The Official Pune Offline Meet(G2G) Thread

[satyenpoojary]

1. What does the term engine capacity(cc) associate with? What is it that we measure with that unit?
2. The RPM that we see on the RPM meter is rotations per minute of what? Of the wheel? or something else?
3. There is usually a misconception about 2-stroke engines to be less efficient compared to 4 stroke engines. Is it true? If true, why?

More to follow...

Did you not attend the 'gyaan' g2g that we had in MotoCafe?
These 3 questions were specifically answered there.


Dr. Antz please do the honours! or it would be cool if someone who attended it tries to answer this

adding to what alibaba has wrote, i also wanted to ask whether adding projectors on HID makes a huge difference in the range or not?

Secondly how much does a projector costs?

Range of the beam..? yes it does
Cost varies... from free to around 4k for basic ones

You simply needed a better HID man...

[ROCKRZ]

Well, I wanted to start a topic on general question answers long back but did not find time to get all the questions in one post and put it up here. I will be posting questions that I need clarification on and these would be about bikes only These questions might sound dumb to some but they are just a noob/non-technical person's thoughts. I know most of those things could be looked up on the net for answers but I thing its better to ask the bikers here rather than lookup on the net. Questions:

1. What does the term engine capacity(cc) associate with? What is it that we measure with that unit?

the cubic capacity of an engine is the volume of the combustion cavity inside an engine. (the cumbustion cavity is the volume between the piston and the head)

to illustrate this, if you have a 50mm diameter piston, moving up and down by 100 mm (this is called as stroke), the volume that this 50mm piston will displace while moving 100 mm is
volume (cc) = ( pi/4 x (square of diameter in centimeters) ) x stroke of piston in centimeters
=3.14/4 * 5 * 5 * 10
= 196.25 cubic centimeters.
the Cubic Centimeters is also called as CC in short form.
2. The RPM that we see on the RPM meter is rotations per minute of what? Of the wheel? or something else?
it is the rotation of the crankshaft.
3. There is usually a misconception about 2-stroke engines to be less efficient compared to 4 stroke engines. Is it true? If true, why?
it is both true and false.
true because in the real world, to allow the 2 stroke engine to function, some port overlap is required. this causes some of the charge (fresh fuel and air mixture) to go waste. this causes low efficiency..
the cesond reason is that generally, a 2 stroke engine is setup for peak rpm power. whereas, in the real world, we use it in the lower rpm. this is something like using the engine for a purpose it is not originally designed for.

the statement that "2-stroke engines to be less efficient compared to 4 stroke engines" is false when you design the engine with minimum port overlap. the mechanical losses in a 2 styroke engine are very low. infact, if you compare a 2 stroke engine with a 4 stroke engine, there is only 1 part that is producing the power.. the piston.. whereas in a 4 stroke engine, you have the piston, timing chain, cam, tappets, valves, seals and many more components to assist the power production. This causes more mechanical losses for power transmission.


to understand this in depth, you need to understand that the 2 stroe engine was developed especially as a light and powerfull power source for motorcycles. when it was developed, fuel was dirt cheap so noone cared about efficiency, simplicity was the prime concern. but as the fuel rates rose, the need for a more fuel efficeient power source was required. on analysis, it was found that the problem was with the combination of the intake and exhaust stroke which caused the charge to go waste hence, the 4 stroke was developed where, the intake and exhaust stroke could be seperated. hence the 4 stroke was always fuel efficient as compared to 2 stroke, since it was the only reason why the 4 stroke was made.

More to follow...

yipeeee... something that is ot but not yet ban-able


my answers in bold

btw, these days, research is on in making the 2 stroke efficient but with the emission norms gettig stricter, its unlikely if they can make a comeback.

[Alibaba]

Did you not attend the 'gyaan' g2g that we had in MotoCafe?
These 3 questions were specifically answered there.

Nopes.. Did not get a chance to attend that session.

yipeeee... something that is ot but not yet ban-able


my answers in bold

btw, these days, research is on in making the 2 stroke efficient but with the emission norms gettig stricter, its unlikely if they can make a comeback.

Thanks man But most of the stuff went over my small brain Am not a technical person wrt. to engines, so do not understand any of those tech. jargons. Need to meet you in person at some G2G to clarify all these doubts.

