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E51 The E51 Catalytic Converter Problem

I know that but just i am thinking why it is happening.. my car been recall in Japan but it is not saying for what ..
Is it happening wrong fuel?
Time and wear?
Faulty cats?
 
Cemmy074 said:
I know that but just i am thinking why it is happening.. my car been recall in Japan but it is not saying for what ..
Is it happening wrong fuel?
Time and wear?
Faulty cats?
Click to expand...

It's a design fault of quad cat system, simple as that really. It's not Nissan specific, or Elgrand specific, it's a design fault. All cats will break down over time, normally there isn't a second cat to block up with the debris.
 
The usual failure of cats is over fuelling and mixture problems and applies to all cars. I think it appears to be more commonly age related due to the likelihood of problems on older cars with fuel ratio issues, bad spark, poor servicing etc etc and that minor issues aren't necessarily spotted and can go on for long periods. It is possible to damage cats on newer engines and this premature failure is what Nissan addressed although I do not know whether they flashed the ECU to adjust fuel management or did something else as well as inspecting and replacing the front cats where necessary.

Theres some discussion about cat failure from here onwards:
https://forum.elgrandoc.uk/threads/lpg-horror-stories-experience.12213/page-3#post-139981
Also search google for something like : catalytic converter failure

As Chris says failure is not a problem specific to the Elgrand, what makes it worse for us is that the broken up core gets stuck at the secondary cats causing blockage, de-coring the secondary cats does not fix the problem it just makes front failure less likely to be terminal.
 
Just to re-iterate @Chris T's point...

Simplify the problem. On a car with an inline 4 cylinder engine... there is one exhaust manifold, one downpipe, one cat, one exhaust system.

Cats are made up of materials that will, overtime, breakdown and disintegrate. Just like everything else in life, they are not made to last forever, they will deteriorate at some point. In this system though... the debris will just flow out the back, and you'll only ever find out that something is wrong when you fail an emissions test. At this point, in a simple system, you just replace the front cat.

Now move on to a slightly more complicated system... a V6 engine with 2 manifolds, 2 downpipes, 2 cats (one for each downpipe) and then merging into 1 exhaust system (the same way the E50 is set up). Again... same as above... over time they will break down and flow out the back and no harm done... if you fail emissions, it's because the cat has failed and needs replacing.

The problem with the quad cat set up is that the front cats (that do 99% of the work) will have the same life expectancy of the cats in the above 2 examples. The problem being that the rear cats (which ONLY work for cold start emissions, so you won't find a quad cat set up on an EU/UK car) provide a barrier, the debris gets caught, and the blockage occurs. The other issue with the quad cat set up is that the first cats are located CLOSER to the manifold, meaning they get hotter than cats in single/dual cat systems as they are placed further back.

The problem, I believe, is exacerbated in the UK by using inferior quality fuel. From what I can tell... although the engine will run perfectly well on 95 ron unleaded fuel... you will cause premature detonation of the front cats as the engine will run hotter, and therefore exhaust gasses are hotter, which means MORE wear on the cats. If you use 99 ron (Tesco Momentum for example), you will slow the rate at which the front cats deteriorate, but it won't STOP it.

If you convert to LPG your exhaust gasses are considerably hotter, and therefore will break the front cats down even quicker than using 95 ron unleaded. But as LPG burns cleaner, you can just remove ALL the cats and test on LPG rather than Petrol and it will still meet emissions testing requirements.

The BEST and ONLY solution to this problem is to remove the rear cats so that any debris does not create a blockage.
 
It happens to every one at some point, yes in Japan too, they had a recall to try & solve it by changing the engine map so that no unburnt fuel entered the front CAT's but it hasn't solved the problem! The fronts simply disintegrate over time, no fixed mileage or age limit to it, it's all in the lap of the gods. Even if you renewed the front CAT's it wouldn't solve the problem they would simply go again.
So the only safe cure is to decore or remove the rears or replace the fronts with an aftermarket sports CAT system (well expensive).
There is no way around it!!
 
Standard catalysts are made from a coated honeycomb ceramic substrate and are very brittle. Simply prone to disintegrate. Best to fit metal sport cats but stick with no less than 400cpi rated ones so it doesn't chuck an error for catalyst inefficiency.

