More on the EGR Bypass Valve....Modify or Leave alone

[Mike Noc]

Originally Posted by HarryM1BYT

As I understand it, it is a botch by the engine designers to reduce some of the NOx emissions. A small percentage of what normally goes straight out the exhaust, is drawn back into the engine to be reburnt.

To be honest there is a bit more to it than that. The reason exhaust gas is recirculated is that it is inert and won't burn, so it lowers the combustion temperature in the cylinders which reduces the NOx emissions.

Nitrogen in the air will react with oxygen to form NOx above 2500 degrees F, and recirculating a small amount of exhaust gas can keep the combustion temperatures below this threshold.

Mike

[Mike Noc]

Originally Posted by BigRuss

It does you know

Most code readers won't find it, T4 will tell you if there's an EGR fault, and a partially open EGR will throw the airflow figures out too (lower than normal).

There is a egr closure proceedure 10 secs at 1500 revs, return to idle then watch airflow figures IIRC.

Russ

To be fair to Harry Russ some cars monitor the EGR valve itself and throw up a MIL alarm when it fails, which ours don't.

My dad's Astra for example, as I found out the other day. Code reader said EGR fault and it took longer to find the EGR than change it!

Mike

[BigRuss]

I wasn't having a go at Harry just pointing out that it's another of those instances where code readers won't pick up some problems on our cars

It's all down to the wonderful way Rover designed the fault logging and diagnostic system, with a lot of stuff it's manufacturer specific codes that can only be read with compatible diagnostic equipment.

T4 doesn't display P codes generally it just tells you what the problem is, the only thing that will throw up an EGR fault on our cars is if it opens at the wrong time (not if it's stuck open or closed as there's no sensors to tell the EMS, just the switching in the ECM that controls the vacuum pump that operates the EGR)

I suppose we have to make allowances for it as the system was an early example of common rail diesel, with later generation common rail systems there's far more monitoring and control systems.

Russ

[Jules]

Originally Posted by BigRuss

I suppose we have to make allowances for it as the system was an early example of common rail diesel, with later generation common rail systems there's far more monitoring and control systems.

Russ

Hi Russ
How you doing?
Allowances for earlier systems. I like that!!!
Much less to go wrong too and more fixable than "modern Cars" wouldn't you say?

[peelaaa]

My car is still on original EGR. Cleaned it when at 80k miles approx and it was not that dirty. Soaked it in petrol and it was very clean. Not going to bother getting bypass as only need to do this every 4 years approx.

[Spanky]

Originally Posted by BigRuss

I suppose we have to make allowances for it as the system was an early example of common rail diesel, with later generation common rail systems there's far more monitoring and control systems.

Might be more monitoring, but they fail just as much, if not more. VX, Ford, Audi, BMW etc... all have failing EGR's on a very regular occurrence. Renaults for example have failing turbo's when they stick open !!

All the diesels I have owned I have blanked/bypassed the EGR valve!

[ChestersDad]

Wow!

It has taken me days to read this thread from top to bottom - absolutely a good (and lively) read too!


Just picking up on the later posts - I have a Land Rover Discovery 1 and I removed the EGR, blanked off the exhaust port and fitted a bypass and boy did it make a difference. That was eighteen months ago and not looked back since. Was gutless now pulls like a train again and tows really well.
Fitted a decat front exhaust maintaining the mid and rear as standard and fitted an uprated inter-cooler to make the most of the free-er flowing gases.

The most difficult thing then was the cleaning up of the inlet pipes and manifold. By crikey there was some marmite in there - about 3mm thick in most places. I have seen the entry port on the manifold down to about 70% of its original opening!

Some even works it way the wrong way into the inter-cooler thereby reducing its effectiveness and results in lost power through lower capacity air.

Brings me to mind the EGR clean just done on my pride and joy Rover 75 where after 51000 miles that same degree of goo was all over the EGR and that means it's all inside the inlet manifold, and down the inlet valve ports in the head, on the back of the valve stems all fundamentally bu****ing up the flows forever unless all taken apart and cleaned.

