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Old 11-12-2002, 04:23 PM   #1
Jon [in CT]
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Default Anyone Sell an EGR Kit for the WRX?

If not, maybe someone should. It appears, according to the papers listed below, that adding EGR (Exhaust Gas Recirculation) to the intake behaves very much like adding water injection, but there's never a chance of running out of exhaust gas. It reduces knock, allowing you to run an A/F mixture with less enrichment and more boost. And the first paper, at the end, hints that the EGR may not even need to be cooled very much. You'd need some way to advance your ignition timing quite a bit (the diluted mixture burns a lot slower than an enriched mixture), but that's not a big problem for many people.

http://www.md.kth.se/~borje/Artiklar/SAE%20982476.pdf
http://www.md.kth.se/~borje/Artiklar...99-01-3505.pdf
http://www.md.kth.se/~borje/Knackpro...r%20O2P-86.doc
http://www.md.kth.se/~borje/Knackpro...e%20OP2-87.doc
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Old 11-12-2002, 04:44 PM   #2
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I could be mistaken but I believe Bell's book on advanced engine management said that EGR devices are more apropriate as emissions devices since it allows a lean burn without misfiring during idle and cruise.

-Michael
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Old 11-12-2002, 04:56 PM   #3
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I'm not familiar with the book you're talking about, but maybe Mr. Bell was unaware of this research at the time he said that about EGR.
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Old 11-12-2002, 05:41 PM   #4
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Maximum Boost by Corkey Bell. It has some good info about the basics, but a lot of it is old. I think most of the factory offered EGR systems ( i.e. GM and Ford) switch off EGR under high load conditions. They mainly use it under light load/cruise for better emissions/fuel economy since they can run outrageous amounts of spark advance with EGR on. I had the opportunity to hook up my Snap-on Scanner to my folk's '96 Chevy Blazer and play some. The scanner has a diagnostic section where you can adjust/switch certain computer controlled devices (in this case the EGR valve). It allowed variation in 10% increments. At an idle anything more than 20 -30 % EGR would flat kill the engine. I managed to get up to 80 % EGR but to do that required an RPM of about 2500, rough and sputtering. All tested were conducted in park with the engine fully warmed. I don't have any way of switching it on and datalogging at the same time, would be nice to watch for knock/ign retard under 50-60% EGR with the engine under a load. Dunno what effect it would have on a charged engine such as ours. I might need more ed-u-ma-cation, but I don't think of it as a benefit at this time. -Chuck
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Old 11-12-2002, 06:12 PM   #5
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The kind of "EGR-injection" discussed in those papers (i.e. used as a knock suppressant) is really only useful for a turbo-/supercharged engine, where you can easily overcome the loss of volumetric efficiency caused by the presence of EGR (more-or-less inert) in the A/F mixture by cranking up the boost. If the idea of more power from less fuel is appealing, then read a couple of those papers.
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Old 11-12-2002, 07:40 PM   #6
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My only experience with turbo cars that use an EGR system from the factory is with the Toyota Supra, and their only use was for emissions purposes. Most people who mod those cars actually end up welding the port shut or using a metal plate to block it off.
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Old 11-12-2002, 07:47 PM   #7
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There is a downside to having EGR on an engine, the nasty carbon deposits you get in the intake. My last car had it and the throttle body required frequent cleaning to get the crap off, and the intake manifold was full of it too. I can only imagine what the valves looked like.
I am very happy that the WRX does not have EGR.
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Old 11-12-2002, 07:52 PM   #8
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Quote:
Originally posted by mulder
There is a downside to having EGR on an engine, the nasty carbon deposits you get in the intake. My last car had it and the throttle body required frequent cleaning to get the crap off, and the intake manifold was full of it too. I can only imagine what the valves looked like.
I am very happy that the WRX does not have EGR.
Yep. If left uncleaned for a while, the carbon deposits become rock hard, cause major restrictions and actually become detrimental to the car's emissions. Go figure!

One of my cars did not pass state smog inspection because of this. After cleaning out the EGR valve and some related parts, the trees in my area were happy again.
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Old 11-12-2002, 08:11 PM   #9
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I'll have to wait till tomorrow to read the links (computer at home doesn't have Word or Adobe to be able to read 'em with. But yes the thought has crossed my mind about making more power with less fuel. I was working on a full time water injection system to be able to run my race car at higher static compression ratios and leaner mixtures. Race gas is expensive around these parts. Of course it was one of those back of the mind projects that didn't get much attention when other projects were more pressing. And I remember reading something about EGR being used as an anti-detonant the same way as water. Need to figure out a way to condense the bad nasty gooey stuff that acompianies the gas and only send the cleaned gas back to the manifold. Some people would say we need better combustion chamber shapes to create a more homogenous (read: less likely to detonate) mixture. Or take the stratified charge side of the argument where there's different layers of mixtures that burn at different rates, thus reducing detonation. There's been a bunch of different things/processes tried to reduce the enemy detination. Personally, I think a lot more research should be done in this area now that advanced engine management is becoming more commonplace/understood these days. More tomorrow maybe.
-Chuck
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Old 11-12-2002, 08:25 PM   #10
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Default What about water injection

What if you used water injection in conjuction with the EGR system. But instead of using the water as an anti detonant use it occasionally for the sole pupose of removing the carbon deposits left by the EGR system.
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Old 11-12-2002, 09:03 PM   #11
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It would need to be a seriuos cfm pumping WRX to make an EGR setup a performance mod, and a vastly redesigned intake system as well....