I had a huge custom metal, dual biscuit, euro 4, 200 cpi catalyst made for my Focus, still good years later with lots of pop n bang going on, and it's been run with over 300hp through it since it was fitted.
Cat01.jpg


Cat02.jpg


CustomCatWeb.jpg


DumpCatWeb.jpg
 
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Exactly right @Robbo . Well illustrated! What a biggun'!! :p

I've often pondered a fix all and forget solution but my! it costs!

My plan was to get hold of a couple of BMW E46 sports cats (constructed as you describe) and fit them into 'Ellie's' but for now have opted for the Forum recommended rear cat removal for instant piece of mind even though not a 100% fix but currently the best practical solution and toppo for those that have brought it to us 'Newbies' attention. Appreciated. :)

Your method I guess (should you wish to keep 4 cats would be, though expensive, of removing the problem for good as all cats would be stainless coated filament and not degrade but for the re-coat being necessary a long way down the road when emissions begin to rise.

Given that most imported 'Ellies' are in good nick underneath and their exhausts, like ours, are very good there can be little justification in changing for a whole stainless system and sports cats (2 or 4) 2 for me)) until the original starts to rot in our climate. :rolleyes:

So what do you have on your Ellie as apposed to your Super Ford?

Nice post! :cool:
 
The Ellie is my wife's car so not doing anything amazing to her but I would like to fit good shocks and do some exhaust work for reliability and a little growl. I decored the rear cats but would like a stainless system with metal cats (just 2) but keep the Rider rear muffler. I reckon it could sound pretty good without being loud and droney. The big middle muffler does most of the silencing so replacing just that would make a huge difference to note.
The Rider S looks pretty tough as is. Doesn't need much doing to it 😋
 
Not sure where to get a 'Good' full system in S/S for an Ellie? :confused:
I heard that the 'modern day' coated sports cats were not so durable as the older ones as in the E46 M3.
Can't recall who I who made those back then? :(:)
 
Forrest said:
Not sure where to get a 'Good' full system in S/S for an Ellie? :confused:
I heard that the 'modern day' coated sports cats were not so durable as the older ones as in the E46 M3.
Can't recall who I who made those back then? :(:)
Click to expand...
My Ellie is converted to lpg and I have had the rear cats decord....if now my front ones break down does this mean I can leave them alone and not bother with new ones as lpg runs much cleaner and would pass any emmision test.....so in theory win win situation if converted to lpg better mileage if rear cats decord no problem with engine failure and if front cats disintegrate should be better emmision flow and pass mot running on lpg.
 
Yep, you can remove cats all together if you're running lpg...
 
Hi, I am new here, just started to investigate the Elgrand. The question I have is why do the rear cats need to be removed. The point I am trying to make is that the front cats deteriorate early because of higher temperatures owing to fuel used. Why not remove the front cats, leaving the rear ones to do the job. Plus being further away will be cooler therefore last longer.
Probably a dumb idea as I do not fully understand.
 
Do a search , and read the information . The fronts are extremely hard to get to first off . Rear dead easy to remove . But please do make sure you get them removed ASAP.😎👍
 
The rear ones are secondary and won't do the job because they are too far from the engine.
 
@Deene if you read through all the information, this has been covered extensively.
 
Deene. Maybe with the front of the exhaust being the hottest part of the system it would also be the cleanest. Towards the rear of the system you would pick up any rust and build up from inside the entire system that would block the cats. This is only a guess and I would not risk it. As I have said in other forums the dealer I purchased it off in Western Australia removes them before you drive away. This protects the dealer also no chance of having to replace a engine while in warranty. If you are going to buy one from a dealer. Tell them cat removal is part of the deal
 
malcolmyz85 said:
He will need his 10 count to read all of forum
Click to expand...

All of the important info regarding the cats issue is in this thread which is available to everyone (even non-members). So he doesn't need 10 posts to read about it ;)
 
Cemmy074 said:
I know that but just i am thinking why it is happening.. my car been recall in Japan but it is not saying for what ..
Is it happening wrong fuel?
Time and wear?
Faulty cats?
Click to expand...

Why is it happening you ask and what are the recalls for? - Some of the recalls were for over-fueling, i.e. too rich a mixture resulting in unburnt fuel in the exhaust gases. This leads to the fuel igniting in the 1st cats which leads to premature failure of the cat material etc etc.
 
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