Thread: Time for new exhaust

My Cats on the Disco are dead and rattling away it sounds Yuk
I was hoping to remove the cats and run with out, Ooops did I say that out loud, no just joking

I was thinking off going dual 2 ¾ to the Y section after the exhaust manifold and then 3 ¼ I’m not going extractors to big of a job and it’s not a ¼ Mile car and I would like it sounding beefy but not to fat LOL

What are some of the suggestions

Sorry Chronic, here was my reply that I was writing the other day when TPG broke my connection:

I have been having a look at the D2 V8 exhaust system lately for its potential in my ute. These are just my thoughts on the systems...

I actually reckon that from the factory the D2 V8 system looks pretty good, with the exception being the lack of balance between each bank from differing lengths.

Earlier V8's had a basic manifold 4-1 setup per bank which was improved in the EFI version which was a equal length 4-2-1 setup per bank but again with unequal lengths per bank, and I'm assuming this was to improve pull from the motor. The later Thor type V8's such as in the Disco2 then changed to a 4-1 header manifold which probably has scavenging etc still with unequal lengths between banks.

I really do like the concepts behind what they've done with the D2, though I tend to think that the using only the very short manifold before the 4-1 collector is probably too short. In that respect I think that more can be gained by aftermarket extractors. I'm not definite, but I'm pretty sure the 4-1 design is meant to give better top end, though from my experiences on other motors it gives a lot down low also, though I'm not sure what it would do to a Rover V8, especially as it would be in comparison to what is already on the engine. Perhaps this system was necessary after the development of the Thor manifold working too well in increasing low down power and the need for more top end for free revving and power. Who knows... Anyway, if it were mine, short of replacing the entire system from the heads, I would leave the front half exactly as it is. Twin cats will breathe better and being near the engine will heat quickly. If the issue is the cats, then I'd gut, omit or replace them, but not move them. I'd also leave the tube size as it is from the factory. I tend to think that LR developed a pretty well breathing exhaust and well muffled exhaust from the factory on the Disco2. The factory sized tubing will also maintain velocity needed in that front section of the exhaust system to make the extraction, scavenging etc work effectively.

After the exhaust from both banks merge though, well... from there on I think look for everything you can get... but I don’t think there is a great deal to be had. The mufflers on there are pretty large. The middle one is a real donk and it flows well. The end muffler is good too. They flow well and muffle well, and I think the challenge will be finding something that flows as well as what’s already in there. I absolutely would not go to single 2". I honestly think you will lose power throughout the entire rev range. A lot of people say that you need back pressure for the exhaust system to make power.... I think that’s a load of crap. You need flow speed in the front section to make the extractors work, but you need it to evacuate without restriction in the rear to not clog the motor. In the rear I would just try a free flow centre or end muffler if you want gains, Hot dogs sound really really cool, and some also say the Vortex is excellent. Or to flare the exhaust after where the banks join into a 3" system and use free flow mufflers also similar to what’s already in it. The rear half of the exhaust has to be able to flow twice that of the front half due to the banks merging, and I don’t think that it’s an issue if the gasses slow down here in the slightest - they will never stall, but you can reduce the back pressure.