80tq drag racing- Intercooler reevaluation [long]

[Bernard Littau]

I've been following this thread with some interest.

>
> Interesting- much of that heat can't be helped, but I've got to wonder if
> the turbo upgrade is really the right answer- if it's heat-soaking that
> badly I think to probably are outside the turbo's efficient range.
>

My understanding is that the harder the turbo must work for a given boost
level and volume, the more it heat soaks.  I guess it is a volume and
contact area sort of thing, as I assume the compression of gas generated
heat would be the same in both a small and large turbo for a given level of
boost.

> You're sure there's no knock? I'd expect a super-hot intake charge to have
> you detonating all over the place, which I would expect to cause your
> timing to be pulled back and kill your power, just as you observed.
>

The Audi ECU has an input charge temperature sensor.  When the temperature
of the charge goes up, the ECU drops the boost (and perhaps the timing) even
before there is detonation.

I am thinking I'll soon need to look into a bigger intercooler, as I
certainly notice the heat build up in my 5ktq.  The stock set up is good for
a quick sprint, but not for any sustained driving at boost.  I do have a
stock intercooler in the stock location converted to single-pass format.  I
can't tell if my percieved better intercooler performance is due to the
single-pass nature, or to the addition of the bypass valve, but in either
case, I sense the car needs more cooling of the intake charge when I go over
the local mountain pass at boost.

Anyone have any BTDT on mounting larger than stock intercoolers on a 5ktq
front end?  I'd like to keep the bumper and the overall grill look :-)

Best,

Bernard Littau
Woodinville, WA
'88 5ktq