The likelihood of that getting done by all of us is pretty remote and I have to say (in my layman's terms) that I cannot can't understand the brains behind engine design coming up with such a rediculous solution to improve vehicle emissions that is fundamentally flawed and self defeating and then to persist in its implementation today 15 years later (Which is how old my Disco is) Rant over.

Has anyone gone on and done the full clean?

If not (like me) what is the likely result of have pieces of sludge (now possible disturbed by partial cleaning) going to do to the valve sealing surfaces and cylinder rings and bores if it dislodges by a much improved airflow?

Suit of armour on

[Roverron]

Although Rover can be excused the responsibility for the weaknesses in the egr system and for the Bosch maf's unreliability, these factors do make a mockery of the whole reason for having them.

What's the point if the system is so unreliable as to result in probably a majority of pre euro 4 common rail diesels having worse emissions than if they didn't have it?

An ex 'factory' member criticised the mafam part of the Synergy because he claimed that millons had been spent developing the engine so it could not be improved upon and should not be 'tinkered' with.
He missed the point.
If it the maf was reliable and long lasting and either worked or failed completely and if the egr valve never became clogged or seized, then he would have had a point...

Needless to say the latest disastrous anti pollution bodge - the dpf is even more trouble and vastly more expensive to replace.
Avoid at all costs buying a used vehicle with one, unless its one such as the Vaxhalls & Saab, and some Pugs and Citroens where the dpf can be switched off in the ecus and then removed or gutted.

Ron

[ChestersDad]

The experienced voice of caution there Ron - and I agree.

There are a few now that can now have their dpf turned off now but presumably one would have to mod elements within the exhaust to get full benefits and improved efficiency.

Back to EGR clean and / or bypass - I have cleaned mine now and will probably bypass but the rest of the restrictive crud in the induction system really concerns me.

Anyway assuming I pop on a Synergy with Mafam - Why is it 'trial and error' and 'guessed' selection settings to compensate for a gradually degrading MAF and not a resistance feedback for automatic adjustment.

I am keen to try out Synergy but for one, outside of normal maintenance, I couldn't really care how aged and effective the MAF was as long as it was working or not (if not then I'd replace it) So surely it's down to your box to assess its effectiveness and adjust accordingly amd on the fly - not for the operator (me) to guess and throw switches - or have I understood it wrongly?

[Roverron]

Originally Posted by ChestersDad

Anyway assuming I pop on a Synergy with Mafam - Why is it 'trial and error' and 'guessed' selection settings to compensate for a gradually degrading MAF and not a resistance feedback for automatic adjustment.

There are only 2 maf compensation ranges so the choice is one of 3 possibilities - non, low or medium so its not too time consuming to find the right one.
But you did hit the nail on the head when you wrote 'GRADUALLY DEGRADING MAF' which means its not possible to anticipate the condition of the maf and therefore give specific recommendations.
(the power setting you choose is entirely a matter for you - not everyone is power mad like me!)

It might seem possible to have designed the Synergy to have diagnostic & self calibrating ability whereby it measured the maf signal and then compared it with what it should be and then produced a correcting map. But in practice this would cause far more difficulties for owners than choosing one of the 3 options.
The main reason of course, is that the maf signal varies with load and rpm so you can imagine how difficult it would be for the average owner to be required to drive his vehicle in a precise manner whilst the Synergy monitored the maf to calculate its own map.
Then when other factors like clogged egr valve, egr bypass, intake mods etc have to be catered for, the whole idea becomes impracticable due to too many variables.
I did consider doubling the memory and fitting a 16 position switch to give 3 maf compensation ranges, but in the 6 years its been on sale, the Synergy as it stands is a well proven design that has stood the test of time.
I do tweak slightly it from time to time in response to feedback but neither the hardware nor the firmware have needed any major changes, which is gratifying.
Still, you'll only know whether its any good when you try one for yourself - it still comes with a 30day money back guarantee for what use it gets!
Ron