inkyboy911

I know little about mechanics say, so whats the point in 100 Cell cats and how many do I need for my C2 ? Are they legal in the UK?

if I have 1000 GBP to spend on engine mods, what do I do first.

I have a G-pipe already but will be getting a 96000mile service in the summer and will possibly do brakes and engine work at this time, but prefer to do engine only at this time, and do brakes in 2007 as my discs and pads are good for a bit yet as they were all replaced a few thousand miles ago!!

Thanks in advance
Paul

Atgani

inkyboy911, depending on when your car was built/registered you can delete the cat altogether and fit a bypass. It makes the engine a lot more responsive especially if you have it remapped at the same time (you should see 275-85hp depending on the health of your engine.
One word of warning, as you already have a G pipe, the noise levels will rise a bit when you decat it, this is acceptable to some people and not to others. Personally I think the best route is decat, remove primary silencer and replace with a "Cup pipe" and retain the secondry (the one on the O/S of the car) silencer. This makes a nice noise which isn't too loud (but may fail noise tests if you plan on doing track days) IIRC the G pipe was originally intended as an option from Porsche for the Turbo cars.

robmug

100 cell cats have fewer cells than standard, so are more free-flowing (each cell takes up space in the can if you see what I mean). I was chatting with Milltek exhausts about this recently.

100 cell cats should still do enough to get through emmissions tests in the UK apparently.

Caveman

I have 100 cell cats on my car and yes they do pass emissions as I had it checked before I handed over the money! They are certainly a lot less restrictive than the normal cat and do greatly improve the sound if you like your car to sound a bit like an off duty race car some of the time.... :-) I haven't had my car remapped yet but do intend to. The normal ECU can certainly handle going from normal to sports cats. If your car is early enough do yourself a favour and dump it as it's more weight and sports cats can cost a fair chunk of change.

Cheers,

David

Red rooster

In the UK if your car is " K " registered it needs a cat . On standard motors I have never seen any significant maximum bhp improvement from removing the cat but the motor does feel better especially at lower rpm and load.
If you remove the cat be sure to keep the lamda probe in place.
The primary silencer is the power looser ( about 10 bhp ) hence the Cup pipe !
Porsche know how to get a few bhp by doing the least !

Good luck

Geoff

inkyboy911

OK, thanks for the explanation about the cells guys, but I'm still lost, oh and Caveman - what does dump it mean?

My car is a 91 J reg.

Do I get 100 cell cats or not?

I think it is chipped already as the PO wa s track driver with several visits to the Ring, he was also an ex racing driver from the Ferrari world, so I guess it's got a good remap, but can this be one better now as technology gets better?

I have a dyno place not too far who remap too, should I go there as the guy is very trutworthy and worked on my problems on my 993 when OPC couldn't work out the fault of loss of 45bhp at the crank!!

Whats the list of engine mods apart froma 3.8 upgrade which for 2k I feel is not worth it!!

Where can I buy a CUP air filter?

Atgani

inkyboy911, by dump it Caveman means get rid of the cat altogether and replace it with a cat bypass (with a lambda probe connected) As mentioned before, get rid of the silencer behind the rear bumper and replace with a cup pipe (this however will mean reinstating an original "final" silencer (buy one second hand) I'd personally have it remapped if I was removing the cat but if Red Rooster says not, don't bother!
What are you referring to when you mention a "Cup air filter" do you mean the filter housing or the element itself ? The standard filter housing works well IIRC
Red Rooster will tell you whether or not a K&N element is worth the extra money over a standard Porsche part (though I suspect its only benefit is the ability to wash and reuse it.
P.S. If you can get a 3.8 conversion for £2000 I'll order ten please

Red rooster

Inkyboy911,
OK , your car needs a cat .I would check on the price of 100/200 cell units.

In olden days guys racing, who had to have a cat, used to open up the standard cat , cut the element in half and weld the box back up !!!!!!!!!!!!!! It works very well !!! but you need to know what you are doing.
Air filter elements have never shown much in bhp terms but some, who love induction roar, fit a cone filter.

It is a good idea to have your car on a rolling road to check fuelling and power.
Not many places have a Hammer to be able to check timing as well .
That will give you a good starting point to know whether any remap work is needed.

Good luck

Geoff

Atgani

Geoff, surely his car doesn't need a cat as its a 91 J (I never ran one in my 91-2 RS)

kusee pee

Is a primary muffler bypass the same as a cat bypass or are they two different things? I know the primary muffler is along the inside of the rear bumper, is the cat elsewhere? I have a G-pipe already and I want more noise. It looks like replacing the primary muffler is relatively easy and cheap. Is this the way to go? And would I need to get the car on a ramp or could I just crawl under and make the change?

And do I always sound this unknowledgable?!?

Marc Shaw

Primary muffer bypass and cat bypass are not the same.

I'm not sure of your location but, on a LHD car, the exhaust comes out of the manifold to the cat (which is inside the left rear wheel well), into the primary muffler (which runs from left to right across the rear of the car), and then to the secondary muffler (located in the right rear wheel well).

A g-pipe (as you know) bypasses the secondary muffler while a cup-pipe bypasses the primary muffler. The function of a cat bypass is self-explanatory.

For more noise, a primary muffler bypass is cheap and easy - a cat. bypass, while also pretty cheap and will give you more noise, will make you fail emissions tests (if that is a concern).

Marc

Red rooster

Sorry , a 91 car doesnt need a cat in the UK.If the idea appeals get a cat bypass with a lamda boss. Keep your cat just in case the rules change !

Check the price for a Cup pipe . You will get better results and its a breeze to fit !!

I have a primary silencer that was a one off development . Its like a cup pipe with a built in straight through silencer , so doesnt have the standard part restriction but keeps the noise down !
Most circuits/trackdays will not accept noise and I have gone past that phase ( old f*rt !) .
I keep waiting for Dansk or someone to make the same thing.

All the best

Geoff

Caveman

Hi Inky,

Yes, that's what I meant about getting rid of the cat if it's either legal to do so or you don't mind putting it in for the MOT each time. Personally the latter option sounds like a pain in the **** ands probably would allow a scheming insurer to get out of paying up, etc, etc. If it is anything like the standard 993 cat then it will weigh a ton so if you are able to bypass it you save weight as well as getting better flow. Mark Budgen has a standard cat with replaced innards that he said worked pretty well.

Is there any way you could adapt a 993 silencer as they are plentiful though a bit restrictive?

Cheers,

David