EGR - to be, or not to be, or et tu, brute

gmctd · **Posted:** Wed Jan 07, 2009 1:27 pm

Agreed on EGT not being a reliably accurate indication of combustion temps, as fully-combusted fuel exhausts as gasseous end-product with no density\mass to retain heat, where thermal content is quickly lost to the metallic surfaces in the exhaust path - however, in black smoke incidence of excessive fuel, combustion temps are lower due to the additional mass of the excess of fuel, the unburned fuel is much denser than normal exhaust gasses, thereby retaining more of the combustion temperature, and EGT's are higher even tho combustion temps were lower - still, EGT's are the best currently-available representative of cylinder conditions that are displayable on the vehicle instrument panel - the thermal-wire alloy in metallic glowplugs not only generate heat, but are affected by external heat, and could be used to directly measure cylinder temps by separating the power-wiring connections, reading the switched individual outputs similar to an EGT guage - that's another project I've occasionally worked on, interest waxing and waning due to ease of installing the commonly-accepted thermocouple-driven EGT guage - I did run two EGT guages, one pre-turbine and one post-turbine, as R&D to post reliable temperature-losses comparison across the turbo under loaded and non-loaded conditions, demonstrating max safe temps for post-turbine probe location - also showed practical demonstration of how rich black smoke effected increased EGT levels at similar loading with no smoke

nursecosmo · **Posted:** Wed Jan 07, 2009 1:33 pm

gmctd wrote:

Agreed on EGT not being a reliably accurate indication of combustion temps, as fully-combusted fuel exhausts as gasseous end-product with no density\mass to retain heat, where thermal content is quickly lost to the metallic surfaces in the exhaust path - however, in black smoke incidence of excessive fuel, combustion temps are lower due to the additional mass of the excess of fuel, the unburned fuel is much denser than normal exhaust gasses, thereby retaining more of the combustion temperature, and EGT's are higher even tho combustion temps were lower - still, EGT's are the best currently-available representative of cylinder conditions that are displayable on the vehicle instrument panel - the thermal-wire alloy in metallic glowplugs not only generate heat, but are affected by external heat, and could be used to directly measure cylinder temps by separating the power-wiring connections, reading the switched individual outputs similar to an EGT guage - that's another project I've occasionally worked on, interest waxing and waning due to ease of installing the commonly-accepted thermocouple-driven EGT guage - I did run two EGT guages, one pre-turbine and one post-turbine, as R&D to post reliable temperature-losses comparison across the turbo under loaded and non-loaded conditions, demonstrating max safe temps for post-turbine probe location - also showed practical demonstration of how rich black smoke effected increased EGT levels at similar loading with no smoke

Absolutely. Youdaman, man

007husky · **Posted:** Wed Jan 07, 2009 2:12 pm

"I did run two EGT guages, one pre-turbine and one post-turbine, as R&D to post reliable temperature-losses comparison across the turbo under loaded and non-loaded conditions, demonstrating max safe temps for post-turbine probe location - also showed practical demonstration of how rich black smoke effected increased EGT levels at similar loading with no smoke"

Do you still have the numbers for this test ?? I would be really intrested in seeing them !

Thanks !

mackruss · **Posted:** Wed Jan 07, 2009 2:48 pm

Quick question, my EGR is blocked and the FCV butterfly removed. Why can i not replace the butterfly for a smoother shutdown, i know the butterfly closes when the EGR wants to suck some exhaust gasses but if the EGR is blocked , what's the purpose of removing the butterfly.

gmctd · **Posted:** Wed Jan 07, 2009 3:04 pm

I may still have those figures somewhere amongst several superceded hard drives, but they would not be accurate for this engine, exhaust, turbo and exhaust system - those tests were run back over the winter of Y2k\ought one on my GMC 3500 crewcab long-bed 4x4 6.5L indirect-injected V8 turboDiesel - that GM forum totally crashed from hackers sometime later, losing all member-posted data - I did prove the generally-accepted figure of ~300* loss across the turbo, post-probe 1" below the down-pipe flange - also proved only couple degrees EGT difference between cylinder banks, increasing in winter climes due to the crossover pipe being exposed to road draft and ice-slush splash - and that's in Houston, well below the 'don't snow much down here' line - that stuff will put a chill on the cockles of yer heart, b'lieve you, me

