JT to Turbo Question

[Jonas K.]

> From: "Erik R" <eringelberg at hotmail.com>
> Subject: JT to Turbo Question

> This may sound like a silly question but I have to ask. If I just bolted on
> the early 5k turbo parts to a 4kJT, without changing the ecu...and just run
> it at 6lbs of boost...would the CIS metering work properly?

None of this is BTDT w/ Audi's, but I've done my homework with VW's and CIS. 

I say go for it. Here's why. The CIS is a very robust system, it will deal with
the turbo just fine. 8.5 CR (as was indicated for the JT) is perfect IMHO for a
mildly boosted street car. as high as 9.0 to 9.5 is also doable, and will help
at the low RPM's where a street car does it's work. As for knock sensing, I'm
not sure about the 4k's system, but for VW's the knock sensing is a stand-alone
system. You need a non-vacuum-advancing distributor with a hall effects sender,
(dunno if the VW would fit on the 4k, probably will) and the box/KS/wiring from
the donor car. (I've wired in knock sensing on a CIS-lambda VW so can assist in
this area). 

BTW, 6-8psi boost sounds like a good range. After that you'll probably need fuel
enrichment. If the JT did not have the load sensing control pressure regulator
of the 5kt, etc. then that should be added and will help. 

HTH
Jonas
90 CQ