[Mohnish]

Hello,

I was wondering if someone could give details on the types of diesel technology. My query being (1) What is Direct injection ? (2) What is Indirect Direct injection ? (3) How does Common Rail figure in all this ? (4) How come the 'older' diesel engines had a heater plug system where you had to wait for the plugs to 'heat up' before cranking the starter ? Today's engines you don't have to wait, so is there no heater anymore ? etc etc.

There is a similar thread at http://www.team-bhp.com/forum/indian...dx-factor.html but the last post is over a year old (01 May 2007) and it does not address these issues. Hence a new thread.

Thanks in advance.

[Mohnish]

Did a bit of googling (which I should have done before posting!), here is the link if anyone is interested:

Diesel engine - Wikipedia, the free encyclopedia

[arunforu1]

1)direct injection: diesel is injected directly into combustion chamber. more powerfull, but more noisy.
2)indirect injection: diesel is injected into a precombustion chamber (can be simple or swirl type). more smooth, but less power than same size DI .
3) common rail: instead of having individual feed-pipe from injection pump to cylinder & complicated design of FI pump to feed,time caliberate the diesel under high pressure, a single pipe is used.

This single pipe from high pressure pump to injectors is called rail. & since it is common feed route to all cylinders/injectors its called common rail.

in common rail the pump is simplified constant pressure pump. The Job of Calibration & timing is done by solenoid activated injectors, governerned by ECU.

So whole process becomes more simple, easy to control with changing RPM+less lag time.

4)even modern diesels have heater plugs, called glow plug. even today one has to wait before glow plug goes off. But timing is far less than the older plugs.

[Mohnish]

Thanks arunforu1 for the explanation, I have a few more queries below if you could address:

Originally Posted by arunforu1

1)direct injection: diesel is injected directly into combustion chamber. more powerfull, but more noisy.
2)indirect injection: diesel is injected into a precombustion chamber (can be simple or swirl type). more smooth, but less power than same size DI .
3) common rail: instead of having individual feed-pipe from injection pump to cylinder & complicated design of FI pump to feed,time caliberate the diesel under high pressure, a single pipe is used.

Is it possible to identify the type of engine between (1) DI & (2) Indirect injection by looking at it like in (3) Comon Rail which has the rail ?

Originally Posted by arunforu1

4)even modern diesels have heater plugs, called glow plug. even today one has to wait before glow plug goes off. But timing is far less than the older plugs.

Ok, then how is it that my Scorpio does not have a heater/glow plug indicator? Or is it not necessary?

My Benz E250 has the heater/glow plug indicator and the light stays on for about 5 secs on a cold engine. Its the W210 series, would that be DI or IDI?

Also, in both above cars, I start them like a petrol engine ie without waiting for the plugs to heat up and they start perfectly.

With regards the glow plugs, I am quoting from Diesel engine - Wikipedia, the free encyclopedia :

"Such systems fell out of favour when electrical glow plug systems proved to be the simplest to operate and produce. Direct-injection systems advanced to the extent that cold-starting systems were not needed and then electronic fuel injection systems rendered most cold-start system unnecessary."

From the above it would seem that glow plugs are not in use in DI engines?

Can you give an example of vehicles today using DI and Indirect injection. The Common Rail ones are quite obvious since they are advertised so heavily!

[arunforu1]

Originally Posted by Mohnish

Is it possible to identify the type of engine between (1) DI & (2) Indirect injection by looking at it like in (3) Comon Rail which has the rail ?

By a plane look distributor(also called rotary) Pump engine is more probable to be DI, but this is not a thumb rule. Unless head is opened, you can not be sure by visual inspection alone.

A good check for trained ears is to start the engine, the charcterstic diesel clutter is prominent & distinguishable in DI. Example Idle clutter of any mahindra engine (most of them are DI).

common rail cn be easily distinguised by looking at fuel feed line (single rail from pump feeding all injectors).

Originally Posted by Mohnish

Ok, then how is it that my Scorpio does not have a heater/glow plug indicator? Or is it not necessary?

I am really not updated if scorpio has glow plug indicator or not or no glow plugs at all.Sorry for my little knowledge on scorpio, but usually it should have.

Originally Posted by Mohnish

My Benz E250 has the heater/glow plug indicator and the light stays on for about 5 secs on a cold engine. Its the W210 series, would that be DI or IDI?

Yes 3-5 seconds is usual time for glow plugs from dead cold start.

Originally Posted by Mohnish

Also, in both above cars, I start them like a petrol engine ie without waiting for the plugs to heat up and they start perfectly.

Indian winters dont warrant a need for a glow plug, but come to north India, even early morning delhi cold start will tell you, that we need it.

Originally Posted by Mohnish

With regards the glow plugs, I am quoting from Diesel engine - Wikipedia, the free encyclopedia :



From the above it would seem that glow plugs are not in use in DI engines?.

