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Any questions you have before you begin buying, building and installing.
By gtn116
#48855
Hello all, I recently got my hands on a 1990 VW Cabriolet with a Digifant 2 system. It's a batch fire 4 cylinder. Basically, the intake hoses are cracked and falling apart. Rather than try to source elusive uncracked rubber parts (likely $$$ if available,) I'm wondering if I can get it running on Speeduino. It has a 4-window hall-effect in the distributor. I don't believe it has a crank sensor of any type, and the injectors are wired in a single-bank that's essentially continually pulsed based on the MAF position (potentiometer on a flapper) if I'm understanding correctly.

Does this seem doable, or should I not waste my time trying to get it running with the current setup? Basically build a whole new harness now vs next winter when I won't be driving it anyway.
By Mancino
#48856
Those digi-2 setups are pretty easy to convert to standalone...there are tons and tons of write-ups on VWVortex about how to do it.

A lot of the 16v crowd used those old harnesses to convert them from Jetronic or Motronic to Digi2. Then converted them to standalone when MS1 was new.
By gtn116
#48863
theonewithin wrote:
Mon Mar 08, 2021 9:35 pm
Simone as .

Run it using distributor mode.

MAF you ignore. Not supported.

Have a read through the wiki.
My main concern is hardware, and that may be answered in the wiki. Basically is it OK to run all 4 injectors on one driver, or do I need to run additional wires to separate banks. I've seen the diagrams and read about 2 injectors per driver, but I haven't seen anything about running 4.

The main point of this conversion would be to eliminate the MAF and simplify the parts-hunting aspect of all this.
User avatar
By Chris Wolfson
#48873
Hi,
parts for these cars are available from VAG or aftermarket. Second for a fraction of the VW dealer price.
These engine run really well in stock trim and are not limited by the injection system in power output. The only thing that can kill them are bad engine oil and missed oil changes. A common cause for their end. Do an cam belt exchange and you are good for another 100.000 miles.
So even with the most perfect Speeduino tune you will not gain anything. Please don´t over estimate batch to sequential fueling. You may find better emissions done right, but hardly any power.
Volkswagen did a good job in limiting these engines all around. To find real power you got to work on hardly anything, like valves, pistons, exhaust, cam, manifold and head. Anything is designed for the stock output, not more.

For more power, there is always another VW engine that can be fitted, which usually is better than any tuning on the existing one.
By soultron
#48875
Sounds like we have similar aims. You're ahead of me, already having digifant. I had a carb swapped car but I'm switching to a fuel rail from a Corrado and other assorted parts.
Eventually I'd like to have wasted spark coil packs but I'll be trying just a distributor signal first.
By gtn116
#48885
Chris Wolfson wrote:
Tue Mar 09, 2021 6:13 am
Hi,
parts for these cars are available from VAG or aftermarket. Second for a fraction of the VW dealer price.
These engine run really well in stock trim and are not limited by the injection system in power output. The only thing that can kill them are bad engine oil and missed oil changes. A common cause for their end. Do an cam belt exchange and you are good for another 100.000 miles.
So even with the most perfect Speeduino tune you will not gain anything. Please don´t over estimate batch to sequential fueling. You may find better emissions done right, but hardly any power.
Volkswagen did a good job in limiting these engines all around. To find real power you got to work on hardly anything, like valves, pistons, exhaust, cam, manifold and head. Anything is designed for the stock output, not more.

For more power, there is always another VW engine that can be fitted, which usually is better than any tuning on the existing one.
It's not cheap or easy to find parts here in the US for these cars. I found the intake pipe I need, but between the price of the pipe, shipping, and import tax, it will be more than I paid for the car, and more than switching to Speeduino!

As far as performance goes, I'm not doing anything wild now. I might do a cam and turbo later, but I don't know for sure. This car is just something for me to tinker with, and I'd like to mess with a standalone EMS, and Speeduino is the most affordable to experiment with.
User avatar
By Chris Wolfson
#48911
Just a simple question: Did you check compression on your engine and monitor how much oil it consumes?

As far as I know the Rabbit was imported in quite large numbers into the US. Maybe you should avoid looking for 1 version parts, as the engine was, basically identical, used in the 3rd one. So you may be searching for parts that are not listed for the one, but dead cheap for a series 3 Rabbit. Finding matching parts in high quality for low prices is time consuming but saves me about 80% compared to VAG prices. As we do import Bettle, BMW and Alfa Romeo parts from the US, there should be a huge aftermarket for the much more common Rabbit too. Maybe you are searching wrong places.

when you think about tuning, even turbo, what do you get with such a car like yours? Usually a worn out engine with leaking gaskets. So, if you plan further, a 10 years younger engine from the scrap yard should be in most cases be the better solution.
Even a 200$ used, dent and rusted series 3 Rabbit as donor has in 9 from 10 cases a better engine. It will fit perfectly into your old chassis. Look for one with the identical looking 2.0 liter 8 valve engine. Can be refreshed with new gaskets, piston rings and bearings for a few bucks and increases driving fun by 100%. With some simple DIYS tuning measures it will outperform anything you can build from your engine, be more reliable and use less fuel.
How to do it and what to take care of can be found on the net anywhere

Maybe the better way for you?
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