EGR Valve

[wildoliver]

nope that is the secret to any engine running well, dirty oil with any particulates in it destroy engines and turbo's, and dirty unfiltered air accelerates bore wear massively.

[supermono]

AntMat said:

rely on the introduction of NOx as a cooling gas to cut emissions. Failure to do so will increase both the temperature of the oil and the exhaust gasses. This, in turn, may well hasten the demise of the turbo.

You sound like you know what you're talking about but I've been doing some thinking. Since the EGR only opens on part throttle at cruise it does nothing to cool the turbo when it's working hardest -- ie at full beans.

Can you explain some more please, because this sounds like BS on the face of it.

Having said that <Bones from Star Trek mode>I'm a software engineer not a mechanic, Jim</>

SM

[ELAN+2]

supermono said:

AntMat said:

rely on the introduction of NOx as a cooling gas to cut emissions. Failure to do so will increase both the temperature of the oil and the exhaust gasses. This, in turn, may well hasten the demise of the turbo.

You sound like you know what you're talking about but I've been doing some thinking. Since the EGR only opens on part throttle at cruise it does nothing to cool the turbo when it's working hardest -- ie at full beans.

Can you explain some more please, because this sounds like BS on the face of it.

Having said that <Bones from Star Trek mode>I'm a software engineer not a mechanic, Jim</>

SM

The sole purpose of the EGR valve on a modern car is to reduce emissions. by drawing exhaust gas into the combustion chamber, less fuel is required to maintain the fuel air ratio (14.7-1), Its a complex subject and my understanding is limited, but the way it was explained to me is as follows:
Imagine a single cylinder engine of say 1 litre, on every induction stroke it will suck in , 1 litre of air (assuming 100% volumetric efficiency, but we wont go there!). For correct combustion, we need to maintain the fuel air ratio, so a given amount of fuel is squirted in (14.7 parts air to one part fuel, by mass). If however we allow the engine to draw in an Inert gas,i.e. exhaust fumes, the volume of air drawn in will be reduced, hence the volume of fuel required will also be reduced, hence reduced emissions and improved economy. This only happens under low load conditions, Idle and cruise being the obvious.
If the EGR circuit is defective, you could have low power (valve open) or more commonly the engine will run too lean(hot), and the management light will come on. In this situation the Lambda (oxygen sensor) will be flagged as giving an incorrect reading. You will also fail the MOT emission test and posibly wreck your engine,turbo and cat.

Hope this helps

Mark

[supermono]

That sounds awfully petrol engine orientated though. Diesels always run very very lean or just right depending on zero to full throttle, right?

SM

[Pigeon]

The main purpose of EGR is to reduce emissions of nitrogen oxides. Because diesels run so massively lean there is plenty of spare oxygen around to combine with nitrogen under the heat of combustion. By replacing part of the air in the fresh charge with exhaust gas under part throttle conditions where there is not a need for a full charge of oxygen, there is less spare oxygen and so less NOx formation.

[GavinPearson]

Pigeon said:

The main purpose of EGR is to reduce emissions of nitrogen oxides. Because diesels run so massively lean there is plenty of spare oxygen around to combine with nitrogen under the heat of combustion. By replacing part of the air in the fresh charge with exhaust gas under part throttle conditions where there is not a need for a full charge of oxygen, there is less spare oxygen and so less NOx formation.

I agree, & I'd like to build on this. In reality on a diesel at part load you run as much EGR as you can to keep NOx down, but that is only in the area where the cert test monitors NOx. Out of that area you optimise for BSFC / peak power, whatever the requirement is. As for the comment about 'throttle', nowadays diesels do have throttles in order to help draw in EGR so it is worth drawing the distinction between part load and throttle position because they can operate totally independently of each other.

[supermono]

But crucially does disabling the EGR valve increase exhaust temperatures? I can't understand why it would if it only operates on part load/throttle when little power/heat is being created by the engine.

