I have been following this thread for sometime and feel I have to ad my few pfennigs.

In my conversion ('82 Diesel Westphalia with '90 8V 1.8L GTI) I specifically chose the Digifant control system after studying all the alternatives for nearly a year. These included the various CIS variants, 2.0L crossflow options, 2.0L Audi's, the 5 cyl. Quantum and Audi motors, turbocharging my existing diesel, adding a Golf/Jetta turbodiesel, putting in a Volvo 760 Turbo diesel (6-cyl VW/Audi) and the Kennedy Subaru option (also studied the Mazda RX-7 rotary twin turbo until Kennedy talked me out of it). Now this was 3 years ago, so some of the pricey conversion options now available were not on the option list. Of all of these my first choice was the Volvo/Audi 6-cyl turbo diesel. Unfortunately, there was no practical way to make it fit. Would have had to pull the engine to replace the notorious timing belt. So, after all the measurements, drawings, torque curve analyses, transmission studies, and cost factors, I settled on the simple I-4 conversion, purposely chose the Digifant engine and purposely stayed with the diesel trans, although I desperately tried to find an '83 diesel 5 speed.

I remain stunned at the wisdom on this list that the CIS and CIS-E systems are more robust, easier to establish performance gains from, and easier to implement in a conversion, more economical, etc., etc. Let me address each of these:

1. Reliability: I now have more than 36 K on this conversion, including trips from Southern California to Banff, Jasper and the Yukon, the southwestern deserts (Godforsaken terrain at best), the Rockies to Colorado, to La Paz in Baja California, and to the Yucatan by way of Texas at 109 F in the shade. I have suffered several reliability problems: Temp sender failure, broken muffler, coolant tank leakage, heater valve leakage, replaced three fuel filters, and had an Air Conditioner failure due to a leaky O-ring on the high pressure switch. Frankly, I'm so pleased! The temp sensor is a standard Digifant replacement item. The broken muffler took three iterations to fix and came down to the need for about $10 worth of flexible muffler hangers. The only other conversion related failure was the replacement fuel filters. When I completed the diesel to gas conversion, I used a small electric pump as a transfer pump to the high pressure Digifant pump, and put a Fram in line fuel filter between the main fuel tank (I have a 10 gallon auxiliary) and the transfer pump. Wisely, I put this in a very accessible place, as rust and other debris keep clogging the filter. This is conversion related because the main tank seems to be rusting after the diesel to gas switch, and I have not yet pulled it for a R&R. If I translate these experiences to my nearly 150 K miles on the original 1.6 L diesel, my abortive Volvo 760 TD experience, my two type 2 van campers ('67 and '72), my Saab 9000, my '87 Porsche 944 Turbo (arg) and the '95 Chrysler New Yorker, this is an amazing reliability record. Also considering the amateur swap (I did have some excellent advice from Alistair Bell), my test vehicle has done everything I could have asked. (BTW, the AC failure could also be a conversion related swap, as I had to engineer the AC transplant into a vehicle which had not contemplated such a device - remember, diesel Westphalia!). In my opinion, no CIS system could have performed any better.

2. Performance: I chose the Digifant because it was a cost effective version of Bosch's Motronic engine control system complete with knock sensor. At the time, I was advised that the performance engine of choice was the CIS unit because it was so easy to modify. After chuckling at the image of a Vanagon Westphalia drag racer, I studied the Bentley wiring diagrams, studied the VAG SAE papers on the Digifant, the 1.8 L engine, the torque and horsepower curves and the data available on engine lifetime in European applications. After going over this material, I concluded that the best compromise for drivability with the torque characteristics of the engine and the mass of the vehicle was the 1.8 L engine mated to the original diesel trans and 27-8.50x14 tires. I also added a dual port exhaust from a Quantum, an adjustable camshaft timing sprocket and a racing (Kent for high temp operation) timing belt. Also went to Nogoly plug wires and picked up an extra ECU for future developments. I found that at valve timing settings (stock cam) of up to 4 degrees advanced, the engine (in the vanagon) would readily spin up to 6500 in all 4 gears. These tests were done on California 14 between LA and Palmdale. Running the Westy at 100 mph gave me a new appreciation for sailing rigged freighters. Kept thinking of the brig at Dana's Point. I then went to AMS in Costa Mesa and had my spare ECU chipped ($200)- remember this is a Digifant II unit and AMS is the only vendor to develop a chip set for this ECU. Result, a stunning increase in power and I quickly found myself revving the engine to 7000 rpm (I believe the change the cutoff point to 7100 rpm from the stock 6500 rpm limit) in the lower gears. Third gear in passing situations on the Grapevine or merging crises is now good for 70 mph. Note that European cars are constantly run at 5500 to 6500 rpm on the Autobahn, Autoroute and Autostrada (at least all my rental cars have been) and this engine routinely turns in lifetimes of greater than 250K kilometers.

