redmuck

heres a question, since redmuck was sucking gas bigtime and my fuel pump leaks at the seal,i decided to look under there to see if its leaking worse and i found a snapped clamp on the fuel pump hose, thats fixed,and so decided to look at my egr system. whoa and behold, i cant find any egr anything on the motor. no valve,no solenoid,no transducer. did they not put them on the 91's? seems strange.

5-90

Correct. The 6-242 had the EGR valve deleted starting with the 1991 Model Year, with the addition of ChryCo OBD-I electronics.

Capital idea - I never liked the idea of the EGR. "Yeah - let's reduce one emission by pushing the other two through the roof, and then crap the whole intake side of the engine with carbon." An irretrievably stupid idea, couple with being put onto engines where it is of dubious utility (NOx isn't much of a problem with low compression ratios...)

redmuck

ahhh ok, i was just in the jy and saw some of the older cherokees- 91 to 95 i believe and they didnt have any egr's either. so i figured it was a factory setup. i have to check a few sensors on redmuck to get him to run a little better. thanx

mrfajita

The High Outputs do not have EGR, as 5-90 said. Good thing too, who would think that is a good idea?

5-90

I know the theory behind using the EGR setup, and I do agree with it.

However, it is the implementation that I find stupid - putting in an additional failure-prone component and gasket in (exhaust can chew through gaskets, and vacuum diaphragms tend to fail when located near excess heat,) plus running exhaust gas through the intake and crapping everything up with carbon, is an irretrievably stupid idea.

Full Stop.

The operating theory is to reduce combustion chamber temperatures in an effort to reduce production of oxides of nitrogen (NOx) emissions - which is a good thing. However, the "solution" presented by the EGR system does so at the expense of significant increases in hydrocarbon (HC) and carbon monoxide (CO) emissions - which then have to be processed as well (typically by a catalytic converter.)

Strip out the EGR system, install a water/MeOH fogger, and then the catalytic converter can be eliminated (and the engine can run even cleaner, if kept in proper tune!) And you've eliminated both a failure-prone component and the elimination of the catalyst bed - which can become clogged with carbon - will also help.

Yes, I do think that many emissions devices can be removed. However, I don't think they should be removed out of hand - there are better solutions to the problems that are more effective, and enjoy greater reliability. Get out of my way and let me work, and I could strip off most of the emissions devices on a modern engine and make it run cleaner as a result - but the people who make these rules suffer from terminal HICS - Head-In-Cement Syndrome...

Desarial

Wait wait wait, I've got an 89 renix engine running the egr, ive wanted to eliminate it but I'm getting mixed messages from forum members. i know the h.o. systems are generally better with emissions than the renix engines, but would i still see some decent change if I deleted it? I've asked this once before and i was told no, but the issue with my engine is the CO levels are too high, I failed inspection because of it. I've got a doner 96 that i wanna swap the intake out of into my 89. but the egr is the biggest issue i'm having, I dont even know if mine works right anymore. my engine stumbles and sometimes stalls at low throttle levels, like, barely touching the pedal, low. I've explored ideas from a crapped up fuel filter to the oversized tires lockin up my drivtrain, but so far nothing has panned out. I'm now thinking that the egr is openning up too soon and gassin my engine. I just want the function of the egr made clear.

5-90 I think you commented on my thread that was similar to this, that water fogger youre talkin about, is that basicly a hookah for your engine? bringing in warm air from wherever passin it through a distilled water resevoir and suckin the vapor from said transaction into the intake using a vacuum system? if so, wouldnt it be easy as crap to replace the egr with one?

Doc Brnard

LOL, I spent an hour looking for the EGR valve on my 91 yesterday. Did some searches on the 'net, only found gaskets for a 91 EGR. Never found the damn thing. Should of went here first.

5-90

The "function" of the EGR is to allow a small, metred about of exhaust gas into the intake stream to "damp the fire" as it were. This is meant to reduce the production of oxides of nitrogen (as I explained earlier,) but by damping the fire you get incompleat combustion - which is why HC and CO both rise sharply. And why exhaust post-processing suddenly becomes necessary (the HC and CO need to be handled - processed into H2O and CO2.)

The catalytic converter is a "three-way" device on most later vehicles - the first stage "reduces" any NOx in the exhaust system into N2 and O2, the second stage "oxidises" the HC and CO into H2O and CO2 (it does three different things - thus, "three-way.")

However, the EGR is suddenly of specious utility on low-compression engines (below 9.5:1 or so static, probably 8.0:1 dynamic.) Per Boyle's Law, temperature of a gas increases as the gas is compressed, and in direct proportion to the compression of the gas (the more a gas is compressed, the greater the delta-T.)

