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Old 28th July 2006, 04:30   #1
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Question Why less engine braking in cars compared to 2-Wheelers ?

Having ridden 2-Wheelers for long before graduating to cars, I've always felt that the engine braking in cars is very less when compared to the 2-Wheelers. Most of my friends also share my view.

For example, in a normal scenario when riding a bike on it's 5th gear at 60 KM/H and when driving a car on it's 5th gear at 60 KM/H; if we stop accelerating, the bike loses it's speed quickly than a car. I also know we need to take care of the engine power/capacity etc to compare such a situation but for a general comparison, I assume that it's not needed.

What's the reason behind the low engine braking in cars compared to 2-Wheelers ?
Is it because the 2-Wheelers needs to be stopped more quickly because of the safety factor associated with them since the stopping power of a car is more when compared to the 2-Wheelers ?

OR is to increase the FE in cars since poor engine braking means more FE ?

OR is it because the cars are meant to be driven fast ?
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Old 28th July 2006, 09:36   #2
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I think it has something to do with momentum....car engines are bigger, so when they move, they carry more momentum and hence reduce rpms (engine brake) more slowly than bikes.

And obviously gearing also has a lot to do with it, taller gears will always give less engine braking than a shorter gear.
My 2 cents.

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Old 28th July 2006, 09:53   #3
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Quote:
Originally Posted by drifter
I think it has something to do with momentum....car engines are bigger, so when they move, they carry more momentum and hence reduce rpms (engine brake) more slowly than bikes.

And obviously gearing also has a lot to do with it, taller gears will always give less engine braking than a shorter gear.
My 2 cents.

Drifter
Well said.

I think it also has to do something with compression ratios (I think.!!).

Have you noticed that Diesel engines slow down faster when you lift the accelerator. But then they use heavy flywheel to carry more momentum that will reduce this.
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Old 28th July 2006, 09:57   #4
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Quote:
Have you noticed that Diesel engines slow down faster when you lift the accelerator.
Infact i have noticed the exact opposite? In which car have you noticed this?

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Old 28th July 2006, 10:19   #5
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Comparison is not appropriate. In bike 5th gear 60 km/h, top speed may only be 80-90 km/h. In car 5th gear top speed may be more than 120-140 km/h. You then need to compare engine braking at higher speed in car or lower gear at same speed.

It also depends on engine management systems. On my ohc, engine braking is very very good, it is as if you have applied brakes. In other cars, especially first 1.6 ikons, lifting your foot off the pedal actually causes surge.

Diesel engines actually there is not much engine braking, and not good for engine also. In fact diesel drivers always press clutch and brakes together, otherwise engine momentum increases braking effort.
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Old 28th July 2006, 10:29   #6
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Quote:
Originally Posted by drifter
Infact i have noticed the exact opposite? In which car have you noticed this?
Drifter
Mostly on M&M Vehicles. But on second thoughts this could be due to gear ratios
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Old 28th July 2006, 10:34   #7
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Quote:
Originally Posted by sandeep108
Diesel engines actually there is not much engine braking, and not good for engine also. In fact diesel drivers always press clutch and brakes together, otherwise engine momentum increases braking effort.
Is that so?? I have always been using engine braking in diesel cars and i never press the clutch and brakes together...
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Old 28th July 2006, 10:52   #8
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I engine brake like hell on my crdi, there is a fuel cutoff, so when you lift off the accelerator, it engine brakes quite efficiently, couple this with the foot brake and your cars braking abilities are multiplied.

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Old 28th July 2006, 10:58   #9
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It's more to do with the overall gearing. The 5th gear on an Indian bike would have the overall gearing of 2nd or 3rd gear on a car.

The 5th gear on the Vtec is good for 250kmph@7100rpm. So if you're to get any sort of engine braking from it, you'll have to be doing in excess of 180kmph. Not very practical, is it?

Next time you need engine braking at 60, shift into 2nd.

