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.
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.
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....
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
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 ?
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.
A base gasket is cheaper. I think you can get base gaskets made up for as thick as you need them. New piston to drop .5 seems crazy. You could also pull the head and take a grinder to the dome:lol: JK don't do that but it would work.
FYI many CP pistons do have room to have material removed from the dome. For example CP's 105.5mm M1054 has about 60 thousandths that can be removed. You may want to contact CP and see if the Tech piston has that additional meat built into the dome.
I was just joking for real but if it did grind a hole in it the compression would be lower no need to worry about pump gas. I know alot of the builders will take some off the dome to lower the compression if it is needed. But they don't do it with a grinder I'm sure but this is usually with the higher compression pistons(14:1)
We do it on the mill and evenly remove material. Tony @ CP recommends a minimum of 200 thou dome thickness for a normally aspirated motor. Depending on the thickness that was designed into the dome I would say a half a point is possible.
Hey Nate do you figure .5 is realistic with a double stack base gasket (oem) ? If I can take this piston down to 11 to 1 by double stacking and it cures my pinging then I will know that a new 11.1 should work . Or should I try a super rich map and see what that does?
Fuel may help. You shouldnt need more than pump gas at 11.5:1 unless your fuel is poor or you have a lean condition. A base gasket is what about 20 thou thick... I would think you could see about 1/4 of a point lower. Have you tried adding an octane booster to see if that stops the pinging?
Nate
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