The first generation Audi 5000 built from 1977 through 1983 was one of the biggest and lightest all steel cars of it's time and is still leading the way in automotive design almost 40 years later.
My 1983 Audi 5000 with the 2.0TD two liter turbocharged IDI diesel engine and a three speed automatic was rated by the U.S. EPA to do 36mpg and German testing at a constant 56mph (90kph) was reported at 35mpg (6.7l/100km). My car was able to get 35mpg, but it required flat ground and the speed seemed to need to be down more like 52mph. In the mountains it got just 30 to 32mpg and in normal higher speed cruising on the freeway it got only 28mpg. Disgusted with the pathetic performance of the car I ripped the automatic transmission out and put a five speed in. I looked long and hard for an MK or ML code five speed out of a gasoline powered first generation Audi 5000 but none were available. After checking with dozens of wrecking yards across California and Arizona I had to settle for the lower overall drive ratio of a five speed out of a normally aspirated 1982 Audi 5000 diesel. The first big difference I noticed was in acceleration. The car went from being one of the slowest vehicles on the road to extremely brisk acceleration at anywhere from 2500 to 4000RPM. Fuel mileage in the mountains also shot up to 38-42mpg. The manual transmission out of the normally aspirated 1982 Audi 5000 diesel yielded the same 2500RPM at 55mph that the stock three speed automatic had provided, so the difference between 35 and 42mpg at a constant 52mph cruise was entirely due to the inefficiency of the torque converter. I was still disappointed with the fuel mileage of the car though as I could never get the 45mpg (5.2l/100km) that the German test for a constant 56mph cruise said was possible for the 2.0TD Audi 5000 with the manual transmission. I suspected that this was due to the turbocharged engine having been offered with a higher overall drive ratio in Germany. The lower overall gearing was not a problem for the mountains, but it made the car seem ill suited to high speed freeway cruising. Although the turbocharged IDI engine with itís Bosch VE linear distributor injection pump was capable of making power all the way up to 5000RPM it only ran well under a light load down at 1800 to 2500RPM. Cruising down the freeway at 70mph and 3200RPM the engine screamed and labored to provide the small amount of power required and fuel mileage was usually down at about 30mpg. See The 2015 Volkswagens and Audis for a more up to date perspective on fuel mileage.
As a side project we put together another 1983 Audi 5000 with the stock automatic transmission and a normally aspirated two liter five cylinder IDI diesel. This really was the slowest car on the road and it would hardly accelerate up a hill at 2200RPM in a cloud of black smoke. If lower gears were selected to keep the engine speed up it was drivable without blowing black smoke and the engine did run amazingly strong and smooth up at 3000 to 3500RPM. What was most impressive about this normally aspirated torque converter equipped Audi was that although it could get no better than 32mpg under any conditions it was able to deliver that same 32mpg all the way up to about 75mph on the freeway. It actually did a bit better on fuel at high speed on the freeway than my 5000 turbodiesel with the manual transmission. The normally aspirated engine with the torque converter however only allowed a maximum speed of 80mph where the turbocharged engine with the manual transmission would zip right up to over 100mph.
The explanation of how the torque converter equipped car did so well compared to the manual transmission equipped car at 65 to 75mph is twofold. First of all it is obvious that the small turbocharger that begins building boost all the way down at 1800RPM is too much of a flow restriction for good light load efficiency up at above 3000RPM. The turbocharged engine just has to operate at a lower engine speed to efficiently support light loads. The other thing going on is that the torque converters that came with the 1983 Audi 5000 cars have a central stator on a separate shaft. This two shaft setup allows quite high peak efficiency to be attained over some narrow range of speeds and loads. These particular torque converters appear to attain impressively high efficiency of about 80 or 85% at a 3000 to 3500RPM input speed and about a 30 to 40hp power output. At lower speeds and lower power throughput levels the torque converter is much less efficient, the torque converter equipped normally aspirated Audi did not get better mileage at lower speeds. At higher power throughput levels the torque converter is also much less efficient, the turbocharged engine felt really slow in heavy acceleration with the torque converter.
Again disgusted with the excessive fuel consumption of both of these Audi diesels I bought a very beat up old 1982 Audi 4000 with a totally worn out 1.6D normally aspirated four cylinder IDI diesel. When I took the engine apart the rings were worn away so much that they were almost taller than they were wide. New 0.020Ē oversize pistons, rings, bearing inserts, valves, valve guides, a gasket set and a giant hand reamer to bore the cylinders came to almost $1000 but the engine ran well when it went back together. It was fun boring the cylinders out by hand, but it was a lot of hard work and although the taper and out of round came out within Audi specs for a new engine the bores were not as straight as a machine shop job. Fuel mileage was initially 40mpg in the mountains, which was disappointing, but it would also deliver 40mpg on the freeway at up to 75mph and top speed was 85mph in a cloud of black smoke. I knew that the smaller car should do better in the mountains and at lower speed, so I swapped out the injection pump for a rusty seized up one from a junk yard. I just poured the putrid water out of the rusty old pump, filled it with oil, turned it over by hand until it moved freely and I mounted it on the car. At first the engine would not start, but after cranking it for a few minutes it started right up and idled smoothly on all cylinders. When I first drove the car though it was obvious that the advance mechanism was not working at all as the engine would not rev above about 1800RPM under a load. To kick the advance mechanism loose I hooked a 7psi electric fuel pump up to the supply line, and this instantly got the car making power all the way up to 5000RPM. After driving the car like this for just a few miles I took the electric pump off and the advance mechanism then worked with just the built in vane pump but it was sticky and would not give enough advance for high power output until up at above 3000RPM. As I drove the car the pump loosened up and the advance mechanism began to work more smoothly with better power all the way from 2000RPM. This yielded 50 to 52mpg at 45 to 50mph and 46mpg at about 60-62mph which was a dramatic improvement over the 35-38mpg I had been getting of late with the other pump. The rusty old pump was inconsistent though, and the advance mechanism never worked entirly smoothly. The engine still made the same big power up to 5000RPM but it seemed to blow more black smoke and after only 50,000 miles the engine was once again kaput. Many people have reported 50 to 60mpg out of the 1.6D normally aspirated IDI engines in the smaller Volkswagen Rabbit, and in 1984 the U.S. EPA highway mileage estimate for the Rabbit diesel was 61mpg. What has also been widely reported is just 70,000 mile engine life from the old IDI Volkswagen diesels. The normally aspirated five cylinder IDI diesel spinning the torque converter also only lasted about 50,000 miles, and itís final demise also appeared to be due to mysterious malfunctions of the injection pump.
