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Yet Another EGR question by Hulk
Started on: 01-11-2014 12:11 AM
Replies: 4 (137 views)
Last post by: Hulk on 01-11-2014 07:36 PM
Hulk
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Report this Post01-11-2014 12:11 AM Click Here to See the Profile for HulkSend a Private Message to HulkEdit/Delete MessageReply w/QuoteDirect Link to This Post
Hey all,

Haven't posted in a good while. But as I was pondering on how to handle my possible EGR problem, I searched through some posts here, and saw over and over where people were saying that the EGR gas helps keep the cylinders cool. Now I'm not a Ph.D. of Internal Combustion, but I'm no rookie either. So I'm wondering how a gas that is, if anything, warmer than the intake air, could possibly help cool the combustion in the cylinder?

I'm guessing that the cooling effect is due to the decreased timing? Since the computer adds or subtracts injector pulse width to keep the A/F mixture the same (assuming steady state driving)

Yes? No?
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speed1
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Report this Post01-11-2014 12:42 AM Click Here to See the Profile for speed1Send a Private Message to speed1Edit/Delete MessageReply w/QuoteDirect Link to This Post
I know just enough about cars to be wrong all the time so take this with a grain of salt. The gases that the egr lets back in to the cylinder displaces some of the incoming air/fuel mixture so that when the combustion takes place it is not as hot. At least that's how I understand the process.

[This message has been edited by speed1 (edited 01-11-2014).]

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Hulk
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Report this Post01-11-2014 02:35 AM Click Here to See the Profile for HulkSend a Private Message to HulkEdit/Delete MessageReply w/QuoteDirect Link to This Post
Thank you.

You are correct. I did consider that, but it would take more info than I can get without lots of instrumentation and a dyno to figure out how much exhaust gas actually gets in there when the valve is open. Also, I believe that there is also some unburned fuel in the exhaust, that far upstream. I can't remember why I think that, so take it with the salt. So anyway, I'm thinking part of it will burn.

Still, maybe that small percentage of inert gas does keep it cooler...
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jhgraham
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Report this Post01-11-2014 09:23 AM Click Here to See the Profile for jhgrahamClick Here to visit jhgraham's HomePageClick Here to Email jhgrahamSend a Private Message to jhgrahamEdit/Delete MessageReply w/QuoteDirect Link to This Post
Happend to see this and thought it may help.

"As engine combustion temperatures approach 2500 degrees, formation of smog producing nitrogen oxides, or NOx, increases. An EGR (exhaust gas recirculation) valve reduces these emissions by recirculating small amounts of exhaust back into the combustion chambers. Since exhaust is mostly carbon dioxide, it does not burn. Less burning reduces combustion temperature, and NOx emissions.

All greek to me.

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Hulk
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Report this Post01-11-2014 07:36 PM Click Here to See the Profile for HulkSend a Private Message to HulkEdit/Delete MessageReply w/QuoteDirect Link to This Post
Thanks!

Yes, that is the same thing (in prettier words) that we were talking about. It seems to be the consensus. I sure am glad this forum is still here!

This fall, I happened on an original owner, red/black 1986 SE V6. It is the first Fiero I've had with the Getrag, and my first impression is that the gears are awful long, but then I am used to the Muncie 4 speed. It has very few flaws, and just a couple problems common to Fieros.

I still have my black 86 GT; that one is light of an engine, and I'm keeping it secret until it's running again. I'm doing a rather unique swap on it. I hope to get it running next year and I'll post a build thread about it.

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[This message has been edited by Hulk (edited 01-12-2014).]

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