Thread: D2a V8 Catalytic Converters.

Howdy!

IMHO the cats aren't really the problem, the front pipes neck down immediately after the flange into 1, and this is where a fair bit of restriction etc begins. It'd be nice to fit some P38a engine pipes as these are a nice shape, and the 3 bolt flanges are quite freeflowing into the cats... but I reckon they'd be a drama to adapt as the chassis and crossmembers etc are in all the wrong places on a D2...

The other option is to make another pair of engine pipes using the D1 system from the flanges and join into one pipe just at the Cat entrys, instead of at the flange. I may have some scrapped engine pipes soon if you want to experiment?

Removing cats in these I reckon won't improve performance noticeably.

A high flow main muffler may also help, have you noticed how the pipes neck down at the inlet and the outlet of each muffler?? Removing these issues will also improve matters.
Bit noisier with the muffler changed, but I guess that isn't a worry

JC

Originally Posted by justinc

Howdy!

IMHO the cats aren't really the problem, the front pipes neck down immediately after the flange into 1, and this is where a fair bit of restriction etc begins. It'd be nice to fit some P38a engine pipes as these are a nice shape, and the 3 bolt flanges are quite freeflowing into the cats... but I reckon they'd be a drama to adapt as the chassis and crossmembers etc are in all the wrong places on a D2...

The other option is to make another pair of engine pipes using the D1 system from the flanges and join into one pipe just at the Cat entrys, instead of at the flange. I may have some scrapped engine pipes soon if you want to experiment?

Removing cats in these I reckon won't improve performance noticeably.

A high flow main muffler may also help, have you noticed how the pipes neck down at the inlet and the outlet of each muffler?? Removing these issues will also improve matters.
Bit noisier with the muffler changed, but I guess that isn't a worry

JC

Great thoughts there JC.

I've been looking into this for my Series V8 and was really surprised at what I found. time time time before I get onto it, but I've just uploaded some pics that I took showing the differences between the exhaust manifold to exhaust pipe joints - just stunning! I don't have P38 stuff unfortunately.

Series V8 manifold:







Disco1 V8:







Disco2 V8:

The Disco2 exhaust manifold outlet is very similar to the Disco1, but this is the exhaust pipe side of the manifold!

Thanks JC
I had a hi flow muffler fitted on friday,a slight increase in noise at idle, bit more of a growl on the highway...but i was expecting it to be a bit louder...(but my hearing isn't the best)...Anyway before i attack the rear resonator, i thought i would look at the cats....thinking these are holding back that V8 roar. & help with performance.....
Cheers Smally

Originally Posted by Slunnie

Great thoughts there JC.

I've been looking into this for my Series V8 and was really surprised at what I found. time time time before I get onto it, but I've just uploaded some pics that I took showing the differences between the exhaust manifold to exhaust pipe joints - just stunning! I don't have P38 stuff unfortunately.

Series V8 manifold:


[IMG]http://www.slunnie.com/coppermine/albums/LRV8exhausts/normal_P1030282.JPG[/IMG



Disco1 V8:







Disco2 V8:

The Disco2 exhaust manifold outlet is very similar to the Disco1, but this is the exhaust pipe side of the manifold!

Thanks Slunnie
The d2 manifold sure looks more restrictive than the d1.

I wasn't going to fit extractors to my d2 ,but that photo shows that the d2 would benefit more with extractors than my d1 i had....
cheers smally

The manifolds themselves aren't bad, and the rest of the system apart from where it joins to the manifold is pretty good.

What I was looking at doing was to use a D1 flange onto the D2 manifold and then go 2->1 which goes into the standard D2 exhaust which is large diameter already. The D2 flange is restrictive,will generate poor flow and is cheap.

You have to have the CC's but if you wanted to further open things up I would look after the 2->1 which is after the CC's. I would also have a serious look at the induction system between the guard and the airbox which I think is the other restriction. The motor sucks more air than it blows and I suspect that passage would flow less than the exhaust after such modifications.

Dont get to carried away

If you fit Extractors then fit a big exhaust on a stock engine it just kills the power and economy

Decide witch end you want to work on front or back

Just remember if its a V8 its only a little one and can be over exhausted really easy

The best and cheapest way to go would be remove the rear muffler and fit a 2.5 inch pipe in its place
You have basically shortened the exhaust by about 30-40 cm

Originally Posted by steve_35

Dont get to carried away

If you fit Extractors then fit a big exhaust on a stock engine it just kills the power and economy

Decide witch end you want to work on front or back

Just remember if its a V8 its only a little one and can be over exhausted really easy

The best and cheapest way to go would be remove the rear muffler and fit a 2.5 inch pipe in its place
You have basically shortened the exhaust by about 30-40 cm

G/day Steve
I happy with the factory exhaust diameter im just trying to free it up & get a better flow....Which would give me a nice note & go a tad better....
cheers smally

Some of the comments on this thread are very interesting and a bit confusing. I have been considering fitting a set of extractors to my D2a as well, hoping for an increase in power.

I'm not wanting to make it much louder, if at all, I'm more focused on looking for potential power improvement over standard.

So the question is, do you just change the restrictive exhaust manifolds to extractors or do you need to change all or just some of the rest of the exhaust or is it a waste of time and money on the D2's because of other factors?

I also have a 94 V8 D1 with a larger exhaust and free flowing mufflers including extractors that has been chipped and the old girl blows the doors off of the D2a. So why would a decent exhaust work on a D1 and not a D2?

Any assistance here would be appreciated.

cheers,
Terry