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[DarnB]

Hello all I'm considering de cating my 3.2 drift omega is this going to cause problems for me like running badly or putting car into limp mode or any other problems down the line? has any one done this and how did the car respond to it... Cheers

[steve6367]

I can't imagine its going to bring much noticeable benefit?

[Webby the Bear]

Lad at work got his Renault clit 2.0l sport de catted. One of the old boy mechanics reckoned that in addition to the way he drives it (slaughtering it from cold  ) he may suffer from bottom end failure in the future.

His reasoning was the reduced back pressure causing oil to be forced up in to the cylinders and being burned instead of lubricating what it's supposed to.

Sounds like bollards to me. But I don't know.

I will say that my understanding was that the back pressure created by the manufactures exhaust system/routing ensured that inlet air / fuel didn't get chucked out the exhaust when there is valve overlap. But I've no idea if what I was told was true or not. So don't shoot the messenger.

But would love thoughts on this?

[05omegav6]

With any luck it will fail the MoT and you'll have to trailer it to the car park

[Sir Tigger KC]

With any luck it will fail the MoT and you'll have to trailer it to the car park

They have MOT's in Ireland?     

[Nick W]

I can't imagine its going to bring much noticeable benefit?

[size=78%]Excatly. It's a small(ish) engine, with a sensibly sized exhaust. [/size]


as for a lack of back pressure sucking oil into the cylinders , the piston rings would have to be so ineffective that the engine wouldn't run in the first place.

[Webby the Bear]

I can't imagine its going to bring much noticeable benefit?

[size=78%]Excatly. It's a small(ish) engine, with a sensibly sized exhaust. [/size]


as for a lack of back pressure sucking oil into the cylinders , the piston rings would have to be so ineffective that the engine wouldn't run in the first place.

S'what I thought. I don't buy anything I hear until I see evidence these days .

Am I right that it could create problems with performance by inlet charge being pushed through the exhaust on valve overlap?

[Nick W]

I can't imagine its going to bring much noticeable benefit?

[size=78%]Excatly. It's a small(ish) engine, with a sensibly sized exhaust. [/size]


as for a lack of back pressure sucking oil into the cylinders , the piston rings would have to be so ineffective that the engine wouldn't run in the first place.

S'what I thought. I don't buy anything I hear until I see evidence these days .

Am I right that it could create problems with performance by inlet charge being pushed through the exhaust on valve overlap?

That's actually something that a thoroughly designed induction system/port/valve/camshaft/exhaust aims to do, as it gives a 'free supercharger' effect. Obviously, arranging it so that you're only 'just' pulling the inlet charge through is difficult.

[steve6367]

With any luck it will fail the MoT and you'll have to trailer it to the car park

Without a CAT it will not be road legal anyway!?

[05omegav6]

With any luck it will fail the MoT and you'll have to trailer it to the car park

Without a CAT it will not be road legal anyway!?

Which might save it from a fate worse than death

[steve6367]

Ah I see - save the Omega!

[Webby the Bear]

I can't imagine its going to bring much noticeable benefit?

[size=78%]Excatly. It's a small(ish) engine, with a sensibly sized exhaust. [/size]


as for a lack of back pressure sucking oil into the cylinders , the piston rings would have to be so ineffective that the engine wouldn't run in the first place.

S'what I thought. I don't buy anything I hear until I see evidence these days .

Am I right that it could create problems with performance by inlet charge being pushed through the exhaust on valve overlap?

That's actually something that a thoroughly designed induction system/port/valve/camshaft/exhaust aims to do, as it gives a 'free supercharger' effect. Obviously, arranging it so that you're only 'just' pulling the inlet charge through is difficult.

So surely a decat would completely bugger this up? 

[Nick W]

I can't imagine its going to bring much noticeable benefit?

[size=78%]Excatly. It's a small(ish) engine, with a sensibly sized exhaust. [/size]


as for a lack of back pressure sucking oil into the cylinders , the piston rings would have to be so ineffective that the engine wouldn't run in the first place.

S'what I thought. I don't buy anything I hear until I see evidence these days .

Am I right that it could create problems with performance by inlet charge being pushed through the exhaust on valve overlap?

That's actually something that a thoroughly designed induction system/port/valve/camshaft/exhaust aims to do, as it gives a 'free supercharger' effect. Obviously, arranging it so that you're only 'just' pulling the inlet charge through is difficult.

So surely a decat would completely bugger this up? 

You're assuming that the X30 actually manages it in the first place. It's very difficult to do, and is normally an attribute of a very highly developed race engine.

[Kevin Wood]

I can't imagine its going to bring much noticeable benefit?

[size=78%]Excatly. It's a small(ish) engine, with a sensibly sized exhaust. [/size]


as for a lack of back pressure sucking oil into the cylinders , the piston rings would have to be so ineffective that the engine wouldn't run in the first place.

S'what I thought. I don't buy anything I hear until I see evidence these days .

Am I right that it could create problems with performance by inlet charge being pushed through the exhaust on valve overlap?

That's actually something that a thoroughly designed induction system/port/valve/camshaft/exhaust aims to do, as it gives a 'free supercharger' effect. Obviously, arranging it so that you're only 'just' pulling the inlet charge through is difficult.

So surely a decat would completely bugger this up? 

You're assuming that the X30 actually manages it in the first place. It's very difficult to do, and is normally an attribute of a very highly developed race engine.

When you look at the "design" of the exhaust manifold, the answer to that one becomes abundantly clear.

I reckon it'd be a hiding to nothing. Cats aren't a bolt-on afterthought these days so I doubt they are very restrictive at all.

[Bojan]

Hello!

With de-cat you might see some marginal gains in the high-revs area, but even that is not for sure. Modern cats aren't really restrictive.
I'm not sure if 3.2 has a lambda-probe behind the cat -> if it has, then you will have a EML with decat.

On the other hand, you will loose some low-rev torque - this I can say for sure, because I was running decat pipes for years on a X30XE, and at the end placed a couple of mufflers on the position where the cats were -> there was a notticable better trottle response on low revs (1000-2500 rpms).
Also, in my experience, exhaust sound with decats is awful, especially on acceleration.

IMO, in generall, if you don't have knowledge and money, keep away from V6 exhaust modifications.

After all, the marginal gain on HP you might see from decat will really make little or no difference on the drifting abbility  - just strip it of all unnecessary (to reduce weight), stiffen up suspension (springs, dampers, bushings), and weld the diff.

PS. As Kevin pointed out, exhaust manifold are really a bottle-neck for any usable exhaust tuning.