Date: Wed, 29 Jul 1998 21:05:17 -0700
Reply-To: David Marshall <vanagon@VOLKSWAGEN.ORG>
Sender: Vanagon Mailing List <Vanagon@vanagon.com>
From: David Marshall <vanagon@VOLKSWAGEN.ORG>
Subject: Re: Eurospec Conversion: Digifant Comment
In-Reply-To: <e8fb9f9c.35bf6ee3@aol.com>
Content-Type: text/plain; charset="us-ascii"
I have had the opposite experience with Digifant II (as used in the
watercooled A series VW, Corrado being the exception). The problem with
Digifant is that it uses fuel maps much like Motronic, but the fuel maps
are as tuner changeable as the Motronic ones are. If you were to take your
1.8L RV engine and install a 2.0L ABA bottom end it will not get the
correct fueling unless you change the chip in the ECU. With CIS it is a
much simpler setup and there is no fuel maps to mess around with.
There are a bunch of different CIS systems that VW used:
CIS - 1976 to 1980 - Basic air / fuel meter configuration. The fuel
pressure regulator when cold gave less controll pressure to enrich the
mixture.
CIS Lamba - 1981 to 1987 - Same as CIS only with O2 sensor to keep mixture
correct when engine was at operating temp.
CIS-E - 1985 to 1987 - Knock sensor and new O2 sensor system, monitors
engine load a bit better as it did away with the controll press reg.
CIS Motronic - 1990 to 1992 - More or less the same as CIS-E only it used
fuel maps.
The setup that I currently use in my Rabbit PU and soon to be in my 1988
Double Cab is simple and bullet proof. It is a mixture of CIS and CIS-E.
The CIS system is from a 1979 Rabbit without and oxygen sensor. CO2 at
idle is manually set to 4% to ensure it doesn't run lean under load. I
have a knock sensor from a 1985 GTI spliced into the system as I am running
with 11:1 compression ratio. Timing is set to 12BTDC with a total advance
of 30deg at 3400rpm. When the engine is under great load the pressure
regulator from an Audi 5000 turbo reduces the control pressure to ensure
that enough fuel is being delivered. This along with a Schrick 276 deg cam
gives a conservative 150hp with my 85 Scirocco head. Fuel consumption at a
constant 100km/h is 6L/100km. .71 5th, 3.94 R+P
I have to say that CIS also easier to maintain than Digifant as all the
components of Digifant must be running perfectly for a smooth running and
non-hesitating engine. Common complaints that I hear about Digifant is a
lack of throttle responce and high idle. These are all curable problems
but it seems that most dealers can't solve them without much time and money
spent. Digifant is better than CIS if you keep things stock and properly
maintained as it is more fuel efficient and has better emmisions.
I think the reason why Eurospec used Digifant is that the newest Vanagon is
a 1991 and CIS wasn't avaible then, only Digifant and Motronic. Personally
I think Motronic is a better setup as this is the stock engine managment of
the 2.0L power plant. Lots of re-mapped chips are available and it is
"a-la-mode" with the mechanics.
At 14:50 7/29/98 EDT, Frank Grunthaner wrote:
>I've been following these exchanges on engine conversion questions for many
>years. As a consequence, I converted my '82 Diesel Westfalia to gasoline
power
>after considerable research and many helpful inputs from list members such as
>Alstair Bell. The conversion began in September of '95, went on the road in
>Jan. '96, and is nearly finished (got the Air Conditioner up this weekend,
>only the subwoofer remains). I used an 8V 1.8L DIGIFANT engine from a '90 GTI
>donor with malice a forethought! I also used a K&N air filter system,
>fabricated an air introduction system interfaced to the original diesel inlet
>system in the driver's side rear compartment, added a adjustable cam gear for
>4 degree retard on valve timing to shift the torque max to lower rpm, added a
>dual downdraft exhaust manifold from a GLI, made a dual pipe exhaust
system to
>catalyst to dual port muffler, modified the alternator to build in the rear
>segment from a Porsche 944 and routed fresh air to the rear of the alternator
>pickup. I also use a dual battery setup in the right rear location, added air
>conditioning using the GTI AC compressor with additional evaporator,
condensor
>air handling components from an '85 Westfalia, and kept the diesel trans.
