Discussion
No it's not legal. If you get stopped by one of VOSA's roadside spot-checks or at your annual MOT, you'll fail on emissions.
Depending on the car, the only possible advantage is a minor gain in power. Some cars - particularly more advanced ones, won't give any improvement because they will have been "mapped" and designed to have the cat in place. You'd have to make other modifications to release any genuine power. It is also likely to sound a bit noisier. I've heard a few de-catted TVRs and to my mind they sound quite "tinny" under the bonnet but some people seem to like it!
Depending on the car, the only possible advantage is a minor gain in power. Some cars - particularly more advanced ones, won't give any improvement because they will have been "mapped" and designed to have the cat in place. You'd have to make other modifications to release any genuine power. It is also likely to sound a bit noisier. I've heard a few de-catted TVRs and to my mind they sound quite "tinny" under the bonnet but some people seem to like it!
If you have two sets of cams then you generally loose power on the 2nd set as the overlap of the valves being open needs the back pressure of the cat from the exhaust to keep the fuel in the cylinder.
I loose a few bhp with mine, but I get extra mid-range torque which my car badly needs.
Passengers also say it's louder, but I can't tell.
I swap the cat back in for the MOT.
I loose a few bhp with mine, but I get extra mid-range torque which my car badly needs.
Passengers also say it's louder, but I can't tell.
I swap the cat back in for the MOT.
Not entirely sure you've quite got the right idea there with the cams.
N/A engines need a bit of back pressure, not a lot just a bit, also power band is altered by cams, inlet manifold length, exhaust manifold branch length and design, exhaust design etc etc, the second cam does not kick in at high rpm as I think your suggesting, normally on a twin cam one cam runs inlet and the other runs exhaust, you may be thinking of vvt or i think its called mvec on your fto? But this is just a change in the cam characteristics by a variety of different methods.
Basically removal of back pressure *should* Increase top end power at the expense of mid range, but all cars are very different, I would not advise removing the cat in your case and believe you will see a better (and legal) performance improvement from a K+N panel filter in your airbox and a decent exhaust system, maybe with a sports cat.
N/A engines need a bit of back pressure, not a lot just a bit, also power band is altered by cams, inlet manifold length, exhaust manifold branch length and design, exhaust design etc etc, the second cam does not kick in at high rpm as I think your suggesting, normally on a twin cam one cam runs inlet and the other runs exhaust, you may be thinking of vvt or i think its called mvec on your fto? But this is just a change in the cam characteristics by a variety of different methods.
Basically removal of back pressure *should* Increase top end power at the expense of mid range, but all cars are very different, I would not advise removing the cat in your case and believe you will see a better (and legal) performance improvement from a K+N panel filter in your airbox and a decent exhaust system, maybe with a sports cat.
Take it off a derv though, don't need them for the diesel test...
Made my turbo more spooly and removing the now defunct EGR has also increased throttle response.
Wouldn't do it on a new car, but on a 6 year old one the cat is gunked up and the EGR starts to shaft response more than any good it does anyway.
If I had a petrol I'd just get a sports cat if it was an older car... Even a new cat on an old car can "feel" as good as a decat simply because the old cat is just past it's best.
Dave
Made my turbo more spooly and removing the now defunct EGR has also increased throttle response.
Wouldn't do it on a new car, but on a 6 year old one the cat is gunked up and the EGR starts to shaft response more than any good it does anyway.
If I had a petrol I'd just get a sports cat if it was an older car... Even a new cat on an old car can "feel" as good as a decat simply because the old cat is just past it's best.
Dave
wildoliver said:
Not entirely sure you've quite got the right idea there with the cams.
N/A engines need a bit of back pressure, not a lot just a bit, also power band is altered by cams, inlet manifold length, exhaust manifold branch length and design, exhaust design etc etc, the second cam does not kick in at high rpm as I think your suggesting, normally on a twin cam one cam runs inlet and the other runs exhaust, you may be thinking of vvt or i think its called mvec on your fto? But this is just a change in the cam characteristics by a variety of different methods.
Basically removal of back pressure *should* Increase top end power at the expense of mid range, but all cars are very different, I would not advise removing the cat in your case and believe you will see a better (and legal) performance improvement from a K+N panel filter in your airbox and a decent exhaust system, maybe with a sports cat.
N/A engines need a bit of back pressure, not a lot just a bit, also power band is altered by cams, inlet manifold length, exhaust manifold branch length and design, exhaust design etc etc, the second cam does not kick in at high rpm as I think your suggesting, normally on a twin cam one cam runs inlet and the other runs exhaust, you may be thinking of vvt or i think its called mvec on your fto? But this is just a change in the cam characteristics by a variety of different methods.
Basically removal of back pressure *should* Increase top end power at the expense of mid range, but all cars are very different, I would not advise removing the cat in your case and believe you will see a better (and legal) performance improvement from a K+N panel filter in your airbox and a decent exhaust system, maybe with a sports cat.
That's why I said two sets of cams and not twin cam.
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