Exhaust question

Hi everyone,
A mechanic friend was looking at my defender 90 today and he said that it still has a "catalytic converter","exhaust middle box"and "egr" on it and that i should take them off and put a straight pipe on instead.
If i do this,what will the results be???i.e better or worse mpg,noise level(im guessing it will be noisier but will it fail an MOT by being too noisy).Also,surely LR put the "egr" on for a reason.Will it not bugger up the engine somehow by taking it off?
On a different note.I have 3 Michelin 7.50 R16C XPC 4X4 tyres on my wheels and would like to get all 5 wheels on XPC tyres.Does anyone know of anywhere that still sells them?Thanks.

EGR: this is fitted so landrover passes the exhaust particle test. the MOT measures exhaust gas emmisions not particles and so will pass ok, however a few grumpy testers will look for its removal and fail it.

CAT: the cat reduces harmfull gas emmisions and this will show up on an MOT test and fail. you may be lucky with a pro-landrover tester. Some people refit for the MOT and then remove after.

Middle Box: Try it

XPC: http://lmgtfy.com/?q=michelin+xpc

colin132 said:

Hi everyone,
A mechanic friend was looking at my defender 90 today and he said that it still has a "catalytic converter","exhaust middle box"and "egr" on it and that i should take them off and put a straight pipe on instead.
If i do this,what will the results be???i.e better or worse mpg,noise level(im guessing it will be noisier but will it fail an MOT by being too noisy).Also,surely LR put the "egr" on for a reason.Will it not bugger up the engine somehow by taking it off?
On a different note.I have 3 Michelin 7.50 R16C XPC 4X4 tyres on my wheels and would like to get all 5 wheels on XPC tyres.Does anyone know of anywhere that still sells them?Thanks.

Click to expand...

EGR is there to reduce peak combustion temps and reduce Nox emissions. These are not tested for at MoT time and it's only there to attain type approval.

Removing it is fine.

As for the CAT, there is no legal requirement to have it fitted. But your vehicle will need to pass the MoT emissions test, without one it is highly unlikely to pass. You'd also fail any road side emissions tests should you be pulled over.

Personally think it's just a faff to remove it and re-fit for MoT times. Just leave it and look at other areas to tune, or if you must fit a freer flowing cat on instead.

Removing a CAT will increase noise unless you fit a different silencer. Although it might not be a huge amount (200Tdi's didn't have CATS).

MPG is likely to be unaffected or maybe slightly better.

Twisted Thread Starter said:

EGR: this is fitted so landrover passes the exhaust particle test. the MOT measures exhaust gas emmisions not particles and so will pass ok, however a few grumpy testers will look for its removal and fail it.

Click to expand...

Do you know on what they fail it on exactly?

Manufacturers only fitted the EGR valve as part of a series of updates so that engines would meet Euro I regulations that the EU had just forced on us all.

The EGR valve WILL start to fail as it clogs up with soot, it then jams open, and you now have a constant stream of exhaust gas going into the inlet all the time. The manifold will also soot and gum up over the years, (even when the EGR is working properly) and restricts the airways, I have seen a 300tdi inlet manifold with so much soot build-up it must have been down to about 2/3 its original size at the point where the hose clips onto it.

Threw it in a bath of petrol and kero or something and let it all soak out, cleaned it up, let it dry and without doing a single other thing I put it back on and immediately the Discovery had a performance boost.

The CAT, I don't have CAT's on two 300tdi's and never had MOT issues. The chances are the CAT failed a long time ago, unburnt diesel through the exhaust will kill the CAT, so a cold start with an iffy battery one winter, or just a super cold morning and it was defunct. Interestingly enough the E900 additive in veg oil, will, in large enough quantities, i.e. if you ran your vehicle on it for many years it would eventually damage the catalyst.

About 11 years ago we had a pretty cold winter and the Discovery wouldn't start after being left for about a week over Christmas (battery was a bit poorly too) and it was kicking out a fair bit of white smoke. From that day forward the CAT was dead, so from 4 years old it was not doing much.

Luckily the diesel emission test is particulate density, not what comes out, so really a hard rev and no signs of heavy smoke means it will probably pass, also, during this test the EGR if installed and working properly would be closed anyway (same as if plated).