I then took my son's G-meter (fresh from calibrating the 944 Turbo), went to the local landfill and weighed the van, and proceeded to run a series of power tests on the engine. In typical engine rating numbers (we calibrated against stock results for two 2 L Jettas, a '97 GTI VR6 and a turbo Passat) the engine is putting out 129 to 132 hp. This is due to the cold-air air cleaner system, the exhaust system and the chip. Certainly enough to make this whale dangerous. There is some power loss as I move the cam timing around. Currently, I am running at 8 degrees advanced, and the engine makes a peak of 121 hp, but it pulls like a tractor from 2000 rpm. Can't rev beyond 6400 in 4th though.

As far as high engine speeds and longevity are concerned... the '90 GTI engine had 82 K on it when I got it, I run Valvoline 20W-50 full synthetic oil, and am down about 0.5 quarts by the 7500 mile oil change interval I use. The compression is still the same as when I installed the engine and varies by 2 pounds over the 4 cylinders. BUT, the oil temperature gets up to 270 when running at 75 here on the LA freeways on a 90 degree day.

So, shy of a slingshot drag vehicle, the Digifant has given me all the power and drivability this chassis and gear shift mechanism can support. Oh yes, I should note that the last trip to the Yucatan included a fully loaded camper (wife and supporting shower equipment, daughter age 11, two dogs, laptop computer, books, food, Westy tent, chairs, Trailer Hitch (Ron's version) and a Honda XL 500 Motorcycle mounted on a Moto-X hitch carrier. AC worked fine but I only got 16 mpg.

3. Ease of installation: When I looked at the plumbing hassle for the CIS distribution box and FI lines, and realized that the Digifant system required a few days with the Bentley, a soldering iron and some heatshrink tubing, I thought the conclusion was obvious. Electrical control systems are everybit as reliable and robust as any mechanical system. The Documentation (Bentley color codedwiring diagrams) are better documented than the mechanical equilivant and easier to test for integrity. Nothing to be afraid of. Just takes patience, attention to detail and the few simple precautions described in the manual. Yes, you can fry the ECU by grounding the wrong input line, but you can also incinerate the engine and vehicle with an improperly tightened fuel fitting. (end of rant)

4. Economy: 1.8 L engine, so many rotations per mile, given air to fuel ratio ... these establish the swept air per mile and the amount of fuel the air pump processes for power. This establishes economy. For a given power level, a Digifant will return a bit more fuel economy than any other gas engine because of the knock sensor. Properly tuned, the Digifant or Motronic systems will provide the maximum timing advance that the engine can carry for any load, rpm, temperature or atmospheric pressure. No mechanically adjusted system can compete. Having said this, one proviso must be made. The new Motronic sensors monitor air mass flow and not just flow, so the inlet drag is more on the all the vane-based AFM's (L-jetronic, CIS, Digifant) and this the efficiency is less for the older systems. The other key variable in efficiency is the design of the air pump (inlet manifold, head and combustion chamber, valve geometry and timing, exhaust flow, etc, etc). For these VW I-4 engines, the engineering is essentially identical between the CIS and Digifant implementations. Only the later cross-flow head 2.0 L engines will be significantly different (more efficient).

In summary, 1) the digifant is easier to install (without the benefit of a pre-engineered kit) than a CIS or CIS-E engine; 2)it is at least as reliable (compared to waterboxer and the diesel - no space to even get started); 3) it offers all the performance the chassis can stand; 4) its readily serviceable by any VW dealer or independent. I would suggest that one stay with the diesel gearing and add a little sound deadening material and a good sound system. Finally, don't use the Fox digifant engine, even though the fit may be somewhat easier because it is significantly detuned.

Sorry for the length, hope this helps someone.

Frank Grunthaner