Member Since: 12 Dec 2005
Location: The Gaff
Posts: 50977
EGR and Cylinder Head temperature
Just read this on another motoring website
Quote:
I strongly do not recomend blanking of any of the EGR's as I have stated before the EGR has a cooling efect in the combustion chamber and can cause hot spots , increase cylinder head temp , the engineers have built these heads to work inconjunction with the EGR, and blanking them off efects this , I know yuo guys are saying it improves performance ,but if it efects reliability, leave off , I am seeing cracked heads again in the workshop and no less that two recently were running with blanked off EGR's, 2.5's by the way .
...anyone care to comment 21 year LR veteran > D2 GS 2003 > D3 S 2006 > D3 HSE 2009 > D4 HSE 2013 > D4 HSE 2015 > D5 HSE 2018 > DS HSE R-Dynamic P300e 2021
2nd Jan 2009 12:10 am
AndrewW
Member Since: 06 Aug 2007
Location: Saddleworth
Posts: 2302
From a point of ignorance but (hopefully) also logic - if this were true then someone who drove a long way without backing off the throttle (500km on the autobahn? towing, perhaps?) would crack his cylinder head? Due to lack of EGR gas induction....
2006 D3 finally swapped for a 2016 D4 Graphite in Graphite grey. No mods
2nd Jan 2009 12:17 am
simonsi
Member Since: 14 Oct 2007
Location: Auckland
Posts: 1264
TDV6/8 EGRs only open on the overrun so under very low load conditions, so hard to see cylinder head temps rising as a result of EGR NOT being recirculated. Also as the (hot) exhaust gases are not being recirculated and if you have removed the butterfly valve then more (cold) air is being introduced to replace the (hot) exhaust gases previously being introduced. As there is no load on the engine then that should result in increased cooling of the chambers vs normal EGR operation.
What engine was being discussed, not petrol by any chance? Comments above only apply to diesel.Cheers
Simon
2nd Jan 2009 12:17 am
DiscoStu
Member Since: 09 Apr 2006
Location: London
Posts: 11412
Member Since: 09 Jun 2005
Location: Ubique
Posts: 16534
Exhaust gas temperature is around 200 degrees hotter than ambient air - even after being 'cooled' (dependent upon engine load of course ) distortion or cracking will occur when gases which are significantly hotter or cooler than the surrounding metal are introduced in large volumes, therefore causing localised fast cooling or heating of parts of the intake system
2nd Jan 2009 12:25 am
simonsi
Member Since: 14 Oct 2007
Location: Auckland
Posts: 1264
Umm, you in favour or not Ten? Cheers
Simon
2nd Jan 2009 12:30 am
10forcash
Member Since: 09 Jun 2005
Location: Ubique
Posts: 16534
EGR - no, butterfly - yes, removing that makes blanking the EGR's pointless, hot'ish gases being drawn in (rather than forced in) post turbo will only cause the cold air to expand creating a greater boost effect, personally I think we need some major recall to give D3'ers something to talk about instead of faffing around with tightly integrated emission systems
2nd Jan 2009 12:48 am
DG Site Moderator
Member Since: 12 Dec 2005
Location: The Gaff
Posts: 50977
I appreciate that the original statement was from a Mitsubishi website concerning their diesels...I am just concerned that the current frenzy of blanking is not without it's drawbacks particularly for those still in warranty...and thought it worthy of discussion 21 year LR veteran > D2 GS 2003 > D3 S 2006 > D3 HSE 2009 > D4 HSE 2013 > D4 HSE 2015 > D5 HSE 2018 > DS HSE R-Dynamic P300e 2021
2nd Jan 2009 1:12 am
Russell
Member Since: 24 Aug 2007
Location: Kent
Posts: 10564
10 are you saying you are in favour of removing the butterfly valve, but you are not in favour of blanking the EGR valves off?MY17 D5 1st Edition Namib Orange
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2nd Jan 2009 8:23 am
simonsi
Member Since: 14 Oct 2007
Location: Auckland
Posts: 1264
DG wrote:
... is not without it's drawbacks particularly for those still in warranty...and thought it worthy of discussion
I'm not sure that quote means even that, he says he is seeing cracked heads, two of which have had EGR blanked and presumably an unknown number have cracked heads without having blanked EGRs.
