Automotive handbooks / manuals

The Mitsubishi Pajero Owners ClubŪ
The Mitsubishi Pajero, Shogun, Montero, Challenger, Raider and EVO 4x4 Owner's Club
 
The POCUK - it's not just a Club, it's a way of life!

 FAQFAQ   SearchSearch   Watched TopicsWatched Topics   MemberlistMemberlist   UsergroupsUsergroups   RegisterRegister 
 ProfileProfile   Log in to check your personal messagesLog in to check your personal messages   Log inLog in 
Click here to link to the Pajero Owners Club UK FaceBook Group!POCUK FaceBook Group  POCUK home pagePOCUK Home  POCUK ForumsPOCUK Forums  CalendarCalendar

egr valve blanking plate

Goto page : Previous  1, 2, 3, 4, 5, 6, 7, 8, 9, 10  Next
 
Post new topic   Reply to topic    The Mitsubishi Pajero Owners ClubŪ Forum Index -> EGR Valve Q&A
View previous topic :: View next topic  
Author Message
PoCUK
Site Admin
Site Admin


Age: 60
Zodiac: Pisces
Joined: 09 Oct 2002
Posts: 3749
Location: S/W New Forest Border

PostPosted: Thu Mar 03, 2005 17:20    Post subject: Reply with quote

JayCee wrote:
Quote:
I'm pretty sure that the 'localised hotspots' first referred to by Ivor were in relation to (for example) what happens when you 'hoof it' rather than what's going on as the engine is 'cruising'.


It is when you "Hoof it" ..that the ERG valve is supposed to open ..
Eliminating one more potential cause of "Hotspots"

It can't open if it's blocked or blanked..

Seems relevant to me in light of the subject we are discussing.. Rolling Eyes

I think you have made my point for me.. Smile


Not quite, I've just referred to something Ivor discussed ... a number of references on the Pajero diesel engines with the EGR valve that I have managed to find refer to the valve opening briefly while the engine is idling, for example at a junction or at traffic lights, in order to reduce the NOx emissions and actually remaining closed on wide-open throttle in order to prevent it interfering with power.

The whole topic seems to be full of inconsistencies Confused

The fact still remains, by far the biggest cause of CH failure is in relation to problems with the engine coolant/cooling system! As I stated earlier, in 10 years of working on imports, mechanics that i have discussed this with have not found a single cylinder head failure that has been attributable to having the EGR valve blanked off.

Simon
Back to top
View user's profile Send personal message Send e-mail Visit poster's website
Google
Sponsor







PostPosted: Thu Mar 03, 2005 17:20    Post subject: Google Ads keep the POCUK free to join!


Back to top
JayCee
Events rep (Ireland)
Events rep (Ireland)




Joined: 22 Feb 2003
Posts: 1957
Location: Portlaoise , Ireland

PostPosted: Thu Mar 03, 2005 17:56    Post subject: Reply with quote

Quote:
refer to the valve opening briefly while the engine is idling, for example at a junction or at traffic lights, in order to reduce the NOx emissions and actually remaining closed on wide-open throttle in order to prevent it interfering with power.


Close ..but wrong..
It's an easy mistake to make ..

The valve on the pajero is operated by vacuum
(about 4lb I measured it with a vacuum gauge)

If you clean the valve until it will operate at that value ..you can observe the following...

On idle /rpm ..It remains closed .
At all steady speeds /rpm ...it remains closed

It is for that moment of "Hoofing it" either on take off from traffic lights
suddenly "Flooring it" at motorway speeds or towing .That the valve opens.
All these sudden high demand / raised temp /raised load events are when the valve kicks in.

All those times "for a moment" the cylinder head temp "Jumps"
and if you combine these events with a cooling system that isn't efficient.
and rob it of yet another safeguard .. your pushing your luck

Quote:
remaining closed on wide-open throttle in order to prevent it interfering with power


Well .. Isn't this what I have been saying .. ?
A properly working ERG valve won't interfere with either power or smoke
production to a noticable degree..but will help protect the engine .
Back to top
View user's profile Send personal message MSN Messenger
PoCUK
Site Admin
Site Admin


Age: 60
Zodiac: Pisces
Joined: 09 Oct 2002
Posts: 3749
Location: S/W New Forest Border

PostPosted: Thu Mar 03, 2005 19:09    Post subject: Reply with quote

Therein lies the mystery ...