Foolishly, I guess, I still depend on forum-storage for my posts - I even yet compose and post directly, not using a processor to edit and correct themes prior to hitting submit - you may note my creative processes by observing the multiple edits in some posts - ce la vie, as it were............

gmctd · **Posted:** Wed Jan 07, 2009 7:26 pm

Removing the FCV 'butterfly' plate opens up the intake for better airflow - plus that eliminates eventual FCV failure - yes, you can re-install the plate for smoother shutdown, even if EGR is defeated, as ECM also closes the valve at key OFF for smooth engine shutdown - some here just removed the plate to prevent further problems

ATXKJ · **Posted:** Wed Jan 07, 2009 7:32 pm

mackruss wrote:

Quick question, my EGR is blocked and the FCV butterfly removed. Why can i not replace the butterfly for a smoother shutdown, i know the butterfly closes when the EGR wants to suck some exhaust gasses but if the EGR is blocked , what's the purpose of removing the butterfly.

because the FCV still chokes down the intake - which may be more of a performance killer than the EGR itself.

UFO · **Posted:** Wed Jan 07, 2009 9:32 pm

I would be very cautious about removing the AFC valve. You get a turbo seal failure that causes a diesel runaway condition, you need to shut the air off.

warp2diesel · **Posted:** Wed Jan 07, 2009 9:45 pm

because the FCV still chokes down the intake - which may be more of a performance killer than the EGR itself.[/quote]

Any thing in the way creates turbulence and will restrict flow, more air to the intake, better performance and fuel economy.

What some development engineers are dreaming/working on now is playing around with dynamic valve overlap to have EGR with out the flap or EGR valve. Then it will be in the hands of the underground ECM remappers to make our future rigs run as they should.

As long as they hand out money for Scientists to dream up problems with out pier review, all they will get is more problems that will result in more legislation and more grants handed over resulting in more legislation. Then we pay dearly for our rigs from automotive companies who have to deal with the legislation from lawyers who become politicians and know less about the environment than my unmarried son's unborn grandchildren.

gmctd · **Posted:** Thu Jan 08, 2009 11:24 am

Problem with using consumer-added additives, such as H2O\CH3OH (simple), to correct\improve engine operation is that consumer soon becomes lax in replenishing that additive, not being critical to operating conditions as is fuel, oil, coolant - the daily expense added to daily fuel expense also plays a large part in that laxity - similar to windshield washer fluid, which reservoir also soon becomes neglected - a government-mandated additive is gonna fare no better, unless the vehicle is locked in inoperable state when emissions-additive reservoir runs dry - that's gonna go over real big in new car sales

FYI: regarding use of spell-checkers: people from English language cultures seldom (most, in fact, seem unable to) use spell-checking programs, and they've lived and (ab)used the language all their lives - people from non-English language cultures are likely not to have enuff basic command of the English language to enable use of those programs, nor understand idiom and vernacular that is common amongst the various geographical regions - 'nuther words, on an internationally available and accessed forum, cut'em a little slack, eh...........................

mackruss · **Posted:** Fri Jan 09, 2009 12:20 pm

Well i now get the impression that the EGR is not such an evil monster as i thought it was when joining this forum. If it is only activated for that amount of time then hell i don't know what all the fuss is about.

Sounds like there were some dud EGR's fitted to the 2005 models and sorted out with the later models :roll:

UFO · **Posted:** Fri Jan 09, 2009 12:58 pm

mackruss wrote:

Well i now get the impression that the EGR is not such an evil monster as i thought it was when joining this forum. If it is only activated for that amount of time then hell i don't know what all the fuss is about.

