How ToLand Rover Discovery

How to fit a de-cat downpipe on a Land Rover Discovery Tdi

Old & new. Old downpipe pipe clearly shows flexi-pipe and catalytic convertorSo far in the quest for an engine which performs better and gives better mpg, I have changed the fuel filter and removed the EGR system.

So to compliment the EGR removal, I bought an exhaust downpipe from a Defender, which has no catalytic converter (cat).

Diesels don't need a cat, and the on a Discovery they clog up over time and restrict the flow of exhaust gases in the pipe, which in turn restricts power & torque.

Another Ebay search brought up a Defender downpipe with no cat for £20. Compare this against £60 for a Discovery version with flexi-pipe, it was a no brainer, I opted for the Defender pipe! (see pic above for the differences)

The only downside with choosing the Defender pipe is that it contains no flexi-pipe. This means you will get more vibration transmitted through the bodyshell of the vehicle, so cab noise will increase slightly. I am prepared to live with this because of the performance benefits it brings.

It's only 5 bolts to remove the downpipe from a Land Rover Discovery, and this is how you do it.

Removing the downpipe

Before you get started, here's what you will need for the job:

  • Socket set with extension bars
  • Car jack
  • Large/thick piece of wood or breeze block
  • WD40

Here's the pipe I bought:

View on eBay

1: Place a chock/brick behind a couple of the wheels to make sure the car won't move.

2: Place the car jack under the main chassis, just behind the nearside front wheel. Jack up the chassis as far as it will go. You may need to place the jack on a large piece of wood or brick to allow it to reach the chassis.

You need to do this to give room to remove the pipe. If you don't do this, you will find you need to remove the middle crossmember to get the downpipe out, and the new one in! So save yourself time and jack the body up!

View of downpipe when viewed from inside the engine bay (EGR has been removed)3: Have a look at the photo on the right, this is the top of the downpipe where it attaches to the exhaust manifold viewed from in the engine bay. (EGR assembly has been removed already).

There is 3 nuts (circled) that you need to undo from underneath the car. You will need a 15mm socket on an extension bar. Use some WD40 as well, to help the nut's come off cleanly.

Downpipe exhaust clamp4: Now turn to the other end of the downpipe, which is secured using a clamp (see pic). Spray some WD40 onto the nuts and undo using a a 13mm socket.

5: The exhaust will now be loose, but before you can remove the down pipe you will need to unclip the rubber exhaust mount which is near the cat.

6: Lower the exhaust and turn it through 90 degrees, with a bit of wiggling about, you will be able to remove it under the front valance of the car.

Fitting the new de-cat pipe

View of exhaust manifold from below with downpipe removedNow you have the downpipe removed, this is what it will look like when viewed from below.

Fitting the new de-cat downpipe is the reverse of removal.

7: Bring the new de-cat pipe in the same way as you took the old one off (under the front of the car). You will need to wiggle it a bit to get it into position, but it will fit!

8: Fit the new exhaust gasket that comes with pipe, and attach the the 3 manifold bolts so it holds the exhaust in position, but don't do them up tight yet.

9: At the other end of the downpipe, tighten the nuts on the clamp.

10: Now tighten the nuts on the manifold.

11: Lower and remove the jack from under the car.

12: Start the engine and check for leaks around the manifold gasket and exhaust clamp.

When fitted, the new de-cat exhaust should look like this:

New de-cat downpipe - viewed from the front, looking back New de-cat downpipe - viewed from the rear, looking forward


When I removed the EGR, I noticed more torque/power at the bottom end. Now with the new de-cat exhaust fitted, you notice this even more.

The engine picks up faster, as the turbo is now being able to spin up more freely. In fact there is a notable increase in turbo whistle as it spins faster. The whole engine just feel's freer, more sprightly, and more powerful.

There is a small noise increase in the car, due to the downpipe not having the flexi-pipe, but nothing that I can't live with.

It's too early to tell on how it effects the mpg, (it should help reduce fuel consumption) but already I have found it's a mod well worth doing!

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