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ianrichardson
Member Since: 31 Aug 2010
Location: Cardiff and Mid France!
Posts: 313
  
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| EGR blanked off but what tells the ECU that? |
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I've have fitted Pete Bells blanking plates as one of my EGR valves was failing according to the Stealers here in Cardiff.
No problem fitting them as Pete's instructions are clear and easy to follow.
I do wonder though how the ECU knows that the EGR valves are non functional as it will still be telling the valves to open and shut and then tell the non existent butterfly to move, the management of the engine will be expecting a different fuel mixture when they are open rather than closed.
So my question I suppose is, how does the engine get the correct fuel mixture if there is no waste gas coming from the exhaust. The ECU must surely be programmed to take the different air/fuel into account.
Now as my car is a 2005 model the EGR valves act on command by the ECU but no feedback is given to the ECU as to the position of the EGR valve, which to my mind makes the whole thing a bit flaky.
Now an engine remap could easily cure this as it could be told not to work the EGR valves at all. So would it be advisable to have a remap?
Ian
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 10th Jan 2011 1:03 am |
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al cope
Member Since: 08 Nov 2005
Location: Oldbury, WM
Posts: 10299
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to be fair - does it matter 
you dont have to do anything else, and the car runs fine after blanking. I had no issues with mine in over two years after blanking the EGR's.
Al Volvo XC90 B5 Plus Dark
Gone - MY18 D5 HSE - Corris on 22's with Black Pack
Now gone - MY16 D4 SE Tech, Loire Blue, Almond Leather, Privacy, plus some other goodies.
Old - MY12 D4 SDV6 XS Auto - Ipanema Sand with Almond Leather - Plus other niceties, and D4.com sticker
Older - D3 TDV6 XS Auto - Lugano Teal with Almond Leather, 20" Stormers, Shiny Tailpipes, DVD/TV - and obligatory D3 sticker
Ancient - D3 TDV6 S - Tonga with Ebony, 20" Stormers, satnav & DVD
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| 10th Jan 2011 10:08 am |
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cheekysnake
Member Since: 13 Jul 2010
Location: UK & France
Posts: 7
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As I understand it, the nice thing about diesels is that the mix doesn't work the same way as for petrol - whereas changing the fuel mix in petrol engines can lead to pinking, detonation etc etc in a diesel all you get is a reduction in rpm, eventually all the way down to an idle.
The reason for the EGRs is to decrease combustion chamber temperatures slightly so that (marginally) less NO is produced - it's a really easy/lazy way for engineers to reduce emissions a bit to meet regs.
The fact that the ECU doesn't even get any feedback from the EGR system on early models shows just how unimportant it is.
Don't worry and just enjoy the fact that your engine is no longer having to breathe rubbish!  Climbing, Paragliding, Camping - better get a Disco then! 
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| 25th Jan 2011 1:38 pm |
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bellautos
Member Since: 02 Feb 2006
Location: NorthYorkshire
Posts: 2532
 
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MAF/IAT & MAP amongst other things measure whats going in and add fuel as needed
The ecu from this information will still adjust the fueling to give the recommended diesel stoichiometric air-fuel ratio set in the ecu mapping, so you worry for nothing lol.
The butterfly is fitted as a means to divert air just as a blend motor does on the HEVAC system to the vents in your car, it does not matter where the motor is set or where the air comes from the car still needs X ammount of air to work and that air is monitored by the sensors above, some of it is just coming from a different place and thats not via the egrs anymore.
The EU4 engines added a few other calcualtions to the mix which is why they cant be blanked easly, but thats for another day
In the case of the EU3 car like yours the ecu still thinks they are fitted and does not care about their postion or actuation state as long as they are not short circuit.
Pete
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| 25th Jan 2011 9:59 pm |
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mik
Member Since: 08 Feb 2010
Location: Skoatland
Posts: 912
 
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bellautos wrote:MAF/IAT & MAP amongst other things measure whats going in and add fuel as needed
The ecu from this information will still adjust the fueling to give the recommended diesel stoichiometric air-fuel ratio set in the ecu mapping, so you worry for nothing lol.
I'd agree that the engine won't know/care whether it gets fresh air, or recycled exhaust, but surely deezal's don't need a stocichiometric mix - they don't have throttles and therefore take a full lung of air on every stroke - you can add a little diesel as you want (or as much as you want until it can't burn any more).
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| 25th Jan 2011 10:35 pm |
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bellautos
Member Since: 02 Feb 2006
Location: NorthYorkshire
Posts: 2532
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They still use a stocichiometry afr calcualtion amongst a few other calculations made in the ecu or it would never know when to stop injecting or what ammount to inject to, It may in some cases be refered to differently but in reality it needs a base setting to work from which is generally based arround the diesel stocichiometric afr.
Pete
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| 25th Jan 2011 10:55 pm |
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mik
Member Since: 08 Feb 2010
Location: Skoatland
Posts: 912
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Ok Pete - using it to calculate a max fuelling does of course make sense.
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| 25th Jan 2011 11:26 pm |
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ianrichardson
Member Since: 31 Aug 2010
Location: Cardiff and Mid France!
Posts: 313
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Hi Pete
Thank you for your very full and informative reply.
Now the cold weather has eased off a bit, and the FBH isn't working as hard, maybe my fuel consumption will improve;-)
Off to France and hopefully Spain in Feb so I'll do a really long mpg test! That said it's always difficult to keep the car to 110 kph even with cruise control as the car just wants to go faster and the roads are begging it to.
I'm trying to write a post on my rear suspension experiences. I'd like to include pictures but am having a great deal of difficulty!
If someone could pm me and give me the abc simpleton guide I'd be grateful.
Thanks
Ian
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| 25th Jan 2011 11:46 pm |
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