View Full Version : Engine Difference Hot or Cold
I have noticed that in the morning when the air is still cold and I start the the bike, during the 10km run to work the engine runs incredibly smooth. It quite literally purrrrrrsssss. It's as if there is perfect harmony between the Air temperature, humidity and engine temperature etc..., I love it it.
[The temperature gauge is barely above the lowest mark at this point ]
In the afternoon when returning from work the engine makes a lot more noise, probably valves, timing chains or whatever and loses that lovely purring feeling.
[The temperature gauge is usually about 1/4 the way above the lowest mark at this point, which is usually its nomal position when warm and running ]
Question : Why does it purr when cold and then become clunky, chinky, metallic when warm. What would I have to do, check, tinker with, in order to retrieve that lovely purring in the afternoon when the air is warmer ?
PS : The bike runs great regardless of morning or evening.
you are travelling in a different direction and therefore the wind is going a different way. Would that be the reason?
you are travelling in a different direction and therefore the wind is going a different way. Would that be the reason?
I could verify that idea if only I could find the bloody reverse gear, where do they hide it ? :lol:
faantjie
20-09-06, 01:28 PM
I don't know why but have noticed the same thing on the Alp. :?: :?: :shock: :roll:
captaincaveman
20-09-06, 04:46 PM
ive noticed it on every vehicle ive had(bike or car) always seens to run better in cold, is it cause the air is denser and therefore more air per bang? and therefore more power? also is the smoothness down to the fact that everythings tight before the heat makes all the metal expand a bit?
oils cooler as well so it thicker :? i suppose its a little bit of all these things :D
faantjie
20-09-06, 09:29 PM
If only I could be so smooth in the mornings :lol: :lol: :roll: :roll: :roll: :lol:
Dilbert
20-09-06, 10:15 PM
Yes, the motor does work better in the morning because of the cooler air (up to a point) and the way it combusts and pretty soon Jenna or someone will be along to give us a dissertation on exactly why :lol:
The other thing I find is that at 6:30 am there is a lot less traffic to hold you up than at 6:30 pm so you can go at your own pace and everything just feels smoother and nicer. :D
djadams
21-09-06, 07:04 PM
More power cos of cold air, smoother and quieter cos of cold (thick) oil.
Most powerful when air cold (dense), coolant cold (so charge doesn't get warmed up too much) and oil up to temperature (so thin and slippy).
Quietest and "smoothest" when oil cold (so thick and gloopy), air temp not really relevant, except that it has an effect on oil temp and coolant temps, obviously.
Last of trio is:
Most economical when air warm (reduced pumping losses), oil warm (thin, slippy), coolant hot (so not much heat robbed to coolant).
GeoBloke
21-09-06, 08:10 PM
More power cos of cold air, smoother and quieter cos of cold (thick) oil.
Most powerful when air cold (dense), coolant cold (so charge doesn't get warmed up too much) and oil up to temperature (so thin and slippy).
Quietest and "smoothest" when oil cold (so thick and gloopy), air temp not really relevant, except that it has an effect on oil temp and coolant temps, obviously.
Last of trio is:
Most economical when air warm (reduced pumping losses), oil warm (thin, slippy), coolant hot (so not much heat robbed to coolant).
Now that the mornings are cooler, I've been wondering why the @ is more "up for it" those first few miles. I put it down to the denser air yielding a bigger bang. Duh. I don't think your brain is as small as your avatar lets on, professor. Get on the wiki with a course on internal combustion physics. I'll sign up! :D
Following on, I have found an interesting article on this website :
http://www.calsci.com/motorcycleinfo/Oils1.html
There's a lot of technical data at the beginning but there are one or two chapter's concerning bikes. ( it's worth reading one or two of the preceding chapters though ).
The motorbike chapter has the following title
Choosing an Oil for Your Motorcycle.
After reading a little of this article I have understood that it would probably be a much bettter idea to use a 15w40 oil rather than a 10w40 oil. Or even a mixture of the two.
