6 Aug
2001
6 Aug
'01
4:57 p.m.
On Mon, 6 Aug 2001, Douglas Quebbeman wrote:
yes.
Want a
fuel injection "brain" from a 1968 VW Squareback?
Had Bosch come up with
EFI already by 1968? Every VW (and
Audi & MB, etc) of that vintage that I've seen used
CIS, which was a purely mechanical system.
Then you've never seen any VWs of
that vintage. In 1968, ALL VW type 1 (beetle) and type 2 (bus) used
a
single carburetor.
What I meant was that if it didn't use a carb, all I'd
seen was CIS. I thought EFI was a 70s invention; I stand
corrected!
And BTW, I seek-and-destroy Solex carbs; they were designed only
for the purpose of being replaced by a Weber!
The type 3 was Botch electronic fool injection (Lots
of wires and senders,
and a "brain" in the left rear fender). There was no type 4 yet.
Ah, yes, the Audifans also use this "fool" designation...
through about 1964, the VW type 3 (squareback/
"fastback"/ and the
"rare" "notchback") had a single sidedraft Solex carb, with
single port heads.
Then they switched to to two Solex carbs ????? -2 and -3
'67 VW type 3 had the two carburetors (with dual port heads)
Audi created a monster in Europe with the Audi Coupe 100, which
came in a version that had dual 32/36DGV Solex's... 130HP, not
bad for that engine, if you know it's history (4 cyl OHV, the
block got redesigned into an OHC for the Porsche 924 and some
VW truck sold only in Europe, not to mention the Jeep).
In 1968, the type 3 switched over to Botch electronic
fool injection.
It was a 1600cc engine. It required a little tweaking to make the EFI
work with 2180 (the maximum size that that block could be readily expanded
to.)
So, prior to the fuel crisis and emission controls, what was
the motivating factor for the use of EFI? And why bother with
CIS once you have EFI (spraying fuel into cylinders at off-times
never maid sense).
I have seen a
1969 Audi Super 90 (wagon) that had an aftermarket
Capacitative Discharge Ignition (CDI) System... by 1974, Audis
had those as stock, while CIS was still 1 year off...
My 1986 Audi 5000 CS Turbo Quattro uses a Motorola 6802-based
controller... very simple to upgrade, too.... ;-)
[every time somebody doubts the existence of stuff, I double
the price on it due to its obvious rarity!] 
6 Aug
6 Aug
5:35 p.m.
Douglas Quebbeman wrote:
[stuff delete]
So, prior to the fuel crisis and emission controls,
what was
the motivating factor for the use of EFI?
Cost, weight and reparability. Mechanical injection pumps have to
be mechanically timed to the engine (either gear or belt driven off
the cam), require their own oil supply and return lines, and have
about 973 parts ranging in size from large to itty-bitty. When the
3D cam starts to wear (and it does) it effectively changes the map of
the engine, and anytime you modify the engine in terms of
displacement or compression (or even futz with the exhaust too much)
you have to re-profile that weird 3D cam -- something that requires
taking the pump to bits and having a Really Good Time in a fairly
specialized machine shop.
With D (and L) Jetronic there are knobs that can be turned (although
there are fewer on D -- and the D MAP sensor, while clever, is also
just plain weird), meaning that engine tweaks -- or completely
different engines -- can be accommodated with more or less the same
hardware.
And why bother with CIS once you have EFI (spraying
fuel into
cylinders at off-times never maid sense).
Actually, it makes perfect sense when you realize that you're not
spraying fuel into the cylinder, you're spraying it onto the back
of the (presumably warm) intake valve, which increases the
thermodynamic efficiency of the injection process. It's not as if
there's bucketloads of time for fuel to pool given how fast the
valve is cycling, even at idle. As for "why CIS", it's basically
the same answer as "Why D-Jetronic" -- save for the fact that the
system is almost completely mechanical and therefore doesn't have
the failure modes on 1960's electronics stuffed into a hostile
automotive environment. Essentially the same hardware works on
everything from VWs to BMWs to the Porsche 930 -- in general the
only real differences are the size of the calibration slot in the
fuel distributor (which is a distinct, changeable unit), the profile
and diameter of the airflow horn (which is a simple and inexpensive
part to make -- and if you're crazy enough can be tweaked with
tape-a-weights) and the bias pressure applied by the warm-up regulator
(which is also pretty much the same across most products).
CIS was great because it was bone-simple but produced results at least
as good as D-Jetronic with far better reliability. L-Jetronic fixed
many of the problems of D-Jetronic, but wasn't good enough to displace
it from existing designs. It took Motronic to do that...
--
Chris Kennedy
chris(a)mainecoon.com
http://www.mainecoon.com
PGP fingerprint: 4E99 10B6 7253 B048 6685 6CBC 55E1 20A3 108D AB97
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