S2 pistons
11-25-2002, 01:08 AM
#3
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Stock CR for an S2 is 10.9:1, I do not know what the CC volume is for the S2 engine though.
I wonder, does anyone know if the S2 pistons can be dished to reduce compression for turbo or supercharging? Is there enough material?
-Joel.
I wonder, does anyone know if the S2 pistons can be dished to reduce compression for turbo or supercharging? Is there enough material?
-Joel.
11-25-2002, 01:30 AM
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SidViscous HA!!! good point! But from what I understand the head is what determines the compression........well.....mabe not....aw hell!!!
what would the compression be for an S2 with a 8V head?
what would the compression be for an S2 with a 8V head?
11-25-2002, 07:11 PM
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The first problem would be finding a head to fit the 3.0 block. I hear the 89 2.7 head fits, but they are hard to find.
If you had a 2.7l head, the compression ratio of the 2.7 head on the 3.0 block is probably somewhat higher than the 2.7 motor's native CR due to the additional displacement. I believe the 2.7l also has a CR 10.9:1, so maybe with the extra 10% or so displacement it'd go up to around 12:1? Perhaps the pistons could be dished to reduce this to a manageable level.
-Joel.
If you had a 2.7l head, the compression ratio of the 2.7 head on the 3.0 block is probably somewhat higher than the 2.7 motor's native CR due to the additional displacement. I believe the 2.7l also has a CR 10.9:1, so maybe with the extra 10% or so displacement it'd go up to around 12:1? Perhaps the pistons could be dished to reduce this to a manageable level.
-Joel.
11-25-2002, 07:27 PM
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Pistons are designed with a certain specific amount of mass in various locations to have controlled expansion within their bores, as well as specific heat transfer ability based on mass of a known quantity. removing any material from a piston will alter these characteristics and will probably have less than expected results. removing material from the top of a piston in a large enough quantity to alter CR will probably cause an expensive melted mess.
11-25-2002, 08:05 PM
#7
I would not want to put boost on stock S2 pistons........THE PISTONS THAT CAME OUT OF MY CAR WHERE NOT FORGED BUT CAST!!!!! the 968 piston was forged on the other hand.......I would look into stock 968 pistons and new shorter connectiong rods.....
I have heard that some people remove material from arround the valves in the head to change the comp. ratio but this idea does not sound so hot to me..........
I have heard that some people remove material from arround the valves in the head to change the comp. ratio but this idea does not sound so hot to me..........
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11-25-2002, 10:54 PM
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I think the Calloway turbo 944's used stock pistons that were dished to reduce the CR, but perhaps those were early forged pistons. If there were enough material in the piston such that dishing was safe, I think it'd be better to dish the pistons then it would be to use shorter rods and end up with no squish band. A cast piston probably wouldn't be strong enough though.
-Joel.
-Joel.
11-27-2002, 06:45 PM
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[quote]Originally posted by Larry Parker:
<strong>I would not want to put boost on stock S2 pistons........THE PISTONS THAT CAME OUT OF MY CAR WHERE NOT FORGED BUT CAST!</strong><hr></blockquote>
Interesting, I was just looking at the 1989 944S2 brochure, and it claims the S2 pistons are forged. I have read that the engine changed a little in 1990 though, and the rebuild kit that Zim's sells for the S2 is for 90-91 only so maybe the forged pistons were 1989 only?
-Joel.
<strong>I would not want to put boost on stock S2 pistons........THE PISTONS THAT CAME OUT OF MY CAR WHERE NOT FORGED BUT CAST!</strong><hr></blockquote>
Interesting, I was just looking at the 1989 944S2 brochure, and it claims the S2 pistons are forged. I have read that the engine changed a little in 1990 though, and the rebuild kit that Zim's sells for the S2 is for 90-91 only so maybe the forged pistons were 1989 only?
-Joel.
