# compression ratio: 16v ABA. 9A low comp. JE pistons?



## the kevin (Feb 12, 2004)

i'm building a boosted (t3/t4 50 trim) aba 16v. i've read all over the place that for high boost i need to use ABA pistons, resulting in a CR close to 7:1. the 9A pistons are supposedly like 9:1.
i was hoping for something closer to 8-8.5:1 because i dont want it to be a total dog off throttle. keep in mind i'll be using an early ABA crank (forged) and forged rods/pistons.
would it be stupid to run regular CR 9A pistons (resulting in 9:1) on 15-20 psi if all of the internals are forged?
so would my best bet be to run ABA pistons, low CR 9A pistons, or the regular 9A pistons?
any idea what the CR would be with the lowered compression 9A JE pistons?
shooting for 300+ whp and maybe crank it up a little for the dyno. mk1 jetta 2-door, btw.



_Modified by the kevin at 2:19 PM 8-15-2006_


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## pozer (Dec 21, 2001)

*Re: compression ratio: 16v ABA. 9A low comp. JE pistons? (the kevin)*

I believe its 8:1 compression. The off boost performance is just fine with ABA pistons. 
You can run 20psi daily on either the stock ABA pistons or even 9:1 JE forged its your choice and your money it all comes down to tuning. http://****************.com/smile/emthup.gif


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## the kevin (Feb 12, 2004)

*Re: compression ratio: 16v ABA. 9A low comp. JE pistons? (pozer)*

so:
stock ABA = 7:1
9:1 9A = 8:1
10.8:1 9A = 9:1
correct?


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## pozer (Dec 21, 2001)

*Re: compression ratio: 16v ABA. 9A low comp. JE pistons? (the kevin)*

Stock ABA is suppose to be 8:1


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## push (Apr 12, 2003)

*Re: compression ratio: 16v ABA. 9A low comp. JE pistons? (pozer)*

stock ABA pistons are 8:1
stock 9a pistons in an ABA block with ABA rods are 9:1


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## the kevin (Feb 12, 2004)

*Re: compression ratio: 16v ABA. 9A low comp. JE pistons? (push)*

the main reason i was considering the 9:1 JEs is because they have the valve relief cuts in the top.


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## pozer (Dec 21, 2001)

*Re: compression ratio: 16v ABA. 9A low comp. JE pistons? (the kevin)*

If you plan on running aftermarket cams and pushing it over 7200rpms I personally would recommend the valve relief you can never be to safe. http://****************.com/smile/emthup.gif


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## the kevin (Feb 12, 2004)

*Re: compression ratio: 16v ABA. 9A low comp. JE pistons? (pozer)*

stock cams, lots of boost.
i'm hoping for 300whp at around 17psi... but i would probably crank it up to the mid 20s for dyno day.
i was thinking the lower comp. 9A pistons would give me a slight compression bump, but the internals would be able to handle that plus 20psi b/c everything will be forged...
i'm definitely going with forged rods/pistons, i'm just trying to figure out which pistons to run.


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## pozer (Dec 21, 2001)

*Re: compression ratio: 16v ABA. 9A low comp. JE pistons? (the kevin)*

The idea of the ABA with the 16v head is so you don't need forged parts and you save allot of money. The stock bottom-end will hold 30psi "depending on the turbo" no prob with the correct tuning. 
I ran 18PSI daily for 11months until my exhaust manifold cracked and this was on chip tuning.



_Modified by pozer at 1:10 PM 8-17-2006_


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## Pats16vGTI (Mar 2, 2004)

*Re: compression ratio: 16v ABA. 9A low comp. JE pistons? (the kevin)*


_Quote, originally posted by *the kevin* »_the main reason i was considering the 9:1 JEs is because they have the valve relief cuts in the top.

you wont need these with the aba bottom end. if you pull the head off the motor and put the bottom end at tdc you will see the pistons dont really come all the way to the deck... 
the better thing to do for cheaper results is to use the aba rods rebushed with the 9a[2l 16v] pistons becasue they have a better ring land design and you will still yeild 9:1 compression... dont forget to get an early aba block for the squiters and forged crank... 


_Modified by Pats16vGTI at 6:44 PM 8-17-2006_


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## Stroked1.8t (Jan 9, 2004)

*Re: compression ratio: 16v ABA. 9A low comp. JE pistons? (Pats16vGTI)*

if you need a set of aba rods rebushed for 9a pistons, I have what you need. pistons and rods. rods are fresh from the machine shop. pistons are used, but in good shape. 
changed my plans and will not be needing them. 
http://forums.vwvortex.com/zerothread?id=2745113


_Modified by Stroked1.8t at 10:49 PM 8-21-2006_


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## rhussjr (Aug 7, 2000)

*Re: compression ratio: 16v ABA. 9A low comp. JE pistons? (the kevin)*

ABA with 16V head = 7.8:1 (must have valve reliefs cut into tops)
ABA with stock compression 16V pistons & head = 9.8:1
ABA with 9.0:1 JE 9A 16V pistons = 8:1 (rebushed rods to 20 mm)


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