Which exhaust system 3.5 or 3.9?

smurphy · Dec 23, 2009

Hi all I need a new system for my car which is a 95 Disco 3.9V8i on LPG. Now what I'm thinking is buying the 3.5i down pipes and y piece and the 3.9i centre and rear silencer.

I know I'll have to modify the down pipes to take the lambda sensors. Has anyone done this or know of anyone doing so? I know I going to get stick about the MOT side but its down to the testers discretion. Merry Christmas and thanks in advace regards Steve.

V8_Disco · Dec 23, 2009

why would you want to get pipes from a smaller engine???? they will be more restricitive and loose power, unless you after the pre catalytic conver pipes then it will fail the MOT and be illegal

smurphy · Dec 23, 2009

V8_Disco said:
why would you want to get pipes from a smaller engine???? they will be more restricitive and loose power, unless you after the pre catalytic conver pipes then it will fail the MOT and be illegal

The size of the pipes are the same on the 3.9EFI Range Rover. And the MOT is down to tester discretion as it's such a grey area, as the would not be any sign they where the same as if people remove the anti roll bars and all the signs of them as if they weren't fitted. Also I don't want to get into the argument of legalities about it, I was wondering if the 3.9 centre box would fit the connector pipe.

V8_Disco · Dec 23, 2009

smurphy said:
The size of the pipes are the same on the 3.9EFI Range Rover. And the MOT is down to tester discretion as it's such a grey area, as the would not be any sign they where the same as if people remove the anti roll bars and all the signs of them as if they weren't fitted. Also I don't want to get into the argument of legalities about it, I was wondering if the 3.9 centre box would fit the connector pipe.

the fitting should be the same, but depending on how the y pipe is routed in each vehicle ( and if it has cats) it might not physically fit in the gap

discool · Dec 24, 2009

A genuine 3.5 Y pipe without cats is the same as the 3.9, if fitted with cats it's still the same as the 3.5 but the cats are a different shape. The mid and tail boxes are the same although being a later model the 3.9 fixing brackets are in different position to those of a 3.5.

You don't need cats for an MOT as long as the vehicle can pass the emmission test specified for that vehicle, which a lean burn engine or a engine running on Propane gas will do.

smurphy · Dec 25, 2009

discool said:
A genuine 3.5 Y pipe without cats is the same as the 3.9, if fitted with cats it's still the same as the 3.5 but the cats are a different shape. The mid and tail boxes are the same although being a later model the 3.9 fixing brackets are in different position to those of a 3.5.

You don't need cats for an MOT as long as the vehicle can pass the emmission test specified for that vehicle, which a lean burn engine or a engine running on Propane gas will do.

Thanks Discool I've decided to bite the bullet and if they're different ends then I'll cut the flange off the system I have and weld it to the new one.

And MERRY CHRISTMAS TO ALL

terratology · Dec 26, 2009

Why you changing to 3.5 manifolds? For us mere mortals with 3.5's using the 3.9 manifolds is a tuning technique as they flow considerably better than the 3.5 ones.

smurphy · Dec 29, 2009

terratology said:
Why you changing to 3.5 manifolds? For us mere mortals with 3.5's using the 3.9 manifolds is a tuning technique as they flow considerably better than the 3.5 ones.

I'm not changing the manifolds just the rest of the system.

tacr2man · Jan 3, 2010

Not quite on topic , but does anyone know is it the discovery pre cat twin downpipes that fit in a 110 , the rangerover ones end up pointing straight at the gearbox cross member? If yes does the Y pipe fit as well ?

discool · Jan 3, 2010

For the Discovery injection V8 with or without cats don't have a down pipe as such but the one piece Y pipe from the manifolds straight to the mid box.
The carburettor V8 has short down pipes clamped to a Y pipe which then goes to the mid box.
Sorry but doesn't help with your question but I believe the injection pipe is a different shape so may go over your cross member as it should.

Which exhaust system 3.5 or 3.9?

smurphy

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V8_Disco

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smurphy

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V8_Disco

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discool

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smurphy

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terratology

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smurphy

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tacr2man

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