>
>My point is that the digifant engine has been superb. It installed quite
>easily compared to the CIS routing nightmare. It has proved extremely
>reliable, highly efficient (I range from 18 to 22 mpg). The van pulls
>beautifully from 2000 RPM and redlines (6500) in any gear (1st through
4th). I
>readily pull the 2 freeway between the 134 and the 210 (Southern California
>coordinates) with a full camper load (wife, me, 10 year old daughter, two
>dogs, Westy tent, provisions, hot shower system, etc) at 70 mph, and the
>calibrated temp gauge holds just below the LED. Under these conditions, the
>engine manifold vacuum is 6 inches. On the open freeway, 65 mph cruise
>corresponds to 12 inches, and this drops to 10 for 75. Max speed I have
had it
>up to on the the interstate is 95 and I am not at full throttle. BTW, the
>weight of the Westfalia also includes my supplemental gas tank which gives me
>a net 26.8 gallon fual capacity. This level of performance is more than
>adequate and stresses the capability of the chassis. I have not yet finished
>horsepower tests (road g-meter) nor acceleration times, but other
measurements
>are consistant with 105 to 110 hp from this RV engine. The added power
>possibilities from the CIS system, from my experience are expensive, and more
>relevant to other watercooled VW applications. Finally the knock sensor/ EFI
>Digifant system does a remarkable job of maximizing timing advance over a
wide
>range on temperatures and pressures (read mountain elevations). Clean
>contacts, and a careful study of the wiring diagram together with a copy of
>the Golf/Jetta/GTI Bentley (a real workshop manual as compared to the joke of
>a vanagon edition) and replacement of simple sensors will handle any problem
>I've encountered.
>
>Second point, all these discussions about changing the diesel trans to lower
>engine rpm. Nonesense. The dynamic range of the engine is well matched to the
>weight of the vehicle --- its a 1.8 liter engine! Torque to the road is
>certainly related to engine displacement, and gearing. Gearing is a good
>substitute for displacement. I did go to 27/8.50x14 BFG tires to reduce rpm
>and correct speedo (less than 0.2% error in my measurements) and odometer.
The
>current engine speed at 70 mph in the vanagon is similar to daily cruising
>throughout Germany on the Autobahn in any rental Golf, Polo, Opel or Ford (by
>my rental experience) and these engines return in excess of 200,000 km
>lifetimes before head work or overhaul. In my application/installation, I
>monitor oil temperature, oil pressure, voltage (both batteries), current,
>manifold vacuum, coolant temperature and exhaust manifold temperature. At 75
>mph, on southern california freeways, full load and 90 F outside
temperatures,
>my engine oil temperature ranges from 245 F to 250 F. Highest temperature I
>have seen with this setup was 262 F (using Mobil 1 synthetic 15W-50) going up
>the Grapevine at a steady 60 mph.
>
>So, in my experience, the 1.8 L/ 8V Digifant engine with diesel trans is an
>outstanding package.. reliable, strong, efficient and fun. I remain
bewildered
>as to why VW didnt standardize on this configuration. Sorry for the length
but
>I had to finally get this comment out.
>
>Of course, the 2.0 liter engine would be even better, and the Digifant/ nee
>Motronic system is just fine. I anticipate that the Eurospec conversion will
>be a screamer. More power to Kyle for putting it together.
>
>Frank Grunthaner
>
>
-- David Marshall, Quesnel BC, mailto:david@volkswagen.org --
-- 78 1.8L VW Rabbit, 80 2.0L VW Caddy, 87 Audi 5KQ --
-- 85 1.8L VW Cabrio, 88 1.6L VW Syncro Double Cab --
-- Volkswagen Homepage http://www.volkswagen.org --
-- USE DAVID@VOLKSWAGEN.ORG WHEN SENDING PMAIL --
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