I have a serious question regarding the possible use of a 240D as a hybrid.
I read more than a year ago about a guy who converted a 6-cyl BMW to a
hybrid by removing the transmission and attaching a very large alternator to
charge a bank of batteries. He then removed the differential and mounted an
electrical motor to each rear wheel. I seem to recall that he also attached
electric motors to each front wheel but that would require a 4WD set up and
I'm not sure BMW did such a thing. In any event he claimed he simply let the
engine idle at a constant speed and got about 100 mpg. Anyone seen anything
about this? I'm wondering if the same could be done with a 240D driving an
alternator with batteries, etc. There was a company north of Los Angeles
that simply coupled a large electric motor to the front of a differential on
a custom car built with a '34 Ford fiberglass body. They had a bank of
batteries under the rear floor but didn't have any means of on-board
charging of the batteries. Their car would go more than 100 miles at freeway
speeds without a recharge. This car would also go from zero to 60 very
quickly but my understanding is it discharges the batteries really fast
doing that. Anyone seen anything with this sort of setup? Inquiring minds
want to know.
Hybridizing a Mercedes is not practical, in my opinion.
Hybrids run off of internal combustion energy (and ONLY internal
They convert this energy to electricity and then use electric batteries
to to store excess power for peak use.
The efficiency of a hybrid does not come from the conversion to electric
power. This conversion actually WASTES power. The efficiency comes
from the special design of the internal combustion engine.
Internal combustion engines have a tight torque curves. This means they
produce power effectively in a very narrow RPM range. Car companies get
around this in two ways: 1. They put gearboxes in cars which allow
drivers to keep the engine speed in a power producing range 2. They
grind camshafts to provide a compromise between efficiency and power in
order to increase to RPM driveability range.
Hybrid engines run at a single speed, and only when the batteries need
charging. They start up when the battery runs low, charge the battery
and then shut down when the battery is charged. Since the engine only
runs at one speed (or a much narrower range of speed) while the battery
is charging there is no need to compromise engine design. The engine
components can be designed for optimal efficiency at this single speed,
and so the engines are (theoretically) more efficient.
Since the ENGINE makes the difference, it makes no sense to try to
hybridize a standard 2.4 Mercedes diesel engine.
Hybrids can recover some energy from braking, and the DC motors have
excellent torque characteristics and make a good drive system, but I
think any efficiency you would gain in the drive train efficiency would
be offset by the extra weight of the batteries, alternator, control
system and motors.
That's my take on it, anyway.
Ernie Sparks wrote:
They also use electric motors to move the vehicle.
This is completely wrong. A traditional vehicle dissipates a LOT of
energy as heat.
For example, the light turns green, you step on it and accelerate to
50mph. The light ahead of you turns red. Guess what? All the the
energy of your moving vehicle is now completely wasted by being turned
into heat at your brake rotors.
Hybrid recapture this energy instead.
No it's not!... EVERY watt-hour of energy that propels a hybrid car
comes from an internal combustion engine! The engine makes power which
is converted to electricity... But the electricity COMES from internal
This goes without saying...
This is NOT wrong.. Any time you convert energy from one form to
another, you waste some.. This is the second law of thermodynamics. In
hybrids, energy is lost in converting mechanical energy from the engince
to electric energy.. And more energy is lost in converting the
electricity to chemical energy and then back to electrical energy...
Hybrids capture SOME of this energy, true.. (They also emply traditional
brakes) However, this recapture alone does not account for their efficiency
The efficiency of a hybrid comes from using a SMALL engine optimized to
run at a single speed... That's all there is to it....
The engines in both hybrids I have driven (Toyota Prius and Honda
insight) do not run at a single speed. They may operate in a much
narrower band of RPM. Still NOT a single speed.
I see your point regarding all the energy being created by the internal
combustion engine, but although seems a good point, it's also not
Imagine rolling down a big hill and stepping on the brake. You are now
getting energy via your scavenging brakes, that isn't (directly at
least) created by the internal combustion engine. Of course you can
make the argument that the IC engine got you up the hill (which is
probably true :~)
Still your dismissal of the energy scavenging system via brakes and
suspension of hybrid vehicles is a mistake. these are energies that
are 100% discarded as heat in a traditional vehicle and are llkely to
continue improving in hybrids.
