D-Jet engine mods (was Re: Typical)

[Greg Merritt <gregm@engin.umich.edu>]

	Here is a quote from Derek in L.A. ('71 Squareback) who worked with
Gene (RIP) on a Berg long block for his Type III:

>Another piece of VW wisdom that is a load of B.S. when applied to the
>later Type IIIs, is the belief in semi-hemi cutting your cylinder heads
>and shimming out your cylinders to lower your compression ratio to 6.9:1.
>On a D-Jetronic motor, the end result of this exercise is lousy mileage
>and loss of power (not to mention hesitation and backfiring).  You should
>always be running at least a 7.7:1 compression ratio and a fuel pressure
>of 28psi.  *Never* mess with the heads of a Type III with fuel
>injection--this means that semi-hemi cutting, porting, running bigger
>valves, and running hotter cams or ratio rockers are all Verboten.  As the
>D-Jetronic needs to see a certain manifold pressure to run correctly,
>fooling with the rate of airflow or the compression can have anywhere from
>annoying to disasterous results.  So keep it stock!
>
>If you are going to build a bigger engine (please, never more than
>1776cc's, as the car can't handle the heat buildup), just make sure that
>you run the correct size injectors with your motor (e.g. 1.6 -> 1.7 -> 1.8
>litre injectors), and maintain the holy 7.7:1 compression ratio.  It is
>alright if you run a bit over 7.7:1, as long as you check your emissions
>for the proper fuel/air mixture.

	I realize that there is room for differing opinions on some of
Derek's points, :) but I remember him going through lots of discussions
with Gene about how much displacement he could get away with and how to
compensate for it, what kind of head work the f.i. would forgive, etc.
>From Derek's experiences, I'm pretty leery as to what D-Jet can handle
without correction.

	If you do want to tweak it, a company called Simple Digital Systems
has a programmable engine management system for D and L Jetronic engines:

        Manufacturer/worldwide sales      U.S. distributor
        Racetech Engineering              Select Sales
        Bay G 1007 55th Avenue N.E.       5411 N.W. 72nd Avenue
        Calgary, Alberta, Canada          Miami, FL  33166
        T2E 6W1  Ph.403-274-0154          USA  Ph. 305-888-2828"

(from Grassroots Motorsports, Nov/Dec '95, Vol. 12, No. 6, p. 20)

	I have never dealt with them, so direct questions to the company.
(Think US$700 and up for the modifications to your stock system!)

-Greg
'71 squareback
'63 Beetle