Oil burner engines with EGR
Discussion
Having recently acquired a Pug 307 HDI 2.0 litre oil-burner Having come from a 106 Rallye I'm pretty disappointed with the performance so far(overtaking and general get up and go) and in my pursuit in deciding whether to do an upgrade or just selling the thing on, I have noticed that a number of forums have advocated disabling the Exhaust Gas Recirculation (EGR herein) pipe.
Unfortuately no one can adequately explain just what disabling the EGR system actually does to the engine, apart from the acknowledged increase in emissions. Obviously I can consider chipping to give a bit more mid-range ommph, but I'd like to take one thing at a time.
So rather than just doing something via hearsay can anyone give a good explaination of exactly why anyone would consider disabling the EGR system?
>> Edited by thepeoplespal on Sunday 28th May 01:09
Unfortuately no one can adequately explain just what disabling the EGR system actually does to the engine, apart from the acknowledged increase in emissions. Obviously I can consider chipping to give a bit more mid-range ommph, but I'd like to take one thing at a time.
So rather than just doing something via hearsay can anyone give a good explaination of exactly why anyone would consider disabling the EGR system?
>> Edited by thepeoplespal on Sunday 28th May 01:09
EGR's intentions are good, but look at what it does to the intake.
I've seen MANY of the XUD9 engines in the early 306 turbo diesels (1998 on) going bang, conrods snapping or the bottom ends giving way.
In alot of cases it's suggested the oil wasn't changed according to the earlier more stringent specifications, and was left in for longer periods. Peugeot made hardly any changes a this point to the engine, but specced longer intervals. A bit foolhardy? The only major change was EGR.
My brother recently took his engine apart to find a HUGE amount of intake manifold sooting up near the EGR outlet.
Oil in diesels does go black quickly, and unfortunately, this sooty material can end up back in the engine rather than down the exhaust pipe like usual. This seems to soot up the oil even more quickly, and some have said that this ends up clogging the oil ways, and without regular oil changes (they were made longer, the oil can manage it, but can it take the sooting up too?) they seems to be breaking
So, early EGR is bad, and I assume in good old Peugeot fashion the new HDi is equally suffocated and badly engineered, with exceptionally optimistic service intervals.
The EGR simply lets in some of the exhaust gasses to lean off the mix, this makes it more efficient when not under full load, like crusing etc, and it also recycles that proportion of exhaust nasties into the engine, which 2nd time round get burnt effectively, making it slightly cleaner.
However, though it reduces some nasties, it increases others, like particulates. There are particulate filters, but these are expensive and clog up the engine even more.
I'd say at least on the early cars, the EGR is a "good will" device, but in reality on a 50k engine that is sooted up, it's actually costing more efficiency than it's providing, meaning it's hurting economy by being crap basically.
I'd take it off simply because like many things on cars, it's only there to *try* do some good, but 99% of the time it's probably making the car less efficient, less responsive and sapping power.
Much like early cats. Took 10 mins to warm up, in which time they COST efficiency over an open system, hence more nasties into the environment. After which they start to work, but most journeys end. On motorways their efficiency impact can outweigh the inherent efficiency the extra power output can give if it were not there.
Really they are only efficient when warm in a city environment where speeds are low and the cycle of driving is sporadic and inefficient.
Then their manufacture, weight and complexity have impacts on the environment anyway, cats are quite a nasty thing to produce in relative terms next to a simple exhaust pipe.
New ones are better, but you can see why alot of these supposed "clean" systems actually hurt your car in the long run!
Dave
I've seen MANY of the XUD9 engines in the early 306 turbo diesels (1998 on) going bang, conrods snapping or the bottom ends giving way.
In alot of cases it's suggested the oil wasn't changed according to the earlier more stringent specifications, and was left in for longer periods. Peugeot made hardly any changes a this point to the engine, but specced longer intervals. A bit foolhardy? The only major change was EGR.
My brother recently took his engine apart to find a HUGE amount of intake manifold sooting up near the EGR outlet.
Oil in diesels does go black quickly, and unfortunately, this sooty material can end up back in the engine rather than down the exhaust pipe like usual. This seems to soot up the oil even more quickly, and some have said that this ends up clogging the oil ways, and without regular oil changes (they were made longer, the oil can manage it, but can it take the sooting up too?) they seems to be breaking
So, early EGR is bad, and I assume in good old Peugeot fashion the new HDi is equally suffocated and badly engineered, with exceptionally optimistic service intervals.
