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Old 24th November 2019, 12:36   #1
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Default Fuel-economy comparison between an 800cc bike & 800cc car

I am not aware if this discussion has happened before, however, have always had this question and never really got an satisfactory answer. Best place to ask is this fantastic forum of absolutely knowledgable people, so here goes.

If you were to compare a 800CC car and a 800 CC bike somehow for me the math doesnt seems to add up.
1) The 800 CC car, with all the additional weight, metal, cooling systems, HVAC, Music systems etc, still seems to cost less and

2) The fuel efficiency, even being hugely lighter etc, is still not that vastly different. A 800 cc car seems to overall be more efficient.

Can someone technical please explain these things. Drag alone does not seem to make sense.

Hope to understand this.
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Old 24th November 2019, 13:29   #2
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Default Re: Fuel-economy comparison between an 800cc bike & 800cc car

Unfortunately, the comparison you make is bizarre. Its similar to my near family asking me why I brought a bike for the same amount as a car since I could have brought a car itself. Engine size is hardly any factor in this comparison. If you havent done this before, try out an 800cc car and bike back to back and you will know where the extra money has gone into. Coming to fuel efficiency, a typical 800cc car engine is built to deliver around 40-45bhp of power while an 800cc bike engine can deliver around three times the power. On the bike, driving will also be more spirited and will obviously consume more fuel. If you ride the bike just like a car, I think the FE will be higher. That means you stick to 60-80kmph top speed and accelerate at the same rate as the car. Then the whole scene with FE will change.

Last edited by audioholic : 24th November 2019 at 13:31.
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Old 25th November 2019, 12:00   #3
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Default Re: Fuel-economy comparison between an 800cc bike & 800cc car

The 800cc sports bike, is built for performance, using expensive/exotic materials, to move 1 rider & 1 additional (unwelcome) passenger from point A to point B, as fast as possible.

On the other hand, the 800cc car is a mass-produced economy machine. It's purpose is to move 4 passengers in reasonable comfort from point A to point B, as economically as possible.

The purpose as you see is completely different.

Lets take some other aspects, one by one.
1. Engine : The 800cc bike's mill will revv easily to a dizzing 12000rpm, compared to the lowly 6000rpm of the car. Obviously, it costs money to built an engine capable of such superb characteristics.
2. Tyres, Wheels : The bike's tyres are in most cases made from high quality super soft rubber. That's expensive. The rims are made from magnesium or it's alloys.
3. Electronics : Modern bikes today offer dizzying level of electronics, various levels of power, adjustable traction control, wheelie control etc, multi axis cornering ABS. These are complex systems in their right, and expensive.
4. Import/manufacturing : Most of these super bikes are manufactured in smaller volumes, and are imported into india after paying massive duties. This adds to the cost.
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Old 25th November 2019, 13:14   #4
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Default Re: Fuel-economy comparison between an 800cc bike & 800cc car

Quote:
Originally Posted by sajaijayan View Post

If you were to compare a 800CC car and a 800 CC bike somehow for me the math doesnt seems to add up.
1) The 800 CC car, with all the additional weight, metal, cooling systems, HVAC, Music systems etc, still seems to cost less and

2) The fuel efficiency, even being hugely lighter etc, is still not that vastly different. A 800 cc car seems to overall be more efficient.

Can someone technical please explain these things. Drag alone does not seem to make sense.

Hope to understand this.
A better technical question would've been to take a car and a bike, both of say around 50 bhp each, and draw a comparison of their acceleration figures, top speed, fuel consumption figures etc.

Your question is leaning towards commercials, in which case the answer is simple = price is the lowest value at which seller is willing to sell and simultaneously the highest value at which buyer is willing to buy, and had nothing to do with the underlying cost of material etc.

Last edited by alpha1 : 25th November 2019 at 13:16.
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Old 25th November 2019, 16:36   #5
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Default Re: Fuel-economy comparison between an 800cc bike & 800cc car

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Originally Posted by sajaijayan View Post
If you were to compare a 800CC car and a 800 CC bike somehow for me the math doesnt seems to add up.
The comparison is totally out of proportion.
First of all one is a two wheeler and the other is four wheeler.
It is quite obvious that a 800cc motorbike would be a performance bike with added features and a good bhp + torque for a two wheeler. On the other hand 800cc car is something which is on the lowest side for cars in terms of power.
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Old 25th November 2019, 16:50   #6
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Default Re: Fuel-economy comparison between an 800cc bike & 800cc car

Noted the points and the general consensus is that basically we are trying to compare Apples and Oranges here. I accept that my query looks illogical when you look at it that way.

