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**aargee** · 01-20-2011, 12:15 PM

Originally posted by Mecho View Post

You dont save fuel as there's no throttle..

You loose fuel because one is holding the clutch. But that's way too negligible. Most importantly, the friction & clutch plates are exposed to regular wear & tear during this engagement.

**Mecho** · 01-20-2011, 12:15 PM

Originally posted by leomax View Post

From a fuel saving perspective,it is advantageous,isn't it?
Say if the slope is long and gradually flattening,it would be ideal i'd think. Probably one has to rev match when coming back to gear.

How do that happen? I mean saving fuel by holding clutch?

**parthd** · 01-20-2011, 12:34 PM

Originally posted by pavanchirmade View Post

No it doesn't.

ok..! thank u..!

**Mecho** · 01-20-2011, 12:45 PM

Originally posted by parthd View Post

Guys does engine breaking affects the engine now or say after a period of time..!

Yes it will (though it's negligible) IMO..beacause while doing the engine braking (about long slopes) there's not much fuel entering the cylinder (That's how the brake occurs) so, if firing air or may be the leanest mixture.. and long running on lean mixture would do harm for your engine. (I would say in engine braking, the momentum of the bike is forcing is to move forward, but the bike cries for fuel, but we are not giving...now does it feel harmful for the engine??)

You might have noticed water dripping down from muffler tips, mainly for cars. Thats the sign of a good and almost perfect combustion taking inside the engine. For that, the air-fuel mixture ratio should be accurate.
Water is formed as fuel is hydrocarbon and it combines with oxygen forming water. If combustion is not proper (excess of very less fuel/air) it results in CO or smoke formation. Which is bad for engine..

so engine braking though it's negligible, it does slight harm for the engine. But when other factors are considered, engine braking is the most adviceable while running down a slope or stopping from a very high speed..

**aargee** · 01-20-2011, 01:19 PM

Originally posted by Mecho View Post

How do that happen? I mean saving fuel by holding clutch?

Read my post above ^^^

Originally posted by Mecho View Post

beacause while doing the engine braking (about long slopes) there's not much fuel entering the cylinder (That's how the brake occurs) so, if firing air or may be the leanest mixture.. and long running on lean mixture would do harm for your engine.

Originally posted by Mecho View Post

(I would say in engine braking, the momentum of the bike is forcing is to move forward, but the bike cries for fuel, but we are not giving...now does it feel harmful for the engine??)

Sorry to say...all the above are 100% WRONG statements.

The engine braking happens because of the speed difference between the gears & rear wheels. Engine braking is effective with 4 strokes because of additional mechanical movements associated with valves, springs, timing chain & cams in addition to gears, conrod & crankshaft compared with a 2 stroke.

Originally posted by Mecho View Post

You might have noticed water dripping down from muffler tips, mainly for cars. Thats the sign of a good and almost perfect combustion taking inside the engine.

Lol; that's happening due to temperature difference & the presence of catalytic converters. But why bring this point in this discussion

Originally posted by Mecho View Post

it does slight harm for the engine.

Only on prolonged REGULAR usage. The harm is in form of wear & tear. The first one to get damaged being is connecting rod followed by piston, cylinder & bearings (in no order)

**Mecho** · 01-20-2011, 01:39 PM

Originally posted by aargee View Post

Read my post above ^^^

Sorry to say...all the above are 100% WRONG statements.

(in no order)

If i'm wrong, then why dont u clearly say the chemical reaction that let form water?

Talking about speed difference btw engine and rear wheels....Dude. I was talking about the how the bread is made and not how we eat it..
Please explain why is there a speed difference..

And ragarding harm. I already mentioned tht it's negligible and also I didnt say that engine will melt dwn

It's pure logic that its due to wear and tear..I just explained the reasons behind it..

I was talking about the reasons behind those and not just the results

**aargee** · 01-20-2011, 01:47 PM

@Mecho - you're getting it too personal now. You may want to go through my post completly, where I've mentioned how engine braking happens & why the water droplets are out of exhaust.

No one said the engine will melt down either, I'd still suggest you go through the post & understand the reality.

BTW, your logic also doesn't seem to apply here because, no matter uphill or downhill (on small hills), a good carb or Fi does it job properly & fuel is supplied properly no matter the throttle is closed, 1/8th open or 1/2+ opened. A good tuned carb (or Fi) WILL never let the cylinder starve for fuel.

**eliksir** · 01-20-2011, 01:53 PM

Originally posted by aargee View Post

Most importantly, the friction & clutch plates are exposed to regular wear & tear during this engagement.

this is what i wanted to know. thanks

**Mecho** · 01-20-2011, 02:12 PM

Originally posted by aargee View Post

@Mecho - you're getting it too personal now. You may want to go through my post completly, where I've mentioned how engine braking happens & why the water droplets are out of exhaust.

No one said the engine will melt down either, I'd still suggest you go through the post & understand the reality.

BTW, your logic also doesn't seem to apply here because, no matter uphill or downhill (on small hills), a good carb or Fi does it job properly & fuel is supplied properly no matter the throttle is closed, 1/8th open or 1/2+ opened. A good tuned carb (or Fi) WILL never let the cylinder starve for fuel.

you took me wrong, There's nothing personal. I just tried to explain it in an easier way.
As you said, there are more additional mechanical movements that makes engine stop. I just said that these "additional Mechanical movements" is stopped as there is no throttle

Engine brake happens when fuel supply is reduced to idling supply.. But the momentum of bike keep it running..but the enigne pulls it back..Thats how it works!

