E51 The E51 Catalytic Converter Problem

[Lezboss]

Just fitted re decats

 

[Lezboss]

Just fitted re decats

Bought from eBay fitted great now just need to address my driver's side arm rest

 

[Snoo]

I have just bough a 2003 e51 that is converted to LPG. My mechanical knowledge is not great so forgive a possible stupid question. Does boring LPG potentially block rear CAT?

Thanks,
Matt

The cat risk is there regardless of fuel type. Get your rears decored. If you wish you can also see about getting the fronts decored. Cats are not a requirement for LPG systems under the UK MOT.

 

[Lpgc]

I have just bough a 2003 e51 that is converted to LPG. My mechanical knowledge is not great so forgive a possible stupid question. Does boring LPG potentially block rear CAT?

Thanks,
Matt

Been covered many times on numerous threads... but it'd probably take me more time to find those threads than just write another reply. Would appreciate if someone else posts a link to such thread though ;-)

Elgrand front cats fail regardless of running on petrol or LPG, even when there are no other engine (or fuel mixture) problems.

The quickest ways to make cats fail on most vehicles is to 1. Add some contaminant to them (an engine that burns oil will contaminate them, as will using petrol that contains lead, as will accidentally putting diesel in the petrol tank). Or 2 Run the engine at higher loads (when the engine produces more exhaust gas) with incorrect (too rich) fuel mixture. But as said above, Elgrand front cats seem to fail all too often anyway when none of these other problems have occurred.

A properly installed and setup LPG system will provide correct mixture during most engine operating conditions and provide a mixture that is slightly rich at high engine loads (but not as rich as the mixture gets when running on petrol at high loads)... Less rich mixture on LPG plus LPG being a cleaner and fuller burning fuel anyway actually means the cats should have less work to do when running on LPG compared to running on petrol, so as long as mixture is correct on LPG cats would normally last longer running on LPG than on petrol - But this is Elgrands we're talking about and (say again) Elgrand front cats fail anyway.

But if the LPG installer hasn't actually properly set mixture for higher engine loads and mixture is too rich for higher engine loads (high load open loop conditions) then yes the too rich mixture could cause a cat failure. On a 3.5 Elgrand (which has narrow band O2 sensors so switches to 'open loop fuelling' at higher engine loads) the only way an LPG installer can properly set high load mixture is to actually drive the car with foot to the floor going up through the gears whilst monitoring O2 readings... This doesn't mean driving at the vehicle's top speed, just maximum engine load (which can be done at lower than top speed whilst accelerating), best done going uphill! There's a bit more to it than this (without getting too techy) a good installer can compare the calibration 'map slope' across the rest of the engine's load range and anticipate what the map shape should be at the higher engine load ranges, will also take into account changing fuelling compensation for gas temperature (gas temp will fall with extended periods of high throttle use but the gas temp readings lag behind the actual gas temp changes).

An Elgrand submitted for MOT test in the UK running on LPG should pass even with no cats fitted - At an early point in the MOT test flow chart a question asks which fuel the vehicle is running on, if it is running on LPG then the 'no cat emissions test' (which is similar to an emissions test for a much earlier carburettor vehicle model) should be done and this test doesn't even ask if cats are in place. Also, the standard of emissions for this 'no cat test' is less stringent (you can pass with higher emissions than would pass in a normal emissions test), also emissions when running on LPG should be lower than emissions when running on petrol - double whammy of less stringent emissions test whilst at the same time more likely to have lower emissions anyway. However (and I always say this)... there is potential for MOT testers (who don't follow the flowchart properly) to fail the car if they think 'tampering / removal of emissions equipment' (cats in this case) takes precedent (which it shouldn't). If they got this wrong you could appeal (and should win an appeal) but it'd be a hassle easily prevented by just making it seem that at least one cat in each side of the exhaust was still fitted - easily done by decoring cats rather than removing.

Simon

 

[Bushkes]

Thanks for this Simon you clearly know your stuff I can barely spell stuff so will speak to me mechanic freind. Its due for MOT soon and by chance met another Elgrand owner in Hereford who put me onto a good garage.

