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Old 12th May 2005, 17:25   #46
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Well, i dunno about power per power stroke but, a 2 stroke engine will provide more power than a 4 stroke engine at any given engine rpm, considering that both engines have the same compression ratio and CC.

An RX 135 produces around 14 bhp from a 135cc engine where as a Pulsar 180 produces around 15-16bhp from a 180cc engine. But, if you race a RX135 against any 135cc 4 stroke bike, the 4 stroke maynot be faster but, it'll surely last longer.

Power isn't everything, reliability is the main issue with 2 strokes. And i'm not even considering pollution and fuel consumed.

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Old 12th May 2005, 17:40   #47
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I am not sure if a 2 stroke would produce more power. I believe 2 strokes should ideally be producing less power than 4 strokes because they are inherently inefficient. When combustion is not efficient we definitely would have lesser power. But they make up for that lesser power by producing more power strokes.

Power developed is directly proportional to the combustion efficiency. Which i have no doubt is pretty poor in case of 2 strokes.

The basic unit for comparison of two engines could either be the outright power produced without considering the efficiency part or the power produced per unit of engine volume

In the first case (as with 2 strokes) it produces power all right but consumes twice as much fuel and uses up only 75% of the charge provided. Also since the exhaust gases are scavenged, some fresh charge is also wasted.

In the second case we are using up every single bit of available resources.

The yamaha rx 100 might be producing more power per cubic inch but it cannot be compared with the pulsar's. The correct way to do would be to have a similarly setup 4s and 2s engines.

One interesting thing to do would be to check how a 15BHP two stroke engine and 4 stroke engine behave. That is their power and torque distribution over the rpm range. the two strokes i believe would peak out while the 4 strokes will have a uniform spread.
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Old 12th May 2005, 17:43   #48
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Some more details :

All 2-strokes use Oil mixed in the charge (fuel + air) for cooling and lubricating. This causes extra pollution, cloggs the spark plug. But then there are lesser moving parts like valves, tappets, cams etc. So they are lighter and less complicated than 4 strokes. For 4 strokes, there is dedicated lubrication system, hence lesser wear and tear. They are reliable in some other sense that, they burn only fuel + air, and not Oil which smears the ports and spark plug.
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Old 12th May 2005, 17:44   #49
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Spot ON, Harrie! What have you studied?
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Old 12th May 2005, 17:47   #50
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Quote:
But they make up for that lesser power by producing more power strokes
Thats why i said "At any given engine rpm". Even i doubt if 2 strokes produce more power per power stroke. It's just that by the time a 4 stroke reaches it's 2nd power stroke, a 2 stroke would be ready for it's 3rd.

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Old 12th May 2005, 17:51   #51
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I studied mechanical engineering at PSG tech, coimbatore. I was most fortunate to be taught by our proffesor and head of department Mr. Rudramoorthi who also happens to be the head of Energy engineering department. It is one of its kind department in SE Asia i believe as of two years ago. Would rate it to be one among the best technical institutes around.

BTW PSG's managing trustee when i joined in '99 was one Mr. Karthikeyan (Narein's dad) but too bad narein himself didnt study here.
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Old 12th May 2005, 17:54   #52
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No wonder Harrie, you are good at your basics. I have a lot to learn and am happy that I am here.
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Old 12th May 2005, 17:55   #53
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Harrie you r correct. just refering to some presentations on net

http://me.queensu.ca/courses/MECH435/285,33,Slide 33

2 stroke looses energy due to heat which is more than enegy lost by moving parts in 4 stroke , also 2 stroke looses lot of fuel from the system.

comments on power developed / fuel consumed??

power delivered / fuel consumed?

ok guys can check out what harrie said in this link

http://www.deepscience.com/articles/engines.html

Last edited by Vulken Auto : 12th May 2005 at 17:58.
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Old 12th May 2005, 17:59   #54
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power developed / fuel consumed? : 4 Stroke is the winner.
power delivered / fuel consumed : Again 4 stroke.

I like my 2 stroke RX though.

Vulken, you agree when you read it in some article on internet, but dont agree when a fellow T-BHPian tells you. So much respect for T-BHPians? Sigh! Alright, I was just kidding! Most likely, I didn't explain it correctly.

Last edited by RX135 : 12th May 2005 at 18:06.
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Old 12th May 2005, 18:36   #55
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it s different learning from a teacher and a student. Any way why do you take it so personel, it was my issue and glad it was cleared. By the by the topic is sooo offfffffffffffffffftopic We might get kicked out of tbhp, the article was from a physics teacher.
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Old 12th May 2005, 18:43   #56
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No, absolutely nothing personal!
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Old 12th May 2005, 18:45   #57
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OK, guys, here's the dope:

- If you consider 100% combustion of fuel a 2-stroke engine is twice as efficient as 4-stroke.. In a 4-stroke, 1 power stroke has to drive 3 non-power strokes for fuel-air induction, compression & exhaust. This is the theory. However, due to mechanical limitations, primarily scavenging of the burnt fuel-air, a 2-stroke engine burns only around 40-60% of the fuel it consumes. So, practically, a traditional 2-stroke is far less effcient. However, people are working on making 2-stroke technology better. I think an example is the 6-stroke story from Australia.

Want to write on the diesel-petrol but have to run a catch a flight.. more tomorrow.
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Old 12th May 2005, 23:10   #58
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Hey Guys
Allow me to bring the discussion back to the topic.

Spark Plug is required for regular petrol engine, but Honda has developed a type of 2stoke engine called ACR that runs on petrol with spark only required initially..........just like SpeedSatya mentioned. Read on........
http://www.motorcycle.com/mo/mchonda/exp2_tech.html
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Old 12th May 2005, 23:55   #59
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What we currently associate with auto-ignition is engine knock, a phenomenon that occurs when the fuel ignites before the spark plug fires, while the piston is still on the up-stroke.

In the EXP-2, Honda has developed an exhaust port valve which raises and lowers the top of the exhaust port, thereby decreasing and increasing the fuel mixture pressure in the cylinder as needed. This valve is similar in shape to a power valve, but larger, and is shown in detail in these two cut-away diagrams. By setting the valve position based on engine RPM and throttle position, the pressure required for auto-ignition can be achieved at exactly the right timing, causing all of the fuel in the cylinder to burn completely


Yeah baby!!! The Power Of Dreams.....................hahaha. U just gotta love what these guys come up with.

If Einstein was alive today, he'd no longer be the smartest.

Shan2nu

Last edited by Shan2nu : 12th May 2005 at 23:58.
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Old 16th May 2005, 13:00   #60
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So what about diesel trucks in the northern regions?
And diesel cars in Europe? How do these vehicles start and operate in cold cold conditions?
Would a diesel be fitted with a spark plug then?

Anyone who knows about this?
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