Thread: 300tdi discovery exhaust modifications

Hi Barjop,

The 300Tdi has a fairly generously-sized system as standard, especially compared to many Jap models. If it's the main muffler under the passenger seat that's holed, I'd just replace it with a length of straight pipe. As long as the small muffler behind the rear wheel is OK, it shouldn't be too loud.

I did this about a year ago, to see what effect it would have: slight but noticeable improvement in pick-up plus a quite pleasant but not anti-social 'note'.

I think the original pipe is 60mm. The local muffer shop inserted a section of 2 1/2" (63 mm) pipe, re-using the original muffler front flange.

As far as so-called "turbo lag" is concerned, that's easily fixed with a bit of judicious 'tuning' of the boost compensator.

Mines got a 3" straight though - Tdi Auto in a Rangie

Spools up better, but would put a muffler on if its your daily driver or the misses shopping machine

LRH

I've posted on this a number of times, but the search function doesn't appear to be working.

As Ian said, the 300Tdi exhaust diameter is 60mm from the dump pipe on. It is also mandrel bent. The centre muffler, at least on a Defender is a straight through perforated centre tube design. This is all good yet can be improved.

I went to a 3" system on my crew cab and these are the results. Note that I opened the throat of the dump pipe/manifold up to 2,1/2" (63.5mm) to match the flange, and increased the pipe from 2.5"-3" starting about 15mm below the flange at an angle of 15* to avoid turbulance in the transition.

Initial spool up better.
Maximum EGT reduced by over 20*C
Rev range increased significantly. eg. 80km/h was maximum speed in 3rd gear (33" tyres), can now rev out to 95-100km/h easily.
Without a muffler or resonator, unbearably noisy.

This was prior to doing pump mods.
The results aren't startling compared to, say, a 4.2 turbo Patrol which are really strangled from the factory, but it is noticeable, particularly the ability to rev out better through the gears. The lowering of EGT's also gives greater scope for tweaking the pump.