EGR block-off: NO!
 

Wanted to share some info with everyone and get some feedback/plausibility on this because a lot of people have suggested removal of or blocking-off of their EGR valves. It turns out doing so can make your engine burn through O2 sensors and Catalytic converters much faster. The EGR gets a bad rap because it occasionally Recirculates Exhaust Gases back into the intake manifold to be reburned. A lot of people who throw on intake upgrades (cones, tubes, etc) neglect the EGR because who wants anything but clean cool air going into the engine? This reburning is not only for the minimal benefit to the environment. Once the engine has reached operating temperature, the ECU tells the EGR solenoid to open, allowing some exhaust from your exhaust manifold to mix with the air going into each cylinder. By increasing the mass of the air, the combustion temperature is lowered. The O2 sensor reads this within an area of tolerance, ECU recieves the measurement and compensates fuel/air mix. The computer adjusts whether the air/fuel ratio is lean or rich, and without the EGR the air is too lean, leading to extremely hot exhaust gases.

Hi,i got the egr valve in bad shape,¿ how i know its working fine? i read i haynes repair manual try to move with the hand,i did this but it feels a little hard and rough, ¿it got to move freely? thanks

What is your source? I was looking into doing an EGR delete so any additional info would help.

With your engine running put a source of vacuum to it and see if the engine stumbles,if it does it is fine,if not replace.

For the EGR or Idle Air Control Valve? EGR should not effect idle speed. If you open the brake booster vacuum source and she dies, I would check the IAC valve.

EGR info,

http://en.wikipedia.org/wiki/Exhaust_gas_recirculation

The correct way to check the egr valve is to do so while engine running and you apply vacuum to the egr valve itself,it should cause the engine to stumble,which means it is good. The egr is only used during cruise mainly,it is used to reduce nox and help burn unburnt hcs.

On a carburetted engine, i would agree with you.

With feedback fuel injection, however, there are better ways to control engine temperature - that wouldn't crap up the intake with carbon (nevermind the "clean cool air" aspect - coating the assorted sensors in the intake with carbon, depositing carbon on all available surfaces, and depositing carbon on the fuel injector nozzles is a purely stupid idea.)

The principal reason for the EGR to remain is an extra control on combustion chamber temperatures (which could be done a couple of ways without the thing - depending on which system you'd like to use.)

How can combustion temperatures be reduced?

1) Run rich. Running at AFR in excess of 14.7:1 (in favour of fuel, by mass) increases the heat capacity of the engine system for a given temperature - by "absorbing" heat in the process of evapourating the excess fuel. This, however, carries the complication of increasing HC and CO (incompleat combustion due to excess fuel) and creating the possibility for accelerated cylinder wear (due to cylinder washdown - from gasoline that is not evapourated. It will wash the oil off of the cylinder walls, removing the lubrication it provides.)

2) Water or water/alcohol fogging of the intake. This actually carries a couple of advantages:
- No cylinder washdown - oil is not water-soluble.
- Increased heat capacity of the system, for the reason given above.
- No potential for deposits if distilled or RO-filtered water is used.
- Increased combustion efficiency, if a water/EtOH or water/MeOH mix is used (right around 1:1 is common. One may also use denatured alcohol.)
- Steam cleaning of internal combustion chamber surfaces, reducing/eliminating carbon buildup (if you've ever torn down an engine after having had a head gasket leak into a cylinder, you've seen what I'm talking about. Think of that sort of thing happening without the green deposits from antifreeze.)
- Little to no increase in HC and CO emissions, while NOx emissions can be reduced significantly.

Given a choice all around, I'd take the water/XxOH fogging - the technology has been around about thirty years longer and it works better - more advantages, fewer disadvantages (EGR was devised in the mid- to late-1970s. Water/MeOH was devised ca. 1941 to improve the operational ceiling of piston-driven aircraft in WWII in an effort to secure air superiority.)

Not to question your knowledge 5-90 but isnt methanol bad for the cat? Ive read in the owners manual not to use anything containing methanol because it will cause premature cat damage. I have also read this in a few other places. I have read of the intake foggers, and actually find it to be a good idea. They have ones that are computer controlled and only release water/meth at WOT or heavy load, they use them alot for sports cars, but Im sure it could be used in a Jeep too....

MeOH/EtOH may be bad for the cat in those forms - but by the time they get there, they'll be H2O and CO2 like the gasoline will. Bear in mind the structure of an alcohol - it's a hydrocarbon chain with an -OH group tacked on the end.

Consider, say, octane. Chemical formula C8H18. In its pure form, when combusted totally, it yields naught by H2O and CO2 (the "ash" from combustion.)

Let's back down a bit - methane. CH4 (essentially, a carbon atom surrounded by four hydrogen atoms.) In order to make it methyl alcohol (MeOH,) you replace one of the hydrogen atoms with an -OH group - yielding CH3(OH).

