To Cat Bypass or not to Cat Bypass ??

[Bomba]

Thinking of fitting a Cat Bypass collector to my recently finished 360R.

Objective to get a little more power and much better exhaust noise.....bangs....pops etc 

Anyone have any experience of whether it makes much difference on the Duractec? 

CC quoting just over £300 for the part - once polished and delivered.

[Geoff Brown]

I fitted a cat by pass to my R400D straight after the IVA. 

A change in performance is unnoticeable but the noise is different - maybe a bit more bass at tick over with a throb of menace & not so muted when giving the beans. There are more & louder pops & bangs on over run accompanied at night by blue flame!

Poor old Lambda sensor.....

The more important thing is the induction noise from the TBs.....possible to frighten small children & animals.

 

 

[JNC]

I was quoted 5% extra power on my Duratec ! If you can tell the difference in power your a better man than I, If you are using RBTB's I wound say the bypass pipe is a must as all the backfiring will destroy a Cat .

[DJ.]

The catalyst will help the packing in your silencer last a lot longer.

[Speedtrip]

Sorry for the hijack but I've also been a little disappointed with the exhaust sound on my 360R. Other cars seem much more roarty in comparison. I've wondered if this was due to the cat...

[ChrisC]

Yep my 360R is the same,  I suspect it’s due to the stock ford cams, and the low state of tune.  It’s not a complaint i have heard from the 420.  

[Speedtrip]

That's interesting Chris, perhaps an upgrade is in order :)

There's a YouTube video of a purple decat'd 360R racing a +500bhp Range Rover. That car does seem to sound better than mine, hence my original thoughts.....prefer the upgrade idea though!

[ChrisC]

I love that video for two reasons.  One, it says it has a 6 speed, but the gearknob (and other reviews of that car on youtube) go with it being a 5 speed, and two, it posts a 0-60 time of 4.5 seconds, lower than the offical 4.8 seconds quoted on the CC website.      

Back on topic - I think the noise is different due to the decat.   I will decat at some stage, but at the moment I have bigger problems to solve.    I also intend an upgrade to full 420 spec at some stage, possibly this year.  

If I decat it's to protect the cat.   I know its working now, but for how long, at £600 (twice the price of a bypass) if it fails due to pops and bangs or vibration before I need it at an MOT then a bypass has saved me money.    It's such a simple job to swap in and out at MOT times.    Years ago I had a Mini (proper one) that during MOT / service at the John Cooper garages, it was discovered the lamda sensor had packed up, they said normally this results in a dead cat, but yours seem fine, yep that's because it was fitted that morning :-)   

[Speedtrip]

Are there any known issues with running decat or smells or running issues?

[Oysterman]

After buying my R500 D last year  I fitted a de cat pipe straight away and to be honest  I cannot tell if it gives more power but hey I don’t think it really is necessary on this car . The noise is a little more deep and the enhanced overrun is louder and as someone else said at night a very quick burst of flame.No odours with the pipe and the engine runs just fine. In the process of polishing up the whole system and fitting the cat again ready for MOT Time.

[CtrMint]

I keep wondering about a bypass too.  I do enjoy encouraging the overrun noises, but having seen the comments I’m probably not doing my cat any favours.  I do wonder about track noise limits though on a decat 420.

[ScottR400D]

Do you get many pops and bangs with the standard intake? I never noticed any until I put the RBTBs on. Plenty now though! 

Anyone know if a remap is necessary between a cat and a bypass? 

[Geoff Brown]

I fitted a cat by pass straight after the IVA........yes more pops & bangs, exhaust note slightly more rorty & lots of blue flame at night. Especially on the overrun.

The cat I know is there to do a job but with all the combustion/exhaust processes going on it is really just acting as an expensive restrictor & flame retarder hence you do not experience the blue flames because they are slowly destroying the cat! 

My cat is having a rest in the airing cupboard wrapped in plastic.......meow.

[Bomba]

I went ahead a “de cated” my 360R and I am pleased I did, i think it’s a little quicker (might be engine loosening up) but the look is much better and the sound more rewarding with a deeper throaty note.

I was a Castle Combe last week a recorded 96dB at the test so easily under 100 and 3 less that the IVA! Conclusion not loader but better sound, or the guy at Combe did not push the me on the revs as much as IVA. 

[John Vine]

Anyone know if a remap is necessary between a cat and a bypass? 

Good question.  IME, the before/after performance seems identical, and the bypass hasn't affected idling, pick-up or general driveability one jot.  So, I suspect the answer is no (unless someone knows better).  Mind you, I'm still running on CC's stock map for an R400D with RBs.  I think 2019 might be the year for a visit to Rainham.

JV

[Mark_]

If I wanted to decat my Sigma 150, is this the right peice ?

https://caterhamparts.co.uk/collectors-catalysts/5126-bypass-exhaust-pipe-sigma-eu-upgrade.html

 

And would it need the mapping adjusted ?

[Eccles]

This is the bit I bought for my 150 ....

https://caterhamparts.co.uk/collectors-catalysts/3664-exhaust-collector-4-into-1-sigma-side-exit.html?search_query=36X025A%09&results=1

..... and it worked just fine without any remapping 

Ivan

 

[Mrp]

As Eccles says, thats what I run 

[Ngmatthewsme.com]

Is it the R500 decat pipe for a 360R ... 

Cheers

[sylvaman]

Presumably Eccles and Mrp, that Pipe from CC 36X025A would fit my 310 S Sigma too ?  Def on my to do list

Interesting the thoughts on popping back, harming the Cat.

My Toyota engined Elise (fitted with a 2ubular tuned exhaust from almost new) used to pop back on the overrun ,  (Loved It )  it was on there for 6 years and was a recognised Lotus upgrade.  Passed Mot's ok, Perhaps I was lucky. 

[Manstein]

I ditched the cat on my R400d four years ago and it seems a bit freer revving and less of a plumbers nightmare. No problem with MOT's.

[ScottR400D]

I did mine last year after this thread. 

Suspicion that it’s a little louder but hardly noticeable. 

[Eccles]

I would imagine that would be the part for you too sylvaman. I certainly noticed the throttle bodies were a lot louder 

I'm in a bit of a quandary with the MOT, I would like to know if it passes with it on or not but the garage I go to have decided it's a visual test only car (which is great!) so if I rock up and ask them to try it they may test it properly next MOT. Not sure if it's the DVLA database that's changed or the guy isn't looking at the chassis number. 

Ivan

[sjl1]

Well i recently sold my decat pipe and reverted to the cat. Reasons? I had upgraded from 180bhp Duratec to 210 cams and the car started to fail the brands hatch drive bu noise tests, secondly, got fed up with the increased noise during normal driving, just too loud, im getting old and don't want to damage my hearing. Also had to refit the cat for the MOT so decided to declutter and get rid (sold £150). Havent noticed any changes in performance but the exhaust noise is less harsh and a little more room in my shed :-)

[John Vine]

Re #21:

I ditched the cat on my R400d four years ago...... No problem with MOT's.

That really surprises me.  Could you elaborate on the following points?   

1. Does the tester enter your reg no and VIN into his gas analyzer (I'm assuming you don't have a Q-plate)? 
2. Does the car pass the Basic Emissions Test (BET)? 
3. If it fails the BET, does the tester then treat the car as non-cat and run a non-cat test, or does he move on to the cat test?

My R400D, with cat, usually fails the BET due to an out-of spec upper lambda reading, at which point the tester selects the relevant Caterham model from the gas analyzer list, and performs a cat test (with a wider lambda range). 

JV