It is used in DI engines as well, a well known Indian example is mahindra DI tractor, they all have glow plugs & all are DI. But as per quoted article i need to update my knowledge about ultra-modern diesels not using glow plugs at all. Till date I havnt seen a common vehicle without it. Thanks for pointing out.

Originally Posted by Mohnish

Can you give an example of vehicles today using DI and Indirect injection.

Indian examples : mahindra marshal DI has direct injection, while Tata Indica V2 has Indirect Injection motor.

[Mohnish]

Originally Posted by arunforu1

...

Thanks so much Arun for the detailed explanation. Now that you pointed it out, the DI is definately more noisy at idle than the IDI eg: Scorpio vs Indica. I used to always wonder why the Scorpio is more claterry than the Indica or some others. Now I know!

[sujaylahiri]

There is another kind of injection system for diesels called the Pump Line Injection (PLI). A similar technology was used by VW as Pumpe Duse in the 1.9 TDi engines from 2004-2006 I think.
It's similar to Common Rail but has a few differences in terms of no. of injection events per cycle and number of fuel injector pumps.

[kuttapan]

With the common rail engines, diesel is injected at higher pressure than normal diesel engines and hence chances of combustion are better, even at cold start. Only when it gets real cold and diesel does not ignite, does it require glowplugs. This is what I think.

[Mohnish]

Originally Posted by kuttapan

With the common rail engines, diesel is injected at higher pressure than normal diesel engines and hence chances of combustion are better, even at cold start. Only when it gets real cold and diesel does not ignite, does it require glowplugs. This is what I think.

Right, so if the glow plugs have failed, you would not know it until you experienced extreme cold weather and the engine doesn't start. This considering the Scorpio does not have a glow plug indicator. Am I correct?

Also, my Scorpio is not Common Rail and it still does not have a glow plug indicator. Is there any explanation for that?

[kuttapan]

I do not have experience with Scorpio, so cannot say for sure. But after some research on google, I found that glowplugs are not really mandatory, technology has now advanced an there are other methods for cold starting. Read on -

"In very cold weather, diesel fuel thickens and increases in viscosity and forms wax crystals or a gel. This can make it difficult for the fuel injector to get fuel into the cylinder in an effective manner, making cold weather starts difficult at times, though recent advances in diesel fuel technology have made these difficulties rare. A commonly applied advance is to electrically heat the fuel filter and fuel lines. Other engines utilize small electric heaters called glow plugs inside the cylinder to warm the cylinders prior to starting. A small number use resistive grid heaters in the intake manifold to warm the inlet air until the engine reaches operating temperature. Engine block heaters (electric resistive heaters in the engine block) plugged into the utility grid are often used when an engine is shut down for extended periods (more than an hour) in cold weather to reduce startup time and engine wear."

Source - PowerPediaiesel engine - PESWiki

[rranjith_kum]

Originally Posted by sujaylahiri

There is another kind of injection system for diesels called the Pump Line Injection (PLI). A similar technology was used by VW as Pumpe Duse in the 1.9 TDi engines from 2004-2006 I think.
It's similar to Common Rail but has a few differences in terms of no. of injection events per cycle and number of fuel injector pumps.

Well I would like to make things much more elaborate here. The Pumpe Düse technology actually consists of the pump and injector assembled as one unit, this is driven by a cam lobe. It injects fuel extremely at high pressures (2050 bar) into the cylinder for individual combustion. this might be of related interest http://www.team-bhp.com/forum/techni...nown-crdi.html
as far as I know scorpios have glow plugs and infact the have a glow plug indicator but I am not sure of m hawk.

[Mohnish]

Originally Posted by rranjith_kum

...as far as I know scorpios have glow plugs and infact the have a glow plug indicator but I am not sure of m hawk.

In that case something is amiss in my non CRDe 2.6 Turbo Scorpio !!! Will speak to the mechs about this and have a first hand look at the head to estabilish the presence of glow plugs.

Tiil date, I always thought all diesel technology required some sort of heat to the combustion chamber / fuel for the inital cold start.

[rranjith_kum]

Here is a picture of the glow plug indicator. Don't you have this in your Scorpio ??

Image:Glowplug.jpg - Wikipedia, the free encyclopedia

[sameel]

being a CRS engineer working in Robert Bosch... this discussion over here is for me.
so instead of me doing a long post..it will take lot of time .
which i dont have.
so post the questions i will answer them when i have the time
peace out
sameel

[gd1418]

Non-CRDe Scorpio's with the 2600SZ plus engines are without glow-plugs. The indicator that you see on your console are part of the standard console that is made for all. In fact if you look closely, you shall also see a the check-engine indicator but it doesn't glow as it is not activated or required. But that indicator works in Rev116.

Originally Posted by Mohnish

In that case something is amiss in my non CRDe 2.6 Turbo Scorpio !!! Will speak to the mechs about this and have a first hand look at the head to estabilish the presence of glow plugs.

Tiil date, I always thought all diesel technology required some sort of heat to the combustion chamber / fuel for the inital cold start.