The EGR simply lets in some of the exhaust gasses to lean off the mix, this makes it more efficient when not under full load, like crusing etc, and it also recycles that proportion of exhaust nasties into the engine, which 2nd time round get burnt effectively, making it slightly cleaner.
However, though it reduces some nasties, it increases others, like particulates. There are particulate filters, but these are expensive and clog up the engine even more.
I'd say at least on the early cars, the EGR is a "good will" device, but in reality on a 50k engine that is sooted up, it's actually costing more efficiency than it's providing, meaning it's hurting economy by being crap basically.
I'd take it off simply because like many things on cars, it's only there to *try* do some good, but 99% of the time it's probably making the car less efficient, less responsive and sapping power.
Much like early cats. Took 10 mins to warm up, in which time they COST efficiency over an open system, hence more nasties into the environment. After which they start to work, but most journeys end. On motorways their efficiency impact can outweigh the inherent efficiency the extra power output can give if it were not there.
Really they are only efficient when warm in a city environment where speeds are low and the cycle of driving is sporadic and inefficient.
Then their manufacture, weight and complexity have impacts on the environment anyway, cats are quite a nasty thing to produce in relative terms next to a simple exhaust pipe.
New ones are better, but you can see why alot of these supposed "clean" systems actually hurt your car in the long run!
Dave
Interesting reply on EGR especially the sooting issue, looking at the service history of the car it looks like the previous owner ignored the service intervals (in a good way) the on board computer suggests by changing oil sooner rather than later than specified.
I know that the torque of my engine isn't what I was expecting from a diesel, I do mostly motorway journeys for which the HDI is okay, but around town it is very easy to get bogged down in too high a gear (although this is good for fuel consumption).
I know more about the benefits/problems of EGR and SCR (uses Adblue Urea to kill the particulates and Nox) on trucks than on cars. SCR appears to more fuel efficient for Euro4 than EGR, but has the added hassle of having to have a separate tank for the Urea.
>> Edited by thepeoplespal on Sunday 28th May 01:19
I know that the torque of my engine isn't what I was expecting from a diesel, I do mostly motorway journeys for which the HDI is okay, but around town it is very easy to get bogged down in too high a gear (although this is good for fuel consumption).
I know more about the benefits/problems of EGR and SCR (uses Adblue Urea to kill the particulates and Nox) on trucks than on cars. SCR appears to more fuel efficient for Euro4 than EGR, but has the added hassle of having to have a separate tank for the Urea.
>> Edited by thepeoplespal on Sunday 28th May 01:19
Yeah, the Hdi 90 is quite flat in standard form, but very frugal. It's main drawback is no intercooler, which limits tuning potential.
The old XUD9 could be mechanically tuned, and the intercooler meant 130bhp could be seen with an hour with a screwdriver or two
My brother has a Hdi90 306... it's got little power (90), but it actually develops it from 3000-4000rpm, so once in the power band it actually can be quite nippy, and the boost kicks in well before 2000rpm, so it's a handy car. I can imagine in town though the lack of response at idle>1500rpm is tiresome!
Try www.pug306.net and have a look in the diesel section (may have to sign up)... plenty of Hdi owners that have fiddled with their engines to get the best from them, so might be worth a read. Not the most technical bunch, but they have the cars and have tested and tried stuff, which is better than anything imho.
Dave
The old XUD9 could be mechanically tuned, and the intercooler meant 130bhp could be seen with an hour with a screwdriver or two
My brother has a Hdi90 306... it's got little power (90), but it actually develops it from 3000-4000rpm, so once in the power band it actually can be quite nippy, and the boost kicks in well before 2000rpm, so it's a handy car. I can imagine in town though the lack of response at idle>1500rpm is tiresome!
Try www.pug306.net and have a look in the diesel section (may have to sign up)... plenty of Hdi owners that have fiddled with their engines to get the best from them, so might be worth a read. Not the most technical bunch, but they have the cars and have tested and tried stuff, which is better than anything imho.
Dave
Mr W said:
The EGR simply lets in some of the exhaust gasses to lean off the mix, this makes it more efficient when not under full load, like crusing etc, and it also recycles that proportion of exhaust nasties into the engine, which 2nd time round get burnt effectively, making it slightly cleaner
This is not quite true. EGR actually richens the mixture by replacing fresh air with exhaust gas. It reduces efficiency because the effect of the gas is to retard the ignition. Burning it a second time is not the main way it benefits emissions - in fact what it does is reduce the combustion temperatures which reduces the formation of NOx.
