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**Aryan** · 09-12-2009, 01:48 PM

General Biking Discussion Approved.

**moeed** · 09-12-2009, 02:22 PM

Nice thought buddy. Even I have the same doubt.

The maruti a-star gives a mileage of 39.4 km/l, which is approximately the same as bikes.

Maruti Suzuki A-star breaks own record of fuel efficiency

**abhichotu.abhi** · 09-12-2009, 02:34 PM

one of the main factor is RPM ..

as cars have bigger engines, so it doesnot have to spin as fast as bike's engine for a same output, but bike's have smaller engine so for same amount of workdone as done by car a motorcycle engine has to spin alot more than a bigger car engine.
so finally
a car's engine spins slower for same work thus reducing friction,and other loses.

i usually travel in my car at RPM between 2k to 3k.. while at the same speed motorcycle engine has to do 5K-6K spins...

correct me if i am wrong??

**Gasolinejunkie** · 09-12-2009, 03:23 PM

Interesting! Fuel economy is directly proportional to size of the engine and horsepower produced but the proportion doesn’t remain constant. For example, a 170 Bhp R1 will return 18Kmpl but a 17Bhp R15 won’t do anything close to 180Kmpl even though both of them are bikes and don’t have that much of a weight difference.
There are a whole host of other factors that determine fuel economy like how hard the engine is being worked. I had a little 4cyl Nissan, if I sat at 130 I’d get 6~7kmpl but there are V8s pumping 400+ bhp that would return 10Kmpl if you cruise at 130.
In general, the larger the vehicle is the greater it’s fuel economy is compared to it’s weight. A decent 2ltr diesel car will get 15kmpl but a 16ltr, 10cyl truck carrying 40 tons will get 2kmpl – remember the truck is 40 times heavier than the car.
If you want to go to a bigger scale, a large cargo ship weighing 70,000 tons will chew through 70,000 gallons of diesel for a 1000 mile journey. If you do the math that accounts to 1 gallon/ton for 1000 miles.

**Samarth 619** · 09-12-2009, 03:31 PM

1. More torque output, which means engine spins @ lower speeds... In bikes, engine speeds are much higher as they don't have to pull much load.

My pulsar has revved upto 10 krpm. How many cars can do this? Maybe a supercar will do it, but then its mileage would be 5 kmpl or so...

2. Use of technologies such as Fuel Injection, etc. which are not in most bikes.

These 2 points are enough. I mean even the 1st point is enough to drop mileage by a big margin.

considering the weight, ratio of capacity to mileage, it should be atleast 150KMPL. Also, power, it should be nearly 15 to 20Bhp.
Y bikes take more fuel to deliver less mileage and less power even though it has less weight.

What??

Dude, This is because cars have multicylinder engines, and you are comparing this to a bike's single cylinder 100cc engine??

Multicylinder engines result in more power strokes per revolution. It results in smoother torque curve with more revs. This has been discussed many times ...

**satyenpoojary** · 09-12-2009, 03:53 PM

The number of cyclinders, the RPM levels, the way the fuel burns in the engine, are some of the answers...

OT: My statistics professor always said this, a man and a women can make a baby in 9 months.... but can a man make a baby in one month by having 9 women?

**vas** · 09-12-2009, 04:10 PM

^^^

**Ayush Singh** · 09-12-2009, 04:23 PM

A diesel engine in a ship is not as efficient as a petrol engine in car, however, its huge in size and has a lot of torque.

It's not just that increasing the size of the engine increases fuel efficiency, as commented by a fellow member, there are other set of factors.

In A-Star the engine has got the (Kappa technology) "apologies Kappa is in i10" , which is absent in any FI bike in India. Also if you compare 800's engine, still there is a lot of difference in the power output of cylinders as compared to the bike.

**Samarth 619** · 09-12-2009, 04:50 PM

^ Kappa? You SURE it's in Maruti A-Star? I think Kappa is a Hyundai technology for its i10?

Basically, the new engines are made leaner, to increase power and comply with BS III emission norms. I doubt there is anything more than making it lean or minor changes... Be it Maruti KB or Hyundai's Kappa.

As far as a ship engine goes, it is almost 4-5 stories long, occupies size of a huge hall, runs on diesel, and gives some 13000 horsepower at JUST 90 rpm ... Now, that's some real torque!!!
Smaller yatchs rev more, around 1800 rpm or so, just like bikes rev more than cars...

Bottom line is more torque needed in big vehicles, makes them numerically efficient.

and secondly, no equation can show mileage of an engine. Depends on Displacement, Cylinders, Gearing, Load, Clutch Usage, Purpose, Fuel Inection, riding quality, etc...

**whizzkid_ram** · 09-12-2009, 07:45 PM

Originally posted by Ayush Singh View Post

In A-Star the engine has got the Kappa technology,

Its derived from hyundai buddy

**manohar_manu** · 09-12-2009, 10:03 PM

Most of them are talking about Diesel engines which produce more torque at lesser RPM.
What about Petrol cars? do they produce same torque at same RPM? i think its not, they do Rev more still fuel efficient.

**manohar_manu** · 09-12-2009, 10:23 PM

Originally posted by Samarth 619 View Post

What??

Dude, This is because cars have multicylinder engines, and you are comparing this to a bike's single cylinder 100cc engine??

Multicylinder engines result in more power strokes per revolution. It results in smoother torque curve with more revs. This has been discussed many times ...

If multicylinder engine produces more power strokes, y cant we have 200 CC engine with twin 100cc.

or 4 inline 50CC

**Gasolinejunkie** · 09-12-2009, 11:43 PM

Originally posted by Samarth 619 View Post

^ Kappa? You SURE it's in Maruti A-Star? I think Kappa is a Hyundai technology for its i10?

What the heck is Kappa?

Originally posted by manohar_manu View Post

Most of them are talking about Diesel engines which produce more torque at lesser RPM.

Originally posted by manohar_manu View Post

What about Petrol cars? do they produce same torque at same RPM? i think its not, they do Rev more still fuel efficient.

Ok, since everyones been talking about 90RPM diesels and 15,000RPM petrol motors, power output, torque and fuel economy – heres my 2 cents on engines.
The power or torque an engine produces depends on a host of factors like intake manifold length, valve overlap and mainly crank (big end) diameter. Diesel engines have under-square pistons that have a long travel, SO the crank is massive and the connecting rods have heaps of leverage on the crank creating great torque but not a lot of engine speed.
On the other hand where torque is not needed, like in motorbikes the pistons travel little and the connecting rods turn a little crank. Less leverage means less torque but a lot more engine speed. Pistons in diesel engines need heaps of travel because diesel is compression ignited, so obviously diesels have heaps of torque.

Originally posted by manohar_manu View Post

If multicylinder engine produces more power strokes, y cant we have 200 CC engine with twin 100cc. or 4 inline 50CC

Yes you can, its called the Kawasaki ZX2R

**nightwing** · 09-12-2009, 11:52 PM

One of the reasons is aerodynamics. Bikes outshine cars as far as rolling resistance and power to weight ratios are concerned but their coefficient of drag is more than cars. The average motorcycle has all the aerodynamic attributes of a barn door........or a bus.

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