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FWD: Fast+Efficient? (long)

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 From detienne@ee.utah.edu  Fri Aug  2 13:28:36 1996
 Received: from ee.utah.edu (detienne@ee.utah.edu []) by coimbra.ans.net (8.7.5/8.7.3) with ESMTP id NAA18927 for <quattro-owner@coimbra.ans.net>; Fri, 2 Aug 1996 13:28:34 -0400 (EDT)
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 	( id AA142016963; Fri, 2 Aug 1996 11:29:23 -0600
 Date: Fri, 2 Aug 1996 11:29:23 -0600
 From: David Detienne <detienne@ee.utah.edu>
 Message-Id: <199608021729.AA142016963@ee.utah.edu>
 To: quattro-owner@coimbra.ans.net
 Subject: Fast+Efficient? (long)
 I currently own a 1990 Audi 80.  It is the best car I have 
 ever owned.  I would immediately run out and buy another 
 exactly like it were it to be wrecked or stolen.  My car has 
 the 2.0 liter VW Jetta motor.  That fact is what got the 
 following chain of thoughts started...
 Engine displacement has a weak correlation to gas mileage.  
 Indeed there are even some examples of cars that get better 
 fuel economy with a larger motor!  However, a diesel motor 
 tends to get significantly better mileage, but you pay for 
 it with poor acceleration.
 So what about doing a diesel/electric hybrid?  I believe the 
 Audi 5000 Quattro might be a perfect candidate for such a 
 project.  They are available for very good prices (in the 
 U.S., at least).  (Stay with me on this one!)  Put a Jetta 
 diesel motor in it.  This would probably give it performance 
 and economy similar to a Mercedes 240D (around 30 mpg, and 
 very slow).  Remove the driveshaft, and at the rear 
 differential and transmission tailshaft bolt on electric 
 motors, powered by some batteries.  The usage would be that 
 the diesel motor would be for cruising and slow starts.  The 
 electric motors would be used just for fast acceleration, 
 passing, and hills.  While stopping, the electric motors 
 could recover some energy by recharging the batteries.  
 There would also be redundancy:  If the diesel motor broke 
 you could limp along for a couple of miles on the batteries; 
 conversely, if the electronics went bad you could drive, 
 albeit slowly, on the diesel motor.  The goal would be to 
 have the economy of a diesel with the speed of a gas car.  
 This leads to the questions Im hoping the Audiphiles can 
 answer or point me to good sources for anwers:
 Will a diesel VW Jetta motor bolt right into an Audi 5000?  
 or perhaps into an 80 or 90?  Has anyone out there tried 
 What are typical fuel economy numbers for the Quattro vs. 
 the two wheel drive?  (My idea is also adaptable, with more 
 difficulty, to the 2 wheel drive car).
 What is the coefficient of drag and the frontal area of the 
 5000 vs. the 80/90?
 I know Audi used to sell diesels, how did their fuel economy 
 numbers compare to the gas versions?
 As this is probably not of general interest, please send 
 your responses to detienne@ee.utah.edu.  For those 
 interested, please send me an email and Ill send you a 
 synopsis of what I find out.
 Following is some technobabble for those that are really 
 interested and still reading at this point!
 Why an Audi?  In some ways it might be easier to start with 
 a diesel car (old Mercedes or VW Jetta, for example), and 
 add the electric motors.  Also, it might be possible to bolt 
 a Jetta diesel into an old Porsche 924 (anyone know if this 
 is true?), but hooking up the electrics would be tricky in a 
 car that small.  So why Audi?
 1.  Longitudinal engine arrangement gives more room under 
 the hood than a transverse placement.  The big size of the 
 5000 would help even more.
 2.  Bolting an electric motor to a tailshaft or a 
 differential is probably easier than fabricating a system of 
 belts or gears to the flywheel, brake disks, etc.
 3.  The Audi is basically a front wheel drive design with 
 four wheel drive added.  Doing a similar idea to a four 
 wheel drive truck could work, but heavy weight and poor 
 aerodynamics would defeat the original purpose of good fuel 
 economy.  A Subaru might work well, but finding a diesel 
 motor for it could be difficult.
