Internal Combustion Engine Qs

Replies

• 

  Keerthivasan Ravisankar

  #-Link-Snipped-# Can you recorrect the questions correctly so that people reading this question will not get any confusion further.
• 

  zaveri

  #-Link-Snipped-#
  
  1) just how were you driving the bike ? in what gear was the vehicle ? was it in neutral ? or was it still in gear with the clutch disengaged ?
  
  and most important of all: was it an automatic scooterette ? or a geared motorcycle ? what brand was it ?
  
  2) if the vehicle was in neutral gear, then the engine will be mechanically disconnected from the driving wheel, and hence the rotating axle will not crank the engine until a gear has been engaged, with the clutch too engaged.
  
  3) choke is a mechanism by which, in situations of emergency, a very lean mixture is sent to the engine cylinders.
  
  a lean mixture consists of a great percentage of air with very less percentage of fuel.
• 

  ABCD ABCD

  Ok, let me be clear, i was using a ungeared vehicle - Honda Activa. So, it neither has clutch nor gears.
  #-Link-Snipped-#
  If it was a geared-bike, then the vehicle would not move when gear is engaged, we need to use the clutch for the bike to move.
  
  Coming to the choke, why is that mixture required? does that save fuel?
  #-Link-Snipped-#, i hope i'm clear now
• 

  zaveri

  #-Link-Snipped-#
  Honda activa uses a CVT (continuously variable transmission) gearbox.
  
  it dosen't really contain gears but has a pair of cone pulleys with a toothed belt.
  
  its clutch is a centrifugal pivoted clutch, which also operates automatically like the CVT.
  
  as i believe, this vehicle, uses a mechanism which returns it to the neutral position , whenever the brake is applied.
  
  so when you turned off the engine, the CVT must still be engaged, and the sound must have been produced due to that. when you applied the brake, the "mechanism" must then have brought the CVT back to the neutral gear position.
  
  the vehicle also remained in motion because the clutch disengaged the driving wheels automatically.
  
  the clutch requires centrifugal force to work, and centrifugal force is a function of engine rpm, and when you killed the engine, you know now how the clutch got disengaged.
• 

  zaveri

  As for the choke, i told you already, that it is used, when there is very very less fuel in the tank.
  
  so the choke is a mechanism, which makes a lean mixture, consisting of a very great percentage of air and very less percentage of fuel.
  
  this helps you to ride your vehicle to the nearest fuel station.
• 

  ABCD ABCD

  zaveri

  As for the choke, i told you already, that it is used, when there is very very less fuel in the tank.
  
  so the choke is a mechanism, which makes a lean mixture, consisting of a very great percentage of air and very less percentage of fuel.
  
  this helps you to ride your vehicle to the nearest fuel station.

  why can't we use this mechanism always? saves fuel!
  moreover, i use choke during cold mornings to start the vehicle. If i dont use that, the vehicle stops after few meters. 😕
• 

  zaveri

  mreccentric

  why can't we use this mechanism always? saves fuel!
  moreover, i use choke during cold mornings to start the vehicle. If i dont use that, the vehicle stops after few meters. 😕

  
  You don't get much power on a lean mixture, which is obtained by using the choke mechanism.
• 

  Ankush Sharma

  @#-Link-Snipped-#,
  dear, choke is a mechanism in which more fuel is sent to the engine as compared to the air so that with the large concentration of fuel there will be more powerful blast in engine and hence more power. and also because of this same reason, we never run vehicle for long distance with choke as it consumes more fuel.
  Actually when we turn on the choke, the pipeline directly attached to the fuel chamber becomes open and fuel directly comes in cylinder instead of going in float chamber.
  
  
  if u still have doubt then feel free to ask.
• 

  white_hat

  A carburetor has different jets, one among them is choke jet. It is used for cold starting, mechanism of choke jet depend on type of carburetor and manufacturer
  design.
  .
  .
  Choke jet is used during cold starting, it sends more petrol into the combustion chamber.It means a rich mixture is send to the combustion chamber.A rich mixture is easier to ignite, so it is easier to start the engine.Once the engine attain normal working temperature choke jet is closed.
  .
  .
  You should not ride the bike with choke engaged.
• 

  zaveri

  hey then when the tank is nearly empty, then the choke lever is engaged, then how is a rich mixture sent to the engine, when there is no fuel in the tank at all.
• 

  white_hat

  zaveri

  hey then when the tank is nearly empty, then the choke lever is engaged, then how is a rich mixture sent to the engine, when there is no fuel in the tank at all.

