High Compression Pistons


K

kiwi

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Mar 31, 2009
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How are some aftermarket pistons claiming a higher CR than standard b16b pistons when they have a smaller Dome Volume??

Example the standard has dome volume of 8.6cc and 10.8 CR

I think a JE has a Dome of 8.1cc claiming 11.5 CR
 
kiwi said:
What you mean they have a larger crown height? Anybody got any reliable data on this?
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All the reliable data you need is in the pictures! go take a look..you can see that some aftermarket pistons have a much more taller crown than PCT pistons.
 
JDMarron said:
All the reliable data you need is in the pictures! go take a look..you can see that some aftermarket pistons have a much more taller crown than PCT pistons.
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Dont think so we are talking less than 1mm! You must be geting confused with dome height/volume.
 
Vtec6000 said:
Yes exactly or compression height as some refer to it.
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Well that would make sense but look at the figures. (Not sure how reliable they are hence asking for figures)

Taken from JE piston site; Dome Volume 6.7cc Comp Height 1.181(30mm) CR 11.5:1

Standard b16b pct piston taken from Comp Calculator on Resource area: Dome Volume 8.63 Comp Height 30.73mm CR 10.8:1

So as you can see smaller comp height and dome volume but giving higher compression ratio!

So if these values are reliable can you take comp ratios provided by piston manufacturers as said?? All this is leading onto my engine build and the quest for higher comp ratio with standard displacement.
 
kiwi said:
b16a (Same chamber volume)
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Well there's your answer, stroke length affects the comp ratio also so you can't compare the pct piston in a b16b block comp ratio to that of a JE piston in a b16a block if you were to put pct pistons in a b16a block the comp ratio would be up around 11.5:1 and actually some claim higher(11.9:1)due to the dome size
 
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b16a pistons will give a lower compresion ratio if used in a b16b block in the same way b16b pistons will give higher compresion if used in a b16a. No one sells after market forged pistons for the b16b. It has a unique rod piston combo
 
Let me know if sale falls through i'll take these!

Even at 8.16cc still smaller than the pct 8.63 with only 10.8:1 CR. Its an understanding thing.
 
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