Early cars can simply have the EGR vaccuum pipe 'blocked' with a screw or similar, but I suspect the HDI will have OBD which will identify a mismatch between requested MAF and delivered MAF and may then go into limp home.
Cheers,
James
The vacuum to drive the EGR has to come from the vacuum pump on the engine, which also supplies a vacuum to the brake servo and the VGT on the turbo if fitted. I know someone who removed the pipe from the EGR valve and put a screw into the end which sealed the pipe and was not going to come out. I guess there is a risk, though I guess in theory you could just run a single length of vacuum pipe from the pump to the servo (assuming wastegate turbo which I think the 90bhp engine has) and reduce the risk in that way. Make sure you use vacuum pipe though - other pipes may collapse under the vacuum.
jmcc500 said:
This is not quite true. EGR actually richens the mixture by replacing fresh air with exhaust gas. It reduces efficiency because the effect of the gas is to retard the ignition. Burning it a second time is not the main way it benefits emissions - in fact what it does is reduce the combustion temperatures which reduces the formation of NOx.
Just to be totally pedantic, the recirculated exhaust gas acts as an inert 'filler' in the combustion chamber. Having already burned, the gas is theoretically inert (though obviously there is some unburnt/partially burnt material in there). So on light load, with 20% EGR, your 2.4 engine is (broadly) operating like a 2.0 litre. The remaining 80% of fresh intake mixture can be much closer to the theoretical stoichiometric ratio of air/fuel, which should give you much better control of both CO and unburnt hydrocarbons in the exhaust emissions (compared to if you didn't use EGR, in which case you would be forced to run leaner or throttle the engine more). Beyond that, it starts to get very complicated as you convert theory into practice.
So it doesn't actually richen the mixture. It ballasts up the intake, and allows the fresh mixture to be closer to ideal. Which is probably what jmcc500 meant.
hil said:
Just to be totally pedantic, the recirculated exhaust gas acts as an inert 'filler' in the combustion chamber. Having already burned, the gas is theoretically inert (though obviously there is some unburnt/partially burnt material in there). So on light load, with 20% EGR, your 2.4 engine is (broadly) operating like a 2.0 litre. The remaining 80% of fresh intake mixture can be much closer to the theoretical stoichiometric ratio of air/fuel, which should give you much better control of both CO and unburnt hydrocarbons in the exhaust emissions (compared to if you didn't use EGR, in which case you would be forced to run leaner or throttle the engine more). Beyond that, it starts to get very complicated as you convert theory into practice.
So it doesn't actually richen the mixture. It ballasts up the intake, and allows the fresh mixture to be closer to ideal. Which is probably what jmcc500 meant.
Right I agree it is an inert filler.
However, there are some bits I disagree on. In a diesel engine your 'fresh intake mixture' is purely air (not really a mixture) so adding EGR reduces the air within the cylinder. When fuel is added your reduced fresh air leads to a lower AFR (ie charge is richer). This does not reduce HC or CO emissions - in fact as you increase EGR you will get to a point where you start to increase CO and HC. This is due to the local mixture in the cylinder being rich (imagine that the 'fresh' air is distributed throughout the cylinder, but the fuel sprays from the injectors are fairly concentrated as they come from the injector). Good in-cylinder mixing and good fuel atomisation enable high EGR rates without increasing CO, HC or particulates (soot).
Because diesel engines rely on compression ignition running lean is not an issue and will not (generally) lead to increased CO or HC - all the fuel 'droplets' ignite independently and the leaner the charge the more chance there is of each droplet burning completely.
The only times you throttle a Diesel engine are when you switch the engine off (to reduce shake) or if you are trying to achieve very low emissions in which case the throttle can be used to reduce the intake manifold pressure to draw more EGR through.
thepeoplespal said:
Having recently acquired a Pug 307 HDI 2.0 litre oil-burner I'm pretty disappointed with the performance so far(overtaking and general get up and go) and in my pursuit in deciding whether to do an upgrade or just selling the thing on, I have noticed that a number of forums have advocated disabling the Exhaust Gas Recirculation (EGR herein) pipe.
Unfortuately no one can adequately explain just what disabling the EGR system actually does to the engine, apart from the acknowledged increase in emissions. Obviously I can consider chipping to give a bit more mid-range ommph, but I'd like to take one thing at a time.
