EGR ???

[jetjock]

From a technical standpoint I somewhat agree with him. From a practical standpoint I maintain it's risky for people with limited knowledge and experience to defeat EGR because of this PCM's aggressive timing strategy coupled with the points made above. Regardless, high combustion temps thin det margins and EGR lowers temps. Remove it and the margin reverts to smaller even if the PCM wasn't programmed to compensate for it being there. It's tough to find the word EGR mentioned without the word detonation being involved. Nor do I feel one should consider the factory documentation as meaningless fluff.

SAE Tech Paper 2007-01-3978 describes cooling EGR gases in SI turbocharged engines for obtaining detonation suppression to the point where a stoichio mixture can be used over the entire operating range, including WOT. That's not the same as making best power of course but if it doesn't prove EGR suppresses det I dunno what does. Imho anyone interested in really understanding automotive technology should join the SAE as it gives one access to an enormous wealth of accurate information developed through extensive research by people who have the resources and skills to get it right.

After all it's not as if this stuff is new. "Infernal" combustion has been around over 100 years. As for EGR research, much was done in the 40s for use in military aircraft, a sector from which many automotive developments evolved. There's also SAE 2003-01-1068 which, although about diesels, plainly states: "Exhaust Gas Recirculation (EGR) has long been of interest to engine designers, researchers, and regulators. EGR was originally considered as a method to suppress knock in spark ignition engines."

 

[Adjuster]

OK, this is now one of the best posts I've read in awhile on EGR, and why/how it works with the TCCS... (Almost wish I'd kept mine in working order...)

Few questions.
Is there a JDM TCCS ECU that will plug and play with the stock USDM 88 turbo harness? (Give the Maft Pro a better starting point EGR wise..)

Second, would the engine running in closed loop at less than WOT conditions, see the lean condition from the reduced fuel injection signal being sent by my TCCS that still thinks the EGR is working like normal... and add fuel to keep it closer to 14.7:1, assuming the EGR and less fuel would result in the right ratio anyway under these conditions?

And finally, with the Maft Pro, this may be something I can tune out, or around right?

Thanks for the great write up on the EGR on the 7MGTE, and how our TCCS works with it to reduce detonation.

On this same note, I noticed that my cruise speed EGT was near 1450f when before with the EGR on the engine, it would run closer to 1250-1300f while just loafing along at under 4000rpm on the highway... Now it makes sense (And sounds like I answered my own questions about adding fuel at less than WOT conditions.. it's running leaner, or has more timing.. but the wideband sits at 14.7:1 so I was not worried about it, and just figured it was the coatings retaining more heat in the exhaust gas flow v/s having it absorbed by the exhaust port, manifold etc.)

 

[7MGTEsup]

This is very intrseting stuff, I had no idea that the TCCS was so finely tuned with EGR. I may have to dig out my EGR bits and screw them back onto the car. I tend to spend alot of my time in that transient reigon between 2500 and 4000 rpm on part throttle and in boost. Could also do with the 5% fuel consumption increase to.

 

[Frank Rizzo]

I noticed that my cruise speed EGT was near 1450f when before with the EGR on the engine, it would run closer to 1250-1300f while just loafing along at under 4000rpm on the highway

This is really the bottom line. I don't care who you are or what you know, taking the EGR off will result in higher exhaust temps which is not good at all.

Jet, you said: There's also SAE 2003-01-1068 which, although about diesels, plainly states: "Exhaust Gas Recirculation (EGR) has long been of interest to engine designers, researchers, and regulators. EGR was originally considered as a method to suppress knock in spark ignition engines."

I've never seen EGR on a diesel before. What do you mean "although about diesels"?

 

[supraguru05]

I've never seen EGR on a diesel before. What do you mean "although about diesels"?

any 2007 product or newer has egr for the usa and europe
and i belive our 2004 products did as well

yea im glad this thread is going so far in depth so ill make some footnotes for people


number one
the usa ecm advances timing and decreases injector duration when the egr system is flowing egr (or supposed to be).