[shrinathrao]

Did you not attend the 'gyaan' g2g that we had in MotoCafe?
These 3 questions were specifically answered there.


Dr. Antz please do the honours! or it would be cool if someone who attended it tries to answer this




Range of the beam..? yes it does
Cost varies... from free to around 4k for basic ones

You simply needed a better HID man...

Are you planning to make a visit to pune so i can ask you some more details about HID and where to procure from in pune as the real test of HID is only at night and when we actually ride.

[Hyperion]

I am not exactly a mech engineer so feel free to point out my mistakes.
Here is what I understand.

Well, I wanted to start a topic on general question answers long back but did not find time to get all the questions in one post and put it up here. I will be posting questions that I need clarification on and these would be about bikes only These questions might sound dumb to some but they are just a noob/non-technical person's thoughts. I know most of those things could be looked up on the net for answers but I thing its better to ask the bikers here rather than lookup on the net. Questions:

1. What does the term engine capacity(cc) associate with? What is it that we measure with that unit?

H : Engine capacity is basically the volume through which a piston is displaced during each cycle of the engine(for single cylinders). For multiple cylinders its generally the addition of volumes through which all the cylinders are displaced. As you may know the unit of volume is cc.

2. The RPM that we see on the RPM meter is rotations per minute of what? Of the wheel? or something else?

H: Not sure. Its actually Revolutions per minute not rotations. Is it the number of rotations on the crankshaft per minute?

3. There is usually a misconception about 2-stroke engines to be less efficient compared to 4 stroke engines. Is it true? If true, why?

H: No idea.

More to follow...

[kartikpai]

1. What does the term engine capacity(cc) associate with? What is it that we measure with that unit?
2. The RPM that we see on the RPM meter is rotations per minute of what? Of the wheel? or something else?
3. There is usually a misconception about 2-stroke engines to be less efficient compared to 4 stroke engines. Is it true? If true, why?

More to follow...

1. For question one , the answer would be engine capacity can be majorly associated with the power and the torque of an engine. If you want to mesure it , it would be an equivalent of

: ((3.14*(bore diameter)^2)/4)*Sweep length

2.For question 2 its the number of revolutions made by your crank in a second. See usually, pistion reciprocates and for converting that rectilinear motion of pistion to circular motion we use the crank and con-rod assembly. This RPM is also related to torque and the power. I forgot the formulae btw

3. Who told you this . . Efficient in what terms ?? Power, mileage, braking ??? Each and every engine is efficient in one category and one has to compromise other features. Law of nature I can say


BTW it feels so good to type some theory and practice that was done some years back

P.S If anything above is wrong please correct. I am expecting at least one person to pound a reply here (antz.bin)

[kartikpai]

4-5 replies within myself typing the replies ! ! Kudos alibaba to make this thread active to such an extent

[Alibaba]

1. For question one , the answer would be engine capacity can be majorly associated with the power and the torque of an engine...

If the engine capacity is associated with power and torque, then by that definition all the 150 cc engine should have nearly the same power output and torque. Is it?

3. Who told you this . . Efficient in what terms ?? Power, mileage, braking ??? Each and every engine is efficient in one category and one has to compromise other features. Law of nature I can say

Thats the reason I said misconception. I meant efficiency in terms of fuel consumption.

[antz.bin]

P.S If anything above is wrong please correct. I am expecting at least one person to pound a reply here (antz.bin)

Dont worry guys.. I am waiting and watching . The replies as of now have been mostly on target. And there are people more qualified than I am in this subject.. currently replying to the query. So I guess everyone should be happy

[shrinathrao]

Well, I wanted to start a topic on general question answers long back but did not find time to get all the questions in one post and put it up here. I will be posting questions that I need clarification on and these would be about bikes only These questions might sound dumb to some but they are just a noob/non-technical person's thoughts. I know most of those things could be looked up on the net for answers but I thing its better to ask the bikers here rather than lookup on the net. Questions:

1. What does the term engine capacity(cc) associate with? What is it that we measure with that unit?

CC's (cubic centimeters) or Cu.In. (in3) (Cubic Inches) of displacement =

The amount of VOLUME in the cylinders, from the top of the piston to the bottom of the cylinder head, when the piston is at it's lowest point allowed by the crankshaft.

