aussie Posted February 12, 2008 Share Posted February 12, 2008 I have noticed that the temp display normally shows 5 bars but in heavy slow moving traffic this rises to 6 bars and the engine sounds stressed (very noisey tappet sound). When servicing the bike I noticed that the air inlet from the front of the bike to the airbox is in two sections without an air tight seal between them. This suggested that at low speeds the engine would pull air from the joint which is directly above the cylinder. This air would be well above ambient. Experiment I placed a temp probe in the airbox adjacent to the inlet and recorded the following temps Ambient 24.8C Idling stationary 5 bars 46.9C Idling stationary 6 Bars 49.6C Driving above 60Kph 22.7C Idling for duration of traffic light change 35.4C Driving away from lights temp drops very quickly to 22.7C and stays at this temp provided the speed exceeds 25/30Kph. Question: Cool air = power/efficiency. Hot air = less power/efficiency Why did BM not seal connection between inlet sections? Are there any disadvantages to sealing joint? Link to comment
ShovelStrokeEd Posted February 12, 2008 Share Posted February 12, 2008 None in particular. The joint is there to allow service/removal of the aft portion of the box. The snorkel is really there to provide some suppression of intake honk (noise). Power requirements of an idling engine are pretty low as is efficiency since the motor isn't moving anything. Once air flow is established, as you noticed, the temperature quickly drops to ambient. Your probe is showing slightly cooler since the effect of the air flowing over it is to evaporate surface water which has a large cooling effect. I doubt sealing the junction in the duct will effect much as what you are probably seeing is radiant heating of the duct and hence the nearly static air within. Link to comment
T__ Posted February 12, 2008 Share Posted February 12, 2008 I have noticed that the temp display normally shows 5 bars but in heavy slow moving traffic this rises to 6 bars and the engine sounds stressed (very noisey tappet sound). When servicing the bike I noticed that the air inlet from the front of the bike to the airbox is in two sections without an air tight seal between them. This suggested that at low speeds the engine would pull air from the joint which is directly above the cylinder. This air would be well above ambient. Experiment I placed a temp probe in the airbox adjacent to the inlet and recorded the following temps Ambient 24.8C Idling stationary 5 bars 46.9C Idling stationary 6 Bars 49.6C Driving above 60Kph 22.7C Idling for duration of traffic light change 35.4C Driving away from lights temp drops very quickly to 22.7C and stays at this temp provided the speed exceeds 25/30Kph. Question: Cool air = power/efficiency. Hot air = less power/efficiency Why did BM not seal connection between inlet sections? Are there any disadvantages to sealing joint? George, usually a few reasons not to seal that joint.. The first is water intrusion.. That opening allows water to exit the joint without fully getting to the air box (think parked nose high & water running down the tube).. This would be my first guess at the unsealed joint.. Next is to keep that front tube from being a tuned part of the intake system to keep the standing wave under control (probably mainly for intake noise reduction).. Good possibility on this one as the front of the tube is rubber mounted.. Could also be some tuning issues due to snorkel inlet size & max amount of air flow needed.. The inlet snorkel can be the primary tuner at nominal air flow but the air gap to the air box can let in additional air at peak demand (maybe,, long shot on this one).. I doubt the intake temperature will change much if you seal that joint.. My Ducati has twin sealed intake snorkels that breath in the high pressure air in the front frame area.. I would imagine the fueling computer has been programmed to deal with that as the AIT sensor is not in the intake tract on that bike.. Twisty Link to comment
Ken H. Posted February 13, 2008 Share Posted February 13, 2008 The first is water intrusion.. That opening allows water to exit the joint without fully getting to the air box Yup, that's absolutely the reason. Water into the air box = bad. Do not seal that joint! Link to comment
Haynes Posted February 13, 2008 Share Posted February 13, 2008 Hot intake air at idle is also desirable under certain conditions. In colder conditions, icing of the throttle plate can occur and cause rough idling and stalling. Of course this would be pretty rare in Brizzy. Link to comment
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