Wild Swap thoughts...

["Mark Nelson" <tahoe@msn.com>]

> O.K., with all the talk lately of swaps, I had a thought. How much work
> would it be to physically put the engine from, say, a '93+ S4 into a '93+
90
> CS Quattro?

Sure...money talks.  Expect to spend upwards of $10K or more for such a swap
done right.  If you're mechanically inclined (meaning mechanically and
electronically savvy) and have the factory workshop manuals for the '91
200Q, S4/S6, and 80/90, as well as a slew of tools

> Could you take bits from the earlier I5 powered 80/90 (such as
> radiator and associated front end bodywork, engine mounts, etc.) and fit
the
> S4 I5 in the car?

You don't have to change any bodywork; just the radiator mounts as far as I
know on the V6 cars.  It will require a little bit of fabricating to fit the
intercooler and oil cooler.  I strongly suggest using a front bumper cover
that can provide more air to the intercooler and radiator, such as the RS2
cover.  Myself and a couple of others make these covers.

 Expect to spend $3000 or more for a '91 200Q 3B motor, or $3500 or more for
an S4/S6 AAN engine, complete with wiring harness and ECU.  Then there's the
problem with the 90 series trannies being rather weak; an 01E from an S4
would be the nicest solution, if a 6-speed is too big for the bill...

> What actually is the difference between the S2/RS2 engine
> and the S4?

Depends which year S2; early S2's had the 3B, same as in the '91 200TQ,
which uses a distributor.  The later S2 ABY (late '93 and later) has the
distributorless ignition, as do the S4/S6 (AAN) and RS2.  The S2/RS2 have a
different intake manifold (same as '91 200Q) than the S4/S6, due to space
limitations in the engine compartment.  The S4 has the intake inlet in the
same location where the radiator sits in the B3/B4 bodies.  The exhaust
manifolds are different between the 3B(early S2, '91 200), the RS2, and the
AAN/ABY (S4/S6/late S2).  The most desirable is the RS2 manifold, while the
least desirable is that from the 3B which has a tendency for cylinders 1 and
5 to run hot.  The best solution is to get a Sport Q or MTM tubular style
manifold.

Mechanically, this is pretty much all that's different.  Electronics are a
another mess.

> What about electronics?

Bosch Motronics for both the AAN and 3B, but that's where the similarity
ends.  The circuit boards are completely different and the ECU code is very
different.  The AAN ECU is difficult to modify in that there is no socket
for EPROM's to plug into; they have to be soldered on the board, where as
the '91 200 ECU can be easily modified by pulling the EPROM out of the
socket.  Talk to Scott Mockry for more information on the ECU's.

Wiring wise, it's going to be a pain either way, but the '91 200 harness
*may* be less painful.  You could conceivably buy the ECU plug and pins, and
build the harness using your old harness.

> I have this gut feeling that there must
> be parts out there to make this basically a bolt-on swap (granted, alot of
> bolts, but still, I'm not afraid of wrenches...)

Of course, the engine will bolt right up to the 01A trans in your 90Q, and
engine mounts should be the same in the V6 (anybody confirm this??).  You
will have to fabricate mounts for the intercooler and oil cooler, and work
out plumbing details.  Then there's that wiring problem; might be a bigger
PITA using a V6 90Q as a base...

>	I had this thought because of the serious lack of performance goddies for
> the 12V V-6, and the fact that the S4 swap would be EPA/OBD2 (US) legal
(as
> opposed to the S2/RS2 engine swap, which would not be legal as it's an
> earlier model...). Not to mention that my 90 is starting to get up there
in
> miles.

I think you've been looking at older S2/RS2's.  The S2 was made from 1991 -
1996.  The RS2 was made from 1994 - 1996.  I suggest looking at
http://www.20v.org/s2 .

>	Related question: Is the only difference between the front struts on the
> early to late model 90's due to the increased weight of the V6 up front?
If
> so, would that mean you could use the early model 90 strut/spring kits on
> the theoretical swapped S4-90?

Springs should fit fine.  I don't know what the rates are though...

Perennially, if I had a V6 90Q, I'd rather invest the money in building a
twin-turbo V6, even using a later 30V V6 as a base, since these motors are
MUCH cheaper to buy than 5-cyl 20vt's.  There's also more ECU options
available for 6-cylinder motors, and you'd certainly have much more power
potential.

Regards,
-Mark Nelson
mailto:tahoe@msn.com
http://www.quattrosport.com

'90 S2 (rally car)
'90 CQ (still trying to figure out my motor situation...)
'94 S4
'85 4ktq