Mulder has got it...9 times out of 10 used as emissions devices on late model cars..all the turbo cars I ahve ever seriously modded had one of some sorts, and on all, we eventually got the the point where blocking them off made alot of sense, and got rid of a host of avaccum lines that are otherwise prone to leaks, etc.

Adam
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Old 11-12-2002, 09:30 PM   #12
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EGR isn't something that can easily be added to an engine and management system that wasn't designed to incorporate it. Although it does reduce detonation it is hardly a desirable means to accomplish this. Its primary function is to reduce NOx emissions, which it does by introducing a controlled amount of non-combustible exhaust gas into the engine and thus lowering combustion temps. The reduced tendency to knock is a byproduct of the lower temps.
It's basically an evil thing to put on an engine, but sometimes a necessary one for mfrs. to obtain emission compliance.
Anyone looking for means to control detonation would be better off looking elsewhere, i.e. water/alcohol injection which can actually help keep the internals cleaner while aiding performance. You do need to keep the bottle filled but there is always going to be some type of tradeoff.
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Old 11-12-2002, 10:45 PM   #13
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I don't think you guys get it. I believe that until now, EGR has been used only as an emissions control measure and for lean burn engines. The reason previous EGR systems had all those hoses and solenoids was to TURN THEM OFF at high load. The car manufacturer engineers programming those stock ECUs had no idea that EGR was useful as a knock suppressant at high loads.

IF you'd read the first two papers, you'd have seen that the authors believe the first report in a paper that EGR suppresses knock at high loads was by C. Brüstle and N. Hemmerlein in a paper titled “Exhaust gas turbocharged SI engines and thair ability of meeting future demands” C484/039/94 IMechE 1994. That is NOT very long ago.

As far as complicated controls and elaborate ECU adjustments, I don't see the need, yet. Just start with what Grandin and Ångström did. Pull the exhaust gas from somewhere upstream of the turbo and feed it into the intake somewhere downstream from the trubo and upstream from the bypass valve. I suspect the pressure ratio between these two points is relatively constant except under vacumm, where the bypass valve takes care of things. All you need to add is a bleeder valve to control the EGR's proportion. Of course, you'd have to adjust the ECU's ignition timing advance table (more) and fuel table (less).
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Old 11-12-2002, 11:26 PM   #14
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EGR actually kills power because it is reburning the leftover gas in the exhaust fumes. Those fumes don't have more oxygen content, it has less. And besides, exhaust gas are hot!
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Old 11-12-2002, 11:41 PM   #15
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The exhaust gas dilution approach seems to be physical via introduction of a cold "inert" gas. Chemical approaches were not covered in the two papers I read. The sought for apparatus for a turbo application could have a filter to remove solid products of the combustion process prior to injection. It could be done. I would rather have a "magic bullet" hydrocarbon with the specific activity of TEL in the fuel. That could be impossible?

Going backward (time reversing) from combustion to compression, we have a mist of fuel undergoing individual vaporizations leaving, for an instant, individual nuclei of ultra-high molecular weight random coil chains undergoing unzipping into tens of thousands of monomers per molecule as covalent bonds break as they streak about colliding with hydrocarbon species. Now we have a complex kinetic mixture waiting to burn. Then the spark occurs. Then the lag time passes. Then the flame begins.

Isobutylene is plentiful and is presently used in the synthesis of MTBE. At cryogenic temperatures it polymerizes explosively to ultra-high molecular weight polyisobutylene. "Experts" can be thorougly flumoxed by the strange behavior of this low-temperature (-170C) initiated, exothermic reaction. This is a cationic polymerization.

As readily as it forms, it can be thermally decomposed to isobutylene (isobutene). Polyisobutylene doesn't fly apart all at once, although it came together basically all at once. It leaves by reversing the polymerization sequence which looks like an end of train box car uncoupling operation. As it does this it takes in thermal energy (endothermic), just as it released energy when it formed. Of course the energy of combustion of isobutylene is much greater than the polymer bond energy.

Tests should tell me where to look next.
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Old 11-13-2002, 12:57 AM   #16
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i thought all the new egr systems
were cooled egr
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Old 11-13-2002, 02:13 AM   #17
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z&cobb you are one smart MF. That little composition is way over my head and I minored in chem . We do have some really smart people on i-club
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Old 11-13-2002, 09:00 AM   #18
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Why couldn't you just use restricted exhaust valve timing to, in essence, "not let so much of that inert exhaust gas out of the chamber" and do what jon [in CT] suggested " just crank up the boost" to regain what's lost by scavenging. No messy deposits in the intake, no vacuum hose monster under the hood. But maybe z&cobb is right, they need new fuel, something that breaks down in the chamber during combustion for cooling purposes, maybe some aqueous form of gasoline, or an emulsion? Of course we could also do some more homework in fluid dynamics to figure out why in the he// we're not getting a completely homogenous mixture in the combustion chamber in the first place, in which case we wouldn't have rich/lean spots to "auto ignite". -Chuck
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