Its pure logic that no carburettor would keep the valve 1/2 open while there's no throttle.

1) Zero throttling - engine is in idling (say 1000 rpm)
2) Full throttle - engine reaches top rpm (say 12000 or so)

I dont want to make it an arguement.. These we just what I learned in classes... from projects and experiences. MY HUMBLE OPINION..

**Mecho** · 01-20-2011, 02:23 PM

Ideally an engine takes in Air (Oxygen and Nitrogen) and fuel (hydrocarbons) and produecs CO2, H2O, and the N2 just passes straight through. The chemical equation is as follows.

2 C8H18 (gas) + 25 O2 = 16 CO2 + 18H2O

This is ideal combustion which not possible and it depends on various factors like air cleanness, fuel octane number and so on. but a near quality combustion can be achieved and then also water formation occurs and not due to any catalyst presence. (it converts toxic exhaust to non toxic ones, and water formation will be there in the absence of catylistic convertr)

Also I didnt make any statements to prove me wrong, its IMHO

**bindyesh** · 01-20-2011, 04:37 PM

Originally posted by Mecho View Post

Ideally an engine takes in Air (Oxygen and Nitrogen) and fuel (hydrocarbons) and produecs CO2, H2O, and the N2 just passes straight through. The chemical equation is as follows.

2 C8H18 (gas) + 25 O2 = 16 CO2 + 18H2O

This is ideal combustion which not possible and it depends on various factors like air cleanness, fuel octane number and so on. but a near quality combustion can be achieved and then also water formation occurs and not due to any catalyst presence. (it converts toxic exhaust to non toxic ones, and water formation will be there in the absence of catylistic convertr)

Also I didnt make any statements to prove me wrong, its IMHO

mecho you are 100% right about the engine braking(less fuel entring the cylinder) and if you have mentioned about vaccume created in the cylinder then it was perfect reason .
one more thing ....engine braking harm two stroke engines more than 4 stroke

**Prith** · 01-20-2011, 06:52 PM

@Mecho: So, "If" I m understanding you correctly holding the clutch while downhill ( and engine in idling RPM) will not consume "excess" fuel, but rather it will consume the bare minimum needed to keep the cylinder fire ... and that means no issues with fuel consumption. Is that right ?

As far as engine braking goes, I guess that can only be solved by holding down the clutch and not releasing it until lower speed is reached..BTW..wudn't engine braking cause heated engine due to clutch engagement .. little murky here

My practise so far has been to hold the clutch down and allow bike to go on a free roll and then engaging the clutch on only when my acceleration decreases. Additionally if speed does not decrease, then I shift to next gear <<read higher>> and carry on from there... this seems to be fine with me..havent had any overheating or sudden jerk issues with my machine.

**pavanchirmade** · 01-20-2011, 09:37 PM

Whoa!!
Didn't know people can argue over such a shitty topic. And bringing in chemistry? Wow!
Amazing.Bravo Prith and Mecho.

Engine braking is a very useful phenomenon in riding a motorcycle. Especially when decelerating, braking and riding downhill.

Holding down clutch when riding and releasing the throttle makes no sense at all.
Just try using engine braking and see how surprisingly easy the bike is to control.

Engine braking doesn't affect the engine in a bad way.

**Mecho** · 01-20-2011, 10:29 PM

Originally posted by Prith View Post

@Mecho: So, "If" I m understanding you correctly holding the clutch while downhill ( and engine in idling RPM) will not consume "excess" fuel, but rather it will consume the bare minimum needed to keep the cylinder fire ... and that means no issues with fuel consumption. Is that right ?

.

Yes.. that's right..It'll take up only that much if it wer in idling - My belief

Originally posted by Prith View Post

As far as engine braking goes, I guess that can only be solved by holding down the clutch and not releasing it until lower speed is reached..BTW..wudn't engine braking cause heated engine due to clutch engagement
.

You are not using clutch for a long time..are you? Changing a gear is a matter of second.
1) Motorcycles have (Mostly Indian) wet clutches..please see my prev posts. Immersed in oil to reduce overheating
2) you dont cause wear and tear to clutch plate when you hold the clutch completely..Its half clutch that cause wear and overheating..( we have to use it usually in traffic)

.
3) There's noo need of waiting till you attain lower speed . If i got u right, you are talking about reaching say a 60kmph at hill top and aplying the clutch down in slope?? If this is what u meant, then there's no need of waiting till u reach lower speed..if the slope takes you to a 70 kmph from 60 kmph. then you just need to wait till the speedo reach the speed in which you are comfortable , and then release the clutch and throttle ...

Originally posted by Prith View Post

My practise so far has been to hold the clutch down and allow bike to go on a free roll and then engaging the clutch on only when my acceleration decreases. Additionally if speed does not decrease, then I shift to next gear <<read higher>> and carry on from there... this seems to be fine with me..havent had any overheating or sudden jerk issues with my machine.

Its fine, but I would recommed you to be in the top most gear when u apply clutch while in steep dwn hills and that doesnt harm the clutch as long as you apply full clutch..

Infact
But you wont be able to stabilize your bike if a cat or dog jumps across and you need to apply brake.. the desired speed is maintained by using engine braking to counteract the gravitational acceleration.

This is what I believe. MHO

Please refer engine braking in Wikipedia for more info..

**eliksir** · 01-20-2011, 11:57 PM

n00b question. whats the difference between holding a full clutch and half clutch internally? :s

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