The "cubes" are the total volume of ALL of the engine's cylinders. For example, a Chevy 350 (5.7L) has 350 cubic inches of cylinder displacement including all 8 cylinders. So, divided by 8, each cylinder would be 43.75in3.

2. The RPM that we see on the RPM meter is rotations per minute of what? Of the wheel? or something else?

RPM usually stands for Revolutions Per Minute. Typically you'll find it on motorized vehicles where it tell you how fast the crankshaft of the engine is turning. Knowing the crankshaft speed can be useful, as too fast can damage the engine. The engine is also most fuel efficient in a certain range, so the RPMs can tell you when you should change gears.


3. There is usually a misconception about 2-stroke engines to be less efficient compared to 4 stroke engines. Is it true? If true, why?

In a two-stroke the engines fires once every revolution. This makes the engine highly efficient and lightweight compared to four-stroke systems. Rather than entering through valves, the fuel/air mixture enters through an intake port and exhaust exits out of an exhaust port. In place of traditional valves the two-stroke engine uses the piston’s position to force out exhaust or suck in fuel mixture.

Reeds are vital to a two-stroke system. The reeds are placed between the intake manifold and the carburetor, open and close to allow the fuel / air mixture to enter the case of the engine and trap it, and ensure the proper exchange of gasses in the engine. This procedure might sound complex, but it is, in fact, extremely effective and easy to understand.

The whole cycle can be explained as follows:

1) As the piston moves from bottom dead center to top dead center it creates a

vacuum to draw the fuel / air mixture through the carburetor and past the reed valve assembly.

2) The piston moves down from top dead center to bottom dead center. The reed closes, causing the pressure to build in the cylinder. The movement of the piston uncovers the intake port and pressurized the fuel / air mixture.

3) The piston now moves up from bottom dead center to top dead center, effectively ending a cycle and starting another. The spark plug ignites the compressed mixture, sending piston back down.

4) At this point the piston uncovers the exhaust port, allowing the spent gasses to escape. As it continues to bottom dead center, it uncovers the intake port and allows the fuel / air mixture through the carburetor and past the reed valve assembly.

A highly tuned two-stroke engine produces a tremendous amount of power per cubic centimeter, and is still effectively raced against larger capacity machines in dirt racing, where lightweight is valued more than raw horsepower. Unfortunately, two-strokes do emit more pollutants than four-strokes, are louder, and tend to use more gasoline. It is unlikely the design can be sufficiently altered to meet current emission control standards, so fewer and fewer two-strokes will be made in the future.

More to follow...

sorry i know only about two strokes as i worked more with them.

Forgive if answers are wrong as i am a non engineer

[kartikpai]

If the engine capacity is associated with power and torque, then by that definition all the 150 cc engine should have nearly the same power output and torque. Is it?

Thats the reason I said misconception. I meant efficiency in terms of fuel consumption.

A simple relation betwen power, torque, rpm would be

power= (2*3.14*N*T) /60000 (Kilo Watts) So, we cannot say that 150cc enginer should have nearly same power and torque output. But there is an interdepndancy among them . And I had done an interesting project in final year where in I had analyzed different performance characterstics of an engine using artificial neural networks . Sounds fuzzy but I still posess the reports which gave us a a nice insight of how this thing works.

And in two stroke engines fuel efficiency is a little low when compared to 4 stroke ones. Still there are methods by which you can have an optimal fuel efficiecny too. Like we had supplied pre-heated air to the carb by utilizing the heat of exhaust . And then went on decreasing the Air/Fuel Ratio until we found that it was not affecting the engine i.e by producing deposits etc.And finally on a 5 speed RX we were able to get Fuel Efficiecy of 42 kmpl. But the best part is carb got screwed in a day Still figuring out the reasons.

BTW there are these two books on IC engines.

One by Mathur and Sharma , Ganeshan. These give you a very basic idea about what engines are about. But only theoritically , for practical experience we have to just stand by it listen to it and analyze .

[antz.bin]

I would now suggest that the googled explanations stop...

Edit: I am mailing Alibaba a copy of the PPT used on that day. I would suggest you to go through it thoroughly first and then ask any further doubts regarding what you did not understand. The presentation is quite thorough and should clear most doubts.

[ROCKRZ]

I would now suggest that the googled explanations stop...

