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Discussion Starter · #1 ·
How big of a difference between the cp 11.5 and the 11.1
Pistons is there? How big of a drop in compression is there?
Is it noticeable in power? The reason I am asking is that I seem
To be having some detonation issues with a brand new 11.5 and
Pump premium 91, and was wondering if it would be worth while changing
To a 11.1 instead. All I can get in town for fuel is 91.
 

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11.5:1 should be good with pump gas. Are you sure you don't have a lean condition contributing to the problem?

Nate
Alba Racing
 

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Thicker head gasket might help if you wanna save some cash. I don't know how much a .5 compression makes but I would think you could get a thicker gasket cheaper then a new piston.
 

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Detonation on our tech piston is very rare. It is usually from poor fuel or poor fuel delivery. I'd check both of those first.

Steve
 

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Discussion Starter · #6 ·
I got a hc3 in it. I am going to try a new pcv first . I just don't want to have to worry about fuel as all I can get is 91 . I got to make this quad 91 compatible.
 

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I got a hc3 in it. I am going to try a new pcv first . I just don't want to have to worry about fuel as all I can get is 91 . I got to make this quad 91 compatible.
The 11.5:1 is the highest compression you can run on pump gas so your good. The .5 to the compression difference from the 11:1 to the 11.5:1 shouldn't be the issue, check out what Steve said....
 

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We have 93 here how many points will octain booster raise the 91 to? I always thought it was bs never tried I run good Pump fuel :lol: I got it out the pump
 

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From The Stix 2 Da Brix
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I always though at 11.5 you should run 93 octane or 91 with a booster additive,if you can get a good one.
 

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99.9% of octane boosters dont do a thing but empty your wallet.
 

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That's why I never used any if I needed more than pump I either got 100 or 110. It's pretty easy to get here.
 

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Discussion Starter · #13 ·
Sure hope this piston works out to be 91 friendly or it has to come out or maybe even grind a bit of the top lol.
 

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You should be fine with 11.5 compression. I run a cp 12.1 on pump gas at 1900 ft of elevation. What is the elevation up your way??
 

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Once you get the PCV in there and tuned up you should be good to go.
 

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My guess is you need to have it tuned its probably lean.
 

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Discussion Starter · #18 ·
Well I went with a pcv a tried a couple different maps and am still having detonate issues , I got a hold of some 94 fuel and that helped quite a bit but did nit cure it 100%. It's happening mid rpm range with a load on , not sure what to do. Not sure if the difference in the 11.1 piston would be worth the change out or not. What is stock comp ratio ?
 

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Discussion Starter · #20 ·
Ya Steve I don't know why it's running like this, I got your map in there now and running some 94 and it is a lot better than last week but still not perfect. Would adding one more base gasket be about the same as changing pistons out to the 11.1 ? I am not worried about the cost of an other piston but don't want to go 11.1 if it's not going to make that much of a difference.
 
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