# ABA 16v compression and pistons question



## Flyingsheep (Apr 24, 2008)

For those of you with an ABA/16v hybrid setup using carbs or ITBs, what kind of pistons are you using? Also what's your compression ratio? I did some searching and couldn't find info on this with these kinds of setups. I could only find this kind of info on turbocharging an ABA 16v. And is there really a difference between an ABA with a 9a head and a stock 9a engine when doing a setup like this?
Also what is a good compression ratio to go for with dual carburetors and or ITBs? I know it depends on your application but I just want an idea. I've been doing lots of reading trying to gather a lot of info. I like learning about this stuff and would someday like to get into it. Thanks.


----------



## B4S (Apr 16, 2003)

*FV-QR*

You'll need to buy genuine ABF pistons, because even with 9A units swapped in it'll only hit 9:1. I ran an ABA 16vT a few years back, and used a stock ABA bottom end. Came out to 8.1:1 or something low like that.


----------



## Flyingsheep (Apr 24, 2008)

Actually I read a lot in the hybrid forum and now I get it. Pretty much everyone says that there is no point in putting a 9a head on an ABA if you're going N/A, because you end up spending a whole lot more (ABF pistons) to get the compression back up than it would cost to rebuild a 9a. Thanks for the response.


----------



## diceman469 (Sep 3, 2003)

*Re: (Flyingsheep)*

You could always do this to stir up the mixture....guarantees 13:1 compression that's pump gas friendly:









/end sarcasm


----------



## goofydug (Feb 5, 2004)

I ordered a set of wiseco pistons that raise the CR to 11:1. 
They weren't that expensive either, don't give up on the hybrid


----------



## Flyingsheep (Apr 24, 2008)

*Re: (goofydug)*

Where can you get those pistons? Maybe I won't give up... other people are talking me into it...


_Modified by Flyingsheep at 2:30 AM 11-1-2008_


----------



## goofydug (Feb 5, 2004)

i ordered mine from a place called import performance parts. they took forever but it all worked out fine in the end. You may also be able to just call wiseco or JE directly and ask what they can make for you.


----------



## Flyingsheep (Apr 24, 2008)

*Re: (goofydug)*

Do you have a part number for the wiseco pistons you got? Did you get the ABF ones? Did you have to bore the cylinders so they would fit?


----------



## GinsterGTI (Jun 25, 2002)

*Re: (Flyingsheep)*

Look into bildon motorsports. They had more than one option on pistons. Only thing I don't really know and still need to find out is what will keep me in pump gas range.


----------



## Flyingsheep (Apr 24, 2008)

*Re: (GinsterGTI)*


_Quote, originally posted by *GinsterGTI* »_Look into bildon motorsports. They had more than one option on pistons. Only thing I don't really know and still need to find out is what will keep me in pump gas range.

Lower compression? I'm not really sure how much compression you can get up to until you can't get pump gas anymore, but I've heard like 11:1 or 11.5:1 is okay with pump gas.


----------



## ClownTrigger (Aug 30, 2006)

You can plop a 16v head on an ABA using ABA rods and 9a pistons. You have to rebush the rods for 21mm pins (bushings availiable from VW) and with a stock ABA headgasket, you'll wind up with 9.5:1 CR or so. If you drill the rivits out of the ABA MLS headgasket, you can remove the .040 thick spacer and bring the CR up to ~10.8:1.
Benefits of using the ABA bottom end are longer rods, which equates to a more square engine, and the 60-2 crank trigger. OBD-I ABA shortblocks also have forged cranks and oil squirters.


----------



## GinsterGTI (Jun 25, 2002)

*Re: (ClownTrigger)*

Is the general idea that 9a pistons on ABA rods/block drop them ~1 compression point from what they would be in a standard 9a setup? Thats kinda what I think I have gathered.


----------



## ClownTrigger (Aug 30, 2006)

*Re: (GinsterGTI)*


_Quote, originally posted by *GinsterGTI* »_Is the general idea that 9a pistons on ABA rods/block drop them ~1 compression point from what they would be in a standard 9a setup? Thats kinda what I think I have gathered. 

Somewhere around 1 point. You're basically trying to make an ABF, but the difference is in the compression height between a 9A and an ABF piston. Everything else is the same aside from the pin diameter, but that doesn't affect the CR. To make up the difference, you can either get a set of ABF or custom pistons (expensive, but really the right way), deck the block or the head (irreversible), or use a thinner headgasket ($50).


----------



## goofydug (Feb 5, 2004)

*Re: (Flyingsheep)*


_Quote, originally posted by *Flyingsheep* »_Do you have a part number for the wiseco pistons you got? Did you get the ABF ones? Did you have to bore the cylinders so they would fit?

I don't remember the part#, but they are forged ABF pistons that raised my CR to 11:1. I had the cylinders bored out .020 over, line honed the crank and used ARP hardware throughout (rods, mains, head studs), everything was balanced, etc.
The pistons were ~$500 - $600 with rings.


----------



## CanadianCabby (Sep 1, 2006)

*Re: (goofydug)*

bildon carries them http://****************.com/smile/emthup.gif


----------



## Flyingsheep (Apr 24, 2008)

What, these?
http://www.bildon.com/catalog/...av=62
That's really high compression. I wouldn't want that high for daily use.


----------



## goofydug (Feb 5, 2004)

*Re: (Flyingsheep)*

that is very high, i'd be worried about tuning that on pump gas.
my pistons for reference:


----------



## GinsterGTI (Jun 25, 2002)

*Re: (goofydug)*

The ABF ones are high, but If you use the 12.3:1 9a ones it would be a bit easier on pump gas I would assume. This is what I plan on doing.


----------



## Flyingsheep (Apr 24, 2008)

*Re: (GinsterGTI)*

I'm guessing these are the 9a ones:
http://www.bildon.com/catalog/...av=62
I'd imagine they'd be taken down to 11:1 CR. That'd be nice if they did, but that's a guess. Let me know how it goes for you. I'm really curious.


----------



## MK2_GTI (Dec 12, 2003)

*Re: (Flyingsheep)*

Does anyone know the answer to this I want around 11.1 so could I use the 9a 12.1 pistons? Or get custom ABF pistons.


----------

