - also mentioned detonation issues... Can someone elaborate on this in laymans terms??
Road Master
Joined: Jan 2011
Posts: 855
Likes: 6
From: Riverside, Ca.
10.5:1 on a water cooled engine is usually no prob. with premium fuel. When it's an air cooled engine and ambient heats up or you get in heavy traffic with minimal air flow then detonation can become a real problem.
Tourer
Joined: Feb 2007
Posts: 252
Likes: 0
From: Arkansas
compression
Calculated compression is one thing, and running compression is another. 10.5:1 with the right cam, and you can easily run pump gas.
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Outstanding HDF Member
Joined: Nov 2006
Posts: 2,144
Likes: 10
From: Mass
...simple rule of thumb...if you want reliability, and longevity...then keep it at 10:1 or less...if you want peak performance and don't care how long the motor lasts...then go over 10:1 to whatever floats your boat.... me personally..I see no need to go over 10:1 with all the cams and gearing out there available..plus..you don't have to get into comp-releases, which can act up if they're electric...
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Seasoned HDF Member
Joined: Mar 2008
Posts: 9,384
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From: Central Texas
I dont know to much about numbers,
but I am runing 10.5:1 compression in
a SE 103 build. I use the highest
octane pump gas that is handy, in hot
Texas weather without an oil cooler and
my bike runs just fine with plenty of pep.
but I am runing 10.5:1 compression in
a SE 103 build. I use the highest
octane pump gas that is handy, in hot
Texas weather without an oil cooler and
my bike runs just fine with plenty of pep.