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Old 19th May 2006, 23:29   #1
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Default Lost Power? - Inefficiencies of the drivetrain and engine

It seems 40% of your engine power is taken up to keep the engine running,transmission and drive shafts ,so that means that by the time The power reaches the tarmac its 40% less than what the engine actually produced....does that mean a 100 bHp car has an effective 60 bHp ????
Does car companies Dyno the car's engine only or the the whole car setup??If its the whole car ,don't you think the companies are giving out false info about the cars they sell??i don't seem to understand whats going on very well.
Guys i am feeling lost !!!! just like the bHp getting lost somewhere in the middle....
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Old 19th May 2006, 23:59   #2
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no no. BHP (brake horse power) is different. I knw there power is measured at various stages or so but wil wait for experts to make posts.
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Old 20th May 2006, 01:22   #3
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BHP(brake horse power) is power measured at the wheels it refers to the final output power....Testing is usually done on a dynamometer.

However for engineering college practicals, you hook a 1980 fiat engine crankshaft to a pulley...I wasn't paying attention after this part..teacher sent me to buy diesel in a bottle.

Mods please correct me if i'm wrong
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Old 20th May 2006, 01:40   #4
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There are both engine dynos as well as chassis dynos.
But, i believe all the Car manufacturers give the reading of the engine dynos which is the engine power.

If anyone here knows companies use Chassis dynos, thats news to me.

Quote:
However for engineering college practicals, you hook a 1980 fiat engine crankshaft to a pulley...I wasn't paying attention after this part..teacher sent me to buy diesel in a bottle.
So, u're the errands guy,heh??

Last edited by nitrous : 20th May 2006 at 01:41.
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Old 20th May 2006, 08:54   #5
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Normal transmission losses are about 15% for FWD cars. The OHC which produces 100 bhp at the flywheel, will produce about 85 bhp at the front wheel.

Every single engine that comes out of any manufacturer's plant is tested on an engine dyno to ensure it is within the parameters set out for it, eg power, torque, emission etc.

I would suppose manufacturers and companies use chassis dynos for R&D more than testing production vehicles.
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Old 20th May 2006, 09:58   #6
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Yea, theres even a term for it, WHP or something. (wheel horsepower, correct me if I am wrong)


Also, there was an article recently in OD, about bikes whose claimed horsepower figures (which was at the crankshaft or some part, I dunno which), are very different. The P180 only delivered 12 bhp at the wheel!!!
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Old 20th May 2006, 10:09   #7
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Dr chill,

As v1p3r mentioned, ~10-20% of the power produced at the crank is lost in the drivetrain. So that 80-90% efficeint. (As a comparison, a bicycle drivetrain is 95-96% efficient).

Where the real inefficiency lies is in extracting the maximum power out from the fuel.
Thermal losses are a huge factor, and when you add everthing up the actual efficiency of an internal combustion engine is ~25% !!!!
That means, a current 100bhp car, if it was 100% efficeint would be putting out 400bhp!

check out this link for a very basic explaination.
(and diagram)

cya
R

Last edited by Rehaan : 20th May 2006 at 10:11.
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Old 20th May 2006, 19:42   #8
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Quote:
Originally Posted by nitrous


So, u're the errands guy,heh??
not so much the errands guy, as the "keep him away from expensive equipment guy" Basically during a fluid machinery practical, i managed to get a hose carrying high pressure water loose...End result, entire batch plus teacher got soaked..wasn't a very pleasant semester for me!!
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Old 20th May 2006, 23:32   #9
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ok this brings me to the second part of the question ?? i believe that compressed air engines have very less or no lose compare to the internal combustion...and can have amazing mileage (across Australia on a single tank full running on compressed air and petrol....Hybrid I guess!!),great power,and almost neutral friction.Isn't it a better bet for the internal conbustion engine to go in that direction??

didn't want to start a thread coz i don't know much about the air engine....but sounds promising ,isn't it?
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Old 12th March 2010, 15:10   #10
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Default Overall Energy Losses In A Vehicle

Hi
Received this bit of information & found interesting to share among all experts here . Since this is my first post, would like to request MODS to guide if any discrepancy observed

ENERGY LOSSES IN A VEHICLE
Only about 15 percent of the energy from the fuel you put in your tank gets used to move your car down the road or run useful accessories, such as air conditioning. The rest of the energy is lost to engine and driveline inefficiencies and idling. Therefore, the potential to improve fuel efficiency with advanced technologies is enormous.

*
Engine Losses - 62.4 percent
In gasoline-powered vehicles, over 62 percent of the fuel's energy is lost in the internal combustion engine (ICE). ICE engines are very inefficient at converting the fuel's chemical energy to mechanical energy, losing energy to engine friction, pumping air into and out of the engine, and wasted heat.
Advanced engine technologies such as variable valve timing and lift, turbo charging, direct fuel injection, and cylinder deactivation can be used to reduce these losses.
In addition, diesels are about 30-35 percent more efficient than gasoline engines, and new advances in diesel technologies and fuels are making these vehicles more attractive.
*
Idling Losses - 17.2 percent
In urban driving, significant energy is lost to idling at stop lights or in traffic. Technologies such as integrated starter/generator systems help reduce these losses by automatically turning the engine off when the vehicle comes to a stop and restarting it instantaneously when the accelerator is pressed.
*
Accessories - 2.2 percent
Air conditioning, power steering, windshield wipers, and other accessories use energy generated from the engine. Fuel economy improvements of up to 1 percent may be achievable with more efficient alternator systems and power steering pumps.
*
Driveline Losses - 5.6 percent
Energy is lost in the transmission and other parts of the driveline. Technologies, such as automated manual transmission and continuously variable transmission, are being developed to reduce these losses.
*
Aerodynamic Drag - 2.6 percent
A vehicle must expend energy to move air out of the way as it goes down the roadѬess energy at lower speeds and progressively more as speed increases. Drag is directly related to the vehicle's shape. Smoother vehicle shapes have already reduced drag significantly, but further reductions of 20-30 percent are possible.
*
Rolling Resistance - 4.2 percent
Rolling resistance is a measure of the force necessary to move the tire forward and is directly proportional to the weight of the load supported by the tire. A variety of new technologies can be used to reduce rolling resistance, including improved tire tread and shoulder designs and materials used in the tire belt and traction surfaces.
For passenger cars, a 5-7 percent reduction in rolling resistance increases fuel efficiency by 1 percent. However, these improvements must be balanced against traction, durabillity, and noise.
*
Overcoming Inertia; Braking Losses - 5.8 percent
To move forward, a vehicle's drivetrain must provide enough energy to overcome the vehicle's inertia, which is directly related to its weight. The less a vehicle weighs, the less energy it takes to move it. Weight can be reduced by using lightweight materials and lighter-weight technologies (e.g., automated manual transmissions weigh less than conventional automatics).
In addition, any time you use your brakes, energy initially used to overcome inertia is lost.

Last edited by Rehaan : 12th March 2010 at 20:10. Reason: Hi, you must always provide a link to the source(s) of the information in your post. Please do add that. Thanks.
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Old 12th March 2010, 22:31   #11
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thats a nice bit of info you have it there.

But in the real world of Petrolheads, these hardly matters. All we need is Poweerrrrrrr!!
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