Sounds like there were some dud EGR's fitted to the 2005 models and sorted out with the later models :roll:

EGR is an evil monster in the US. So much EGR is reqired to meet the standards, it harms the engine. This is true with the VWs as well, but it's relatively easy to clean the manifold out. Trust me, the EGR will be deleted on my VW soon as well, without the CEL of course.

gmctd · **Posted:** Fri Jan 09, 2009 2:15 pm

Yep, we got it easy - oughtta hear the wails and curses on the forums where urine is the replacement-required element in the government-mandated emissions device............

UFO · **Posted:** Fri Jan 09, 2009 3:03 pm

gmctd wrote:

Yep, we got it easy - oughtta hear the wails and curses on the forums where urine is the replacement-required element in the government-mandated emissions device............

Hey, where is that device, I wish to make a donation.

nescosmo · **Joined:** Sat Jul 14, 2007 11:17 pm **Posts:** 202

UFO wrote:

I would be very cautious about removing the AFC valve. You get a turbo seal failure that causes a diesel runaway condition, you need to shut the air off.

Well I took a closer look at the AFC and I let my wife turn off the engine and the flapper did not close at shot down ( I have the segr). The flapper close after the engine was off.( It took about 10 to 15 second to shot off.).Maybe there is a problem with my segr or something.

Turbo Tim · **Posted:** Sun Jan 11, 2009 12:57 pm

The fact that the AFC did close shows that the SEGR is working. In anything but Park and Neutral, the valve is electrically disconnected.
Now you state that it closed way after shutdown raises a few questions.
First, was the CRD in Park?
If so, then possibly the AFC valve itself is damaged, as in stripped gears, etc.
Push on the butterfly with the key off, and it should move freely closed BUT spring to the open position.

gmctd · **Posted:** Sun Jan 11, 2009 1:47 pm

The only factual reports of Diesel-engine runaway I have heard and seen results of were from the oil-patch - Diesel-engines have 'run-away' where line-valves were being blown-down or were leaking, where there was enuff airborne methane to feed an engine left running to keep the batteries charged for the computerized field equipment, or while burning the air conditioner for heat-relief - kill the ignition switch, engine no slow down or stoppee - I have read posts of engine-surge from excessive blowby due to engine wear at excessively high mileage, with oem-installed CCV-type system - I've heard only unsubstantiated tales of run-away due to turbo-seal leakage, which doesn't happen because the compressor makes Boost pressure, always higher than atmospheric pressure, even at idle, in H2O" - and, mainly because Diesel engines make no intake vacuum to "suck" oil past the labyrinthine slinger-type seals, as used in Diesel turbochargers - gasser (patooie!) engines, more likely, which turbos have positive-contact seals due to the vacuum-infested nature of that particular breed - in fact, I know of one documented incident where a Diesel turbo was used on a racing gasser (you know!) engine, which self-destructed due to excessive oil "leakage" past the non-contact-sealed shaft

So, if EGR function is disabled, and vehicle shudder at engine shut-down isn't bothersome, the FCV plate can be removed, thereby also removing possibility of failure - except at federally-mandated vehicle inspection event

ATXKJ · **Posted:** Sun Jan 11, 2009 6:17 pm

There are a couple of folks on the board who have have VW TDI's runaway
apparently something with a broken oil control ring.

didn't sound too common - but it has occurred so Turbo Tim included the FCV shutdown in the SEGR.

gmctd · **Posted:** Sun Jan 11, 2009 6:28 pm

Just saying it's not the Damocles' sword of the KJ CRD world, as some may fear - no chicken-little, here...................

nescosmo · **Joined:** Sat Jul 14, 2007 11:17 pm **Posts:** 202

Turbo Tim wrote:

The fact that the AFC did close shows that the SEGR is working. In anything but Park and Neutral, the valve is electrically disconnected.
Now you state that it closed way after shutdown raises a few questions.
First, was the CRD in Park?
If so, then possibly the AFC valve itself is damaged, as in stripped gears, etc.
Push on the butterfly with the key off, and it should move freely closed BUT spring to the open position.

Well this time I bypass the SEGR and the AFC shot down and after a few seconds went back open and stay open.
With the SEGR when I shot down the CRD shakes, but when I bypass the SEGR the CRD shot down with no shakes, what could it be.

EGR - to be, or not to be, or et tu, brute

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