Anyway, even if you were to compare a non performance oriented bike there seems to be a mismatch for me. Have been abroad most of my life and driven and ridden most types of cars and bikes. Somehow this nagging query persisted.

Anyway, thanks to all the members for writing in with their points of view.
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Old 25th November 2019, 17:02   #7
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Default Re: Fuel-economy comparison between an 800cc bike & 800cc car

I think the question in the original post is fair and objective if emotions can be kept out

What are the gear ratios of the typical 800c bike? I guess they are shorter than that in an 800cc car.
Also, no turbo-charging, no direct injection (generally) in a bike's engine - things that are so common in a car engine.

Yes, 12000RPM redline is a much touted thing of pride for a sports bike, but it's also there out of necessity. A simple NA engine isn't able to generate so much power at low revs.
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Old 26th November 2019, 13:46   #8
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Default Re: Fuel-economy comparison between an 800cc bike & 800cc car

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Originally Posted by sajaijayan View Post
I am not aware if this discussion has happened before, however, have always had this question and never really got an satisfactory answer.
Technically - this is a very very valid question. And the answers will all be very deep in how the engine is constructed, how it behaves under load & what materials are used to make it work like that for a long run.

As for the commercials - the pricing is absolutely at the discretion of the bike maker & they are in business just to make huge profits. Like everyone else. Since such performance bikes are aspiration items & owned by those who have the money to spare, inherently they are very high price. They are the Mercedes & the Bentleys of 2 wheels basically. One never asks "why" its so costly . The elite buy them because they are costly! Pricing of the bikes is not at all related to cost to make it. Its related to the money the Ducatis and Hondas and Kawasakis want to make.
Quote:
Originally Posted by sajaijayan View Post
2) The fuel efficiency, even being hugely lighter etc, is still not that vastly different. A 800 cc car seems to overall be more efficient.
Its down to low level tuning, compression ratios, power/torque curve & gearing. Above all - how the driver/rider actually uses the vehicle.

In fact - you don't need to go so far for this comparison. A light weight modern Alto tends to give mileage threateningly close to a 125/150cc commuter scooter / bike now a days if used smartly. Even more with CNG! Just an example to give you perspective.

While the cylinder volumes are 800cc in both - the amount of fuel-air mixture & their ratios will be vastly different. An 800cc car is philosophically built for mileage and mileage only. The ECM's goal is to inject the minimum possible fuel spray to keep the car moving at satisfactory speeds.
In a sportsbike - the mixture is tuned to RICH (If you follow F1/MGP) mix. It ensures the most powerful "explosion" in the chamber to always give an adrenaline rush to the rider. Not mileage. This means the block & cylinders need to be strong to contain such sparks for years. What does that do? Make them costly to build...And so on. See where that's going?

Last edited by Reinhard : 26th November 2019 at 13:52. Reason: Formatting
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Old 27th November 2019, 00:34   #9
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Default Re: Fuel-economy comparison between an 800cc bike & 800cc car

Noted the above, and makes sense. Decided to just check some specs and put in a simple comparo. Chose a non performance bike and a simple low cost Car

Model Street 750 Maruti Alto

CC 749 2 Cyl 796 4 Cyl
Power 53 Bhp @ 8000 47.3 @ 6000
Torque 60 Nm 69 Nm
Mileage Arai 20 K mpl 24.7 Kmpl
Weight 233 Kgs 730 Kgs

Price 5.5 Lakhs 2.88 Lakhs


Power and Torque figures don't vary much, almost identical engine output I would say.

But the car is 3 times heavier, with way more additional equipment, but still more efficient and costs half as much.

Yes of course the Harley may be aspirational, hence allowing the manufacturer to choose what they charge. But somehow its all skewed for my limited understanding.

Considering the trouble Harley is in, maybe they should rethink!!