The science of what's occuring sounds exactly right ...

The EGR valve should open very briefly when, for example, you 'hoof it'. The revs go up, more heat is generated which causes more NOx emmissions to be produced. To counter the excessive NOx emmissions, a small injection of the 'dirty' exhaust gas is put back in to the engine to effectively retard the burning process by starving the fuel/air mix of some oxygen - more or less, deliberately causing a flat spot.

But here's the rub ... the EGR valve is not in place to protect the engine from hot-spots ... it is designed with one task ... to feed exhaust gas back in the engine to reduce NOx emissions.... exactly why it can be 'manually' vacuum operated and is not operated in relation to the temperature in the engine.

In actual fact, what you seem to be saying is that if you have a perfectly operating EGR valve, but you 'cruise', rather than 'race around' the EGR valve may as well be blocked off as it's never going to open anyway?

Add to that equation, the fact that many of the older Pajeros display some signs of poor engine heat management, (losing water, dirty rad water, etc), you could have hot-spots that are never affected by the EGR valve because you're a 'light footed' driver and the valve won't open anyway?

It seems there are even more inconsistencies Confused

Simon
Back to top
View user's profile Send personal message Send e-mail Visit poster's website
more x 4
Shining Star
Shining Star




Joined: 18 Dec 2003
Posts: 8104
Location: stevenage,herts

PostPosted: Thu Mar 03, 2005 19:23    Post subject: Reply with quote

PoCUK wrote:

But here's the rub ... the EGR valve is not in place to protect the engine from hot-spots ... it is designed with one task ... to feed exhaust gas back in the engine to reduce NOx emissions....


and remember that this engine was designed with this in mind
Back to top
View user's profile Send personal message
PoCUK
Site Admin
Site Admin


Age: 60
Zodiac: Pisces
Joined: 09 Oct 2002
Posts: 3749
Location: S/W New Forest Border

PostPosted: Thu Mar 03, 2005 19:28    Post subject: Reply with quote

more x 4 wrote:
... and remember that this engine was designed with this in mind


More inconsistencies though ... the 4D56 engine block and the cylinder head are identical on the Shogun and the Pajero.

If part of the engine design requires the EGR valve, why don't they all have one fitted?

All I'm saying is ... it's not black and white by any means!

Simon
Back to top
View user's profile Send personal message Send e-mail Visit poster's website
more x 4
Shining Star
Shining Star




Joined: 18 Dec 2003
Posts: 8104
Location: stevenage,herts

PostPosted: Thu Mar 03, 2005 19:33    Post subject: Reply with quote

there are differences,pump setup and so on,but i know (personally) of more shoggies WITH the egr fitted than without
Back to top
View user's profile Send personal message
PeteMillis
*****
*****




Joined: 08 Jul 2003
Posts: 845
Location: Sussex, UK

PostPosted: Thu Mar 03, 2005 21:34    Post subject: Reply with quote

Here's a FACT.....the vacuum operated EGR system on Mitsubishi engines operates in the low to medium load range of the engine, not the high load.
See here http://www.mitsubishi-motors.com/corporate/about_us/technology/review/e/pdf/2003/15E_03.pdf

It is only on the newer engines that technologies are ebing developed to recirc gases at high load. The reason recirc only occurs at low to mid load on a 4M40 and similar engine is this - on a turbocharged engine the inlet manifold pressure under boost is too high to enable any exhaust gases to be reciruclated into the inlet manifold. Obvious really - if the EGR valve opened at high boost then all that boost pressure would be lost straight into the exhaust manifold. The EGR is opened at low to mid load by the pressure differential between the air before the turbo and the air after the turbo.
Quote:
∆P = (turbine pressure – boost pressure) > 0


So, as I have said, a properly working EGR WILL NOT affect power when under load. However a stuck open one will allow boost pressure to leak directly into the exhaust. This is probably what causes excessive smoke - a loss of boost pressure will result in over-fueling as there is not enough air to combust the fuel in the cylinders. The smoke is nothing whatsoever to do with exhaust gases being recirculated when they shouldn't be, as the higher manifold pressure when under boost would not allow exhaust gases to enter the inlet - the exact opposite occurs...air pressure forces out of the EGR and into the exhaust.