Given that blanking the EGRs isn't a panacea for all engine problems, any given engine design will continue to suffer whatever range of problems it had, blanked or not.
I personally wouldn't blank or butterfly a car in warranty but that is purely to do with warranty terms that have nothing to do with whether the blank or butterfly caused the failure leading to the warranty claim.
Post warranty I'm happy with the science and the lack of overall negative feedback specific to blanked EGRs, and the vast improvement in driveability is certainly worth having.
Compared to running air filters with dubious filtration reports I'm quite comfortable.
Great point to raise!Cheers
Simon
2nd Jan 2009 9:36 am
norto
Member Since: 10 Apr 2006
Location: batemans bay
Posts: 1605
EGR - no, butterfly - yes, removing that makes blanking the EGR's pointless, hot'ish gases being drawn in (rather than forced in) post turbo will only cause the cold air to expand creating a greater boost effect, personally I think we need some major recall to give D3'ers something to talk about instead of faffing around with tightly integrated emission systems
So how come removing the butterfly vv makes blanking pointless? The main reason for blanking, for most people, is because the EGR valve design is unreliable and driving the vehicle with 1 or 2 failed EGR valves is almost impossible. So the EGR is blanked to prevent a failed valve affecting engine performance, and the butterfly is removed to prevent the intake vaccuum that the engine would suffer with closed (blanked) EGR valves and closed butterfly valve. Any performance benefits (improved 'pick up' as reported by some) of the blanking procedure are a bonus, but not the main reason.
Regarding the recirculated gas increasing the boost effect - I can't see that being true as any boost increase will be cancelled out by the increased percentage of non combustible gas drawn / pushed into the engine.
If mine was still in warranty then I'd leave well alone, but now any recovery and repairs are paid for out of my own pocket I'm happier running with the blanks fitted, rather than pay LR £hundreds to fit new (flawed design) valves every couple of years. IMHO, and all down to personal choice of course Previously:
2005 D3 2.7 TDV6 S
1984 90 2.25 Petrol CSW
1992 90 200TDi Hard Top
1995 Discovery ES 300TDi
2003 90 TD5 Truck Cab
Last edited by ridgeback_moor on 2nd Jan 2009 10:21 am. Edited 1 time in total
2nd Jan 2009 10:20 am
SteveNorman
Member Since: 14 Oct 2005
Location: Somerset
Posts: 1145
EGR stands for exhaust gas recirculation. The purpose of this is to lower oxides of nitrogen emissions from the combustion chambers (& out the exhaust). When the combustion temperatures increase, so do the oxides of nitrogen produced. To this effect, exhaust gas is used to add into the combustion chamber to reduce temperatures, this seems a strange thing to do, exhaust gas being hot! The temperature of the exhaust gas is less than cylinder temperatures, when added back into the cylinders, less oxygen is available to be burnt, reducing temperatures & oxides of nitrogen. EGR can also be cooled via cooling system coolers to reduce temps further, as is the case on later TDV6's.
The increased temps by not having EGR will not increase temps by more than the engine can cope with, as there were many engines running without EGR before, & they coped
As MOT's smoke tests only measure visible smoke, blanking the EGR will not make the vehicle fail. In fact as EGR increases particulate emissions (soot) there is a likelyhood that visible emissions could well be less.
HTH
Steve
2nd Jan 2009 10:20 am
MacLeod 313
Member Since: 18 Apr 2008
Location: away
Posts: 10723
To be honest, if its in Warranty I would'nt go near the EGR plates. LR are checking if you have a break down, well they did on mine .
Even if you are out of warranty, but with a lower mileage fully serviced D3, and a major componant gives up, you still have a claim against LR, blanking the EGR's just takes away your ability to claim
2nd Jan 2009 10:54 am
simonsi
Member Since: 14 Oct 2007
Location: Auckland
Posts: 1264
MacLeod 313 wrote:
...blanking the EGR's just takes away your ability to claim
Depends, I've had 1x EPB rebuild and 1x replacement steering wheel when out of both factory and LR ext waranties, both done by the same dealer who is aware the car is chipped (its obvious when driving a chipped D3!), and no queries about blanked EGRs.... perhaps you have too honest a face Cheers
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