Originally posted by Primaris: Stop the Greeness. No one is saying the EGR doesn't clean up NOx. Take the green blinders off.
If you think the EGR is performance hit free, then how does forced induction work? It adds more air into the cylinders there by increasing the power.
The EGR takes away air.
Now just like forced induction in order to gain the lost power you have to tune the engine (carb/ecu). The gains will be small, but they will be measurable.
yes - but again - EGR is closed during WOT. the only possible power loss is due to turbulance created at the exhaust & intake ports of the EGR.
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02:15 PM
Doug85GT Member
Posts: 9695 From: Sacramento CA USA Registered: May 2003
It depends on the kind of driving that you do. I have seen a 4 mpg drop on highway milage when I had a leak in my EGR vacuum hose. I would speculate very little change in city driving since the EGR is not that big of a factor in stop and go traffic.
Some people have disconnected their EGR and said there was no change in gas milage at all. I am skeptical of that claim since not matter what happens, you can't break the laws of nature. Without the EGR system, more O2 goes into the engine at cruise which needs more gasoline to burn properly. You can reprogram the ECU to burn leaner to make up for it but you can only go so far before you start knocking and you lose significant amount of power so you have to open the throttle more to maintain the same speed. Most people are not sophisticated enough to reprogram the ECU for a lean burn.
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02:54 PM
Pyrthian Member
Posts: 29569 From: Detroit, MI Registered: Jul 2002
Originally posted by JazzMan: The typical reason for disabling the EGR system is because of the inability or unwillingness to keep it repaired/working properly. Being that it's only got three main parts and is easy to troubleshoot, I wonder why anyone would consider it easier to disable it rather than repair it.
Because a replacement EGR tube is $100 and a block off plate is free.
The drop from 28 mpg highway to 27 mpg highway takes a long time to amortize that $100. At $1.50 gas, 28 mpg is $.053/mile and 27 mpg is $.055/mile. The difference will take 50,000 miles to amortize $100
[This message has been edited by Will (edited 01-05-2009).]
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03:38 PM
Will Member
Posts: 14249 From: Where you least expect me Registered: Jun 2000
Originally posted by Doug85GT: Some people have disconnected their EGR and said there was no change in gas milage at all. I am skeptical of that claim since not matter what happens, you can't break the laws of nature. Without the EGR system, more O2 goes into the engine at cruise which needs more gasoline to burn properly. You can reprogram the ECU to burn leaner to make up for it but you can only go so far before you start knocking and you lose significant amount of power so you have to open the throttle more to maintain the same speed. Most people are not sophisticated enough to reprogram the ECU for a lean burn.
This is backwards reasoning. You need X power to go down the highway at your chosen speed. Without EGR, manifold pressure Y is required to produce that power. With EGR, manifold pressure Y+ is required to produce that power. Because of the higher manifold pressure required to produce the same power, the engine experiences less pumping loss and gets better mileage with EGR. If the cruising speed is high enough that manifold pressure is already pretty high, then the mpg gains from EGR will be minimal. EGR should show the most gains at low speed light load cruise. I never do that, so it won't help me much.
There are some basic misconceptions here on how engines work.
Essentially, Otto cycle engines work by bringing air into a chamber, heating that air, and using the increase in pressure from heating to push on a piston and thus convert thermal energy into mechanical energy. Air is composed of two basic parts as used by an engine: inert gas and oxygen. The inert gas is mainly nitrogen with traces of CO2, Argon, etc. The oxygen is used as an oxidizer for the fuel burned to create the heat. Since the heat is created inside the working volume it's called an internal combustion engine, as opposed to something like a steam engine which is an external combustion engine.
The amount of fuel (for gasoline engines anyway) that is supplied must match the amount of available oxygen perfectly. As long as that occurs it absolutely doesn't matter what the inert part of the air being used is composed of. The inert portion could be 98% CO2 instead of nitrogen, it absolutely doesn't matter. Want to test this? Go get a bottle of CO2 and a bottle of O2 and use a manifold to give you a 79% CO2 and 21% O2 mix and fed that into a gasoline engine, it'll run just fine.
Now, if you decrease the O2 content you have to decrease the fuel added proportionally. It'll burn slightly slower since the O2 molecules are further apart, but not much slower. The main effect is that since less gasoline is being burned being that there's less O2 available the peak combustion chamber temperature will drop 50 or 100 degrees (depending on the engine design). The more you dilute the O2 the bigger the temperature drop. This will produce a slight power drop, of course, after all the amount of push on the piston is directly related to the amount of heat added to the inert gases in the cylinder, but a slight increase in throttle opening (really slight) solves that problem. The key is to dilute the incoming O2 just enough to get peak temperature below 2,550°F; at that temp NOx production essentially turns off like a light switch. Above that temp, lots of NOx, below it, almost none. Most engines don't require much, and some engine designs don't require any such as one of the Quad4 variants.
To sum it up, it makes no difference whatsoever where the inert gases come from, exhaust or nitrogen in the air, and since EGR systems on modern cars isn't enabled during WOT there is, and can be no, effect whatsoever on maximum power. If anything, EGR allows running higher compression without increasing NOx at cruise, and increasing compression definitely increases power output.
Oh, and the reason why forced induction "works" is because it helps make up for pumping losses and packs more inert gas into the cylinder, though at a net cost in efficiency because of frictional losses in the supercharger and drive system. Turbos give a net gain in efficiency because some of the heat energy in the exhaust is converted back into mechanical energy to drive the turbine. Neither form of forced induction gives a rat's patootie about whether the gases being compressed are nitrogen or CO2.
