re: intercooler ramblings

[C1J1Miller@aol.com]

As I understand it, a recommended upgrade for chipped 10v turbo 5000/200's is 
a better  (more efficient) intercooler than the stock 2-pass unit.  The 
factory upgrade is the single pass slightly longer length '91 200q20v 
intercooler, which requires a new cross-pipe and some metal work to fit into 
the 10vt cars (as I understand it).

Another recommendation is to rework the factory 2-pass intercooler into a 
single pass intercooler, using new end tanks and some custom plumbing.  Any 
idea on why the factory used the 2-pass?  As I recall, it was used on the 10v 
turbo cars in USA/Canada through '91; the 10vt cars in europe got a single 
pass intercooler at some (earlier) point.

Third option is to have a custom unit fabricated (Spearco etc.); however, 
there's not much room for a bigger system.  Listers have done this and 
reportedly got a larger more efficient system to fit in the stock location.

Anyone considered adding a second intercooler into the system, rather than 
adding a larger unit?  Seems that the intercooler off an A4 1.8t or other 
small car, or an urS4/S6 unit could be plumbed in place prior to the stock 
10vt intercooler, perhaps placed down low like on the urS4/S6.  Or, if you're 
fabricating a custom cross-pipe from the turbo across the front of the car to 
the intercooler, perhaps that cross-pipe could be "finned" or designed to aid 
in cooling (might require slotting the bumper cover?).  Or placed down low 
where the auxiliary radiator is on the 200q20v.  Or perhaps a good place to 
add that air-to-water intercooling from a small radiator placed elsewhere...

I would expect that the drawbacks would be: more drag from internal friction, 
and a higher volume of (pressurized) air in the system, leading to more 
perceived lag.  Isn't that why they moved the intake on the later 20vt cars 
to the front, to reduce the pipe lengths?  I would have swapped the radiator 
and air cleaner positions as well to isolate hot and cold sides of the engine.

A second intercooler (i.e., larger system) should have the capacity to cool 
more air before heat soaking and reducing efficiency; a tradeoff against lag 
and pressure loss through friction.  On a track car, where the turbo is kept 
spooled up, this might be acceptable.
chris miller, windham nh, c1j1miller@aol.com
'91 200q20v ==> http://members.aol.com/c1j1miller/index.html