Has anyone compared a 10w40 and a 15w40 in relation to general noise and running conditions of the engine.
I know the winter is coming up so I am little hesitant in changing for a 15w40 during this period.
djadams
22-09-06, 08:19 PM
I don't think your brain is as small as your avatar lets on, professor.
Gee, shucks... :D :D
Get on the wiki with a course on internal combustion physics. I'll sign up! :D
Well, that'd take a whole lot of effort, see. I'd have to think about it in a structured way and write about stuff in a coherent order. What works better is if peeps just ask stuff on here and I answer it... Like:
After reading a little of this article I have understood that it would probably be a much bettter idea to use a 15w40 oil rather than a 10w40 oil.
Having just read a few lines of his article, it seems interesting enough, though in the little I read he's wrong about a couple of things - API classifications of S and C are for "spark" and "compression" ignition engines (i.e. gasoline or diesel) not "service" and "commercial". I'm not slagging him off mind, cos anyone who has the patience to do what I can't be bothered to do and write a web guide for peeps is clearly a sound bloke. Just that as with so much info on the net, you need to heed his statement that he's no oil expert and take it all with a pinch of salt and cross check everything before doing anything rash...
So - swapping to 15w40 would make it even quieter when cold, but it would raise your fuel consumption and give your oil pump an even harder time, particularly when cold which is when it has it's hardest time anyway. The bearings have been designed for a specific viscosity - Honda don't pick the oil spec out of thin air any more than any other manufacturers do.
Really when it comes to oil the best advice possible is use what the manufacturers recommend. Rarely will a more expensive oil give you real benefits (when was the last time you wore out a bike engine before the rest of the bike died around it?). And rarely will a change of viscosity spec give you an advantage without a penalty. I know peeps who have run thinner oils than specified to improve fuel consumption. Which is fine until the oil film in the bearing collapses at full throttle and you spin the shells...
piguglyshandydrinker
23-09-06, 08:59 AM
I don't think your brain is as small as your avatar lets on, professor.
Gee, shucks... :D :D
Get on the wiki with a course on internal combustion physics. I'll sign up! :D
Well, that'd take a whole lot of effort, see. I'd have to think about it in a structured way and write about stuff in a coherent order. What works better is if peeps just ask stuff on here and I answer it... Like:
After reading a little of this article I have understood that it would probably be a much bettter idea to use a 15w40 oil rather than a 10w40 oil.
Having just read a few lines of his article, it seems interesting enough, though in the little I read he's wrong about a couple of things - API classifications of S and C are for "spark" and "compression" ignition engines (i.e. gasoline or diesel) not "service" and "commercial". I'm not slagging him off mind, cos anyone who has the patience to do what I can't be bothered to do and write a web guide for peeps is clearly a sound bloke. Just that as with so much info on the net, you need to heed his statement that he's no oil expert and take it all with a pinch of salt and cross check everything before doing anything rash...
I think in the US "C" and "S" ratings are referred to as service and commercial which is effectively the same as us using spark (petrol) and compression (diesel).
So - swapping to 15w40 would make it even quieter when cold, but it would raise your fuel consumption and give your oil pump an even harder time, particularly when cold which is when it has it's hardest time anyway. The bearings have been designed for a specific viscosity - Honda don't pick the oil spec out of thin air any more than any other manufacturers do.
Really when it comes to oil the best advice possible is use what the manufacturers recommend. Rarely will a more expensive oil give you real benefits (when was the last time you wore out a bike engine before the rest of the bike died around it?). And rarely will a change of viscosity spec give you an advantage without a penalty. I know peeps who have run thinner oils than specified to improve fuel consumption. Which is fine until the oil film in the bearing collapses at full throttle and you spin the shells...I was particularly bewildered at the fact that most oils ie, a 10W40 have lost such grade in 1500 miles that it renderes them effectively a 10W20!
Surely, Honda specify a 10W40 (no mention of semi or fully synth) at change intervals of 8000 miles or 1 year.
I think I'll take their word for it (and change it a bit more often to be on the safe side!)
Phil
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