So rather than just doing something via hearsay can anyone give a good explaination of exactly why anyone would consider disabling the EGR system?
The key reason EGR was fitted was to reduce cold start emmisions, ie recuirculate exhaust gases to get the cat upto maximum operating conditions as quickly as possible, to reduce overall emmisions. Recirculating gasses will also reduce emmisions /consumption when cruising, though this could be mapped into the EM without EGR
Disconnecting / blocking EGR will not help, engine management will step in and either adjust fueling or go limp home (3500rpm redline)
HDi 90 can feel flat without a cooler but as you said serv history wasnt good, I would start with oil & filter, air filter and clear the soot with a good run, get it warm and thrash it hard.
Afraid I disagree. Catalyst warm up is not really an issue for Diesel's as the HC and CO emissions are very low. The driver for EGR is NOx emissions, and the catalyst is then required to clean up the consequent increase in HC and CO. Compared to a gasoline engine, HC and CO emissions from a diesel are tiny because you have so much excess air (until you start putting EGR in!).
For early engines with EGR whip the vacuum pipe off and block it up to stop the valve opening. For any common rail engines I would suggest not doing this to avoid problems with the OBD.
For early engines with EGR whip the vacuum pipe off and block it up to stop the valve opening. For any common rail engines I would suggest not doing this to avoid problems with the OBD.
Sorry, but I've realised I've been talking complete bollox - I really should spend more time soaking in the bath pondering things!
With the exception of EGR acting as inert ballast in the combustion chamber, and therefore (at part load) making your engine act like it was of smaller capacity, ignore everything I've said. It's clearly too long since I studied this. Apologies jmcc, and anyone who thought I was being helpful.
And i do agree that EGR is not about warm-up. As far as I remember, it's about part-load use.
With the exception of EGR acting as inert ballast in the combustion chamber, and therefore (at part load) making your engine act like it was of smaller capacity, ignore everything I've said. It's clearly too long since I studied this. Apologies jmcc, and anyone who thought I was being helpful.
And i do agree that EGR is not about warm-up. As far as I remember, it's about part-load use.
jmcc500 said:
Afraid I disagree. Catalyst warm up is not really an issue for Diesel's as the HC and CO emissions are very low. The driver for EGR is NOx emissions, and the catalyst is then required to clean up the consequent increase in HC and CO. Compared to a gasoline engine, HC and CO emissions from a diesel are tiny because you have so much excess air (until you start putting EGR in!).
For early engines with EGR whip the vacuum pipe off and block it up to stop the valve opening. For any common rail engines I would suggest not doing this to avoid problems with the OBD.
So they put on EGR to reduce NOx but in return that generates HC and CO which then requires a catalytic converter to reduce.
Seems like they are chasing around in circles and making the overall engine efficiency lower.
So if you disconnet the EGR you reduce the HC and CO, so a cat isn't really needed, but then you have more NOx overall? Is it a worrying multiple quantity or just a fraction higher?
I believe you can disconnet the EGR on the Hdi simply by unplugging it. Many people with the Hdi's have done this with no adverse effects except better response around idle >1500rpm!? Who knows. I just see it as another thing to go wrong and clog up on a Peugeot car, and the cats' need replacing every 5 years which is another excessive cost and waste of rare metals and production energy!
Dave
My new car (hdi 306) was being weird.
Was like a light ticking noise on very low throttle openings, just feathering it around 0 load, a bit like the noise a petrol makes on throttle when the exhaust manifold gasket is leaking a bit.
Anyway, was worried my new car had a duff turbo. Disconnected the EGR and wow, the noise was gone, and throttle response was much more instant. The turbo felt connected to the throttle position, rather than a seperate entity.
Main time I noticed the difference was mid-bend adjustments to power, with the turbo coming back in when I pressed the throttle rather than a fraction of a second after.
I guess EGR can't differentiate from town driving and just tootling around, and a spirited drive mid-corner adjustment or similar where a quick lift and re-apply of the throttle is more happily met with a more instant response.
Not sure if my EGR is a bit broken because it's audible, or if thats normal, or if it's being slow to respond, but either way even on a fully Peugeot serviced car it's just something else to go wrong! Will be removing my cat too and expect to find even more efficiency and response and low-end urge which will likely out-weigh the minimal savings to NOx that the whole system set out to reduce. Stupid emissions control making things more inefficient and dirty 5 years down the line when they have gunked up and failed no dobut!