 4.  Used Audis in good condition can be had for a good 
 5.  I have very long legs, and the leg room in Audis is 
 6.  Four wheel disk brakes.
 7.  Good aerodynamics.
 8.  Commonly available with stick shift.  The longitudinal 
 arrangement allows the shifter to go right to the 
 transmission, making for unusually good shifting feel for a 
 front wheel drive car.
 The arrangement described is known as a parallel hybrid.  
 By way of contrast, a series hybrid typically powers a 
 generator by a gas or diesel motor, which then recharges 
 batteries that drive the electric motors that drive the 
 wheels.  The parallel hybrid has some advantages over the 
 series hybrid and pure-electric cars:
 1.  As the power sources work together, better acceleration.
 2.  Redundancy allows the car to be driven even if either 
 system (diesel or electric) are down.
 3.  As both systems work together to drive the car, the 
 losses of going from gas to electricity to batteries to 
 electric motor in the series hybrid case are lessened 
 (although this point might be argued by some.  Ill 
 forestall the argument by saying it depends on the type of 
 driving done.).
 4.  Keeping the batteries warm (batteries lose around = of 
 their energy capacity at cold temperatures) and keeping the 
 car warm are challenges for an electric car.  The diesel 
 motor provides plenty of heat.
 5.  The cars existing systems for power steering, power 
 brakes, heating, etc, can be retained.
 6.  A ton (literally, in some cases) of batteries would not 
 be needed.
 7.  Having two motors would allow for parallel / series 
 hookups for economy or speed modes.  In addition, a 
 series mode would allow for better regenerative braking at 
 lower speeds.
 8.  Probably cheaper to do than a pure electric or series 
 hybrid vehicle.
 9.  Can be done and debugged incrementally:  First the 
 diesel conversion, then one electric motor with just a 
 couple of batteries, then add more batteries and a second 
 motor later.  Eventually, possibly solar panels.
 10.  Safety:  Diesel fuel is less flammable than gas, and 
 since a smaller number of batteries would be needed none 
 would be put in the passenger compartment (as is often done 
 with electric cars).  Less electrical power would be needed.
 11.  Since the car would likely be plugged in nightly to 
 recharge the batteries, this could also be used to warm the 
 engine.  This would reduce the startup emissions and make 
 those cold winter mornings a bit more bearable.  Likewise, 
 if the car were plugged in during the day the electrical 
 power could run a small air conditioner or swamp cooler, 
 offloading the pollution creation for that to the usually 
 cleaner power plant.  Solar cells might be adequate to run a 
 small air conditioner.
 12.  Solar panels cannot collect enough energy to drive a 
 typical car in real time.  They are also expensive.  With 
 the parallel hybrid, however, solar panels and regenerative 
 braking might be enough to keep the batteries charged, as 
 there are fewer batteries and they are only used a fraction 
 of the time.
 13.  A parallel hybrid has a much better range than a pure 
 electric vehicle.
 14.  While the parallel hybrid would pollute more than a 
 pure electric, it would hopefully pollute less than a 
 typical gas car, and certainly use less fossil fuel.
 15.  If it has the same performance, less fuel costs, and 
 better reliability (redundant power), a parallel hybrid 
 could gain rapid acceptance with the car buying public.  
 16.  Diesels have been run on fuels ranging from plant oils 
 to kerosene, potentially making them good candidates for 
 alternative fuels.
 Possible negatives:
 1.  I might wind up with a car that is slower and uses more 
 fuel than the original gas engine!  Since the batteries are 
 heavy, this might be true for stop and go driving.
 2.  The differential gearing is not adjustable, unlike 
 bolting an electric motor to a transmission where you can 
 change gears.
 3.  Battery weight would reduce payload and lengthen 
 stopping distances.
 4.  Extra battery weight and limited battery capacity would 
 mean the electric powertrain may run out of energy up long 
 grades, or after several hard accelerations.
 Please send comments to detienne@ee.utah.edu.  Thanks!

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