SM

[Rebuilda]

What I know about diesel engines will fit on the back of a postage stamp and my poor old transit is a bit poorly. This EGR valve thingy, does it sit on the top of the inlet manifold and have two wires running to it?
If these wires should become ... err... damaged in anyway could it cause the engine to malfunction?
Has it a 'normal' state ie normally open or closed, should there be current flowing down the wires when at low rpm or high?
I get intermittent (but frequent) episodes when there is little or no power on the lower end of the rev range but when it gets up about halfway it really gets off its ass and goes, I also get a small puff of light grey smoke from the exhaust on start up. The company who normally services the van said 'it needs new injectors, oh for a turbo is it, that will be about £48 each!'
Assuming I then take the van to them and shell out £200 to have the injectors replaced and what they actually do is replace the EGR valve (which fixes the problem) it costs them a whole lot less than the injectors would?
I am going to try just unplugging the valve thingy in the morning anyway, just to try it out.
I will post again tomorrow with the results.
Another small question, Will fitting a freeflow air filter instead of the normal transit airbox give me any noticeable gains in performance or economy?

[Mr Whippy]

supermono said:

But crucially does disabling the EGR valve increase exhaust temperatures? I can't understand why it would if it only operates on part load/throttle when little power/heat is being created by the engine.

SM

I think thats the crux. EGR only operates when the engine is running super cool anyway. If I don't rev my diesel (de-egr'd) it doesn't actually get hot. I can go 15 minutes and still be under 70 degree's on the temp gauge if I keep under 2000rpm and small throttle openings.

In winter it's worse. I have to actually knowingly use the engine to get some heat into it, and this is on a car without an intercooler and the EGR unplugged, AND it's remapped!

EGR also looses you some transient response as the EGR steals the turbo's turbine thrust. Take a look at implementation, it's also inefficient to flows on alot of engines.

Yes I'm adding a few more NOx particles, but I've made sure my engine is now going to run more efficiently generally as it's not full of black tar, my CAT has been removed after it failed, so I'm not supporting the extraction/manufacture/distribution/inefficiency in operation of that device now.

It passed it's MOT perfectly fine, cleaner than most newer Mondeo's and the like, and thats with a remap on, de-egr and de-catted. It gets 43mpg and it got the same when I first bought it with less power, egr and cat fitted. I've sat in red hot summer traffic sat on the M1 for an hour and the water temp never went over 80deg, and it only ever spikes to ~ 80deg after a proper hard run through the gears upto high speeds, and this is mainly due to massive exhaust gas temps, right where EGR wouldn't work anyway.

Basically, it's a waste of metal, and adds inefficiency everywhere, and longer term is a financial and resource liability as parts fail and cause cascade inefficiency/replacement of expensive parts made from more exotic materials, ie catalytic converters.
It does however allow the car to pass some 'legislation' that makes sense when the car is brand new and ignores the long-term dust to dust operation/increased obselete nature of the car at a younger age.

Dave

[delboy85]

I bought a 57 plate Avensis 2.2D-4D 12 months ago with 8000 miles on the clock. I recently experienced a lack of power and the VSC/TRC lights came on. I took the car to the Toyota agents and they have decided to renew the injectors, EGR valve and the turbo at a cost of £5000. The car is still under warranty but has only done a little under 20,000 miles. The warranty expires at the end of the year so I am thinking is it time to be rid of it. My opinion on Toyota reliability has taken a big dive especialy since I have been advised by a Toyota mechanic that it has been a common fault on vehicles after 15000 miles.For 6 months after buying the car I was doing 100+ miles a day mainly on the motorway but now I am retired and even if I take the 2 year extension on the warranty I am unlikely to have done another 20,000 miles before it expires. Having read various threads concerning the EGR valve I am now concerned that having reduced to a small urban mileage the problem may return even sooner.

[Mr Whippy]

What a weird collection of parts to replace.

Surely if a turbo, injectors and EGR valve all fail independently of each other at 20k miles you have made your car a bit badly

It was probably just a sticky EGR valve or something, so Toyota franchise/dealer do a load of labour and charge parts to Toyota UK under warranty work!?