So here we now have another problem - EGR does reduce combustion temps (FACT) at low to mid load. But EGR does not operate at high load. SO blanking of the EGR WILL INCREASE combustion temps at low to mid load (FACT) but is this increase, combined then with further increase when under high load, what could cause a problem. It seems probable that by blanking the EGR, if the engine has been working at high load and getting hot, the temperature will remain elevated when coming off load as there is no exhaust gas recirculation. This heat is therefore not dissipated so quickly. This is not conjecture, but scientific fact. The question is, is this accumulation of heat sufficient to cause a problem?

Another FACT is that overfuelling increases combustion temperature. Now, for a UK spec Shoggie with no EGR to pass emission testing, the fuel pump is turned down lower. This results in lower combustion temperature. In Japan, there is not the concern with soot so the fuel pump can be turned up higher causing an overfuelling condition, BUT the EGR keeps the combustion temps much lower at low and mid load. Now then, if a Jap import arrives in the UK and is smoking due to overfuelling, blanking the EGR may reduce the smoke if the EGR is stuck open as blanking it will increase boost pressure and hence the fuel will be better combusted. However there is then no longer the cooling off time at low to mid load. The only way around this would be to also turn down the fuel pump to reduce combustion temperature.

I suggest the if someone turns up the fuel pump, or keeps it turned up after import, and then blanks the EGR then this will DEFINITELY result in higher combusion temperatures and possible CH failure. The only guaranteed way to safely blank off the EGR would be to reduce fueling as well.

I've thought a lot about this so please don't attack me. I know!
Back to top
View user's profile Send personal message
more x 4
Shining Star
Shining Star




Joined: 18 Dec 2003
Posts: 8104
Location: stevenage,herts

PostPosted: Thu Mar 03, 2005 22:30    Post subject: Reply with quote

no pete,i think thats what a couple of us were trying to say. well put Wink
Back to top
View user's profile Send personal message
PoCUK
Site Admin
Site Admin


Age: 60
Zodiac: Pisces
Joined: 09 Oct 2002
Posts: 3749
Location: S/W New Forest Border

PostPosted: Thu Mar 03, 2005 22:48    Post subject: Reply with quote

No attacks ... honest Pete! but a few observations...

It's a really interesting article... from the horses mouth indeed!

But justs adds to the inconsistency ...

The purpose of the EGR valve is to reduce the NOx emissions - higher at higher temperatures - eg when under load, or 'hoofing it'.

Because of the pressure differential in the combustion chamber under load, the exhaust gas doesn't have enough pressure to enter the chamber, so is no use whatsoever in reducing the temperature under load? (correct me if I've mis-read something)... this is already going against what has been discussed in this thread ... soooo... it seems that a working EGR valve neither operates at idle, nor under heavy load Confused

[At this point, it may be worth mentioning that the test engine was not a 4D56 2.5 Pajero engine, but a 12L truck engine - I suppose the principle must be about the same?]

I have to say ... it is an interesting article, but it specifically considers pressure differentials and NOx percentages but nothing about the valves' purpose being anything to do with reducing the temperature to protect any of the components of the engine?

The MMC article that you've referred to seems to confirm that the sole purpose of the EGR valve is to try to optimally reduce the NOx emissions to meet tighter emissions standards in many countries.

I have nothing to gain by promoting the blanking plates, (around a pound a plate after original cost, p&p, VAT, and online transaction and bank charges), and if you check the main site, (http://www.pocuk.com/faq/belcher.htm) you will see that it is offered as one of the solutions to the common 'belching black smoke' problem. Servicing / cleaning the EGR valve is offered as an option, but blanking the valve is a cheap, quick and effective way to stop the problems caused by the valve being stuck open, including reducing the black smoke, lowering the CO2 emissions, improving the power and raising the mpg.

I will state again - the mechanics we use to service our PJ have stated that in over ten years of blanking EGR valves on a range of imports, they have never seen a cylinder head failure that was attributable to having fitted an EGR blanking plate.

Finally ... (sorry to go on!) ...

PeteMillis wrote:
The only guaranteed way to safely blank off the EGR would be to reduce fueling as well.

It seems that you're agreeing that the EGR valve can be blanked off safely, (providing the fuelling is reduced too!) ... which gets interesting ... we have many reports of the fact that Pajeros are regularly de-tuned in order to get them through the emissions test ... (and every subsequent MOT!) ... but this combination seems to be a fix-all!

