D2 Fuel Economy

**Redback** · 15th February 2008, 06:59 AM

A couple of weeks ago i did this modification to my exhaust manifold

Since then the fuel economy has improved dramaticly, our towing economy has gone from averaging 15l/100k to low 13s per 100k and the non towing tank is on it's way to being the best ever, so far with 260ks on the clock the needle has only got to a 1/4, this is for us, amazing.

Factor in larger tyres, roof racks with an awning, pole carrier, shovel, drawers and this is amazing, the biggest killer to fuel economy are the bigger tyres and roof rack.

I think it is a number of things that has improved our economy, the heat at the manifold has been reduced, all the gaskets are new, the manifold is finally attached properly with no leaks and is not warped, something i feel that the standard size studs weren't doing the job and were braking soon after being replaced and over time the manifold was warping, i think the bigger studs i had put in are doing a far better job than the standard TD5 manifold studs, because after replacing the studs before we never noticed this big of an improvement, there was a slight improvement but that soon dropped off over the first week.

Not only has our economy improved but also the power has too, it is pulling right off the bottom at around 1400rpm, instead of 1900rpm when the turbo kicks in, no more slipping the clutch while keeping the revs up around 3000rpm

So from this i would recommend that all owners of chipped TD5s do this mod if your having problems with the exhaust manifold warping and broken studs on a regular basis, which for ours was evry 6mths or so.

Baz.

**WildOne** · 15th February 2008, 07:05 AM

G'day Baz,

Does your D2 also have the Catalytic converter? Mine does but apparently some D2's don't. By all accounts this is also a major restriction that should be removed? Unsure of the legalities though?

**Ken** · 15th February 2008, 07:23 AM

Originally Posted by PhillWilde

G'day Baz,

Does your D2 also have the Catalytic converter? Mine does but apparently some D2's don't. By all accounts this is also a major restriction that should be removed? Unsure of the legalities though?

Totally illegal to remove catalytic converters as far as emission laws go although you can get a High Flow Cat to reduce back pressure which helps greatly as far as turboed engines go

**Franz** · 15th February 2008, 01:02 PM

Baz,

Forgive my ignorance

(I'm not very technical) - what exactly did you do?

Don'y know what the manifold looked like b4 so it's hard to comprehend what you did.

**Redback** · 15th February 2008, 02:06 PM

Originally Posted by PhillWilde

G'day Baz,

Does your D2 also have the Catalytic converter? Mine does but apparently some D2's don't. By all accounts this is also a major restriction that should be removed? Unsure of the legalities though?

It's a TD5 not a V8

Originally Posted by Ken

Totally illegal to remove catalytic converters as far as emission laws go although you can get a High Flow Cat to reduce back pressure which helps greatly as far as turboed engines go

AS ABOVE

Originally Posted by Franz

Baz,

Forgive my ignorance

(I'm not very technical) - what exactly did you do?

Don'y know what the manifold looked like b4 so it's hard to comprehend what you did.

Franz it looks like this

Baz.

**feral** · 15th February 2008, 02:13 PM

Franz,

Baz has removed the webbing from the manifold. The manifold is cast and during manufacture there are webs between the ports. Baz has circled the shiny bits.

The fuel economy most likely would have come from all the new gaskets and the proper sealing of the exhaust manifold.

P.S.....stuff you Baz

I must not let work get in the way when on this forum

Cheers.

**Franz** · 15th February 2008, 02:45 PM

Originally Posted by Feral

Franz,

Baz has removed the webbing from the manifold. The manifold is cast and during manufacture there are webs between the ports. Baz has circled the shiny bits.

The fuel economy most likely would have come from all the new gaskets and the proper sealing of the exhaust manifold.

P.S.....stuff you Baz

I must not let work get in the way when on this forum

Cheers.

Thanks Feral.

Would removing the webbing make for a better (non leaky) fit? I did see the shiny bits but did not know there was webbibg there - Baz's b4 picture explained that.

If that's what it takes to improve fuel economy, I was going to break out the angle grinder (although that looks more like a die grinder job!)

**Franz** · 15th February 2008, 02:52 PM

Originally Posted by Feral

Franz,

Baz has removed the webbing from the manifold. The manifold is cast and during manufacture there are webs between the ports. Baz has circled the shiny bits.

The fuel economy most likely would have come from all the new gaskets and the proper sealing of the exhaust manifold.

P.S.....stuff you Baz

I must not let work get in the way when on this forum

Cheers.

Baz,

I haver no noticeable increase in fuel consumption when running the 265/75's - There might be a difference in the hard stuff but I never use my standard tyres off road and therefore have no basis for comparison.

On road, I have no discernable difference in my fuel consumption when running 265/75's.

**WildOne** · 15th February 2008, 04:08 PM

Originally Posted by Redback

It's a TD5 not a V8

AS ABOVE

Franz it looks like this

Baz.

Baz, my D2 is a TD5 also mate, a 2001 model like yours i believe, and mine has a catalytic converter just after the banjo joint on the exhaust.

**BigJon** · 15th February 2008, 04:47 PM

Some Disco II TD5s have the convertor, some don't. As a matter of interest, the non convertor engine pipe is a direct bolt in replacement for the convertor type, and is a LOT cheaper. I think the TD5 would pass the relevant emission tests regardless of whether it had the convertor or not (but that is my opinion, not a fact). As far as I know, the Australian standard of the day was a lot less strict than the Euro equivelant.

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