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Old 28th July 2006, 13:30   #10
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I have never driven any 2-wheeler so can't comment on that.
However, I have noticed that in buses, if the driver simply lifts foot of the accelerator (say ~60 km/h), the bus immediately slows down. It is quite natual, as the accelerator is releases, the engine rev falls, so torque produced drops - the engine can no longer develop enough power to pull the vehicle, so it slows down.
In cars, I think it depends on tuning of the engine. If your car is tuned in a way that it loses RPM faster when accelerator is released, more engine braking will result.
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Old 30th July 2006, 10:56   #11
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Quote:
Originally Posted by mithun
Having ridden 2-Wheelers for long before graduating to cars, I've always felt that the engine braking in cars is very less when compared to the 2-Wheelers. Most of my friends also share my view.

For example, in a normal scenario when riding a bike on it's 5th gear at 60 KM/H and when driving a car on it's 5th gear at 60 KM/H; if we stop accelerating, the bike loses it's speed quickly than a car. I also know we need to take care of the engine power/capacity etc to compare such a situation but for a general comparison, I assume that it's not needed.

What's the reason behind the low engine braking in cars compared to 2-Wheelers ?
Is it because the 2-Wheelers needs to be stopped more quickly because of the safety factor associated with them since the stopping power of a car is more when compared to the 2-Wheelers ?

OR is to increase the FE in cars since poor engine braking means more FE ?

OR is it because the cars are meant to be driven fast ?
All indian bikes are single cylinder..and all the cars have more than 1 cylinder..hence the braking seems more pronounced on a bike. It has got nothing to do with safety factors etc..
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Old 30th July 2006, 10:59   #12
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Quote:
Originally Posted by drifter
I engine brake like hell on my crdi, there is a fuel cutoff, so when you lift off the accelerator, it engine brakes quite efficiently, couple this with the foot brake and your cars braking abilities are multiplied.

Drifter
Hey drifter, the engine braking is very effective on a CRDi as it has a lot of electronics to cut off fuel pump etc.. On normal diesel cars, the braking effect is not as pronounced.

Please drive a Diesel Amby..[the hieght of technological advances..sorry amby lovers] to understand how effective the engine braking is.
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Old 31st July 2006, 04:45   #13
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Quote:
If your car is tuned in a way that it loses RPM faster when accelerator is released, more engine braking will result.
Please explain more...

Quote:
The 5th gear on an Indian bike would have the overall gearing of 2nd or 3rd gear on a car.
I couldn't get on what you are saying, what I'm saying is that the engine braking in cars is very less when compared to the 2-Wheelers. So the 5th gear on an Indian bike means low engine braking when compared to it's lower gears like 2nd or 3rd.

If the 2nd/3rd gear of a car is having engine braking equivalent to the 5th gear of a bike, then that means 5th gear of a car is having low engine braking compared to bikes in general, Right ?
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Old 1st August 2006, 15:10   #14
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Quote:
If the 2nd/3rd gear of a car is having engine braking equivalent to the 5th gear of a bike, then that means 5th gear of a car is having low engine braking compared to bikes in general, Right ?
Yup. Infact, even if you take a Hayabusa for example, it will not provide the amount of engine braking in 5th@60kmph as an Indian bike would, in the 5th@60kmph.

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Old 1st August 2006, 18:00   #15
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I'm really bad at math guys... and I hated Physics formulae... but I did have to mug a few, so...

Momentum = Mass * Velocity

Hence momentum is directly proportional to mass...
We all agree that the car has more mass (weight) than the bike, so the car will have more momentum than the bike too. It would take more force to stop the car than it would for the bike.

Coming to the source of the force (wow, it rhymes ) ... assuming that both are running 4 stroke petrol engines, their compression ratios would be similar, hence the intake resistance with the throttle closed would be similar as well. Also, if we assume that the bike has a 4 cylinder engine (I'm sure the Hyabusa does!), then we can safely assume that the amount of engine braking is similar too.... If we select similar gear ratios on the bike and the car, still the bike would "feel" like it has more engine braking because what you would feel is the RESULT of the engine braking; you would feel the deceleration of the bike...

Since the bike requires a lot less force to stop it (because it is lighter), it would decelerate faster, hence you would feel that it's engine braking is stronger.


- T u r b o C -
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