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V8 Cat to Run on Leaded


NickHodgson
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I am taking a V8 Auto 1997 Disco to Africa where it will run on leaded fuel. The current mileage is 86,000kms.

Do I need to remove the cats? I understand that I do not have to remove them but they will be damaged and will eventually clog up.

Is it possible to get the front exhaust section with no cats for this car and then what do I do with the Lambda Sensors?

Thanks

Nick

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I have run my cat Discovery 2 (it was built wrong) on leaded for several years with no problem, they have only just introduced unleaded here. Exhaust just smells funny that is all.

You can get a non cat exhaust system for Discovery 1 because my old Discovery (1996MY) was a non cat one, and this would be the best option and may give a slight power increase. The engine ECU can be told to use a "non cat tune" using a "tune select resistor" in the wiring harness (I'm assuming it is a standard 14CUX 3.9 V8), the resistor is built in to the harness under the drivers side dash (RHD) and there are non-cat low compression, non cat high compression and cat high compression ones I think, maybe others. Simple job to change it and the ECU will then ignore the oxygen sensors and run "open loop".

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I always understood that leaded fuel "plated" the HO2S with lead and so they didn't work and led to the vehicle running very rich?

I didn't notice any difference between closed and open loop economy in my Discovery but that is a Thor engine of course, different EFI system entirely.

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Not heard of that one, I know they don't like silicone sealant.

Thor engine would be relatively new and a smarter system so you probably wouldn't notice a great change as it has other sensors that help it stay in a happy place. Older systems, on older engines, you should see a bit of benefit but then this is Lucas we're talking about :rolleyes: the MS running closed-loop with a carp fuel map beats the Lucas system which in theory should have a far better developed map in it.

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It is my understanding that leaded fuel will 'poison' the cats, not physically damage them. The engine will run fine on it, BUT it is my understanding that when you return to england, you may have trouble passing an MOT emissions test because the cats won't work.

I know that Stephen (bogmonster) lives in the falklands where it is my understanding that the vehicles don't have to pass the same emission tests as uk vehicles do every year.

If it were me, I would definately find some replacement pipes (or have some made up) and temporarily remove the cats and refit on my return. (Assuming the pipes are a lot cheaper than replacement cats!)

Aside from the 'poisoning' issue I understood that the cats had potentially fragile honeycomb cores which can get damaged by impact etc. There are often a lot of stones bouncing around under a landy in Africa, and these, coupled with the appalling vibration etc from corrugated dirt roads may hasten their internal demise.

Regards,

Diff

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