WOW !! what Jazzman said,,I think..this post will really add to the forum members info on this part which is much maligned.. Try to run your EGR on the V 6,,, it will not hurt to drive the car with out it at normal old stlye Granny around town speed .. TO run with out an EGR you must compensate in some way,,there are forum members who drive many miles with a faulty EGR and do no permanent damage . the gas sent to the combustion chamber is "inert" and helps the engine ,,a EGR leak will do more damage than a blocked EGR !! the inert gas will not reburn,//simplefied!!! It lowers chamber temperature.. that is what all this mumbo Jumbo means A V6 with precise tune and timing can run with out the EGR tune /timing retard 1 to 2 degree ,, you should be able to run around town with no ping ,,if you run hard/rapid acceleration you should have EGR
I think you can run 89 octane and precise stock timing(look up ,jetman distributor replacement ) and no EGR ,but you need good vacuum control.. Who has run many miles with out EGR ?? speak up now or forever hold your distorted views I will not be running one if I ever master the skill to put a V6 GT on the road,, the great spirit waka tankaful has deemed I should learn more about fiero,s and throws a new roadblock every day.. when I had a 88 duke I drove Fiero,s ,,now I work on Fiero,s because I have a V6 ..... ha ha
[This message has been edited by uhlanstan (edited 01-05-2009).]
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07:45 PM
Jan 6th, 2009
m0sh_man Member
Posts: 8460 From: south charleston WV 25309 Registered: Feb 2002
i guess ill throw in my 2 cents since everyone else has:
ive got two fiero's 3.4L manual transmissions, one has the trueleo intake system EGR delete, i get 34.5 MPG highway out of this car, it runs smooth and has done so for about 10,000 miles now with the egr removed.
the other is a stock intake and everything else, it runs well and gets 30.4 MPG highway, i attribute the difference in mileage to the fact the first car is a 5 speed, second is a 4 speed, the EGR delete car got worse gas mileage before the EGR delete, it only got 32.8 MPG, me personally i think the increase in MPG was due to the intake, the EGR had little/no effect for me, that doesnt mean it wont effect you (my disclaimer) but i never have to worry about egr tube leaks on my 5 speed car again.
matthew
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09:05 AM
Lee Phillips Member
Posts: 42 From: Ridgecrest, CA Registered: Nov 2008
EGR is just a machine version of anal feedback. It was originally intended to reduce combustion temperatures as an aid in preventing formation of oxides of nitrogen. They really did not WNT to use anal feedback, but they did not know what else to do [for almost free]. Think about it - if you make a million cars, and have to charge an extra $5 per car, that $5 million bucks out of the profits. CEO's would rather that $5M went into THEIR pockets.
The idea that it can in any way improve fuel economy is specious at best. There is NOT ENOUGH of this anal feedback to make a difference.
EGR sure does not make a positive contribution to the health of intake valves or guides. It does not add power. It IS another layer of complexity. Mostly this is managed pretty well by the ECU, assuming that everything is in good repair. Of course, if you aren't going to maintain your machine, someone else needs it more than you do. No sympathy from me on that.
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12:21 PM
Will Member
Posts: 14249 From: Where you least expect me Registered: Jun 2000
Originally posted by JazzMan: Above that temp, lots of NOx, below it, almost none. Most engines don't require much, and some engine designs don't require any such as one of the Quad4 variants.
Over the years, we've come to associate emissions and performance as being diametric opposites. However, in the case of EGR, this is ironically not true. Bigger cams that make more high RPM power leave more exhaust in the cylinder at medium RPM and light load... exactly the conditions under which it is desirable to activate EGR. The performance modifications done to the LS1 to make it the LS6 used in C5 ZO6 Corvettes actually made the engine no longer require EGR to pass emissions. I'm amused by this. We've come full circle in a lot of ways in the emissions/performance arena.
quote
Originally posted by Lee Phillips: The idea that it can in any way improve fuel economy is specious at best. There is NOT ENOUGH of this anal feedback to make a difference.
Yes, there is. The exact amount of difference is small and very dependent on driving habits. My typical 80 mph highway speed won't show me much mpg gains at all from EGR operation, but a 55 mph speed can show significant gains.
Why do you think that GM went to roller cams? The real reason was emissions. The roller cam was worth 0.5 mpg on a 350 through reduced valvetrain friction. OEM's DEFINITELY worry about fractional mpg in their cars.
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03:02 PM
May 16th, 2009
White 84 SE Member
Posts: 812 From: Chicago, Illinois USA Registered: Nov 2008
yes - but again - EGR is closed during WOT. the only possible power loss is due to turbulance created at the exhaust & intake ports of the EGR.
I think the turbulance can be reduced while keeping the EGR functional. One can reduce the size of the Y passage where it meets the throttle passage......via some fancy aluminum carving and implants etc..
------------------ 84 2.5L Holley TBI Manual Trans White
[This message has been edited by White 84 SE (edited 05-16-2009).]
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09:47 AM
PFF
System Bot
Pyrthian Member
Posts: 29569 From: Detroit, MI Registered: Jul 2002
Originally posted by White 84 SE: I think the turbulance can be reduced while keeping the EGR functional. One can reduce the size of the Y passage where it meets the throttle passage......via some fancy aluminum carving and implants etc..
yes - many options. when I blocked mine tho, I filled the hole with epoxy. made a smooth path from the throttle body to the plenum. If you look down the neck of the plenum, you can see the problem.
but, anyways - I did the 7730 late year, and am planning on re-adding the EGR system. I have a brand new EGR solenoid pack, and a buddy with a welder. Gonna mount the solenoid pack onto my gutted stock intake, and add a bung to exhaust y-pipe. I get pretty consistant milage right now, and this will give me a good idea how much fuel the EGR actually saves. but - this wont be until next summer, being this is going to be a winter job.....