Simon.
Back to top
View user's profile Send personal message Send e-mail Visit poster's website
more x 4
Shining Star
Shining Star




Joined: 18 Dec 2003
Posts: 8104
Location: stevenage,herts

PostPosted: Thu Mar 03, 2005 23:07    Post subject: Reply with quote

simon,the temperature reduction is a by product,a side effect if you will. this is known about and incorperated into the design. then injector and pump settings are mapped accordingly. in this country on the whole,shoggies dont have the egr,and their injector and pump settings are mapped accordingly. these engines are set up region specific (like in IT). even the plugs are different in the north/south japan.
changing these settings effects the way the engine runs,things like mpg,smoke,starting,and temp
so,even a small change( like a line of code) can mess it all up. if you dont belive me,try changing the code on your o/s and see what happens.
there have been some very good points raised here,and as you said,for a pound a plate,i cannot understand why your view is so blinkered on this subject
Back to top
View user's profile Send personal message
JayCee
Events rep (Ireland)
Events rep (Ireland)




Joined: 22 Feb 2003
Posts: 1957
Location: Portlaoise , Ireland

PostPosted: Thu Mar 03, 2005 23:15    Post subject: Reply with quote

Quote:
blanking the valve is a cheap, quick and effective way to stop the problems caused by the valve being stuck open, including reducing the black smoke, lowering the CO2 emissions, improving the power and raising the mpg.


Er.. Cleaning it is cheaper ..
And complys with the original design ..!
Back to top
View user's profile Send personal message MSN Messenger
PeteMillis
*****
*****




Joined: 08 Jul 2003
Posts: 845
Location: Sussex, UK

PostPosted: Fri Mar 04, 2005 1:03    Post subject: Reply with quote

Simon, that paper points out that up until now, EGR has only been effective at cooling combsution and therefore reducing NOx emissions at low to mid load. And it does work at reducing NOx emissions which is why EGR is necessary to get the vehicles through the Japanese emissions test.
It is only now that systems are being developed to enable EGR to take place under high load - and this doesn't apply to our Pajero and Delica engines as these use the old technology.
Yes, the NOx emissions are higher at higher temperatures, but combustion temperatures are high generally (only more so when under load) so even reducing temps at low to mid loads will reduce NOx emissions. What I was trying to get at was that by making things cooler when not under load, then heat produced when under load can be dissipated more quickly when the high load situation ends. This means that the next time you put your foot down and increase the load, then starting temperature will be lower than if there was no exhaust gas recirculation to cool things when off load.
A simple analogy would be someone running in the desert. Run for two minutes, get really hot and slow to a walk - then have someone chuck a bucket of water over you to cool you down. You can then run for another two minutes starting off at a lower temperature than if you didn't have a bucket of water chucked over you when you slowed to a walk. Are you going to collapse from heat exhaustion sooner with the cold bucket of water or without?
We all know that a stock Pajero in Japan will produce more soot than a stock Shogun in UK. This is purely because in Japan you can get away with pumping more fuel in than you can in the UK. And it's not because the Japanese turn their pumps up - most still have the tamper seals intact when they arrive in the UK, and indeed they have to be intact for the Shakken. It's only when they get here that the seals are often broken to turn the pump down to get through emissions.
What I'm saying is that the cooling effect of the EGR allows higher fuelling to be used. If you run the higher fuelling without the EGR then the temperatures will be higher. UK Shogies without EGR tend to be less smokey as they run lower fuelling so the exhaust gas temps will be lower anyway. This is why the same head can be used with and without EGR, but also explains why blanking the EGR on one set up to run with the EGR will result in higher combustion temps, unless the fuelling is reduced to compensate for it.

And finally (I'm, sorry to go on now!) - I contend that a Pajero isn't necessarily "detuned" to get through the emissions at MOT, but is instead "correctly tuned" to comply with UK smoke tests. A benefit of this correct tuning is a reduction in combustion temperatures which could potentially reduce the risk of cylinder head failure.

Nighty night Wink
Back to top
View user's profile Send personal message
PoCUK
Site Admin
Site Admin


Age: 60
Zodiac: Pisces
Joined: 09 Oct 2002
Posts: 3749
Location: S/W New Forest Border

PostPosted: Fri Mar 04, 2005 8:56    Post subject: Reply with quote

PeteMillis wrote:
...A simple analogy would be someone running in the desert. Run for two minutes, get really hot and slow to a walk - then have someone chuck a bucket of water over you to cool you down. You can then run for another two minutes starting off at a lower temperature than if you didn't have a bucket of water chucked over you when you slowed to a walk. Are you going to collapse from heat exhaustion sooner with the cold bucket of water or without?


