CrazyEngineers Archive
Old, but evergreen and popular discussions on CrazyEngineers, presented to you in read-only mode.
@nitesh604 • 08 Apr, 2009
Please tell why we cannot use diesel engine in bikes? It is the cheapest.
@ShrinkDWorld • 08 Apr, 2009 I think there are some disadvantages of diesel engine like. It have high pressure to produce a spark also it have more weight
but I am not sure about it....
@deeps31 • 09 Apr, 2009 there are motorcycles running on diesel engines right? like Bullet Enfield & some other cruiser motorcycles, but they have got quite big engines~350cc
@raj87verma88 • 09 Apr, 2009 There are Motorcycles running on Diesel Engine.

@Gaurav: Diesel Engine does not require spark to ignite the fuel mixture.
@ShrinkDWorld • 09 Apr, 2009 @raj87verma88
yes but they have large engine
@gohm • 10 Apr, 2009 That depends, laugh. Here 350cc is very small. There is nothing with the diesel engine technology or design preventing it from being used on small bikes/mopeds/scooters. The infrastructure is set up to be more gasoline friendly. Also, getting the motor to meet some EU standards would lead to the bike being more expensive and complex. A company produces a diesel klr650 for the USMC (so all their vehicles run on the same fuel: cars,planes,bikes) that might go public. It would be great to convert these over to veg power!
@raj87verma88 • 10 Apr, 2009 No they are not large. They can be of various size. Even petrol engines can be made large. It is just that large diesel engines are used in heavy applications like trains, trucks etc. They produce higher torque than petrol versions and therefore are steady and can carry heavy loads.
@ShrinkDWorld • 10 Apr, 2009 but the quection is still here that is "'Why can't we use diesel engines(mostly) in motorbikes?'''(mostly)
@harish sinha • 11 Apr, 2009
nitesh604
plz tell why we cannot use diesel engine in bikes it it cheapest
because in diesel engine burn takes place lots of time,and more noisy in comparsion to petrol engine,and one of the most point is it is bulky i comparison to petrol engine.
@Dhanareds • 18 Apr, 2009 For bikes normally in a range of 100- 250 cc diesel engines cannot be used. This is because the engine will b big and heavy, which would decrease the fuel efficiency of the bike on whole as well. The diesel engines need high pressure ratio around 20:1 as compared to petrol engines 10-15:1 which calls for heavier engines, which subsequently are more expensive as well.
If u want to make a bike of ur own with a diesel engine u can very well make. Make a 600cc bike atleast. and the bike is going to be real heavy. But its definitely not recommendable for mass production in the commercial market.
@nicholas • 18 Apr, 2009 well two reasons came to my mind....donna know for sure they are cent percent right....
1.)the greater are the vibrations produced in case of a diesel ingine and it would rather be very difficult to vibrationally isolate engine from rider resulting in a uncomfortable ride.
2.)the starting problem...whether by kick or by a battery....a heavy & large battery will be required which will be pretty difficult to accommodate in such a less space...
and remember why royal enfield diesel model (still used by army) was a failure-ALL BECAUSE OF STARTING PROBLEMS....
@ShrinkDWorld • 18 Apr, 2009 now we are discuss in right direction!!
@raj87verma88 • 18 Apr, 2009 Regarding Starting of Diesel Engine, I found some stuff

A diesel engine has no spark plugs. Because the air is so compressed and hot at the top of the stroke, the fuel ignites right away when it is injected. This is why a diesel engine is called a "Compression Ignition" engine. This also means that there are no ignition breakers, ignition coils, distributors and ignition wires to go bad. This allows diesel engines to start no matter if it is dry or rainy and wet.
Some modern diesel engines are starting to come out with electronically controlled injection pumps, but the vast majority of them out there have purely mechanical pumps. No electricity is required to make a diesel engine run, except for a simple fuel cut off solenoid so that you can hut the engine down. I once drove from Madison, WI to Rochester, MN with a dead alternator on my diesel at night. Even with the lights on I made it home because the engine used no battery power.
So there is no requirements of a heavy battery, as the diesel engine does not require current to start. The current is used to produce the spark in the spark plug of a Petrol Engine.

Vibrations in a diesel engine and the noise was a problem but the technology has increased and the newer versions of diesel engine are quieter and produce less vibrations.

The reasons why Diesel Engines are unpopular for use in Motorcycles:-

With a traditionally poor power-to-weight ratio; diesel engines are generally unsuited for use on a motorcycle which requires high power, low weight, and rapid acceleration.

