Discovery TD5 exhaust system replacement

[boaterboy]

Please could I have some help regarding the replacement of the exhaust system on my TD5 Discovery.

I see ones advertised made in stainless steel and others in mild steel. I assume those in stainless would last longer but is the additional cost justified? How long would each be expected to last? Is there any variation in supplier quality when considering each material?

Also, the one currently fitted to my vehicle has 3 boxes. I guess the first one (nearest the engine) is a catalytic converter? However, I've seen systems advertised which only have 2 boxes. Is it the catalytic converter which has been omitted? And, if so, is it legal to replace the 3 box system with a 2 box one?

Sorry for so many questions, but I'll be extremely grateful for some help in understanding the pluses & minuses of the options.

 

[Pawl12]

From my experience you're lucky if a typical aftermarket plain steel exhausts last 18 months. They're cheap for a reason & it's usually nasty thin steel & really poor paint with minimal rust resistance. They are often not even the same pipe diameter as the OE part - so make performance worse than standard (I gave up with various suppliers of aftermarket exhausts a few years ago when they kept supplying undersized parts & said all they could be certain of was that it should fit).
The Land Rover OE system on the TD5 was a mixture of mild steel & stainless & the mild steel was obviously very well protected (my original TD5 rear section is still on the car at 20 years old.
I wouldn't trust any OE / OEM or genuine exhaust system bought now to be to the same quality.

A good stainless system will last the life of the car.
However, it's possible to produce exhausts in low chrome "stainless" steel which will rust after a few years - meaning it's best to choose a supplier via recommendations than just whatever's cheap on ebay.
Well known branded exhausts will probably be made to a higher standard,using thicker material & better silencer content than "no name" ebay specials to avoid the negative impact of repeated failures / warranty returns.
Whether the cost of stainless is justifiable is upto you.
If you're aiming to keep the car more than 18 months, do you want the hassle of buying another replacement or would you prefer to fit something that will last your ownership of the car.
If you're a regularly immersing the car in water above the exhaust, the life of a mild steel exhaust will be significantly reduced.

Yours is probably a later model with a catalytic converter - earlier TD5s didn't have 1. The 2 box systems will be missing the cat and will considered suitable for early & late models (no-one in their right minds would add a performance sapping cat if not fitted originally). Because some models have the cat & some models don't, it's likely MOT testers don't check what's fitted - only if the emissions are OK. I think technically they should be retained if originally fitted.

[boaterboy]

First of all, Pawl12, I would like to apologise for my very late reply to your most considered answer to my question. I have been without a means of communication for a while.

My TD5 is a 52 plate which, I suppose, is at the middle of the Disco2 series production run. The exhaust system definitely has three boxes, from what you say the front one will be a cat. 

I'll try and make a few enquiries wrt the likelihood of the vehicle failing an MoT due to a switch from three to two boxes, ie omittng the cat. 

Do you know how significant the cat is in reducing emissions?

I will aim for two boxes, if legal, in order to reduce the cost and then go for one of the better material combinations that you outline.

Thank you so much for your most comprehensive reply, I really appreciated it.

[Pawl12]

As a quick response : the CAT would have been critical to the car meeting the EC emissions requirements for NEW vehicles applicable back in 2002 - Otherwise Land Rover would have not gone to the considerable Development cost & vehicle cost of adding one.

It's NOT critical to meeting MOT emissions standards applicable for the age of car - As many owners have removed the CAT & are happily passing the MOT emissions test comfortably (the MOT standards are much looser than for a new vehicle to allow for reasonable wear & tear on the engine).

Removing emissions related equipment from a car I believe is now technically illegal in the UK - but many do is it as said in my 1st post.

[boaterboy]

Very many thanks for your most informative follow-up, Pawl12.

Very much appreciated.

 

[Maverik]

I had a stainless exhaust fitted by Powerflow in Southampton last year to my 90.

Absolutely superb product and great service from them.

Mav