The turbocharged 2.0TD engine also suffered from numerous injection pump problems but held up to the abuse much better. Even after 100,000 miles the engine seems about the same as it was. Maximum torque at 2500 to 3500RPM is impressive, and the engine also runs fairly smoothly under a light load down at 1800 to 2500RPM but efficiency always remains stubbornly poor. Part of the problem of course is the fixed injection flow rate of the metering collar equipped injection pump, but the real problem is the IDI combustion system with the radically large in-head pre-combustion chambers. Although the injection flow rate is quite high the radically large in-head pre-combustion chambers hamper high speed engine performance under heavy loads. At lower engine speeds the injection flow rate is really too high for efficient light load operation.
Interestingly it was the old transmission that already had 350,000 miles on it when I put it in the car that suffered most from the injection system problems. The 2.0TD had been running for quite some time with too much advance at 1800 to 3500RPM. The static timing was spot on, and the engine ran as well as it ever had under a load up at 3000 to 4000RPM but fuel mileage had dropped off to where it would never get better than 28mpg. I was very confused by this because I could not imagine how the Bosch VE injection pump could have worn or failed in a way that would cause earlier injection start timing when the static timing setting remained correct. After many years of wondering how this could have happened I finally decided to just go ahead and re-map the advance curve. What finally convinced me to work on the advance curve was that the old transmission with over 400,000 miles on it by this time began to buck and protest under the excessively early injection start timing. What I finally settled on was five degrees of crankshaft rotation later start timing across the board using the same spring that had been on the advance mechanism. This was accomplished by adding shims so that the spring would push harder against the advance mechanism. The result was the exact same static timing setting but five degrees later timing from 1500RPM all the way up to the 5000RPM maximum engine speed.
The result of this adjustment was that the engine was once again smooth under a light load from 1800 to 2500RPM and the transmission stopped bucking. Power output was up considerably from 1500RPM to 3,000RPM, but from 3500RPM up power seemed to drop off a bit. Fuel mileage jumped back up to where it had been when I first put the manual transmission in, but the engine still seemed to be unbelievably fuel thirsty.
Another major problem that had often cropped up on the Bosch VE pumps was the injection of fuel even when the accelerator was not depressed. This had been a problem of varying degrees on all of the VE pumps I had. On the 2.0TD I took to turning the fuel solenoid off going down hills so that I would not have to use the brakes so much. Doing this made me realize that even when the VE pumps had been working as well as they ever did some fuel was being injected on deceleration. Turning the fuel solenoid off provided a whole lot more engine braking, but after I had been doing this for some time the fuel solenoid began to be reluctant to turn back on.
The first generation Audi 5000 sedans are great cars that have a huge amount of interior space for the 2900 pound weight of the vehicle. I have always been very fond of the suspension and handling of the Audis, and the first generation 5000 with their very strange combination sway bar and lower forward control arm deliver much better overall handling and tire wear than the smaller 4000 which needs the camber readjusted for different operating conditions. The big five cylinder engine hanging out the front leads to some strange handling characteristics if the car is put into a skid on dry pavement, but in compromised traction situations such as dirt roads or snow the handling is solid and controllable even in a skid. The big five cylinder hanging out the front also gives quite good drive traction in snow and mud even with no traction aid in the differential and no electronic traction control system. Being rated to carry 1200 pounds the first generation Audi 5000 is also a very substantial vehicle and the ventilated front disk brakes donít have any of the overheating problems that the non-ventilated disks on the smaller Audi 4000 do.
The only problem with the two 1983 Audi 5000 cars I have is that there are no engines or transmissions available for them. I have often been told that I should drop a later 1.9TDI into the 5000, but the problem with this is that the overall drive ratio for the longer stroke 1.9TDI needs to be much higher. In the 1998 Volkswagen Passat Wagon that can get 65mpg the 1.9TDI spins only 2100RPM to cruise at 65mph. I also have two of the 2.1 liter five cylinder gasoline engines for these cars, but the gasoline engines are really only for racing. With the under square configuration and two valves per cylinder they donít run all that well as normally aspirated engines. They did deliver impressive (for the time) 34mpg in the big 5000 with the higher overall drive ratio of the MK or ML code five speed, but they just donít rev up like a gasoline engine. What they really are is forced induction engines that were rated at as much as 280hp stock from the factory. In the U.S. the turbocharged versions were rated at only 160hp, but that was still so much that front wheel drive was inappropriate. With the turbocharged gasoline engine the car was supposed to have the full time four wheel drive system which was surprisingly not very popular at all on the first generation 4000 and 5000 cars.
In stock form the normally aspirated under square two valve per cylinder gasoline engines pooped out above about 4500RPM, but with forced induction they would make big power from 5,000 to about 8,000RPM with the lightweight valvetrain of the direct acting overhead camshaft. And there is the origin of the extremely low gearing available on most of the cars. At 8,000RPM top speed would be the 175mph required for the touring car championship that Audi did win in 1982.