I feel that the exposure is the greatest issue, rather than length or size of exhaust. All catalyzing agents currently in use rely on being at a certain temperature to even work, and tend to, within reason, improve in efficiency as their temperature rises.
As such, the relatively high surface area of the catalyst and exhaust exposed to the air, coupled with a relatively low volume of gases flowing through especially at idle, no doubt conspire to pull the average catalyst temperature down. I wonder if this is partially the reason that exhausts passing under the seat area have seemingly begun to increase in popularity in recent years? Placing the catalyst behind the engine, in the warm air wash from the cooling system versus the cooler outside air, then trapping it in a pocket of panel and insulation, would undoubtedly improve heat retention. It is likely that, as emissions regulations become more stringent as they are often prone to doing, that the field of insulating coatings for exhaust flows, as well as lightweight insulation and lower temperature catalysts will be explored. They undoubtedly exist in some form now, but are not at present cost effective. Also very likely is open embrasure of variable valve timing and direct injection, as both are very compact systems that, while complex, can promise very dramatic improvements in power output, with the salutary effect of also reducing fuel consumption and emissions. Kurt On Oct 11, 2011 9:30 AM, "Noah Goodall" <[email protected]> wrote: There's been some published research on this, and they generally agree with mythbusters. From the abstract: ----------- Even though the motorcycle, fleet is small in comparison with the car fleet, and logs lower yearly mileage per vehicle, their contribution to traffic emissions has become disproportionately high. Exhaust emissions of CO, HC, NOx, and CO2 from 8 powered two-wheelers were measured and compared to previous measurements from 17 gasoline-powered passenger cars performed at EMPA with the aim of ascertaining their relevance. Using exhaust emission ratios from both vehicle types, comparisons based on mean unit, mean yearly, and fleet emissions are considered. Present-day aftertreatment technologies for motorcycles are not as efficient as those for cars. A comparison of mean unit emissions shows that motorcycles exceed cars in NOx emissions. All comparisons reveal a significant HC ratio, to the detriment of two-wheelers. Overall, the relevance of emissions from powered two-wheelers is not negligible when compared with modern gasoline-powered passenger cars. ----------- Here's the listing. I don't have access to the full article. http://trid.trb.org/view/2006/C/782272 Noah On Mon, Oct 10, 2011 at 11:39 PM, Pat Patterson <[email protected]> wrote: > Bikes have all sorts of p... -- You received this message because you are subscribed to the Google Groups "Nighthawk Motorcycle Lovers!" group. To post to this group, send email to [email protected]. To unsubscribe from this group, send email to [email protected]. For more options, visit this group at http://groups.google.com/group/nighthawk_lovers?hl=en.
