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Old 22nd August 2009, 12:11   #1
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Default Do non-common-rail diesel engines work better with warm air?

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Originally Posted by vinod_nookala View Post
Air at the top is much cooler than what is fed from the engine bay and lot cleaner as well. The life of air cleaner increases and hence the engine life. engine also runs a little cooler.
Does this apply to Diesel engines? I know cool air helps petrol engine, but I was told diesel engines work better with hot air.

Edit: I heard this from a top expert, or else I would have ignored it.

Last edited by Samurai : 23rd August 2009 at 14:10.
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Old 22nd August 2009, 19:41   #2
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Quote:
Originally Posted by Samurai View Post
Does this apply to Diesel engines? I know cool air helps petrol engine, but I was told diesel engines work better with hot air.
Samurai,
Its applies for diesel engines aswell. If you notice all the medium and heavy commercial diesel engined trucks from major truck manufacturers have snorkels or extended air intakes which pulls cold air from above the cabin/roof.

I think diesel engines need air in normal temperature and not too hot which will result in poor fuel burn. Hence its good to have snorkel and more move snorkel gives engine cleaner air to breathe.

Experts please correct me if I am wrong.

Shibu
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Old 23rd August 2009, 00:53   #3
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The cold air is denser then the hot air. means the oxygen content will be more in cold air compared to hot air. this will lead to λ nearly equal to 1 or above, which the diesel engines expect. a turbo will boost up the oxygen density, but will result in heating up the intake air upto 150 C. hence a intercooler is used to bring down the temperature to atleast 50 C. the stoichiometric ratio aka lambda should be nearly equal to 1. if λ >1, it will result in the emission of nitrogen oxides(NOx) which are highly unstable elements. if λ<1, it will result in emission of particulate mass(unburnt carbon). a forced induction motor produces more toxic gases then the naturally aspirated motor. it is because of λ being >1. hence to overcome this issue an EGR is added to maintain the λ=1. but many people disconnect it without knowing why it is used for.

Last edited by star_aqua : 23rd August 2009 at 00:54.
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Old 23rd August 2009, 01:40   #4
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Quote:
Originally Posted by star_aqua View Post
The cold air is denser then the hot air. means the oxygen content will be more in cold air compared to hot air. this will lead to λ nearly equal to 1 or above, which the diesel engines expect. a turbo will boost up the oxygen density, but will result in heating up the intake air upto 150 C. hence a intercooler is used to bring down the temperature to atleast 50 C. the stoichiometric ratio aka lambda should be nearly equal to 1. if λ >1, it will result in the emission of nitrogen oxides(NOx) which are highly unstable elements. if λ<1, it will result in emission of particulate mass(unburnt carbon). a forced induction motor produces more toxic gases then the naturally aspirated motor. it is because of λ being >1. hence to overcome this issue an EGR is added to maintain the λ=1. but many people disconnect it without knowing why it is used for.

Sir, I understand you are trying to really give some useful tip here, but I'm unable to understand anything as I'm not good at equations etc.

Can you please put this in a lay man language for the benefit of people like me ?

What is EGR ?

Sorry, but I really wanted to understand what these equations explained for ?
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Old 23rd August 2009, 08:52   #5
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Quote:
Originally Posted by star_aqua View Post
the stoichiometric ratio aka lambda should be nearly equal to 1. if λ >1, it will result in the emission of nitrogen oxides(NOx) which are highly unstable elements. if λ<1, it will result in emission of particulate mass(unburnt carbon). a forced induction motor produces more toxic gases then the naturally aspirated motor. it is because of λ being >1. hence to overcome this issue an EGR is added to maintain the λ=1. but many people disconnect it without knowing why it is used for.
Sir, I'm aware of AFR which is 14.7:1 for IC engines! Most modern ECU vehicles follow this ratio based on the various vehicle sensors and inputs from the driver.

This is common for both petrol and diesel engines AFAIK.

BTW, are you referring to lamba as the oxygen sensor?

Siva:
EGR is Exhaust Gas Recirculation - A device that is present in the exhaust manifold that senses unburnt gases and feeds a portion of that into the intake again.

2 effects - 1: Improve Nox Emissions
2: Improve FE

Most modern diesel engines have EGR nowadays!
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Old 23rd August 2009, 09:22   #6
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Quote:
Originally Posted by headers View Post
Sir, I'm aware of AFR which is 14.7:1 for IC engines! Most modern ECU vehicles follow this ratio based on the various vehicle sensors and inputs from the driver.

This is common for both petrol and diesel engines AFAIK.

BTW, are you referring to lamba as the oxygen sensor?

Siva:
EGR is Exhaust Gas Recirculation - A device that is present in the exhaust manifold that senses unburnt gases and feeds a portion of that into the intake again.

2 effects - 1: Improve Nox Emissions
2: Improve FE

Most modern diesel engines have EGR nowadays!
I appreciate your answer.