You now have, essentially, an "oxygenated hydrocarbon." This makes it actually burn more readily, into CO2 and H2O.

The water itself can yield molecular hydrogen and oxygen - when it's flashed at the 1600*F^ temperature typically found in the combustion chamber when fired, it will literally "break" into hydrogen and oxygen. The hydrogen works like a "primer" for the hydrocarbon fuel, and the oxygen will recombine with the hydrogen - encouraging the combustion reaction.

Win freakin' win! The problem with EGR is not that is "recirculates the exhaust gas to be burned again," but that it "recirculates the exhaust gas" to begin with - bringing along all of the carbon and other crap (the reactions generally described above presuppose a pure hydrocarbon fuel. We haven't had that since it was still called "motor spirit..." EPA and CalEPA mandates have required that the fuels be crapped up with more additives than strictly necessary, most of which pollute the combustion reaction and make things worse instead of better. But, they're usually done in response to pressure groups and lobbyists.)

Why is water fogging not used? Most people aren't aware of the fact that the oil needs to be changed regularly in their engine, and therefore aren't quick enough to keep the water/MeOH reservoir topped off. The engine will work fine without it - but the emissions will increase.

A shift toward an increase in user maintenance would be needed to make such a system generally useful. The problem here in CA is simple - CalEPA and CARB won't approve a "non-OEM" change, even if you can prove that it would work better than the OEM system to begin with (and water/MeOH or water/EtOH fogging would work much better than EGR all around... Addition of EGR spikes both HC and CO - and, with our relatively low-compression sixes, it isn't really necessary anyhow. A high-compression engine would get more potential use out of an EGR setup - but we don't have them.)

Good point on the h2o and co2.. I know your thoughts on the EGR system and agree, its a stupid idea. I can imagine how much carbon and crap are in the intake of my 89 after 204,00 miles and 20 years :wacko:

And yes, I did read the whole post, I just edited out the parts I wanted to talk about..

My father was my source for the information about the EGR, he's pretty familiar with IC engines and after exhausting (no pun intended) every other solution I went to him and he explained it as an important part of the mass of the air during combustion. 5-90, I really appreciate your input and I've learned a lot from your posts... I just finished my BS in physics and this stuff is really interesting to me. I would think the drawback to water injection would be the dew point of exhaust gases, leading to a quickly rusted muffler, but it does beat the deposits going back into the motor from the EGR. Correct me if I'm wrong, but I remember hearing somewhere it was the Japanese Ki-84 Hayate (the "Frank") that we captured and modified the octane in, which eventually led to use of water-methanol injection our own P-47 Thunderbolt. Changed the HP from 2000 to 3800, pretty cool.

I won't deny that the concept behind EGR is useful, it's the implementation that blows.

I ran water/MeOH in my Bug for about 75Kmiles (before I sold it, after I'd had it restored) without any trouble - and with the more modern exhaust being typically aluminised CRES, it really shouldn't be a problem - as long as you let it warm up well while you're driving (just like engine oil, short point-to-point trips are the killer. If you've got a bunch of small errands, do the farthest one first to warm up all systems, then come back in as you go. This applies generally, as engine oil tends to collect condensate if it's not allowed to warm up fully, and that leads to sludge. "Hot starts" aren't a problem.)

I was working on several degrees when I got clobbered a few years ago - one of them would have be a BS/MET. I took every chem and phyzzies course I could on the way up - because I have a keen interest in just how and why things work. Still do - just have memory problems now (dammit.)

If you really want to know more about the IC engine, I suggest getting both volumes of The Internal Combustion Engine in Theory and Practise, by Charles Fayette Taylor (MIT Press.) Design and Simulation of the Four-Stroke Engine, by Gordon P. Blair (Queen's University, Belfast, as I recall) is also an excellent source for much of this, and a couple of decades more recent (although the essential principles of the ICE haven't changed since inception - whether Otto, Diesel, or Wankel cycle. The Miller and Crower cycles are much newer.)

Trivia - did you know that the Diesel cycle was originally intended to use coal gas as a fuel, and then it was adapted for peanut oil? This is why Diesels have no trouble being adapted to WVO (Waste Vegtable Oil) or "greasel" conversions (the two are slightly different - WVO operation still requires proper Diesel fuel for cold starts, while "greasel" is treated WVO which more fully simulates Diesel fuel.)

Interestingly, the three basic engine cycles were all developed by Germans - Nikolaus Otto, Rudolf Diesel, and Felix Wankel.

OK OK forget all the Mumbo Jumbo the easyist way to check it is 1 start engine let it get to operating temp. 2- apply a vacuume to EGR llike from a mighty vac. 3- if engine stumbles it is good, no change in idle it is bad. is that correct?

Correct. Or the passages in the head are plugged.

You do not need to let it warmup,just supply vacuum the valve either with a hand held vacuum pump,or even a vacuum line from the engine. egr is not suppose to be open at idle that is why it stumbles,it will actually die if you do not remove the vacuum.