Fuel consumption more in 2stroke?

In summary: A 4 stroke has more work per cycle and therefore requires more fuel to produce the same amount of power. Additionally, the 4 stroke takes more time to reach top speed.
  • #1
monty37
225
1
is it true that fuel efficiency is better in a 4stroke engine ?
since the number of strokes are more in case of a 4stroke engine,the energy
required would be more ,right?
 
Engineering news on Phys.org
  • #2
monty37 said:
is it true that fuel efficiency is better in a 4stroke engine ?
since the number of strokes are more in case of a 4stroke engine,the energy
required would be more ,right?
If you read up on the diff between the 4 stroke and a 2 stroke, you will see why the 4 strokes are more efficient. In a nutshell, they separate out the 4 components: fuel intake, mixing/compression, ignition/expansion and exhaust. In a 2 stroke, those are crammed into only two steps.

2 strokes have their place. They are much smaller, simpler and more user-repairable.

http://www.deepscience.com/articles/engines.html
 
Last edited:
  • #3
the link was helpful,thankyou.

now does this vary for petrol and diesel engines,or can i say
every 4stroke engine(no matter petrol or diesel) has a better fuel efficiency.
 
  • #4
Small 2-strokes tend to have pretty poor fuel consumption partly because a lot of unburnt fuel gets blown straight out of the exhaust during scavenging.

Large 2-strokes can be extremely efficient (far more efficient than any four stroke) because of their high volume to surface area ratio, high compression ratio, heavy forced induction, and careful combustion control.

So, no, you can't say that every 4 stroke has better fuel efficiency than any 2 stroke.
 
  • #5
From what I have learned recently, two strokes have a bit of a stigma surrounding them as being dirty, noisy and inefficient. There are companies trying to change this by furthering the technology to improve cylinder scavenging and oil consumption, leading to much cleaner and efficient two strokes which still produce much more usable power than an equivalent four stroke. Orbital in Australia have developed their air assisted direct injection technology, which gets rid of the need for crankcase induction as the (compressed by means of a blower) air is injected into the cylinder directly, along with the fuel. This means that the crank can run a normal oil pan, no oil is mixed with the fuel, and the cylinder scavenging is much more efficient resulting in emissions-compliant engines that are fuel efficient and very powerful.

Can you tell I like two strokes?
 
  • #6
Note, too, that in general a two-stroke engine provides roughly twice the power for a given cylinder size than a comparable four-stroke because it has 1 power stroke with 2 strokes per cycle while four-strokes only have 1 power stroke for every four strokes per cycle.
 
  • #7
negitron said:
Note, too, that in general a two-stroke engine provides roughly twice the power for a given cylinder size than a comparable four-stroke because it has 1 power stroke with 2 strokes per cycle while four-strokes only have 1 power stroke for every four strokes per cycle.

Correct me if I'm wrong but, you need to qualify this with "pound for pound" since this is definitely not a fair comparison. It's kind of like comparing an SUV and a mini and saying the mini uses more gas (i.e. forgetting to mention that you are talking about per pound).
 
  • #8
Erm, I did:

negitron said:
Note, too, that in general a two-stroke engine provides roughly twice the power for a given cylinder size...

Although, that should probably read "total displacement" which is what I actually meant.
 
  • #9
2-strokes are lighter, cheaper, more powerful, louder, and less efficient. 4-strokes are heavy, quite, efficient, and have more torque in mid range rpm. 2-strokes are less efficient because they spray in fuel while the exhaust port is open, hence some fuel mixture goes straight through the engine. Also, 2-stroke's have very little hp at low and mid rpm, this is bad because they can't accelerate as fast as 4-strokes and there is not that "instant" power. 4-stroke's have good hp through out the entire rpm range and they have time in the unpowered stroke to cool off and get all the exhaust out without leaking fuel mixture. So 4-strokes can be more efficient per hp especially at mid range, but 2-strokes have insane power at high rpm while being super light and cheap. So they trade off on efficiency depending on the application.
 
  • #10
YupHio said:
2-strokes are lighter,cheaper, more powerful, louder, and less efficient... while being super light and cheap.
Not necessarily

http://people.bath.ac.uk/ccsshb/12cyl/rta96c.jpg [Broken]
 
Last edited by a moderator:
  • #11
mgb_phys said:
Not necessarily

http://people.bath.ac.uk/ccsshb/12cyl/rta96c.jpg [Broken]
[/URL]

Necessarily, a comparable 4-stroke would be more expensive, quieter, more efficient, and heavier.
 
Last edited by a moderator:
  • #12
A four stroke is thermodynamically less efficent.
 

1. What is the difference between 2-stroke and 4-stroke engines?

A 2-stroke engine completes a power cycle in two strokes of the piston (one up and one down), while a 4-stroke engine completes a power cycle in four strokes (intake, compression, power, and exhaust). This makes 2-stroke engines simpler and lighter, but they also tend to have higher fuel consumption.

2. Why does fuel consumption tend to be higher in 2-stroke engines?

In 2-stroke engines, a portion of the fuel and air mixture is lost during the exhaust stroke, leading to incomplete combustion and higher fuel consumption. Additionally, 2-stroke engines tend to have a higher oil to fuel ratio, which also contributes to higher fuel consumption.

3. Can anything be done to improve the fuel consumption of a 2-stroke engine?

Yes, there are several ways to improve the fuel consumption of a 2-stroke engine. These include using higher quality fuel, properly tuning the engine, and regularly maintaining and cleaning the air and fuel filters. Some advancements in technology, such as direct fuel injection, have also helped to improve the efficiency of 2-stroke engines.

4. How does fuel consumption in 2-stroke engines compare to 4-stroke engines?

In general, 2-stroke engines tend to have higher fuel consumption than 4-stroke engines. However, this can vary depending on the specific engine design and usage. Some 2-stroke engines, such as those used in motorcycles, can be more fuel-efficient than certain 4-stroke engines.

5. Are there any environmental concerns related to higher fuel consumption in 2-stroke engines?

Yes, because 2-stroke engines tend to have higher fuel consumption, they also produce more emissions. This can contribute to air pollution and have a negative impact on the environment. However, advancements in 2-stroke engine technology have helped to reduce emissions and improve fuel efficiency.

Similar threads

  • Poll
  • Mechanical Engineering
Replies
34
Views
3K
  • Mechanical Engineering
Replies
2
Views
90
  • Mechanical Engineering
Replies
22
Views
3K
  • Mechanical Engineering
Replies
1
Views
959
  • Mechanical Engineering
Replies
8
Views
4K
  • Mechanical Engineering
Replies
10
Views
2K
Replies
1
Views
1K
Replies
55
Views
3K
  • Mechanical Engineering
Replies
5
Views
2K
  • Mechanical Engineering
Replies
8
Views
1K
Back
Top