  If there is no petrol in the tank then choke jet is not going to work.
• 

  ABCD ABCD

  yep, i remember a driver of us saying that choke is engaged when there is very less fuel in the tank. He also said that it helps in reaching the nearest petrol bunk when in need. Also, i had heard that choke will be used to travel in a very bad condition road.
  
  Won't the diesel engines have choke?
• 

  zaveri

  #-Link-Snipped-#
  
  what happens in the case of motorcycles ? like in splendor ? when there is no fuel, the engine does not start, but when the choke is engaged, the engine starts instantly, ?
  
  now what is the mechanism behind this ?
• 

  white_hat

  zaveri

  #-Link-Snipped-#
  
  what happens in the case of motorcycles ? like in splendor ? when there is no fuel, the engine does not start, but when the choke is engaged, the engine starts instantly, ?
  
  now what is the mechanism behind this ?

  From what I have learned,choke jet is used for easy starting , not when there is low fuel in petrol tank.
  .
  .
  There are mainly 5 jets in a carburetor namely, pilot jet , main jet , pump jet , idle jet and choke jet.
  Pilot jet is used when there is little throttle valve opening, as throttle valve is wide open petrol is supplied through main jet.When sudden acceleration is required the pump jet comes into play.When throttle valve is completely closed petrol is supplied through idle jet.Choke jet is used for coldstarting.
  .
  .
  #-Link-Snipped-# in your case , maybe there was some fuel trapped in the choke jet.Choke jet gets fuel directly from the fuel tank. Other jets takes fuel from a float chamber inside the carburetor.As long as there is fuel in the float chamber the vehicle runs.Now when you press the choke lever any trapped fuel present will fire up the engine.The amount of fuel maybe very less but for a bike like splendor, which has got very high gas mileage it is enough to take it to the next petrol bunk.It even runs on fumes.
• 

  white_hat

  mreccentric

  yep, i remember a driver of us saying that choke is engaged when there is very less fuel in the tank. He also said that it helps in reaching the nearest petrol bunk when in need. Also, i had heard that choke will be used to travel in a very bad condition road.
  
  Won't the diesel engines have choke?

  Diesel engines does not have a carburetor.It uses a fuel injector instead.
• 

  zaveri

  white_hat

  .
  #-Link-Snipped-# in your case , maybe there was some fuel trapped in the choke jet.Choke jet gets fuel directly from the fuel tank.

  well that it says it all. i like that !
• 

  ABHINAV RANJAN

  See, When you are running out of fuel in the tank; applying choke reduces the quantity of air entering into combustion chamber of a cylinder. Due to which more quantity of fuel enters the combustion chamber and your scooter gets started. It's not possible to do on regular basis as engines are designed to perform on a specified fuel - air mixture for optimum performance. Also Remember in this case you have not saved fuel Instead you have consumed the more fuel. Only help you get in this case is even with low petrol you are able to drive to few kilometers and lucky enough to refill your tank if you have money and petrol pump nearby.
  
  We also use to apply this technique on regular basis during college days. But this certainly reduces engine life and affects vehicle performance adversely.
  
  Hope this can't be done in four wheeler; so sad.
• 

  ABCD ABCD

  Another question. What happens inside when vehicle is stopped, but the engine remains working? Will the 4 strokes of the vehicle happen during this?
  
  Also tell me how alternator is connected to engine. With Diagram if possible.
• 

  riteshbstkr

  u means what happen to engine whether it working or stopped?
  ans is that
  whenever u apply a clutch there is disengagement of a crank shaft and a driven wheel shaft hence engine is in working but no coupling between them
  hence no power transmission takes place.