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?

 

anyone?

 

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.

 

ok, so does that mean i can fit them with the thin gasket??

how do i know what age my block is as i bought it from a scrap car

 

As Mark has said - they are different and not interchangeable - Post some pictures up of the Piston crown and underside of the piston,it makes it easier to identify what you have.
Version 5 UK WRX spec pistons are normally HB twin dots.

Mick

 

any idea what age engine i have from these pistons? and if they are standard sized? was told block was removed from a 95 wrx, its a cdb.

 

My Ver V STI pistons are different to yours mate. Mine are almost flat from the dish. Will get some pics for you when I'm home.

Daniel

 

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

 

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.

 

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 !

 

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.

 

What Version heads are you going to use for your build ??

 

v3 or v4 sti heads

 

You will need Vers 3~4 pistons (forged if your going to run big hp) and thick steel head gaskets to keep the Compression Ratio/squish correct.

 

ok so what years are v3-v4?

 

v.3... MY97 (between Sep 96 and Aug 97)

v.4... MY98 (between Sep 97 and Aug 98)

 

this thread has not helped me out at all lol

do i need pre 98 pistons or 98 on pistons to fit my cdb if i'm fitting v3 or v4 sti heads?

 

This should have helped

 

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>

 

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?

 

Yes that is correct

 

thanks guys.

 

i have the same issue, im running a cdb and v3 heads so im going for the early style pistons

hopefully im right

 

yeah they will be ok, i only asked the question as the company i was looking to buy from only had the 98 and on pistons in stock.

 

I have more pre-98 on order

 

good man