PISTON COMPATIBILITY????
01 November 2008, 03:24 PM
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PISTON COMPATIBILITY????
hi guys can anyone tell me if the pistons in a pre 98 2.0 turbo engine is different from 98- ???
cdf racing think these are different but will still fit with a thicker headgasket?
cdf racing think these are different but will still fit with a thicker headgasket?
01 November 2008, 05:05 PM
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Up to version 4 mid' '98 uses a different piston to a version 5 late 98 (99) on.
The pistons have a different compression height, and dish volume.
Early pistons are designed to go with the thicker 2.0lt steel gasket, and the late pistons, the thinner steel gasket.
Using a thick gasket on a piston designed for a thinner gasket can adversely effect piston "squish".
Mark.
The pistons have a different compression height, and dish volume.
Early pistons are designed to go with the thicker 2.0lt steel gasket, and the late pistons, the thinner steel gasket.
Using a thick gasket on a piston designed for a thinner gasket can adversely effect piston "squish".
Mark.
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01 November 2008, 07:45 PM
#8
The piston pics you have posted are Version 2 WRX Cast "Dog Bone" pistons.
If they are oversize, they will be marked .25/.50 on the crown ( under all that carbon ).
These are the same Version 2 WRX pistons
These are Version 3 ~4 pistons - WRX Cast on the left and STi forged HF on the right
Mick
If they are oversize, they will be marked .25/.50 on the crown ( under all that carbon ).
These are the same Version 2 WRX pistons
These are Version 3 ~4 pistons - WRX Cast on the left and STi forged HF on the right
Mick
01 November 2008, 08:16 PM
#9
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Well in the course of my build I got quite involved in figuring out piston types because I have a v4/MY98 car with an early STi2 RA CDB and STi4 heads.
As already stated, pre and post 98 are different. The pre-98 Wiseco pistons that I am using have a taller compression height, i.e. they protrude over the deck slightly. The later model pistons (and most other aftermarket 'off the shelf' forged pistons are one-size-fits-all for this later design) are the opposite, they come up slightly underdeck. Hence earlier use a thicker gasket, later use a thinner, 1.3 and 0.6mm as standard respectively IIRC.
You could use later pistons on early heads, but would need a thin gasket. Bottom line is the head and piston combo determines the gasket requirement to keep the CR in the right range of 8.0-8.5:1 depending on what you want. As for the effects on squish, I'll leave that to others.
As already stated, pre and post 98 are different. The pre-98 Wiseco pistons that I am using have a taller compression height, i.e. they protrude over the deck slightly. The later model pistons (and most other aftermarket 'off the shelf' forged pistons are one-size-fits-all for this later design) are the opposite, they come up slightly underdeck. Hence earlier use a thicker gasket, later use a thinner, 1.3 and 0.6mm as standard respectively IIRC.
You could use later pistons on early heads, but would need a thin gasket. Bottom line is the head and piston combo determines the gasket requirement to keep the CR in the right range of 8.0-8.5:1 depending on what you want. As for the effects on squish, I'll leave that to others.
01 November 2008, 08:51 PM
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You really don't want to use the later Wiseco piston (K588M925) with thin gaskets, & V4 heads unless you want 9.2:1 cr +. As it is, those pistons will give circa 8.9:1 with thin head gaskets, and V5 > heads.
That's before you take into account any head, or block skimming !
That's before you take into account any head, or block skimming !
01 November 2008, 09:01 PM
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ok does that mean my engine will need the pre 98 pistons?
is there anything special about "dog bone" pistons or are they just standard issue in all engines.
i'm not gonna fit the wrong pistons and try to figure out the compression ratio as i'll only get it wrong and bend my valves or summit.
is there anything special about "dog bone" pistons or are they just standard issue in all engines.
i'm not gonna fit the wrong pistons and try to figure out the compression ratio as i'll only get it wrong and bend my valves or summit.
02 November 2008, 01:06 PM
#19
adzer, so to summerise, I think 
what people are saying is that if you go for either a v.3 or v.4 head, then you can fit either v.3 or v.4 pistons into it (plus a thick head gasket) i.e. the v.3/4 heads/pistons are interchangeable.
<I've probably just unwittingly added to the confusion now, lol>
what people are saying is that if you go for either a v.3 or v.4 head, then you can fit either v.3 or v.4 pistons into it (plus a thick head gasket) i.e. the v.3/4 heads/pistons are interchangeable.<I've probably just unwittingly added to the confusion now, lol>
Last edited by joz8968; 02 November 2008 at 01:08 PM.
02 November 2008, 01:27 PM
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all i'm told from the seller is that he sells pistons for -98 and pistons for 98 on.
so would the 98 on pistons be for v5 and up?
which means i need pre 98 pistons?
so would the 98 on pistons be for v5 and up?
which means i need pre 98 pistons?
02 November 2008, 06:06 PM
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