[Es2] 3B vs. AAN

Steve Eiche seiche at shadetreesoftware.com
Wed Feb 18 12:34:12 EST 2004

You would use the AAN bearings.  Supposedly the AAN rods are stronger 
than the 3B, but they look identical to me.  Most people use aftermarket 
rods like Carillos.

As for the AAN being a better bottom end, I can tell you this much; a 
local 3B converted ur q has gone through two 3B engines and now has an 
AAN bottom end.  The first 3B broke a rod, which subsequently ventilated 
the block and broke off the starter and motor mount.  The second 3B was 
luckily shut off after it started making noise.   It bent a rod.  
Neither time was there evidence of a spun rod bearing.  The AAN bottom 
end has been in for over a year now, with several track days and no 
problems, running the same or more power with the same 3B injection.


Patrick Yam wrote:

>Wow Steve, thank you very much for all the info and experience. I know these
>messages take up time and I appreciate your efforts.
>So, let's say I get a 3B motor and plan for a complete rebuild. Am I able to
>use the AAN internals to rebuild the motor in the 3B block?
>What parts could significantly improve the internal engine mechanics of the
>Thanks, Pat
>----- Original Message ----- 
>From: "Steve Eiche" <seiche at shadetreesoftware.com>
>To: <desmo888 at comcast.net>
>Cc: "Patrick Yam" <pkyam at bitstream.net>; <es2 at audifans.com>
>Sent: Wednesday, February 18, 2004 11:43 AM
>Subject: Re: [Es2] 3B vs. AAN
>>I would not agree with this at all.  I assume that you are looking to
>>put a 20V into a B2 (4kq, ur q) or B3 (CQ or 80/90q), using a 3B from a
>>'91 200q, or AAN from a '92-95 S4/S6.  I done or helped with conversions
>>on both types on six different cars, from purely stock 20Vts to full
>>race setups.  From a performance standpoint, the AAN has greater
>>potential right out of the box.  It already has the better bearings, a
>>stouter block (little known fact), and the more advance engine
>>management system than the 3B.   If you plan on a performance rebuild of
>>the engine (most of these have pretty high mileage now, so it's not a
>>bad idea) and replacing the rods and bearings, etc., the only advantage
>>the AAN will have mechanically is the slightly better block, and perhaps
>>the nicer timing belt tensioning system.  There are 20Vt engines out
>>there running over 500hp WITH distributors (though not with Motronic
>>injection), so I wouldn't say that the distributor is necessarily the
>>limiting factor, unless you stay with Motronic, which most of us would do.
>>The AAN will cost alot more to convert to fit in an early car.  First
>>off you have the intake manifold which will interfere with the radiator
>>in the side mount radiator cars, necessitating the change to late S2
>>(ABY) or RS2 (ADU) intake, or one of the aftermarketing intakes, like
>>the Wagner Tuning or MTM intakes.  These intakes also require a
>>different fuel rail, as the AAN rail in not compatible.  Then  you have
>>the plumbing from the intake to the intercooler.  If you use the ABY or
>>ADU manifolds, you will need the matching tubes or fabricate your own.
>>The Wagner Tuning manifold requires lots of tweaks, like
>>drilling/tapping the fuel rail bosses, welding on a throttle cable
>>bracket, etc.  It also has no provision for an ISV, so you will need to
>>add the port somehow if you want idle control.  With any of the
>>manifolds, you will need to lengthen/modify the TPS and IAT sensor
>>wiring to fit the new TB location if you use the AAN harness.
>>Next is the water manifold on the head.  The AAN water manifold has the
>>fittings designed for the front mount radiator, and is not easily
>>modified to work on a side mount rad.  This means that you need the
>>3B/ABY/ADU/RR (20V ur q) water manifold.
>>Accessory belt.  The AAN uses a serpentine belt setup.  This is not
>>easily adapted to the early cars, mostly because of the accessories, so
>>most people convert the crank pulley to a V belt setup.
>>Wiring.  The AAN harness is very different in layout than the 3B
>>harness, meaning a lot more labor to get the wires where they need to
>>go.  I can convert a 3B harness to be "plug and play" in about 10
>>hours.  The AAN harness takes twice that time, and requires lengthening
>>wires, etc., which is a real PITA.  For those that haven't done it
>>before, multiply those times by four.  Having the ABY or ADU harness
>>would greatly reduce the time and effort.
>>Flywheel/clutch:  If you are putting the engine in a B2 car with an 016
>>transmission, you need the 016 flywheel, like that of the '91 200q.  The
>>ur qs have the timing pin 2 degrees off from the later 10V turbos, so
>>you really want the lighter 200q flywheel.  If you are using an 01A
>>(CQ/80/90q) transmission, you can use the stock flywheel from the car or
>>the S4/S6 dual mass flywheel with the appropriate clutch.   The timing
>>pins are in the right place on any of the later flywheels, so you do not
>>have to worry about that.
>>What would I recommend?  If you want an AAN in your car, try REALLY hard
>>to find ADU or ABY parts (water and intake manifolds, harness, plumbing,
>>etc.)  used in Europe.  You can find this stuff quite regularly on
>>ebay.de, and many of the sellers will ship to the US.  Watch out though,
>>as fraud is much more common there.  I've gotten complete junk a couple
>>of times.   There are also some suppliers that commonly ship to the US
>>outside of Europe if you look.  I'm not going to give away _all_ of my
>>secrets here.
>>There are some other "detail" issues, but that is the major stuff.
>>Quick overview:
>>AAN: slightly better performance with relatively simple mods, more
>>money, more effort
>>3B: cheaper and easier, takes a bit more to "beef up"
>>desmo888 at comcast.net wrote:
>>>Very little as long as you have all the elecronics and harness...
>>>Dave K.
>>>>What are the main transplant issues concerning choosing 3B versus AAN?
>>>>Es2 mailing list
>>>>Es2 at audifans.com
>>>Es2 mailing list
>>>Es2 at audifans.com

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