Dave
Was like a light ticking noise on very low throttle openings, just feathering it around 0 load, a bit like the noise a petrol makes on throttle when the exhaust manifold gasket is leaking a bit.
Anyway, was worried my new car had a duff turbo. Disconnected the EGR and wow, the noise was gone, and throttle response was much more instant. The turbo felt connected to the throttle position, rather than a seperate entity.
Main time I noticed the difference was mid-bend adjustments to power, with the turbo coming back in when I pressed the throttle rather than a fraction of a second after.
I guess EGR can't differentiate from town driving and just tootling around, and a spirited drive mid-corner adjustment or similar where a quick lift and re-apply of the throttle is more happily met with a more instant response.
Not sure if my EGR is a bit broken because it's audible, or if thats normal, or if it's being slow to respond, but either way even on a fully Peugeot serviced car it's just something else to go wrong! Will be removing my cat too and expect to find even more efficiency and response and low-end urge which will likely out-weigh the minimal savings to NOx that the whole system set out to reduce. Stupid emissions control making things more inefficient and dirty 5 years down the line when they have gunked up and failed no dobut!
Dave
Just done some more reading.
I'm guessing EGR never adjusts fuelling, only tries to richen the mix as much as possible by adding inert filler to the intake gas.
How does this work with a petrol, because the air intake is limited by the throttle butterfly anyway? Do we simply displace some of that air with inert gas, effectively throttling back? Surely just using a smaller throttle opening would achieve the same as less air is let in and then a lower amount of fuel can be mixed?
Or is it simply better to run a richer mix when maximum response and power is not desireable, ie, at a cruise?
On a diesel I assume the same applies? A diesel runs very lean on a light throttle as they are a lean burn engine, only running richer as you pump more fuel in due to throttle.
So would a diesel EGR simply send inert filler in to effectively de-throttle the engine in a way a diesel can't normally do, and run closer to the stoichometric ratio and run "cooler" in the process reducing NOx.
If this is the case then disconnecting a diesel EGR simply does nothing to anything fuelling related, only to the intake mixture of the air.
Just my derv seemed to smoke a bit too, and has done for a while from the service records, had diesel conditioner at 30k and 60k services. I wonder if the EGR has been faulty (that ticking noise) and active where it shouldn't be (full throttle), and basically injecting filler into the pistons and leaving the mixture too rich and hence more smoke that usual?
Hmmmm...
Dave
I'm guessing EGR never adjusts fuelling, only tries to richen the mix as much as possible by adding inert filler to the intake gas.
How does this work with a petrol, because the air intake is limited by the throttle butterfly anyway? Do we simply displace some of that air with inert gas, effectively throttling back? Surely just using a smaller throttle opening would achieve the same as less air is let in and then a lower amount of fuel can be mixed?
Or is it simply better to run a richer mix when maximum response and power is not desireable, ie, at a cruise?
On a diesel I assume the same applies? A diesel runs very lean on a light throttle as they are a lean burn engine, only running richer as you pump more fuel in due to throttle.
So would a diesel EGR simply send inert filler in to effectively de-throttle the engine in a way a diesel can't normally do, and run closer to the stoichometric ratio and run "cooler" in the process reducing NOx.
If this is the case then disconnecting a diesel EGR simply does nothing to anything fuelling related, only to the intake mixture of the air.
Just my derv seemed to smoke a bit too, and has done for a while from the service records, had diesel conditioner at 30k and 60k services. I wonder if the EGR has been faulty (that ticking noise) and active where it shouldn't be (full throttle), and basically injecting filler into the pistons and leaving the mixture too rich and hence more smoke that usual?
Hmmmm...
Dave
Mr.Whippy, EGR at cruise will lean out the mixture not richen it (delution of the fuel charge), you are adding an inert gas not more fuel, there for you get a much smaller burn and that is why EGR is only introduced during cruise when power demands are low and there is no risk of stalling the engine. Lean mixtures bring up cylinder temps because there is not enough fuel being added to cool them down. By adding the inert gas to cool the cylinders it allows lean mixtures to be burned at cruise without temps getting above 2500F where nitrogen and the oxygen in the cylinders mix to form NOx (oxides of nitrogen).
NOx in the atmoshere when mixed with sunlight causes smog.
