Cat Bypass - Myth or Legend

[djmcfish]

Hi Guys,

My mates got a 1.8RT which hes breathing on and was after a Cat bypass. Talking to the guys in Motormania Motorsports and they look up the power increse for a bypass on a standard Clio with a standard exhurst. I asked him to look up my 16v while he was there (as Ive got a bypass). He recons just the bypass will give 9 Bhp on a 1.8 RT and 11 - 12 bhp on a 16v!!

This must be BS as thats very close to a chip or cams!!

Someone out there know what a bypass will actually do, and what it will do with full s/s, induction and chip?

 

[Ben H]

Hmmm...

I understand that the 16v came without a cat initially, then had one put on to compl with regs after 8/92. As far as I know, there was no/negligible difference in power and 0-60 times. But obviously thats with a standard exhaust set-up.

I reckon that a cat replacement wouldnt do anything like the figues the guy told you anyway, and even then, only if you had the rest of a free-flow exhaust. Plus, theres the problem of sticking the cat back on for the MOT (unless its a really early 16v) - and some Police cars carry pollution/exhaust testers which your car would fail if no cat was fitted.

I reckon the guy makes a nice profit on cat-bypassers - and will tell you what you want to hear to sell one!!!

 

[steve a]

I wish they did give that amount of power but they dont.
What he told you is bull.
I have one on my 1.4 along with a backbox and induction kit and I ve had it on the rollers at 85bhp, 5bhp up on standard.
I found that it made the engine rev more freely and also made the engine pick up slightly better.
Also gets rid of the "stink" made by a cat and increases the noise of the exhaust system.

hope this helps

steve a

 

[jon16v]

the early clios in france without a cat had 4bhp extra using the standard exhaust. So in theory with no cat and say a Magnex full system you could get 10bhp but be sceptical about power figures. The dealer will tell you itll get 20bhp if he thinks he can sell you one!!!

 

[nedbeard]

Ive just fitted one and I can tell you that you do get a big power increase, much more that a filter or back box. Im very happy with the results. You loose the cat stink but then you have to put up with the "older" engine fumes - and they still pong!
I reckon Ive experienced a 10-12bhp gain on standard with only a custom cold-flow K&N filter and s/s back box with the cat supressor. I didnt really notice any gains with just the filter and box alone.
Power also depends on the brand of supressor you buy - Supersprint=pricey but quiet, some gains Devil=cheaper, noisier (GR.A), more gains.
I chose a supressor over a chip as there arent any rolling roads in the area and for 10000km a year I do Im not really fuc#ing with the environment that badly.

btw - here are the figures I went by:
http://www.multimania.com/renaultsport/site2/zcliochif.htm

Ned.

 

[Nick Read]

Ive got a Magnex decat pipe on mine and it probably gives under 5 brake at most. Its more like the last piece of the puzzle that you need to get your engine flowing properly before you start to get serious with head-work, throttle bodies etc.

I had a Hill Power induction kit and a Magnex s/s cat back system first then put the decat pipe on. Altogether it probably made between 5 and 10bhp tops. You cant really quote a figure for the decat pipe on its own because it is so closely linked to the exhaust system especially the system from the cat back. A decat on a standard exhaust wouldnt give you much on its own really.

 

[Dave Hester]

Im putting a prima racing s/s decat pipe on my williams at the weekend and was thinking about getting some new seals for it to! does anyone know if the seals for the 16v decat pipe are the same as the ones for the willy?



thanks


Jim

 

[Ben j]

how much is it costing u? hill power do em for about £40