Teach me exhaust

[dn38416]

Links or bare bones explanation (like i'm 5) appreciated.

Got a 4th gen VFR750 (beauty, sort of). It's obviously not ULEZ NOx compliant and I need it to be at some point next year. (Yes hate the situation, agree with you, separate thread).

Lots of these bikes have been put through the test and bought up to compliance. The very reasonable man at the test station tells me they usually weld a catalytic converter into the exhaust, no messing around with the carbs etc. Now as per title I know very little about exhausts, but I have two questions:

i) I'd prefer I do any work on the bike anyway, I can only find one place selling slip on cats (louis-moto), but not much else as i spose it's not that common a mod. Do they really need to be welded in?

ii) Will they really just work without any other modifications to the carbs or rest of the exhaust? I'd guess that the temperature needs to be in a certain range for it to work. My initial thinking was to richen the mix for reducing the emissions, but that would bring the temp down.


As much as it would be good for the bike to be compliant, i'd rather not spoil it in the process. Spoil in a very mild sense, but still.

[MarJay]

I suspect it will affect the power delivery. Is this Riverbank motorcycles? It may be a requirement of the certification to add some level of anti tamper which might equal welding I guess?
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British beauty: Triumph Street Triple R; Loony stroker: KR1S; Track fun: GSXR750 L1; Commuter Missile: GSX-S1000F
Remember kids, bikes aren't like lego. You can't easily take a part from one bike and then fit it to another.

[dn38416]

[WD Forte]

As the CAT will increase back pressure you may find you want to lean it out a wee bit as wont 'breath' as well but only testing will tell.
You may get better low end torque but lose high end power with a CAT.

That London eh?



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bikers smell of wee

[Robby]

Carbed bikes will poison a cat fairly quickly. There were some early carb and cat cars, mostly in Scandinavian countries with tight emissions requirements back in the 80s. Even on those factory setups, the cat would only last a year or two.

So it would only be a modification to pass the test, not a long term way of reducing emissions. For that reason, bolting it in would be preferable to welding it in.

I doubt it's a fixed requirement. I have an aftermarket exhaust on my Guzzi, but it's also homologated to Euro IV, with cats. The cats are removable, they are built into the baffle. Even car cats are typically a bolt-in section of the exhaust.

So I assume the weld-in bit is mostly Riverbank trying to cover their own backs, which is fair. They would be on fairly shaky ground anyway if TFL did a thorough investigation into them. If they want to stick with the idea that they're trying to help riders reduce emissions, instead of trying to get around the ULEZ, it would be in their interest to make emissions-reducing modifications harder to remove right after the test.

[Irezumi]

Have contacted them about exactly this. Did'nt ask further but I would assume it would be a good idea to get hold of a second hand exhaust and fit the cat to this, install to pass the test then remove afterwards, I would assume it will be welded in.

Alternatively buy a newer bike which is the other idea I am toying with.

[Bhud]

Carb tweaking is a part of the service that they provide. Therefore, the best plan may be to get a second-hand exhaust as suggested, and leave it to them.

[grr666]

It's all bowlocks though really isn't it? I could go buy a decat link pipe, have a flash done and ride on in for free
spitting flames and sounding like Royal Jordanians Nuda without any worries about emissions or daily fees just
because the bike is designated as Euro 5 at manufacture. It's not even an MOT failure to have taken the cat off,
not that mine will be anywhere near an MOT test centre for the next three years anyway. This isn't about emissions,
it's about getting older vehicles off the road so they can sell more new vehicles, preferably ones on message
i.e. electric ones or ones like mine with umpteen catalytic converters. That's the problem now that reliable, durable
vehicles are commonplace, there's no need to keep buying new ones.
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[Easy-X]

Well yes getting an old bike certified is all about "this model could meet the emissions target but we can't be faffed with the infrastructure to check every year." The one advantage of motorcycles is they're running on a "candles and windows tax" scheme; I suppose we should be grateful to be overlooked.

So the path is: buy second-hand exhaust, weld in cat, get certified, fit back original exhaust

Without going on a rant and derailing the thread the thing of it is if all journeys done in cars, where possible, were done on motorcycles the air pollution in cities would drop to the point of not being a thing. And nothing to do with the bikes' emissions, purely down to the reduced congestion.
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[dn38416]

Cheers guys, yeah well i spose the policy is semi-successful if the objective is to make me chuck away a perfectly good bike and buy a new one I don't like, on a finance deal that isn't going to do anyone any good

At least I can probs spread out the cost a bit if they do it and it doesn't have a noticeable hit on performance (I don't really rag it anyway tbf) in the few years after.

Has anyone spotted some universal slip-ons that i can just try and putty in on the off-chance i can get it through? I looked again at the ones on louis-moto and I think they're all brand-specific.

[Robby]

[grr666]

[MarJay]

[Irezumi]

[Robby]

[Easy-X]

ULEZ. Nice idea, poor execution.

There's no doubt that air pollution is bad m'kay but if your target is "less pollution" then why not tackle the major contributor: congestion? 4+ wheeled vehicles stop, start, sit in queues, trundle and very slowly wend their way around the city. This is not what the ICE was designed for.

Not so on a motorbike. Light traffic? Takes me an hour to get into the City. Heavy traffic? Takes me an hour to get into the City I could hazard between saving money on CC, ULEZ, parking and fuel my bike's practically paid for itself and spat less pollution into the air to boot just down to the engine running efficiently rather than the stop/start/stop/start of my car.

But I dunno, even though I'm doing the smart thing I get a general impression of disapproval from central government, the mayor and certainly the councils. Why is that?
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[sickpup]

I was reading some studies a few years back concerning city commuting and all the studies concluded that if something like 10% of car commuters changed to PTW's pollution was cut in the region of 30% due to the engines running and idling for less time.

We do need to cut pollution but the major change from Petrol powered vehicles to Electric vehicles won't do it due to the absence of clean power, it just moves the pollution elsewhere.

[Robby]

[sickpup]

[grr666]

[Robby]

[dn38416]

[Easy-X]

[Irezumi]

[Easy-X]