Why is it that the current crop of new bikes have the most ghastly-looking exhaust systems? Why is it that, while the rest of the bikes is attractively styled, the exhaust system, that most public and noticeable part of a bike, seems to be an after-thought, or, worse still, a blot on the design?
The GSX-R1000 dual exhausts most certainly spoil the purity of line that the single-pipe K3’s and so on had. The ’08 750 is retrograde also, returing to an appalling version of exhaustion after the tucked-away style of the ’07. And don’t even START me on the current crop being put out by Kawasaki!!
Why is this so? Well, the answer is that all exhaust systems these days have to meet more and more stringent emissions targets and the only way to get them to do that is to make them bigger (fatter).
I think Honda had the answer with the now-superseded Fireblade, but now they have gone back to an under-engine exhaust which, while it appears to work brilliantly, is still far from elegant.
So, what is the thing that makes the pipes so hard to conceal? It’s the cat; the catalytic converter. All modern bikes (and cars) have them, but they’re easier to disguise on a car (obviously). So, a quick tour of the cat.
Even under normal running conditions, the gases leaving the cylinder head of your motorcycle are in the vicinity of 850 degrees centigrade. As they pass down the exhaust headers, they cool considerably, but, for the catalytic converter to do its job properly (purging the exhaust gases of toxic emissions), the temperature of the gases as they enter the cat must still be in the region of 300 degrees. Because all motorcycles must now conform to Euro III standards and the test requires that emissions be measured immediately after a cold start, engineers are moving the cat further forward each time, closer to the headers and in search of the hotter gases.
Given that sportsbikes especially are getting smaller and smaller and their fairings become more and more abbreviated with each successive model, finding space to hide the cat is getting correspondingly harder and harder. So that presents a styling and engineering challenge.
What actually IS a cat, though? Well, despite the mystery surrounding it, it’s really quite a simple device. The internals of the cat are made up of a length of metal foil, crinkled up into a sawtooth shape and rolled up to form a honeycomb. The foil is covered with a ceramic coating to roughen it up, and to increase its surface area. It is then covered with another coating of precious metals. Rhodium reduces nitrogen oxide emissions while platinum and palladium oxidise carbon monoxide to carbon dioxide and hydrocatbons to water and carbon dioxide. The term “3-way catalytic converter” refers to these three processes.
Some cars already have electrically-heated catalysts to meet tougher emissions standards. The implications for motorcycles if this becomes necessary are obvious and worrying. Heaters would increase motorcycle mass and expense and would lead to even greater complexity (and even uglier exhaust systems) to say nothing of necessitating heavier-duty and bulkier batteries.
So, a tour of the cat. I hope you were paying attention to all that because there will be a short quiz at the end of the period.