This increases the base temperature of the intake charge in the cylinder, and that delta-T adds to the delta-T that results from combustion - thus elevating the temperature beyond a threshhold value that is necessary for the dissociation of the N2 in the atmosphere, which allows it to be oxidised into various oxides of nitrogen.

The idea behind the water/MeOH fogger goes back a way - it was first devised as a means to improve the operational ceiling and high-altitude performance of piston=-driven aircraft in the 1930s and 1940s. What we are interested in, from an automotive point of view, is this: The addition of a fine mist of water and methanol in the intake stream provides a means for "using up" some of the heat in the system - by vapourising the water and methanol into vapour. It also helps to cool the combustion chamber, and even "steam-cleans" the combustion chamber surfaces of carbon - which helps to eliminate hot-spots and helps to prevent detonation due to "hot-spotting" of the carbon deposits.

This is why I think using a water/MeOH fogger would be vastly superior to the current EGR setup - but the EGR was probably used simply because it requires no user intervention on a regular basis (the water/MeOH tank would need filling.) As far as tuning, the work that goes into determining the size of the orifice for the EGR valve would duplicate the effort that would go into determining the amount of water/MeOH to fog into the intake, so that's not any extraordinary effort. Use a large enough reservoir for a tank and a half of fuel, remember to top it off whenever you fuel up, and that takes care of that.

Adding a water/MeOH fogger, coupled with effective engine tuning (pyrometer tuning or effective emissions analysis) would allow the elimination of the EGR valve, the catalytic converter, and probably a number of other emissions control devices - which simplification of the system I would find vastly preferable to what we have now (simpler to work on, easier to keep clean, more reliable, fewer parts; what's not to like?)

fishtaconc

X2^^ http://www.turbomirage.com/water.html very good site.

Desarial

Thanks for the info 5-90. I'll prolly run atleast 2 shots through inspection, one with the egr one without. unfortunately i gave away important parts of my 96 engine otherwise i'd use it to experiment with the water/methanol fogger. I trust your judgement but if I dont get everything running in the right quantities I might put my dd at risk. the only thing I'm unsure about is the air intake for the fogger, in order to vaporize the water/methanol you would need to have a source of hot air, like, passing through embers hot. I'm not sure you can reach those tempetures by simply pulling in air from around the exaust manifold like most hot air intakes. I'm def going to try and do this fogger setup though, if nothing else it'll be fun to work with.

K-SKI

I bought a 90 renix about 4 months ago and has never had the egr lines hooked up and it runs fine

Sent from my ANDROID using Cherokee Forum

5-90

Oh, it will run fine without the EGR! The EGR doesn't have anything to do with engine operation, just with theoretical reduction of emissions.

RENIX actually runs cleaner overall without the wretched thing anyhow - my 87 had a failed EGR when I bought it, HC and CO were nearly nil and NOx was agreeably low. I had to replace the damned thing anyhow ($200, just for the part!) and the net effect was an increase in HC and CO (no real change in NOx.)

As far as water/MeOH tuning, it's easy enough - you just start with no fog, then slowly ramp it up until you note a power decrease at cruise RPM. In the absence of pryometer tuning or exhaust gas analysis, that's the easy way to go - a properly-constructed fogger setup should not have the potential to cause hydrolocking. You're using a fine spray through a small tube, so you set it up and you can't really deliver enough liquid to "go solid" with the cylinder charge.

Just set it up so that the mist is as fine as possible (relatively high pressure and small orifices if you force-feed it,) and put the fogger nozzles centrally in the intake plenum or in a sammich plate below the throttle body.

K-SKI

So I want to know can I run a 91 and up DJ headset in a renix motor to just by pass the egr

Sent from my ANDROID using Cherokee Forum

Desarial

dj headset?if you mean the intake, sure. as far as iknowthe intakes are all compatible. there'sa guy on her that did a writup about a renix system with an h.o. engine and a 99+ intake. his writeup shouldhavesome details on the compatibilty. they also market on advance autoparts an egr delte plate, it just bolts on where the egr is and you take off the egr components and hoses, cap the hoses with vacuum line caps and your good to go. also, simply removing the egr vacuum lines from the manifold is enough to delete it, but it aint as pretty and it wastes space. I was going to swap out my 96 intake and air cleaner box into my 89. it has less vacuum connections and no egr port. should be bolt on.

K-SKI

Thought of that but my prob is after market headers all I find is for 91 up and, on eBay they have one that fit all years and it doesn't have the egr valve I just want to know are all years compatible will they just bolt in with nothing changed

Sent from my ANDROID using Cherokee Forum