Edited to add that variable valve timing is doing away with the need for EGR because they can control the exhaust valves opening and closing. Closing the exhaust valve sooner than normal traps the inert gas in the cylinders.
>> Edited by Trooper2 on Sunday 14th May 01:40
NOx in the atmoshere when mixed with sunlight causes smog.
Edited to add that variable valve timing is doing away with the need for EGR because they can control the exhaust valves opening and closing. Closing the exhaust valve sooner than normal traps the inert gas in the cylinders.
>> Edited by Trooper2 on Sunday 14th May 01:40
Sorry, I thought the mixture would richen in theory.
Surely less O2 (displaced by inert exhaust gas) and the same amount of fuel = richer mixture?
Afterall, a diesel is lean burn anyway at low throttle openings, TONS of cool intercooled air, and very little fuel being added. The EGR adds an inert filler, not MORE O2, so how can it be leaner?
Thats what I gathered from all the posts above anyway.
Dave
Surely less O2 (displaced by inert exhaust gas) and the same amount of fuel = richer mixture?
Afterall, a diesel is lean burn anyway at low throttle openings, TONS of cool intercooled air, and very little fuel being added. The EGR adds an inert filler, not MORE O2, so how can it be leaner?
Thats what I gathered from all the posts above anyway.
Dave
By diluting the fuel charge with inert gas you are reducing the amount of flame and temperature that can be produced by combustion, I may very well be wrong but to me that indicates a very lean condition, oxygen is just a catalyst it can't burn on it's own.
Rich means more fuel and less oxygen, lean means more oxygen and less fuel, so the more I think about it the more that I'm inclined to say that yes it does falsely make for a rich mixture, I guess the important point I was trying to make was that the inert gas displaces some of the room available for oxygen and gives the fuel less catalyst to work with reducing cylinder temps. While it may in fact be a rich condition it is acting like a very lean condition.
Rich means more fuel and less oxygen, lean means more oxygen and less fuel, so the more I think about it the more that I'm inclined to say that yes it does falsely make for a rich mixture, I guess the important point I was trying to make was that the inert gas displaces some of the room available for oxygen and gives the fuel less catalyst to work with reducing cylinder temps. While it may in fact be a rich condition it is acting like a very lean condition.
Yeah, it's essentially being just as efficient (same fuel pumped in), but it's burning it with less excess oxygen (richer) to make for a richer combustion. I guess a rich burn is a cooler burn for whatever reason, hehe
Still, the fact remains that as long as EGR doesn't alter fuelling, which I'm guessing it doesn't, then all disconnecting the EGR plug from the EGR solenoid/vacuum valve controller, is that the valve simply won't open and the EGR just never activates.
Considering my ticking noise around light throttle on and off with slight movements, I guess that was the EGR opening and closing as it went from idle rpm (off) to light load (on), and then I assume off again as you demand full power.
Assuming it was that not functioning quickly enough for whatever reason, it may be the source of a bit more smoke than normal, ie: super brisk acceleration from a light throttle opening (ie, get rolling in 1st at low throttle, then 2nd gear and boot it), so EGR is open then you suddenly open the fuel pump fully and it runs over-rich until the EGR closes again...!?
Or maybe it's just because my service is due and the air filter could be due a change
Should EGR be audible though. Is it simply a vacuum actuated pushrod valve type mechanism that just lets exhaust gas into the intake? Guess it could be noisy...
Dave
>> Edited by Mr Whippy on Sunday 14th May 02:43
Still, the fact remains that as long as EGR doesn't alter fuelling, which I'm guessing it doesn't, then all disconnecting the EGR plug from the EGR solenoid/vacuum valve controller, is that the valve simply won't open and the EGR just never activates.
Considering my ticking noise around light throttle on and off with slight movements, I guess that was the EGR opening and closing as it went from idle rpm (off) to light load (on), and then I assume off again as you demand full power.
Assuming it was that not functioning quickly enough for whatever reason, it may be the source of a bit more smoke than normal, ie: super brisk acceleration from a light throttle opening (ie, get rolling in 1st at low throttle, then 2nd gear and boot it), so EGR is open then you suddenly open the fuel pump fully and it runs over-rich until the EGR closes again...!?
Or maybe it's just because my service is due and the air filter could be due a change
Should EGR be audible though. Is it simply a vacuum actuated pushrod valve type mechanism that just lets exhaust gas into the intake? Guess it could be noisy...
Dave
>> Edited by Mr Whippy on Sunday 14th May 02:43
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