Edit: I am mailing Alibaba a copy of the PPT used on that day. I would suggest you to go through it thoroughly first and then ask any further doubts regarding what you did not understand. The presentation is quite thorough and should clear most doubts.

please everyone.... please dont listen to him.. .....
he is conspiring against our clan.. i am enjoying refreshing my mailbox and seeing the replies that we are getting... that to in my core competency field.....

btw, small correction @"kartik calling kartik " and alibaba,
power of and engine is dependent in BMEP and RPM

power = BMEP x RPM

BMEP is the mean pressure that is exerted on the piston top
RPM is revolutions per minute

[satyenpoojary]

If the engine capacity is associated with power and torque, then by that definition all the 150 cc engine should have nearly the same power output and torque. Is it?



Thats the reason I said misconception. I meant efficiency in terms of fuel consumption.

The first person answering your question gave you more information than you asked for.

When we talk about the CC, we refer to the amount of 'charge' that a cylinder accomodates for.
So a 150CC 'engine' is referred to as a 'cylinder' which holds the fuel + air in its 'VOLUME'
The jazzy mathematic formula is for the 'Volume' of the Cylinder

Imaging a cylinder with both its end open... you obviously cannot hold any charge in there... hence the measurement accomodates for the piston which is on one end of the cylinder.
This is what my expert friend Shrinath wrote as the The Bottom Dead centre.

The other end is closed by the 'head' (for now just remember it as a closed head)


For the second confusion, just like Rockrzz, me, antz and Shrinath have identical head size (the human head) it does not mean they churn out the same amount of 'power' each head is different. My head is mostly vaccant, whereas Shrinaths has more brains\muscles.

To put is simply Power - Is not a direct indicator by the size of the cylinder.

Power generated by the enging is what Rockrzz = BMEP x RPM

BMEP is nothing but the power that piston has been exposed to due to the blast in the charge.

RPM - Already clarified. This blast pushes piston which is attached to the rocker arm which pushes the crank and so the circular rotations per minute.

(Not an Engineer, But a certified googler from the University of Mr. Saikamaldoss)

PS: Chevy? Seriously?

PPS: A noob question.
If someone said that energy cannot be created or distroyed , but can simply take another form then:
1) What would happen if in the cylinder, along with the connecting rod the piston has spring attached to it somewhere on the end of the cylinder to hold and harvest the power?
This question might be stupid (and I have many more stupid questions) but I could never get in thru the hardships required to 'qualify' for engineering... hence couldnt ask it to any! ..

[ROCKRZ]

The first person answering your question gave you more information than you asked for.

When we talk about the CC, we refer to the amount of 'charge' that a cylinder accomodates for.
So a 150CC 'engine' is referred to as a 'cylinder' which holds the fuel + air in its 'VOLUME'
The jazzy mathematic formula is for the 'Volume' of the Cylinder

Imaging a cylinder with both its end open... you obviously cannot hold any charge in there... hence the measurement accomodates for the piston which is on one end of the cylinder. The other end is closed by the 'head' (for now just remember it as a closed head.
This is what my expert friend Shrinath wrote as the The Bottom Dead centre.



For the second confusion, just like Rockrzz, me, antz and Shrinath have identical head size (the human head) it does not mean they churn out the same amount of 'power' each head is different. My head is mostly vaccant, whereas Shrinaths has more brains\muscles.

To put is simply Power - Is not a direct indicator by the size of the cylinder.

Power generated by the enging is what Rockrzz = BMEP x RPM

BMEP is nothing but the power that piston has been exposed to due to the blast in the charge.

RPM - Already clarified. This blast pushes piston which is attached to the rocker arm which pushes the crank and so the circular rotations per minute.

(Not an Engineer, But a certified googler from the University of Mr. Saikamaldoss)

PS: Chevy? Seriously?

i sincerely doubt if anyone can explain this better than you or antz... nice way to explain..

by the way if anyone noticed, we have more replies in the last 3 hours that we had for the last 1 day combined... people were lurking on the thread for a discussion topic and when it came, everyone pounced on the topic... this has 2 meanings...
1) people are paid way too much than they are loaded with work. so they keep checking the thread for gossip updates...
2) people are not paid too much so they dont work and keep checking the thread for gossip updates...

and both mean that there are people lurking beneath the thread looking for updates..

so this thread is not dead as yet... just full of lazy people who dont want to be labled as ot creators... lol....