Regarding the R.E. Diesel Version.
In India, motorcycles built by R.E. could be bought with 325 cc single-cylinder diesel engines due to the fact that diesel was much cheaper than petrol (gasoline) at the time, and of more reliable quality. These engines were noisy and unrefined and not very popular because of lower performance and higher weight penalties and also the unique kick-starting techniques. The engine were originally designed for use in commercial applications such as electric generators and water pumps.
R.E. in India was the only manufacturer that has built a diesel motorcycle in mass production. A 6.5 hp industrial diesel was installed in the frame of the British-based Royal Enfield. However, due to pollution laws this bike is no longer produced. It was one of the most fuel efficient Bikes in India returning over 200 mpg (Imperial Gallons). Initially street mechanics were mounting this engine in used Bullets (It is a retro Royal Enfield Bike, with the 350 cc retrofit engine developing 18 hp). On seeing the success of these bikes; Royal Enfield, themselves, started manufacturing Bullets with the diesel engine and named it as Taurus.
@raj87verma88 • 18 Apr, 2009 The diesel Motorcycle would produce a lot of horse power and Torque, be more fuel efficient, cost less in the wrong run...etc but its acceleration would be rather poor. People usually do not wish to drive a motorcycle that moves like a heavy truck, surely but slowly.
@ShrinkDWorld • 18 Apr, 2009 raj87verma88=>
yes you are right.
@EDDY • 24 Apr, 2009 Bcoz we need a heavy engine to run diesel as used in heavy duty veichles or a multi cylinder engine which gives best efficiency ........... and if used in bikes it would req. a huge space which contradictes the name bike>>>>>>>>
@Rohan_sK • 25 Apr, 2009 The Diesel Engines are all CI ( Compression Ignition) engines.
@Rohan_sK • 26 Apr, 2009 My earlier reply remained incomplete guys, it seems there is a reoccuring trouble with my account which just denies me right to post reply, I have to again get it sorted with Big_ k's help, tired of it man!
Anyway, back to the topic. The diesel engines as said are CI ( Compression Ignition) engines. wherein the air in the cyliinder is compressed to a very high compression ratio of about 21:1 precisely. The pressure and tempeature of the air rises tremendously due to this large compression. The tempreature reaches almost to the ignition point of the fuel ie diesel. The diesel is introduced in the cylinder at the end of this compression stroke . The very highly compresed air causes the diesel to immediately ignite and the power stroke starts.
The air being already compressed to very high pressure, when the combustuion takes place the overall pressure is much more than the pressure produced otherwise where the fuel air mixture is compressed to smaller compression ratios as in case of petrol engines. This high pressure on the piston produces greater power and greater torque. The result of which is that the engine can take more load for the same speed of the vehicle using a petrol engine instead. Thus the fuel efficiency of a diesel engine is greater than a petrol engine of the same size.
There is a drawback to this however. The diesel when in atomised form comes in contact with the highly compressed air, it suddenly ignites with a very fast rate of combustion, almost like an explosion. This blast like ignition produces a shock in the cylinder. This shock is called KNOCK , and it has a peculiar high pitch sound . The Knock creates very high VIBRATIONS in the engine with high magnitude. Thus the engine components like the connecting rod and the engine cylinder walls have to withstand much hihger stresses and pressure than the petrol engine. Thus the design requires to be more robust and strong, which adds to the weight of the diesel engine making it heavier than the petrol one.
The diesel as a fuel has a lower rate of ignition than petrol atomised to the same degree with same quality mixture. This reduces the rate of acceleration produced by the diesel engine than the petrol one, which means that vehicles using diesel engines accelerate slower than the petrol engines.
The diesel produces a more pollutant exhaust than petrol due to its greater sulphur content.
The reasons mentioned above make diesel engines to be a lesser opted choice for large scale production of bikes, where lower vibrations, lower noise, quicker acceleration rate, and low weight and compact size of the vehicle is desired.
There are actually no functional problems which can prevent the use of diesel engines in bikes.
@raj87verma88 • 26 Apr, 2009 But buddy, Knocking can occur in Petrol Engines too. And with the increase in RnD of Diesel Engines, the newer ones are proving to be much better than their Petrol Counterparts.

The only points where they lose to Petrol Engine when vying for a spot in Motorcycles are:-
Slower Acceleration
Low Power-to-Weight Ratio
High Vibration (in case of older Diesel Engines)
@Kaustubh Katdare • 26 Apr, 2009 Off topic:

@Rohan SK: Please post your queries related to the website in our New Members' Joint section.
@Rohan_sK • 26 Apr, 2009
The_Big_K
Off topic:

@Rohan SK: Please post your queries related to the website in our New Members' Joint section.
Big_K , that was simply what normal ettiquitte asked for; my earlier post could not be completed as I was denied the right to post, and an incomplete post was wierd for the reades. So it was my duty to explain to the readers why they had to face the inconvinience of reading just one line inccomplette taking the discussion no where. It would be rude and wierd otherwise. Dont you think so?
And for the problem, you'll surely find my mail to the admin if the problem resurfaces.
@g_rakesh2 • 28 Apr, 2009
  1. Diesel engines, because they have much higher compression ratios (20:1 for a typical diesel vs. 8:1 for a typical gasoline engine), tend to be heavier than an equivalent gasoline engine.
  2. Diesel engines also tend to be more expensive.
  3. Diesel engines, because of the weight and compression ratio, tend to have lower maximum RPM ranges than gasoline engines. This makes diesel engines high torque rather than high horsepower, and that tends to make diesel cars slow in terms of acceleration.
  4. Diesel engines must be fuel injected, and in the past fuel injection was expensive and less reliable.
  5. Diesel engines tend to produce more smoke and "smell funny."
  6. Diesel engines are harder to start in cold weather, and if they contain glow plugs, diesel engines can require you to wait before starting the engine so the glow plugs can heat up.
  7. Diesel engines are much noisier and tend to vibrate.
  8. Diesel fuel is less readily available than gasoline.
One or two of these disadvantages would be OK, but a group of disadvantages this large is a big deterrent for lots of people.
The two things working in favor of diesel engines are better fuel economy and longer engine life. Both of these advantages mean that, over the life of the engine, you will tend to save money with a diesel. However, you also have to take the initial high cost of the engine into account.
As mentioned, the list above contains historical disadvantages for diesel engines.
Many of the new diesel engine designs using advanced computer control are eliminating many of these disadvantages - smoke, noise, vibration and cost are all declining. In the future, we are likely to see many more diesel engines on the road.
But these advanced control systems are very costly.
Instead of these much disadvantages you can see alot of diesel cars like Ambassador Diesel, Indica etc.
And even you can see 2-wheeler with diesel engine like Royal Enfield diesel
@Corvus • 28 Apr, 2009 The diesel engine requires a high compression ratio, and a good fuel injector. plus, if the profile of the piston is not good, we need to use a supercharger to increase the efficiency.
350cc stroke volume provides a good space for the piston crown with turbulence.
Plus, the diesel engine produces more vibrations due to autoignition & flame collision within the liner; hence the weight to counteract.

Can u suggest whether the Enfield Bullet engine is a 2-stroke or a 4-stroke engine?
@Ernesha • 28 Apr, 2009 a diesel has more low end power and torque than the equivalent gasoline engine. The evolvement of the gasoline motorcycle has been one long ride from the beginning of the twentieth century until now.
In the beginning the diesel engine was used mostly in Europe while the gasoline engine thrived in the US. gasoline distribution and sales made gasoline readily available at many locations and vehicles including motorcycles were designed with this fuel distribution in mind.
Another factor was that the early diesels, were underpowered and difficult to start in the beginning. It was many years later when turbo charging and computer controls were incorporated that the diesel began to rival and surpass the gasoline engine in torque and economy.
By that time the design of motorcycles was well established with gasoline powered engines being the standard.
The military has been interested in diesel powered trail bikes for a while. Diesel powers everything else in the field, why have to have a separate fuel for a recon bike? It made sense and the turbo made it possible.
@Corvus • 28 Apr, 2009 I think the diesel engine produces more power than the equivalent gasoline engine???😒
@raj87verma88 • 28 Apr, 2009
Corvus
Can u suggest whether the Enfield Bullet engine is a 2-stroke or a 4-stroke engine?
It is a 4 stroke Engine
@g_rakesh2 • 28 Apr, 2009 I agree its a 4-S engine
@mlabhi • 04 May, 2009 wel my point of view is that,since diesel engines manufacturing are costly, due to the high pressure requirements inside the cylinder and also large initial cost of using a fuel injector instead of very cheaply available spark plugs,petrol is the fuel of motorbikes.
@nithyanandan • 04 May, 2009 since diesel cannot be used because the thermal power is low
it takes large time to starts it does not have spark & size of engine is big
it takes large space
@rajmech • 04 May, 2009
nitesh604
plz tell why we cannot use diesel engine in bikes it it cheapest
In ENFILED we can use only diesel engine.due to heavy weight and more space requirement most of the motorbikes not using diesel engine
@raj87verma88 • 04 May, 2009 Why are the discussions now restricted only to Royal Enfield? There are a number of other Brands of Bikes that have Diesel run steeds in their stables.
Any way, there are no new points now, everyone just seems to be repeating what has been said in earlier posts. Don't see any point in continuing with this thread. What do others say?
@g_rakesh2 • 05 May, 2009 Yes everybody is repeating the same points about the diesel engine....
@salman momin • 06 May, 2009
nitesh604
plz tell why we cannot use diesel engine in bikes it it cheapest
hi....
as u know diesel engine require more space to assmble so it canot be used in motorbike
@raj87verma88 • 06 May, 2009 The discussion in this thread seems to be going nowhere. I am closing this thread for now, if anyone has some new points to add fuel to the debate, he or she can request for the re-opening of this thread.
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