Slightly smelly bottom

[Anonymous]

On my journey to tweak more out of my N20 powered E89 I fitted a VSRF catless downpipe..

On the one hand found the extra growl slightly amusing and there was a contribution to some extra torque/BHP as part of many other mods and adaptations..

However, when it came to MOT time it failed by a country mile on emissions..

In addition, I drive most of the time top down (is there any other way?)..and can't quite get used to the smell of unburnt fuel wafting around my bottom..

So.. I've bought an Evolution Race Werks 200 cell catted downpipe as a compromise..

http://www.evolutionracewerks.com/node/272

The standard cat is a 400 cell unit and these guys burble on in typical witch doctor style about smoother flows, lower back pressures etc..

I did ask my favourite tuning boys in Sunderland to take yet more money from me and re-run / re-tweak it..but they said in their experience it will work as well as the VSRF de-cat and make zippo difference..

What I'll do is try and do a back to back audio track when I get it fitted, if possible..

Got the ceramic coat for that warm glow inside (pun)..does look very well made and retains all the factory mounts unlike the VSRF..

May get rid of a slight exhaust pipe induced vibration into the cabin too!

 

[enuff_zed]

Hmmm, is this some weird new technical term?
A 'downpiple'

 

[Nictrix]

I thought there was quite a few on here with the VRSF downpipe fitted and not read anybody else having problems MOT time.
I wonder why yours has failed when others seem to be fine.

 

[biZ4rreMids]

I’ll be interested to see how you get on with the new pipe Pete. I’ve got a supersprint decat pipe and I quite like the growl from the pipe when the roofs down and the crackle and pops when changing down using the paddles is addictive but the smell of petrol when reversing out of the garage or standing at traffic lights is a negative. A guaranteed MOT failure too as the N20 doesn’t have secondary cats like the 35i or 35is.

 

[Anonymous]

Hmmm, is this some weird new technical term?
A 'downpiple'

Joys of a lacque of speel chucker on my peec

 

[Anonymous]

I thought there was quite a few on here with the VRSF downpipe fitted and not read anybody else having problems MOT time.
I wonder why yours has failed when others seem to be fine.

I suspect nobody has put the exhaust gas analyser up the tail pipe..that's one way of passing..another is to swap the catless pipe over for the OE one for the MOT..I'm aware of some that do that too!

 

[Anonymous]

I’ll be interested to see how you get on with the new pipe Pete. I’ve got a supersprint decat pipe and I quite like the growl from the pipe when the roofs down and the crackle and pops when changing down using the paddles is addictive but the smell of petrol when reversing out of the garage or standing at traffic lights is a negative. A guaranteed MOT failure too as the N20 doesn’t have secondary cats like the 35i or 35is.

Its a first world problem, but SWMBO doesn't like the smell of unburnt fuel either..of course if you had a coupe it would be mostly OK..but no point have most Zeds (E86 excepted) if the roof is not down all the time except maybe when its raining..

May swap it out sooner than later since the season is nearly upon us!

 

[Nictrix]

I thought there was quite a few on here with the VRSF downpipe fitted and not read anybody else having problems MOT time.
I wonder why yours has failed when others seem to be fine.

I suspect nobody has put the exhaust gas analyser up the tail pipe..that's one way of passing..another is to swap the catless pipe over for the OE one for the MOT..I'm aware of some that do that too!

Just read above, maybe most of the others are 35i and 35is that I have read about. Maybe you are the first with an N20.
I noticed years ago after removing the cat from my bike that there was a different smell especially noticeable when idling.

 

[Anonymous]

I thought there was quite a few on here with the VRSF downpipe fitted and not read anybody else having problems MOT time.
I wonder why yours has failed when others seem to be fine.

I suspect nobody has put the exhaust gas analyser up the tail pipe..that's one way of passing..another is to swap the catless pipe over for the OE one for the MOT..I'm aware of some that do that too!

Just read above, maybe most of the others are 35i and 35is that I have read about. Maybe you are the first with an N20.
I noticed years ago after removing the cat from my bike that there was a different smell especially noticeable when idling.

A few of the N20 guys have done the de-cat pipe and a couple have privately discussed the issues..as you say its a very different system from the N54 and maybe N52..

If you've got a tame MOT man its maybe OK, I don't want to put my chap in a compromised position..plus..as I say its the whiff of fuel everytime you come to a stop/crawl with the top down.. maybe put a shot of some Castrol R in there ?-

 

[flybobbie]

My 23i stinks of fuel when i start, is that just cold cats?