Thanks all and the intention of this post is not to offend anyone. Love bikes more than cars anyway and would prefer the Street to the Alto any day.
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Old 27th November 2019, 06:52   #10
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Default Re: Fuel-economy comparison between an 800cc bike & 800cc car

Quote:
Originally Posted by sajaijayan View Post
Can someone technical please explain these things. Drag alone does not seem to make sense
Will, summarize in one...
Word - Weight
Sentence - Weight of 1200cc motorcycle (forget alone 800) vs weight of 800 cc car makes the huge difference in R&D which affects the selling price
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Old 27th November 2019, 10:08   #11
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Default Re: Fuel-economy comparison between an 800cc bike & 800cc car

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Originally Posted by sajaijayan View Post
Power and Torque figures don't vary much, almost identical engine output I would say.
Bring the 0-100 and 0-200 figures also on the table & you'll take one more step towards the answer. The gearing.

A superbike is made to take you from A to B with the least amount of TIME.
A commuter car is made to take you from A to B with the least amount of FUEL.

That's where the offset happens.

A chain driven bike also has losses in transmission to account for.
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Old 27th November 2019, 10:46   #12
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Default Re: Fuel-economy comparison between an 800cc bike & 800cc car

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Originally Posted by sajaijayan View Post
I am not aware if this discussion has happened before, however, have always had this question and never really got an satisfactory answer. Best place to ask is this fantastic forum of absolutely knowledgable people.
All your queries are sorted by Abhishek46.
Still if you are not able to digest or justify yourself means you have sympathy with cars.
Ill put across in easy words, I ride a 800 cc bike and it's not very performance oriented still pumps out close to 95 BHP, almost double the power of old skool 800 cc car, hence it's obvious it's going to consume more fuel and these bikes are tuned for performance not fuel efficiency.
I have never measured mileage of my bike but people says it returns 16-24 KMPL depends upon rider and riding condition, which is still more or less same as 800 cc car which hardly produces half the power but carries more weight.
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Old 27th November 2019, 11:32   #13
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Default Re: Fuel-economy comparison between an 800cc bike & 800cc car

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Originally Posted by sajaijayan View Post
Noted the above, and makes sense. Decided to just check some specs and put in a simple comparo. Chose a non performance bike and a simple low cost Car

Model Street 750 Maruti Alto

Power and Torque figures don't vary much, almost identical engine output I would say.

But the car is 3 times heavier, with way more additional equipment, but still more efficient and costs half as much.

Thanks all and the intention of this post is not to offend anyone. Love bikes more than cars anyway and would prefer the Street to the Alto any day.
You should also consider the engineering mindset of the manufacturers. The Harley engine was never designed keeping FE in mind. If you give the Harley engine to MSIL engineers, they might extract 30kmpl+ in the ARAI tests out of it. In the same way, if you give an Alto to a tuner and bump up the performance, you might end up with far lower FE figures in it.

Next topic is that of what Ajaybiz has explained. A modern 800cc bike will return as much as FE as an 800cc car or even more depending upon how much power you extract out of the engine. Like I mentioned in my first post, if you ride these two machines exactly side by side, I still feel that the bike will return same or even better FE. For example, an Alto would be in its mid range at 70kmph in top gear. The bike would be slightly above idle in its top gear at 70kmph. If this scenario is fixed, the bike would obviously return better FE and thats where the lesser weight and all would come into picture.

Hence, if we really have to compare, we should use a car and bike with similar engine capacity and use them side by side travelling at the same speed all the time. Only then we can come to a concrete conclusion as to which one is more fuel efficient. I will place my bet on the bike in such a condition. But, if we let them travel at their own paces between two points, then it will be the car which will be more fuel efficient.
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Old 27th November 2019, 12:46   #14
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Default Re: Fuel-economy comparison between an 800cc bike & 800cc car

Haha, take it easy BHPians. OP has a very valid question. We're here to learn and help others learn too.

Hi sajaijayan, I too believed that Suzuki Hayabusa and Maruti Exteem/Swift had the same 1.3 liter engine during high school.

Here's the answer to your question:
1. Small car engines are made for torque, large motorcycle engines are made for power.
2. Mass market car engines are designed to be efficient, performance motorcycle engines are supposed to give you maximum power
3. There are other differences in tuning, radiators, intake and exhaust manifolds.
4. Gear ratios are different in a car vs a Motorcycle
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Old 27th November 2019, 13:40   #15
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Default Re: Fuel-economy comparison between an 800cc bike & 800cc car

A thought experiment question:

What would happen if you plonk a Alto 800 engine into a motorcycle frame?.
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