It is true the in the case of current designs, the energy recovered
isn't a great % of total needed. Still it is significant and likely to
"A standard combustion engine is required to operate over a range of
speed and power, yet its highest efficiency is in a narrow range of
operation. Also, an engine designed for a reduced operating range can be
more efficient than a standard engine. The battery storage and electric
motor allows the engine to operate at its point of maximum efficiency,
to be of a higher efficiency design, and to be smaller than non-hybrid
Brake recapture rate is about 30%...
"Regenerative braking is any technology which allows a vehicle to
recapture and store part of the kinetic energy that would ordinarily be
lost when braking. A simpler technology that can only convert the energy
to heat but which uses similar principles is known as dynamic braking.
Both are most commonly seen on electric or hybrid vehicles. Braking is
accomplished by electrically switching motors to act as generators that
convert motion into electricity instead of electricity into motion.
Traditional friction-based brakes must also be provided to be used when
rapid, powerful braking is required. Estimates currently see 30%
efficiency; however, the actual efficiency depends on numerous factors,
such as the state of change of the battery, how many wheels are equipped
to use the regenerative braking system, and whether the topology used is
parallel or series in nature."
On Tue, 22 Mar 2005 04:44:05 +0000, Paul Valois wrote:
What kind of power is wasted in a convential rear-wheel drive by turning
it 90 degrees via differential?
Seems I recall that Ferdinand Porsche built a hybrid about 1907-1908.
There was in interesting picture in a magazine - popular mechanics or
popular science - something like those anyway.....
I don't know, but hybrids would lose similar amounts of power through
their gearsets too...
The way hybrids attain greater efficiency is by having a small,
optimized engine which is designed to be the size of the AVERAGE power
used in the car.. Which is MUCH lower than the PEAK power used...
Rather than run a big engine at a bunch of different speeds, hybrids run
a smaller engine much more contimuously at a constant speed.
Porsche did build a prototype hybrid, but it was much later than this, I
Try querying the Regional Transit District, the public transportation
agency in Denver, Colorado. That agency built its own hybrid
all-wheel-drive right-hand-drive coaches for its use on 16. Street Mall
Shuttle. The motor is 1,6-litre Ford four-cylinder running constantly on
compressed gas, turning the generator to provide the electricity for
four motors and for batteries. I am sure they can point out the
companies that manufacture the software and hardware necessary to make
the hybrid system possible. The agency was forced to manufacture its own
when no coach builders would accept the design specification for one-off
Ernie Sparks wrote:
I think all the answers/debates on the efficiency of a hybrid are very
interesting but I think that any serious, expensive work on a car of the age
of yours is very unlikely to pay for itself.
Why would you want to undertake the work? Hobby? Learning experience?
For direct contact replace nospam with schmetterling
"Ernie Sparks" < firstname.lastname@example.org> wrote in message
My main purpose would be to sort of prove a point concerning the use of a
small diesel to turn an altenator to charge the batteries. A friend of mine
put a 190 diesel in his sail boat and went off into the sunset. That engine
would run at about 1,500 rpm forever (it seemed) on a gallon of diesel.
The method pure electric cars use is to drive the vehicle into the garage at
night and recharge the batteries. The electricity to do so is produced by a
power plant many miles away, using coal, natural gas, diesel, etc. This is a
rather complicated way to turn the rear (and maybe front) wheels of a
vehicle to propel it forward. All I'm suggesting is that the power plant
used to produce the electricity be located in the vehicle itself and
turning, perhaps, at idle speed. A 240D engine can produce a lot of torque
even at idle. This is especially true if you don't have to use any of that
energy to drive the rear wheels. Imagine a 200 amp altenator being turned at
three times idle speed via a large drive pulley, perhaps one with two V
belts instead of one. This would produce a lot of juice to charge the
batteries. One could even keep the original altenator to charge a small
12-volt battery for lights, radio, etc., while a 24 or 36 volt altenator
could be used to charge a battery bank for the electric motors.
Incidentally, electric motors can produce a lot more torque than a similar
sized gas and/or diesel. Anyway, there was apparently one company that tried
something like this and used a suitcase-sized diesel which burned very
little fuel to generate electricity for a battery bank.
Wow. I'm impressed by the input on this topic. Good job guys. Keep it up.
On Wed, 23 Mar 2005 01:48:19 +0000, Ernie Sparks wrote:
I'd love to see you do it and offer plans. I've got my $29.95 ready.
The real problem with today's hybrids is that they are a bloodly mess to
service. In a few years, we'll start hearing horror stories from
consumers who had to have megabuck repairs of current units. There's
absolutely no reason these vehicles could not be made with "modular"
mechanicals (think original VW bugs). The 240 has enough space that
should accomidate a good sevicable design.
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