de cat

[VW BUSH]

Can I add that modern cats don't lose that much, I know someone that fitted a sports car and only gained 2bhp.

I was taught that only big turbo's realy gained from sports cats/de cat's but that was 13 years ago, sure i will be corrected though

[Wayne]

Can I add that modern cats don't lose that much, I know someone that fitted a sports car and only gained 2bhp.

I was taught that only big turbo's realy gained from sports cats/de cat's but that was 13 years ago, sure i will be corrected though

Not really sure, you might get a bigger gain on a turbo.

[boneybradley]

On a turbo car once the gas passes through the turbo it is beneficial to get rid of them as quick as poss while on a n/a car the cat will slow the gas and help compression/efficiency (and if you loose this you'll find the rev range higher you'll gain..maybe a few bhp but it will loose torque!)

remember turbo boost effects compression so after the turbo it won't affect the power

[VW BUSH]

Can I add that modern cats don't lose that much, I know someone that fitted a sports car and only gained 2bhp.

I was taught that only big turbo's realy gained from sports cats/de cat's but that was 13 years ago, sure i will be corrected though

Not really sure, you might get a bigger gain on a turbo.

I know some N/A cat cars respond well to de cats and sport cats, the MK3 GTI 8v does not seem to gain much from it even with a full SS system behind it, 16v aint much better either but i could'nt comment on the VR

[VW BUSH]

On a turbo car once the gas passes through the turbo it is beneficial to get rid of them as quick as poss while on a n/a car the cat will slow the gas and help compression/efficiency (and if you loose this you'll find the rev range higher you'll gain..maybe a few bhp but it will loose torque!)

remember turbo boost effects compression so after the turbo it won't affect the power

My "cough" 760 intercooler gained from a de cat made it super loud though, exhaust fitter couldnt stop giggling at me

[AudiA8Quattro]

On a turbo car once the gas passes through the turbo it is beneficial to get rid of them as quick as poss while on a n/a car the cat will slow the gas and help compression/efficiency (and if you loose this you'll find the rev range higher you'll gain..maybe a few bhp but it will loose torque!)

remember turbo boost effects compression so after the turbo it won't affect the power

The cat actually is very restrictive on na cars.
A good example of this is the 9A engine 2.0 16v fitted to early 90's corrado and passat.
The engine was 200cc larger than the KR 1.8 16v in the golf, but actually produced 3bhp less.
The 9A engine produced much nearer to the ABF engine once de-catted and the 'soft' profile inlet cam was changed.

[Wayne]

On a turbo car once the gas passes through the turbo it is beneficial to get rid of them as quick as poss while on a n/a car the cat will slow the gas and help compression/efficiency (and if you loose this you'll find the rev range higher you'll gain..maybe a few bhp but it will loose torque!)

remember turbo boost effects compression so after the turbo it won't affect the power

The cat actually is very restrictive on na cars.
A good example of this is the 9A engine 2.0 16v fitted to early 90's corrado and passat.
The engine was 200cc larger than the KR 1.8 16v in the golf, but actually produced 3bhp less.
The 9A engine produced much nearer to the ABF engine once de-catted and the 'soft' profile inlet cam was changed.

Fair point but newer cats are a lot better designed and the losses if any are small, I decatted my Vectra as it was knackered and gained nothing bhp wise but did feel a little bit smoother.

[AudiA8Quattro]

I can't speak for brand new cars.
Just pointing out that a cat won't improve compression/efficiency, it is restrictive and will reduce volumetric efficiency.
Turbo cars should see better gains because the flow into the engine is higher than atmospheric pressure, so de-restricting any part of the exhaust will see a much better flow.
The principle is the same on non turbo cars, but the gain will not be quite as exaggerated.
People on the mk4 section are claiming some quite big gains from fitting a larger turbo back exhaust.
If 1.8T engines gain then non turbo engines ie. v6 should see good gains too.

[tweed]

I've had a decat on most of my cars, also induction kits , or a good panel filter. I can honestly say the cars always seem to be a lot more responsive. I'm going to get one for my 16v if I gain 2bhp or not.

[Mikester]

Ive always had go faster stripes on my cars, and it seems to make it faster.