[image: View Post]kaldek, on 28 May 2010 - 02:01 AM, said:
I've never had an overheating problem. We had a 47 degree day here recently (117 degrees fahrenheit) and the bike coped fine. Stop-go traffic too.
If it's so crap, why did Honda do it in first place. Please, no comparisons to flapper valves, VTEC, or cam chains. Gimme something better than THAT, puh-leeez!
Well I have a couple of questions for you on your hot day.
1. What was the humidity? As the heat index effects the engines ability to cool as well. If you look at this table
NOAA heat index, you can see how much the humidity effects things. Around here through June/July/August and into September the humidity and temperature regularly push us into the extreme danger zone past where they even list an equivalent temperature. Especially in stop and go traffic in the afternoon. I've seen huge thunderstorms blow up and dump everything on stopped traffic and you can just watch the steam rise off the pavement, while the rain is still falling.
2. How long were standing dead still? How long did it take you to move a Km at the slowest point?
The answers around here are stopped dead in traffic for twenty minutes or more sometimes and Half an hour to go roughly a KM.
Its all clutch just about out, back to the bar and wait crap.. Now no bike or car likes this kind of operating conditions, but other bikes I've ridden in these conditions get hot, the fan comes on and the temperature stabilizes until I can get moving again. The VFR before the fan swap, would come on and the temps would just keep going, I'd frequently end up cutting the motor at 245 and paddling the bike along with my feet, until it cooled off a bit. I'd even gotten pretty good at bumping the bike, so that the fan wouldn't kill the battery before I could start the hot engine with its heat soaked starter. These oem's should forget doing heat durability testing in the open desert, they should have to do it in some downtown area (Baltimore MD, Wilmington DE, Philadelphia PA, the rt42 & RT 55 interchange in NJ). All these spots are parking lots in the summer heat and humidity just about every rush hour all summer long (and forget friday nights).
Anyway, those are the conditions that my vehicles have to survive some do it well right from the factory, some can't hack it without help. Lately most newer vehicles have all needed help with the cooling in traffic issues.
Now why did Honda design so many of their bikes with suck fans instead of blow ones?
Well I don't know what the biggest reasons were, but I have heard a few reasons.
1. Pulling the air inward keeps the exhausted heat from baking the riders leg (and possibly arms). Instead it makes the whole bike hot enough to roast all of the riders anatomy.
2. Its supposedly quieter, which it might just be. But I would think that three or four minutes of a slightly louder fan running would be better for everyone's health, than the constant running fan and the heat altered emissions (the NOx emissions that everyone is paranoid about around here can be easily cut back by just cooling the intake air and exhaust).
3. Supposedly its more efficient since the fans in suck mode draw cooler external air through the radiator core and push it out the right side. Unfortunately that doesn't work when moving slowly or stopped. The fan sucks air in one side, them pushes it in to the heated space around the engine and it never gets out, the right hand side. Even on the RC51 with its two fans, the heat just built up, since the only place it had to go is up around the frame, triples and tank. The bars would reach, burn you hands hot quickly in traffic before I reversed the airflow.
I just get the feeling that Mother Honda did not do enough real world testing of the fan designs for handling traffic induced heat soak conditions.
I can tell you this, the GL1800 debuted with a tractor fan, but after a couple of years and lots of complaints from owners all over the world, Honda changed the fan blade to a pusher style unit to cure the cooling issues. It was drop in retrofit to earlier 1800's and a lot of dealers did them.
Heat management and control of air flow through the engine bay has not been one of Honda's great achievements in the past. So I'm kind of curious to see how the new layered fairings on the new VFR1200 really work.