 

[Anonymous]

My 23i stinks of fuel when i start, is that just cold cats?

Yes its a combo of cold running enrichment and cold cats..these smells eminate when the car is warm as well as when its cold..

 

[enuff_zed]

Hmmm, is this some weird new technical term?
A 'downpiple'

Joys of a lacque of speel chucker on my peec

:rofl:

 

[mcbutler]

Maybe you got one of the 'chinese' VRSF cats that were doing the rounds for a short while Pete!

 

[Anonymous]

Maybe you got one of the 'chinese' VRSF cats that were doing the rounds for a short while Pete!

I hope not..it would be a bit of a pisser if you buy direct from VSRF and then they ship a Chinese copy.. :tumbleweed:

Not that in this case it would matter ..from a pollution control perspective they are all empty tin cans...the flow performance may vary but the unburnt fuel would be the same for all versions..Chinese or not

 

[R.E92]

If the N20 has no secondary cats then it's not a surprise it smells. Also 0 chance of passing an MOT legitimately.

With the N54 it's close, you can just about pass with secondary cats provided you get some heat into them before testing. I have a custom tune that I flash before MOT which leans the fuelling out and pulls timing to further add heat into the cats.

I think high flow cats are the best solution for you provided they allow you to pass. It's quite common for after-market cats to be poor due to the raw material cost so I'd certainly take the car to a tester after fitting the high flow units to make sure they pass rather than wait another year to find out.

 

[Anonymous]

If the N20 has no secondary cats then it's not a surprise it smells. Also 0 chance of passing an MOT legitimately.

With the N54 it's close, you can just about pass with secondary cats provided you get some heat into them before testing. I have a custom tune that I flash before MOT which leans the fuelling out and pulls timing to further add heat into the cats.

I think high flow cats are the best solution for you provided they allow you to pass. It's quite common for after-market cats to be poor due to the raw material cost so I'd certainly take the car to a tester after fitting the high flow units to make sure they pass rather than wait another year to find out.

Yes the tester not knowing the architecture said that quite often those (I assume with 2 stages of cats) can get through when warmed up..mine was around 0.04 with cat and 0.4 without, limit being 0.2... :thumbsdown:

I've got quite a bit of motoring planned in the Zed with SWMBO starting on April 26th (Sister Nicola permitting) so think I'll try and get it swapped across in the next week or so and get them to stuff the 'sniffer' up the tailpipe to satisfy everyone's curiosity :tumbleweed:

 

[MACK]

Just read this thread. Did you get it fitted, how do you find it? I haven't noticed any fuel smell with mine. Now the weather is improving that might change with a bit more top down driving, or driving of any description for that matter!

 

[enuff_zed]

Just read this thread. Did you get it fitted, how do you find it? I haven't noticed any fuel smell with mine. Now the weather is improving that might change with a bit more top down driving, or driving of any description for that matter!

I reckon it's all down to Peter's humungous new turbo. It's firing the charge through so quick the fuel doesn't have time to burn.

 

[Anonymous]

Just read this thread. Did you get it fitted, how do you find it? I haven't noticed any fuel smell with mine. Now the weather is improving that might change with a bit more top down driving, or driving of any description for that matter!

Just picked up the car from the garage, went for a 30 mile hoon to check it out..

So its as you might expect somewhere between the normal cat and the tin can..

There is less noise than the tin can and its a much more pleasant sound..it doesn't sound like a raspberry in a dustbin..for me just perfect..(for a 4 cylinder car,yes I know)..

HP/response wise.. it sounds and feels slower, but that's because there is less vibration resonance from the tin can as this new cat is much better mounted and less racous noise always feel slower.

The tuning guys and the seller both reckon that its as close to a de-cat from a restriction viewpoint, without a dyno run who knows.

The de-cat was just a bit too raspy and a bit of vibes came into the car..the car feels fast but very smooth now..I found I was actually putting more throttle down as its not as anti-social..(although compared to many cut n shut exhausts it still was relative quieter)

For Boltz, the car now passes all emissions tests..the undocumented de-cat Fast Idle CO was 0.5 against a limit of 0.2 and the HC was in the 250-500 area (depending on how warm the engine was) against a limit of 200..

I've attached the last two MOTS plus this re-sample for comparisons

 

[Anonymous]

Pictures of the de-cat VRSF and the 200 cell cat