Let's say you have your own private cool shower and fan blowing cool air on you the whole time (a bit like an effective coolant/cooling system for an engine) - you could run and run as fast as you can and for as long as you have the energy and you won't overheat.

Then let's say that somebody turns the shower pressure down, turns up the temperature of the shower water and then keeps blowing warm breath on your forehead every time you fart ... and it turns out you your arteries are partly blocked, you have to agree, it won't be long before you overheat Confused

I'm sure there are loads of analogies that can be used to represent the part of the argument that you're trying to support, but not a single one that covers the 'whole picture'.

There is no argument about the fact that the EGR valve is a component added to the engine management system to reduce NOx emissions, the question is, is it included to protect the cylinder head?

Speaking to mechanics who have been servicing imports and blanking EGR valves for over 10 years, and spending more time than I should trawling the internet (usually a very reliable media to find support for any argument), there is no evidence that the EGR valve has anything to do specifically with heat management and protection o the cylinder head, nor is there any suggestion nor evidence that cylinder head failure has occurred as a result of blanking off the EGR valve.

If there was 100% proof that a failed Pajero cylinder head was directly attributable to the blanking of the EGR valve, then then this would, of course, cast a whole new light on the subject.

Simon
Back to top
View user's profile Send personal message Send e-mail Visit poster's website
PeteMillis
*****
*****




Joined: 08 Jul 2003
Posts: 845
Location: Sussex, UK

PostPosted: Fri Mar 04, 2005 9:30    Post subject: Reply with quote

This is actually a good thread and it's refreshing to have one that gets the ol' brain cells working.
My take on
Quote:
There is no argument about the fact that the EGR valve is a component added to the engine management system to reduce NOx emissions, the question is, is it included to protect the cylinder head?
......
no, it's not included in order to protect the cylinder head. It is an emissions control device. But the fact it is there results in the cyclinder head being cooler (that's how it works - by cooling the combustion and diluting the O2 concentration the NOx production is reduced). This cooler running of the cylinder head permits higher fuelling than that in the UK Shoguns to be used.
In summary, keeping the higher fuelling of the Japanese spec Pajero but removing the EGR will, without doubt, result in higher cylinder head temps whether under load or not. The crucial question is - can this increase in cylinder head temp be sufficient to cause damage? That's something that maybe we as a club should ask for some advice from Mitsubishi on.
Back to top
View user's profile Send personal message
PoCUK
Site Admin
Site Admin


Age: 60
Zodiac: Pisces
Joined: 09 Oct 2002
Posts: 3749
Location: S/W New Forest Border

PostPosted: Fri Mar 04, 2005 9:52    Post subject: Reply with quote

PeteMillis wrote:
...In summary, keeping the higher fuelling of the Japanese spec Pajero but removing the EGR will, without doubt, result in higher cylinder head temps whether under load or not. The crucial question is - can this increase in cylinder head temp be sufficient to cause damage?


Semantics I know, but I believe the question is not 'can it' but 'will it'.

PeteMillis wrote:
... That's something that maybe we as a club should ask for some advice from Mitsubishi on.


I agree with you Pete we really do need some formal advice from MMC... I suspect that it will be more easily drawn from MMC technical division by somebody already inside the 'MMC network' though!

It needs to be quotable too, otherwise it will be classed as 'heresay'.

I look forward to the conclusion!

Simon Smile
Back to top
View user's profile Send personal message Send e-mail Visit poster's website
Display posts from previous:   
Post new topic   Reply to topic    The Mitsubishi Pajero Owners ClubŪ Forum Index -> EGR Valve Q&A All times are GMT + 1 Hour
Goto page : Previous  1, 2, 3, 4, 5, 6, 7, 8, 9, 10  Next
Page 8 of 10

 
Jump to:  
You cannot post new topics in this forum
You cannot reply to topics in this forum
You cannot edit your posts in this forum
You cannot delete your posts in this forum
You cannot vote in polls in this forum
You cannot attach files in this forum
You cannot download files in this forum


All contents © Hobson's Choice IT Solutions Ltd 1997 on
Powered by phpBB © 2001, 2002 phpBB Group