Middle box, I don't think it makes much of a difference, it's a through pipe with perforations into a sound deadening chamber on the one I recently removed/replaced on a Discovery. In theory it will create turbulance in the exhaust but I think when the engine is running at a constant rev band say sitting on the motorway at about 2500rpm a resonance will set up in the mid box that, once set up, will not hinder the exhausts ability to pass through the silencer.

300bhp/ton said:

Do you know on what they fail it on exactly?

Click to expand...

300bhp/ton do you mind changing your signature images, it lengthens the thread up considerably with loads of images.

discomania said:

300bhp/ton do you mind changing your signature images, it lengthens the thread up considerably with loads of images.

Click to expand...

That better?

forgive the bone question, but the EGR, is that on 300TDi and later, because i've heard alot about it, only can't find it on my 200TDi!

300bhp/ton said:

That better?

Click to expand...

lol - Cheers!

bouncingllama said:

forgive the bone question, but the EGR, is that on 300TDi and later, because i've heard alot about it, only can't find it on my 200TDi!

Click to expand...

I am not sure if none of them had it, but plenty of 200's I've seen don't even have the mounting/passage drilled on the exhaust manifold.

Look at the exahust manifold about central, you will see an oval bit in the casting i expect, thats there it would go.

bouncingllama said:

forgive the bone question, but the EGR, is that on 300TDi and later, because i've heard alot about it, only can't find it on my 200TDi!

Click to expand...

I don't think any UK spec 200's had EGR.

300's might vary, I know not all had cats to begin with.

Right just read something while looking for some information on synthetic diesel.

This is just based on some web article so I can not substantiate this information, but I think newer diesels now get some sort of emission check similar to petrol’s, whereas our old 30tdi's can be decatted without any issues because it makes not a blind bit of difference to the smoke test, just the makeup of the gasses in the smoke.

I have just called someone who can confirm MOT diesel tests which would clear up the can or can't question and put a manufacture date on the vehicles which will get the more advanced test.

But it would make sense if on the older vehicles they didn't check the gasses which would explain why I have never had any issues with 1990's land rovers with no CAT, yet you see guys tuning their relatively new diesel cars failing MOT for lack of CAT's.

OK you can decat the 300tdi without any MOT issues.

Thanks people.
After reading what you've said then i think i'll just leave the exhaust as it is.I don't know enough yet to start tinkering.
My mechanic friend was showing me his new suspension on his Defender today,i think he said it was "dislocating" or something or other and he talked for half an hour about LR's and all the thing's you can do to them.About 15 minutes in,i realised just how little i know and i haven't got a clue what most of the acronym's mean....I've got a lot to learn...Thanks for the info everyone,i'm going to be busy reading for a while.

300bhp/ton said:

As for the CAT, there is no legal requirement to have it fitted. But your vehicle will need to pass the MoT emissions test, without one it is highly unlikely to pass. You'd also fail any road side emissions tests should you be pulled over.

Personally think it's just a faff to remove it and re-fit for MoT times. Just leave it and look at other areas to tune, or if you must fit a freer flowing cat on instead.

Click to expand...

Diesels are not emmissions tested in the UK so would not fail an MOT if the CAT is removed. There is only a smoke test as far as I am aware.

I removed the CAT on my 300 disco and never had an MOT problem with it. I also had a 4.6 P38 with the cats removed and that passed while running on LPG

bobbler said:

Diesels are not emmissions tested in the UK so would not fail an MOT if the CAT is removed. There is only a smoke test as far as I am aware.

I removed the CAT on my 300 disco and never had an MOT problem with it. I also had a 4.6 P38 with the cats removed and that passed while running on LPG

Click to expand...

Think you might be right.

how is this smoke test actually performed? i hear of people having trouble with tweaked pumps..?

Karlos28 said:

how is this smoke test actually performed? i hear of people having trouble with tweaked pumps..?

Click to expand...

I think anything pre 79 is visual. Post 79 uses an analyser.

ahh right, so they do measure the gas in there then? or does it just measure 'particles' or smoke..

Karlos28 said:

ahh right, so they do measure the gas in there then? or does it just measure 'particles' or smoke..

Click to expand...

Have a look here: MOT Testers Manual