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dmftoy1
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Exhaust Gas Recirulation - ??
#1327757 - 08/03/03 05:04 PM
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Can someone explain to me how EGR causes lower combustion chamber temperatures? I would think that pumping hot exhaust gases into the intake would increase the temps.
Thanks in advance,
Dave
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nickleinonen
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Re: Exhaust Gas Recirulation - ??
#1327962 - 08/03/03 08:12 PM
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the amount of exhaust that is plumbed into the intake air charge with the egr system is not all that much [but as far as i am conserned, no engine should have one  ]
what the egr does is introduce a small amount of exhaust into the incoming air charge to dilute the oxygen content in the air charge. lower oxygen amount, lower flame temp, lower overall combustion temp, less nox created. think of an oxy-acteline torch setup. the more oxygen you add, the hotter the flame. the egr system works backwards from that setup. the egr makes the flame colder...
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Iluvsteelies
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Re: Exhaust Gas Recirulation - ??
#1328049 - 08/03/03 09:20 PM
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It acts as an inert gas to slow the rate of burn in the cylinder.
The of it as a seperator between the diesel and oxygen in the cylinder.
This keeps the combustion temps from going over 2500 degrees under certain conditions which is when Nox begins to form.
Contrary to what some say, it's not there to reduce the amount of 02 in the cylinder.
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Gone Fishen
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Re: Exhaust Gas Recirulation - ??
#1328327 - 08/04/03 12:57 AM
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The series 60 engine has an exhaust cooler that cools the temps to a lesser degree before it is mixed in the intake system. Yes I agree, the system is a pita. 
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dmftoy1
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Re: Exhaust Gas Recirulation - ??
#1328471 - 08/04/03 07:42 AM
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So does it lower power then also? Sorry for my ignorance, but all my "logic" seems to think this has to be a bad thing and I'm just trying to understand it.
Have a good one,
Dave
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Dave Whitmer
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Re: Exhaust Gas Recirulation - ??
#1329623 - 08/04/03 08:21 PM
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From what i understand,EGR serves to reduce combustion temperature. If you reduce combustion temperature, you reduce cycle efficiency. More fuel, less power, probably more particulates as well.
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roofeditor
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Re: Exhaust Gas Recirculation - ??
#1329774 - 08/04/03 09:30 PM
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Quote:
So does it lower power then also? Sorry for my ignorance, but all my "logic" seems to think this has to be a bad thing and I'm just trying to understand it.
Have a good one,
Dave
It introduces CO which can not support fuel burn.
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dmftoy1
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Re: Exhaust Gas Recirculation - ??
#1329777 - 08/04/03 09:31 PM
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So that would say to me that it's in effect reducing the available power. (or am I missing something?)
Regards,
Dave
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Iluvsteelies
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Re: Exhaust Gas Recirculation - ??
#1329825 - 08/04/03 09:58 PM
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It doesn't "reduce" power at anything other than part throttle.
Its not active at wot or high loads.
Very narrow operating range.
325 fwhp on the new 6.0 speaks for itself.
35 miles per gallon on my civic speaks for itself.
Egr is a good thing for clean air. Its necessary, its been around a long time and its here to stay.\
Wether or not the system has a downgrade on engine performance or reliability is strictly up the manufacturer and how much R&D and care they put into the systems design and calibration. 
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Jarlaxle
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Re: Exhaust Gas Recirculation - ??
#1329838 - 08/04/03 10:06 PM
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On a gasser, EGR is worth as much as a 15-20% mileage boost, with essentially zero power loss.
On a diesel...it, bluntly, scares me.
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Fred Hemer
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Re: Exhaust Gas Recirulation - ??
#1330057 - 08/05/03 12:05 AM
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Quote:
The series 60 engine has an exhaust cooler that cools the temps to a lesser degree before it is mixed in the intake system. Yes I agree, the system is a pita.
Amen
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Gone Fishen
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Re: Exhaust Gas Recirulation - ??
#1330102 - 08/05/03 12:40 AM
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Ya Fred, maybe we will prevail.  Not.
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nickleinonen
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Re: Exhaust Gas Recirculation - ??
#1331078 - 08/05/03 07:20 PM
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many import compact cars no longer have egr valves in them. they use their variable valve timing to introduce the exhaust into the combustion process... gm's new 4.2 I6 gasser does the same thing... my 4.7v8 in my dodge 1500 has no egr... the 2003 dodge hemi has no egr [but the 2004 will]
Quote:
It doesn't "reduce" power at anything other than part throttle.
Its not active at wot or high loads.
Very narrow operating range.
325 fwhp on the new 6.0 speaks for itself.
35 miles per gallon on my civic speaks for itself.
Egr is a good thing for clean air. Its necessary, its been around a long time and its here to stay.\
Wether or not the system has a downgrade on engine performance or reliability is strictly up the manufacturer and how much R&D and care they put into the systems design and calibration.
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Birken Vogt
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Re: Exhaust Gas Recirculation - ??
#1331162 - 08/05/03 08:28 PM
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'91 Chryco 3.3L did not have EGR...I don't pay much attention to gas engines though...
Birken
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Iluvsteelies
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Re: Exhaust Gas Recirculation - ??
#1331568 - 08/05/03 11:52 PM
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Nick you are correct, I do however have an older civic which does not have variable valve timing. It also does not have an egr valve but the valve overlap causes some of the exhaust to stay in the cylinder.
This type of egr has been around since the early 80's (lots of american cars use this type of egr), but a cam profile that allows this is not conducive to making power. Its also not very accurate and can't be shut off when the engine is cold.
The new hondas (not vtec but the i-vtec) have a constantly variable intake cam that allows accurate control of egr without a valve.
The v-tec hondas all used egr valves.
On the ULEV cars the egr runners are of equal length. It looks like the valve body to a trans when you take the plate off. 
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YARIC008
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Re: Exhaust Gas Recirculation - ??
#1331724 - 08/06/03 01:59 AM
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Not sure about how ferrari's work the EGR stuff, probably don't have the valves, but they use a like.. 3d cam shaft, there are individual parts for each cylinder as usual and at each little thing the cam shaft is skinier at one and and fat on the other. To control valve timing some sort of a mechanicsm pulls the cam shaft one way or pushes it the other way to change when the valves open and close.
V-TEC has like.. two or three different settings. Ferrari's basically have anything from the skinny end of the cam shaft to the fat side, lol. It's like analog compared with digital, analog being better in this case.
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