 

[DetSam]

I had my front cats removed at a cost of $330. Service manager asked me why I wanted them removed, so I guess it's not a common thing in Australia. I felt for such a piddling amount of money it was insurance against having to potentially replace the engine.

Hi G-train, may I ask where you had the cats done? Was it a specialist? Went to Exhaust specialist (Perth, WA) and was refused when I enquired about removing the rear cats.

 

[G-train]

Had them done at Sinergy Motorsports in Adelaide. Sinergy are JDM importers. They removed the front cats only. I don't think legally they were supposed to do it because on the bill it said 'inspect catalytic converters', but the fronts are definitely gone, replaced with straight pipes.

 

[DetSam]

Thank you, G-train. Will continue to look for a reasonable workshop.

 

[Ja2432]

There's a poll going on at the moment on the Facebook page that is actually being voted on. To get some perspective on how many have been affected. It was 60 for no and 2 for yes last time I looked.

 

[Ja2432]

There's a poll going on at the moment on the Facebook page that is actually being voted on. To get some perspective on how many have been affected. It was 60 for no and 2 for yes last time I looked.

Now 73 to 2. Moving fast. Should put some perspective on it if everyone gets involved

 

[Claptrap]

Now 73 to 2. Moving fast. Should put some perspective on it if everyone gets involved

can you post a link please?

 

[Serra]

104 to 2 at the moment

 

[Ja2432]

can you post a link please?

I'd love to help but I'm not Internet savvy. It's the Nissan Elgrand group on Facebook.

 

[Ja2432]

I'd love to help but I'm not Internet savvy. It's the Nissan Elgrand group on Facebook.

The Nissan Elgrand Club | Has Your Nissan elgrand | Facebook

Has Your Nissan Elgrand suffered a complete catalytic Failure resulting in a damaged engine 6000 members it will benefit us al If we can put some perspective on this once and for all Yes or no

www.facebook.com

 

[Ja2432]

The Nissan Elgrand Club | Has Your Nissan elgrand | Facebook

Has Your Nissan Elgrand suffered a complete catalytic Failure resulting in a damaged engine 6000 members it will benefit us al If we can put some perspective on this once and for all Yes or no

www.facebook.com

Is that it? I think I've sussed it

 

[Winchester]

I’ve voted NO on the survey, however I’ve imported maybe 30-40 Elgrands with all of them having clean and clear front and rear cats prior to de-catting them. I’ve also de-cored the rears on 100’s of customer cars now , so one NO vote doesn’t really match up to my experience.

 

[Just Japanese]

I’ve voted NO on the survey, however I’ve imported maybe 30-40 Elgrands with all of them having clean and clear front and rear cats prior to de-catting them. I’ve also de-cored the rears on 100’s of customer cars now , so one NO vote doesn’t really match up to my experience.

There seems to be a lot of scaremongering about the fronts on the Facebook pages lately.
I’m sticking with doing the rears on our imports.

 

[LeStempy]

Indeed, someone has been eating sour grapes.

 

[Just Japanese]

Indeed, someone has been eating sour grapes.

I personally believe using correct fuel, regular servicing with decent oil and having plugs and PCV changed will help prolong the life of the fronts.
I’m not a mechanic and don’t claim to be, but I have experience and I’m happy to continue with doing rears, I feel the MOT emissions issue each year outweighs the worry of the fronts breaking up on a properly cared for E51.
We’ve only had one fail, this was a series 1, we don’t know the cause but that vehicle also had a faulty PCV, and as simon @Lpgc said above, using / burning oil can cause cats to break down on any vehicle.
There are going to be a lot of worried E51 owners on the Facebook pages after seeing some recent posts, and I agree it will probably help SOME people but I don’t think it’s enough to start causing extra worry.
I dread to think what the people writing the negative posts would do if they owned a bmw with the timing chain issues .

 

[LeStempy]

Sadly too many folk live their lives via Facebook and put way too much credence into what is posted on there by vindictive trolls.