I honestly don't believe ALL those parts can break at the same time in an inter-related fashion.

I wouldn't find fault with the car, I'd find fault with the stupid diagnostics/repair methods of main dealers.

Dave

[annodomini2]

Mr Whippy said:

What a weird collection of parts to replace.

Surely if a turbo, injectors and EGR valve all fail independently of each other at 20k miles you have made your car a bit badly

It was probably just a sticky EGR valve or something, so Toyota franchise/dealer do a load of labour and charge parts to Toyota UK under warranty work!?


I honestly don't believe ALL those parts can break at the same time in an inter-related fashion.

I wouldn't find fault with the car, I'd find fault with the stupid diagnostics/repair methods of main dealers.

Dave

More likely if they are common failure points and its so close to the end of the warranty, the garage can replace the parts and charge Toyota for the privelage without argument.

[Mr Whippy]

Tis a fair point, but then it doesn't fill you with faith that Toyota are replacing parts so early in their operational life... ie, you are not going to hang on to the car out of warranty for long, and 2nd hand buyers are not going to be filled with reassurance either.

Either way surely it only harms residual value!?

Hmmm

Dave

[delboy85]

It has been suggested that the failure of the Toyota EGR valves due to being choked with carbon is related to the original surface condition of the insides of the valves i.e. rough as a bears arse. Does this just apply only to Toyota, are other makes smoothed on the inside?

[Petemate]

My God - what a mess. FWIW - my experiences with diesels. Some years ago, had a Metro with the good old TUV 1.4 - dunno if it had any EGR stuff, wasn't very up on stuff like that at the time, but at 90k plus miles it was a good 'un. Daily commute Oxford-BHX - full throttle everywhere - AND 50 MPG. Great little tool. Then came the Focus TDDi - blanked off the EGR when it started to play up - once the smoke had finally cleared - excellent MPG & performance. Next my current car - Rover 45 TDi - 2002 model. Egr removed once it started to flutter and play up - smoking cured, excellent power and MPG, no warning lights. (I understand that the later ones, although not CR, flag up the MIL if the EGR is disabled) Anyway, looking later in the inlet manifold, it actually cleaned up over a period of about six months, saving me the bother of taking it off and de-tarring it. (It was seen to be filthy in there when I replaced one of the IC hoses before removing the EGR) I do not know what my exh or oil temps are, but the coolant temp needle has never wavered from midway even in the recent three hour stint LHR to Wycombe in the snow. On non-cr engines I just do not see a) the need for the bleddy things or b) any harm in winging them over the nearest hedge.
My 2 pennorth!

[Mr Whippy]

They are great on paper, crap in practice, imo.

Dave

[skid-mark]

delboy85 said:

I bought a 57 plate Avensis 2.2D-4D 12 months ago with 8000 miles on the clock. I recently experienced a lack of power and the VSC/TRC lights came on. I took the car to the Toyota agents and they have decided to renew the injectors, EGR valve and the turbo at a cost of £5000. The car is still under warranty but has only done a little under 20,000 miles. The warranty expires at the end of the year so I am thinking is it time to be rid of it. My opinion on Toyota reliability has taken a big dive especialy since I have been advised by a Toyota mechanic that it has been a common fault on vehicles after 15000 miles.For 6 months after buying the car I was doing 100+ miles a day mainly on the motorway but now I am retired and even if I take the 2 year extension on the warranty I am unlikely to have done another 20,000 miles before it expires. Having read various threads concerning the EGR valve I am now concerned that having reduced to a small urban mileage the problem may return even sooner.

they should of also carried out an ecu update to prevent this from happening again, most of the time its just the egr valve gets blocked up but the turbo to can get really sooted up to making the variable vains stick, as for the injectors they can some times leak which causes the engine to make a loud knocking noise when first started, i'm sure thou that now it's been sorted you won't get it second time round, most of the time this problem is caused while leaving the engine idling for long periods.
biggest problem we are seeing with these engines at the mowment thou is head gasket failure with warped heads or heavy oil consumption which req modified piston rings.