Mark Fish exhaust mod

[TrophyDan]

Has anyone had the Mark Fish exhaust mod done? - He said he'd done a couple of Trophies.
Basically he cuts a 1/4 of the cat off and welds in a nice shiny, new, larger bit of tube to replace the crappy cat to exhaust joint - he reckons its good for 5 bhp??

Cost £125 - anyone think its worth it?
It would fix my blowing exhaust for a start - however, it would mean i cant put the std exhaust back on for selling time.

Thoughts anyone?

 

[Matt X2C]

Haven't heard of anyone else getting this done yet, but it makes sense. The cat slims down to 2.25 inches, so if he is enlarging it to 2.5 then it will generate more flow and more power, but nothing like 5bhp.

Personally I would just take the standard exhaust off and keep it, and just replace it with a full system aftermarket system and decat.

 

[murcod]

Has anyone had the Mark Fish exhaust mod done? - He said he'd done a couple of Trophies.
Basically he cuts a 1/4 of the cat off and welds in a nice shiny, new, larger bit of tube to replace the crappy cat to exhaust joint - he reckons its good for 5 bhp??

Cost £125 - anyone think its worth it?
It would fix my blowing exhaust for a start - however, it would mean i cant put the std exhaust back on for selling time.

Thoughts anyone?

My first post

I've got a 2005 182 Cup (Aussie spec) and my cat narrows down from 2.5" inlet to 2" outlet. I have been thinking about doing exactly the same thing - cut the rear off it and get some 2.25" or 2.5" pipe welded on. But, I'd also look at replacing the centre resonator which is also that size (or close to it) and the section of pipe immediately after it. The pipe actually enlarges again to 2.25" (IIRC?) just before the bend to go over the rear axle.

I have got all the measurements somewhere, I got underneath with a pair of vernier callipers and measured it all about a year ago. I believe the Trophy system would be the same?

 

[TrophyDan]

Yup, its a 182 at the end of the day so its all the same.

 

[Jimboss]

I had it done at Mark Fish. This option is alot cheaper than K-Tect racing solution see below

http://www.k-tecracing.com/show_product.asp?id=2493

Not too sure about power gains itself as i had a maxogen added at the same time. But the free flowing arrangement must give you some more power (perhaps not 5 Bhp). its a good mod to have with an upgraded air induction system as the engine can draw in air and expel gasses out of ther engine easier. Once both fitted my car a alot more pick up especially over 4K revs and can reach double figures quicker than before. All this would have then been married up to a custom remap to nicely tie everything together but im looking at selling now so i dont think i will bother now.

 

[murcod]

Jimboss, is the rest of your exhaust system standard? I wouldn't have thought there would be much to gain unless the pipework between the cat and res, and the res itself was replaced?

BTW here's my post from another forum with the measurements I did back in September 2007 (and I still haven't done anything about it! ) From http://www.ozrenaultsport.com/forum/vie ... php?t=6674

I spent quite a bit of time crawling around under the Clio this morning measuring all the exhaust system after recently noting how much difference there is in tubing sizes.

The results are below:

Collector after extractors : 65mm
Catalytic convertor inlet : 65mm
Catalytic convertor outlet : 49mm
Resonator inlet : 49mm
Resonator outlet : 55mm (pipe expands slightly about 30mm after res outlet to 60mm)
Piping before Y : 60mm
After Y into rear mufflers : 2 x 45mm (possibly slightly larger, but all bent with no straights to measure?)
Muffler outlets to tips : 2 x 49mm

As you can see, there is a significant reduction in cross section at the cat outlet through to just after the res. Out of interest the 2 x 45mm tubing after the Y works out to more cross sectional area than the single 60mm tube before the Y junction.

Another point of interest is the cat is cylindrical with conical ends and IMHO it would be dead easy to cut the small outlet off and fit a larger size that matches the inlet better. Space to fit a larger res is however limited due to the bizzarre shape of it. Out of interest it is around 50cm long as well.

 

[Jimboss]

I had a CAT back Miltek system on already however there was a pinch point between the zaust and the CAT oulet arrangement that was causing restrictions in flow. Mark cut out the pinch point and contined the wider bore of the zaust and married it up to the CAT to give a full unrestricted system (it looks just like k-tech arrangement now).

I would have thought the mod will only really be beneficial if you have an aftermarket zaust on (due to larger diameter of pipe). Mark Fish only bought the mod to my attention because i already had the zaust fitted. Some garages when fitting the new CAT back arrangement will do this as part of the standard fitting proceedure however not all do.

 

[murcod]

Ahhhh... that makes more sense then.

I reckon even with the stock system there would be gains to be made. Going by my measurements the outside diameter of the pipe after the cat and through to res is only 49mm (less than 2"!), but just after the res it enlarges to 60mm. That's something like only 66% of the cross sectional compared to the 60mm.

One day when I'm feeling a bit richer and have a more agreeable insurance company I'll give it a go.