Last edited by trammway : 23rd August 2009 at 09:23.
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Old 23rd August 2009, 14:11   #7
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Quote:
Originally Posted by trammway View Post
I understand you are trying to really give some useful tip here, but I'm unable to understand anything as I'm not good at equations etc.

Can you please put this in a lay man language for the benefit of people like me ?

What is EGR ?

Sorry, but I really wanted to understand what these equations explained for ?
Hi Shiva,
Lambda(λ) is the short name or symbolic representation for stoichiometric ratio which is nothing but AFR. I was trying to explain in terms of emissions that come out of a diesel engine when the AFR is altered.

Lambda(λ) is said to be 1 if the AirFuelRatio is 14.7:1.

Lambda(λ) is said to be <1 if the Air is less than 14.7 units for 1 unit of fuel.

Lambda(λ) is said to be >1 if the Air is more than 14.7 units for 1 unit of fuel.

λ<1 indicates rich mixture in which there is no enough oxygen for the complete combustion of the fuel that is injected which leads to black smoke emitting the unburnt carbon. this happens when you lug the engine or during the quick acceleration. you might have observed in turbo vehicles, black smoke is emitted during hard acceleration(here λ<1) and suddenly goes off when the turbo kicks in(now λ>1).here you will have visible air pollutant.

λ>1 indicates lean mixture(most turbo vehicles run on lean mixture) in which you have excess of oxygen then what it is required for the complete combustion. the disadvantage here is, the excess oxygen in the combustion chamber will react with nitrogen(available in intake air) at peak temperatures forming NOx. here you will have unvisible air pollutant which is more problematic to mankind than the black smoke.

now when you recirculate a portion of the exhaust back into the intake(called as EGR), this will dilute the oxygen concentration and also acts as heat absorber by reducing the peak temperatures that causes excess oxygen to react with the nitrogen which avoids the formation of NOx.

Hope i am clear to you.


Quote:
Originally Posted by headers View Post

BTW, are you referring to lamba as the oxygen sensor?
I was referring to AFR as Lambda.
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Old 23rd August 2009, 14:12   #8
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Guys, let's keep the discussions to non-CRDi engine since it was raised in context with a DI Diesel engine.
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Old 23rd August 2009, 17:03   #9
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Quote:
Originally Posted by Samurai View Post
Guys, let's keep the discussions to non-CRDi engine since it was raised in context with a DI Diesel engine.
Whether CRDi or not, the above holds true sir!
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Old 23rd August 2009, 20:34   #10
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Quote:
Originally Posted by Headers
EGR is Exhaust Gas Recirculation - A device that is present in the exhaust manifold that senses unburnt gases and feeds a portion of that into the intake again.
EGR is bad for the engine. Imagine sending unburnt exhaust gases into the intake and its valves. Its just a emissions reduction gadget.
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Originally Posted by samurai
Guys, let's keep the discussions to non-CRDi engine since it was raised in context with a DI Diesel engine.
Oh! When did you get a DI engine?
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Old 23rd August 2009, 20:41   #11
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Originally Posted by nitrous View Post
Oh! When did you get a DI engine?
I didn't, we were talking about Sachin's MDI3200 engine with Sudhirji when he made that comment.

Last edited by Samurai : 23rd August 2009 at 20:49.
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Old 24th August 2009, 07:21   #12
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Quote:
Originally Posted by nitrous View Post
EGR is bad for the engine. Imagine sending unburnt exhaust gases into the intake and its valves.
Correct Nitrous, thats why WORLD over, vehicle manufacturers are going in for EGR so that they can screw vehicles and we can buy more of it!
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Old 24th August 2009, 08:17   #13
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E.G.R is not a bad thing as it improves fuel efficiency too!!
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Old 24th August 2009, 09:11   #14
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Quote:
Originally Posted by Samurai View Post
Does this apply to Diesel engines? I know cool air helps petrol engine, but I was told diesel engines work better with hot air.

Edit: I heard this from a top expert, or else I would have ignored it.
Quote:
Originally Posted by Samurai View Post
Guys, let's keep the discussions to non-CRDi engine since it was raised in context with a DI Diesel engine.
Quote:
Originally Posted by Samurai View Post
I didn't, we were talking about Sachin's MDI3200 engine with Sudhirji when he made that comment.
Reading all this I can give a start forward answer to the "diesel running better with warm/hot air".Older engines [with no feedback] ran 'quieter' and hence 'smother' gave a impression of running 'better' with warm air [or engine warming faster ] which usually happened comparatively earlier in warmer climate, than places with cooler climate.
All diesels event today have this issue only thing is due the electronic control the noise levels are reduced to give a impression that new engines run better.

Last edited by techn0l0gist : 24th August 2009 at 09:15.
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Old 24th August 2009, 09:49   #15
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Basically colder air is denser, so the power will be more. I am not aware of any engine which gives more output with warmer air.
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