2.
if you remove the egr this timing advance and fuel decrease will occur without the exhaust gas there to protect you from knock

3.
egr is piviotol in reducing nox emmissions

4.
jet jock can fill this in hopefully pretty specifically
egr is flowing in these conditions
not at idle
not at WOT
never above 4500 rpm


so in summary for people who are just wondeirng what happens if they removed egr off their engine without any other changes in the cruising regime you will be more prone to knock because you will have advanced timing and less fuel (this does not guarentee you will knock however)

you will also expel more NOx and have significantly higher exaust gas temperatures which in itself can result in glowing a exhaust valve resulting in preignition (correct use of the word just for you jet jock )

and some general information something thats interesting between disels and SI engines. we are actually able to utilize egr alot more then a spark engine. at the lower rpms a spark engine has a very low threshold for egr. it will put the flame out very easily probably why we dont flow egr at idle. our disels however flow egr pretty much all the time



and for reference i am running a na block and pistons that i rebuilt with gte electronics and a ct26. my egr is removed and i have absolutely no fear of knock in the transient regime. of course the car is not my daily driver so it really only sees the track but still lol.

and to answer the question of ecms. i am under the impression that the turbo jdm ecus will connect to the correct year and model us harnesses.

o and dont forget that some cars have egr temp sensors (cali turbo cars i think)

 

[jdub]

On this same note, I noticed that my cruise speed EGT was near 1450f when before with the EGR on the engine, it would run closer to 1250-1300f while just loafing along at under 4000rpm on the highway...

I had the exact same experience with EGT when I had it off. Had to install the EGR to pass emissions and EGT dropped in the mid-range rpms.

Is there a JDM TCCS ECU that will plug and play with the stock USDM 88 turbo harness? (Give the Maft Pro a better starting point EGR wise..)

A JDM TCCS is plug-n-play with the respective year harness and tranny, just get the correct year (in your case an '88). I played around with one trying to pass emissions a while back.

 

[7MGTEsup]

I've never seen EGR on a diesel before. What do you mean "although about diesels"?

EGR has been fitted to diesel cars for years in europe, my girlfriends Rover 620 SDi has EGR and that was made in 1996.

 

[Frank Rizzo]

My 95 cummins turbo diesel has no EGR.

To find a US, fuel injected, gasoline powered engine that does not use EGR from the factory is rare.

I've only seen 1 gas engine, sold in the US, that did not have EGR from the factory. 89-95 Ford Taurus SHO 3.0L 24 valve V6. 220hp NA. How about some more examples, if you know of any?

 

[thelonerider]

I got a NOOB question as I am no where near as informed as several of you here... You keep mentioning reduced injector duration as well as advanced timing. Other that higher octane, would raising the fuel presure help in compensating for this ECU / EGR adjustment? I guess it would mean that your engine would be running a little rich in the idle and above 4500 / WOT ranges, but would the increase of fuel help to overcome the removed EGR issue (knock risk) in the cruise mode? How much increased pressure would be required to compensate for this? Am I barking up the wrong fire hydrant here?
Other than a standalone ECU, what other electronic add-ons can help overcome the ECU/EGR removal issue?
Thanks, you guys are my techno guru heros

 

[jetjock]

You'd have to run the engine in open loop, not something you want during cruise. Otherwise the ECU will do whatever it can to bring the mixture back into fuel control. Much of this discussion is somewhat theoretical in nature with multiple variables involved so I don't want people freaking out over this. There's no need to. Keep the engine in tune, run a bit more octane, and sleep like a baby.

 

[thelonerider]

There's no need to. Keep the engine in tune, run a bit more octane, and sleep like a baby.

Is the 91 to 93 octane range the right mix (as compared to somewhat cheaper regular 87 here in Canada)? Sometimes on a long 6h+ highway cruise I would have put in the 87 to save a few pennies but I guess it's going to be gourmet meals for the 7M-GTE from now on.

 

[7MGTEsup]

My 95 cummins turbo diesel has no EGR.

To find a US, fuel injected, gasoline powered engine that does not use EGR from the factory is rare.

I've only seen 1 gas engine, sold in the US, that did not have EGR from the factory. 89-95 Ford Taurus SHO 3.0L 24 valve V6. 220hp NA. How about some more examples, if you know of any?

All Peugeot,Citroen and Renault HDI engines built from 1999 onwards have EGR.