[Es2] 3B vs. AAN

[Steve Eiche]

Dave,
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"

HTH!

Steve

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?
>>
>>Pat
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