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EGR question
Posted: September 12th, 2006, 11:40 pm
by WingleBeast
i just put my new genie headers in and there is no place to put the EGR pipe. will this cause problems letting it in the open air?
Posted: September 13th, 2006, 12:51 am
by ariesdude
Yes it will let in unmetered air when EGR valve is open - you can just cap/block it....
Posted: September 13th, 2006, 5:43 pm
by WingleBeast
whats better, blocking or letting it open?
Posted: September 13th, 2006, 8:12 pm
by ariesdude
Block it
Posted: September 13th, 2006, 11:35 pm
by WingleBeast
think i could get a fitting that fits the threaded part, or should i just crimp the tube?
Posted: September 13th, 2006, 11:43 pm
by ariesdude
whichever works - you need it to be airtight....
Posted: September 14th, 2006, 11:06 am
by WingleBeast
only if the sold "illegally modifying your exhaust system threaded tube plugs" on corksport
Posted: May 9th, 2007, 7:50 pm
by SuperK
curious, I'm placing my headers in as well
I'm wondering if anyone can testify a difference in performance in their vehicles due to no EGR.
Obviously it's designed to lower emissions and improve efficiency.
I'm expecting my milage to drop due to this. Can anyone tell me how much in their own experience?
Posted: May 10th, 2007, 11:40 pm
by WingleBeast
lower idles, and rougher starts, just because it dosent warm up the incomeing air.
you wil be able to tell a difference at idle, but i think the performance otherwise makes up for it
Posted: May 15th, 2007, 11:15 pm
by SuperK
Oh, I didn't realise you made this thread. Odd to see it back from the grave, eh?
So Wingle, any difference in your milage?
I calc'ed almost 40MPG doing 70MPH on the highway.
But it drops considerably, down to about 30 or maybe lower traveling ~80-85-ish.
EGR cutoff is at 3125RPM on the B6. I'm guessing part of the difference is that 70MPH below the cutoff, and 80 is right above it. But I could be wrong in my assumption.
I just would like to know what I can expect.
Posted: May 15th, 2007, 11:22 pm
by cyclonekid78
EGR works by recirculating a portion of an engine's exhaust gas back to the engine cylinders. Intermixing the incoming air with recirculated exhaust gas dilutes the mix with inert gas, lowering the adiabatic flame temperature and (in diesel engines) reducing the amount of excess oxygen. The exhaust gas also increases the specific heat capacity of the mix lowering the peak combustion temperature. Because NOx formation progresses much faster at high temperatures, EGR serves to limit the generation of NOx. NOx is primarily formed when a mix of nitrogen and oxygen is subjected to high temperatures.
Notice it says INERT GASES.
Posted: May 16th, 2007, 12:13 am
by WingleBeast
i see cyclone kid, but when you take it off, and dont plug it, it will be sucking oxygen rich atmosphear.
and yes, my gasmilage takes a plunge on highway. im relieved you noticed this, cause whenever i drive to and from college i get crappy milage, but around town it the same. i was pissed! but now that you have that issue as well it must be the header. not sure how it makes sense but at least we are on the same page
Posted: May 16th, 2007, 5:31 am
by SuperK
From the Wiki:
5 to 15 percent of the exhaust gas is routed back to the intake as EGR (thus comprising 5 to 15 percent of the mixture entering the cylinders). The maximum quantity is limited by the requirement of the mixture to sustain a contiguous flame front during the combustion event; excessive EGR in an SI engine can cause misfires and partial burns. Although EGR does measurably slow combustion, this can largely be compensated for by advancing spark timing. Contrary to popular belief, a properly operating EGR actually increases the efficiency of gasoline engines via several mechanisms:
Reduced throttling losses
Reduced heat rejection
Reduced chemical dissociation
Reduced intake charge density
Reduced specific heat ratio
Maybe i'm defeating the purpose of performance headers here, but if I could reinstall the EGR pipe back, possibly thread it's own hole or something, does anyone have an opinion of why I shouldn't do that?
Quite frankly, I had a great feeling when I saw the big 40 on the MPG-ometer, you know, the one that our cars don't have.
Also, regarding your rougher idles... your EGR isn't enabled during idle and again, above 3125RPM. Might want to check into that?
*
EGR is typically not employed at high loads because it would reduce peak power output, and it is not employed at idle (low-speed, zero load) because it would cause unstable combustion, resulting in rough idle.
<3 the Wiki
Posted: May 16th, 2007, 11:08 pm
by WingleBeast
im was going to cut a hole and thread it to hook it up, but im going BP as soon as ariesdude finds himself escort engone, so its no longer worth my time