scttydb411

i just figured out the pistons i was about to buy (great deal) are 9.0 compression z6 pistons. every spec is the same from the 9.0 compression y7 pistons with the exception of the dish volume. the z6 are -11cc while the y7 are +12.4cc.

anyone know what my compression would be using the z6 pistons? stock on my y7 is 9.4 and i'm willing to go 9.0, but i don't know if i want to go significantly lower than that and i don't know if i want to go higher either. looking at the 10.5 pistons for my car the dish is -4.6cc.

am i correct in thinking that using these will put me at 11.0:1?

Dr.Boost

No way would your compression be that high with a 1.4cc increase.

I tried to ---- with the compression calculator, but came up with some bullshit numbers.

http://www.knology.net/~jediklc/D.htm
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scttydb411

i couldn't use the compression calculator because it uses z6 and y7 as the same selections (older y7 i guess/not 2000 model).

here are the specs and the path i'm thinking, but i'm f#cking confused right now:

10.5:1 2000 y7
Piston Set of 4 - CX/DX/LX D16-Y7 1.6L SOHC non-VTEC - Bore 2.953 - Stroke 3.543 - Rod Length 5.394 - Grams 232 - Dish Volume -4.6cc - Compression Height 1.181 - CC's 34.6 - Compression Ratio 10.5:1 - use ring set 135+3026

9.0:1 2000 y7
Piston Set of 4 - CX/DX/LX D16-Y7 1.6L SOHC non-VTEC - Bore 2.953 - Stroke 3.543 - Rod Length 5.394 - Grams 233 - Dome Volume +12.4cc - Compression Height 1.181 - CC's 34.6 - Compression Ratio 9.0:1 - use ring set 135+3026

z6 piston looking at
Piston Set of 4 - EX/Si D16-Z6 1.6L SOHC VTEC - Bore 2.953 - Stroke 3.543 - Rod Length 5.394 - Grams 228 - Dish Volume -11cc - Compression Height 1.181 - CC's 34.6 - Compression Ratio 9:01 - use ring set 135+3026

looking at this the z6 piston has all the same specs w/ the exception of the weight and dish volume. now it'll yield 9.0:1 in a z6 because of the head, but looking at this info leads me to think if i dropped it in my y7 it would be more like the 10.5:1 piston, but more.

since i'm totally ignorant when it comes to cracking open my engine i always thought a domed piston yeilded higher compression and a dished piston yielded a lower compression. this info above must be using dish volume in a different way than i would've thought of originally.

now using math (not totally ignorant here/i hope) there is a 17cc difference between the 2000 y7 pistons and a 1.5 difference in compression=.0882353/cc. now multiply that by the extra cc difference of 5.4 from the y7 piston and z6=.4764706. now adding that in it would look like 10.9764706 or 11:1.

where's jeff when you need him??

scttydb411

i got those specs from the nopi order page for those pistons and i think the dish/dome cc's are reversed for the 9.0 and 10.5 pistons. if that's the case using my math above it looks like they'd be 8.5:1 in my car...still looking for the answer before i buy these.

i'm getting them for 300 if it looks like they'll work for pistons and rings.

scttydb411

went to the je/srp site and it turns out the y7 pistons are -12.4 for the 9:1 pistons. it looks like the -11 might actually yield 9.3 if i'm correct. still waiting to see if someone knows first hand.

88crxSi

what are you talkin about.. z6/y7 are the same.. only for the block/head dimensions.. the pistons are different.. look again :P

scttydb411

yeah, it looks like if i use a y8 2 layer gasket and the z6 pistons w/ -11 dish i should have 9.2:1.

stillnoturbo

I came up with a 9.3:1 using a 2 layer y8 HG. That last part with the piston to deck height screws me up!

scttydb411

piston/deck height shouldn't change...the compression height of both pistons is exactly the same. it looks like the comp ratio will be determined by which dish i get and headgasket. looks like using the z6 9:1 forged pistons i want i can get anywhere between 8.8:1 and 9.2:1 depending on the headgasket using stock head.