heat and horsepower

[tlfreek]

I'm sure this is related to heat, but those of you who know feel free to chime in.

Today I went for a hard ride in the heat (103 degrees) and found that my bike lost the umph it usually has. It seemed like it took a longer period of time for the engine to wind up.

Anyone else experience horsepower loss due to hot weather?

[TLstreak]

Im guessing here because im not one of the engine spec internal working guru types. I just ride the wheels off it

Cooler air with the fuel lets the bike "breathe" better or more or less cooler means better airflow into the bike. The hotter the air the less air mass= less air going in.

I know sounds stupid and when I learn this math equation at school ill probably be able to explain WTF im typing. Take an ice cube at 32f/0c frozen and has tighter molocules, heat that up past vapor goes in the atomosphere yadi yadi yadi the molocules speed up. The hotter it gets the more spread out everything gets the less movement of air. cool it off a little and everything works better due to more oxygen entering the bike. That probably doesnt make a damn bit of sense to anyone but me

[tlfreek]

right on I think i got it

hot air makes molecules move in an elliptical pattern and inturn forces a backward pressure resulting in a slower motorcycle.

makes perfect sense now....

seriously thanks for the reply it sounds like heat is the culprit.

[Reddevil76]

Re: heat and horsepower

Originally posted by tlfreek
I'm sure this is related to heat, but those of you who know feel free to chime in.

Today I went for a hard ride in the heat (103 degrees) and found that my bike lost the umph it usually has. It seemed like it took a longer period of time for the engine to wind up.

Anyone else experience horsepower loss due to hot weather?

I just took out the water pump yesterday as I needed to remove the entire engine case on the right side to push back a loose oil separator.

If you look at the passage ways for the coolant flow after being pushed by the impeller, you will see lots of potential for porting!

90 degree elbows for coolant flow! Not good at all!

[Guest]

uhhh....not to rain on anyone's parade, but somehow i don't think that's the way it work. One, i understand the ice cube analogy...but its a poor one, consider water when frozen actually takes up more space as opposed to when it is a liquid. Two, i believe the reason you experienced less power is because when the air is hotter, it is less dense. Thus there is fewer particles in a certain volume of air as ooppsed to when it is cold. This is why people use intercoolers to cool the air in their airbox, and thust create more power (especially when used with some sort of blowing system, tubro, supercharger, etc). This is also why people use a "cold air intake" system. I don't think it has to do with how excited the particles are...ultimately were not counting electrons here, more particles.

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[TLstreak]

'This is why people use intercoolers to cool the air in their airbox, and thust create more power (especially when used with some sort of blowing system, tubro, supercharger, etc). This is also why people use a "cold air intake" system. I don't think it has to do with how excited the particles are...ultimately were not counting electrons here, more particles.'

Pretty much what I was trying to say, and the reason for the first sentence "Im guessing here because im not one of the engine spec internal working guru types. I just ride the wheels off it"

I JUSt strated covering all this dense/mass/volume stuff today, and havent quit finished learning all of it, and sure dont understand it all yet

Thats why im a goin to school , so i's can be edjumacated

[rzarobbie]

Originally posted by crashtd
Two, i believe the reason you experienced less power is because when the air is hotter, it is less dense.
-

Bingo. Dumbing it down a whole lot leave me with saying this, Less Density means you need more air to do the same job more dense air will do.

Ha.. hope that wasn't to simplistic

[Duken4evr]

Hot air is less dense than cold air. Less dense equals less power.

When I ride my TL on a cold day (50's F in CA) at sea level, it is pretty darn hard to keep the front end down. I picked one up in 3rd last time I did that. Unreal

[Steve TLS]

You've all got it. More heat air expands = less dense is less molecules of oxygen per whatever cubic metre, cc, ci etc.

Cooler more dense / compact air = more molecules of oxygen.

Also air pressure comes into play. Sea level with max airpressure is way better than high altitudes and low air pressure, I can't remmeber it now, something like 3% power per 1000 feet.

I knew it all when I had to plug a correction factor into my dyno so any run at any atmospheric could be compared.

[TLRipley]

Originally posted by Duken4evr
Hot air is less dense than cold air. Less dense equals less power...

...because there are fewer molecules per a specific volume of gas. Pilots refer to this phenomenon as "density altitude". On a hot day, the airplane will behave as if it is at a higher altitude than it actually is. Performance charts in the pilot's operating handbook take this into account because important things like takeoff and landing roll have to be lengthened when the weather is hotter than standard.

But, I digress. The ECU doesn't know this, so it keeps the fuel injection dumping the same amount of fuel into the engine, thus effectively making the mixture too rich, which causes a loss of power.

[N2wheelies]

when i race in san diego its 70 degrees or so and i turn 11.10 quarter miles and
have to back off in 1st and 2nd to deal with wheelies.

in palmdale, at only 2000 more foot elevation but 100 degrees i dont even get a first gear wheelie and turn meager 11.55s.

air density

[Steve TLS]

Originally posted by TLRipley
But, I digress. The ECU doesn't know this, so it keeps the fuel injection dumping the same amount of fuel into the engine, thus effectively making the mixture too rich, which causes a loss of power.

The ECU has an air temperature sensor in the airbox, and an atmospheric pressure sensor in the front of the TLR and the side of the TLS.

The ECU does make corrections for air temperature and pressure.

Doesn't matter how rich or lean you make it, with hot air there is less oxygen to burn the fuel, so no matter how much tweaking of the mixture you do, if the oxygen isn't there, neither is the power.

[MonkeyClaw]

Crashtd's right - warmer air is less dense, which means there's less oxygen to burn and therefore less effiecient combustion and less power in the end.

It's all in chemistry and physics (if you can stay awake for it!!).

[doug]

seeing how we are on this subject what happens when you add moisture or humidity to the air does the engine make more power or less, or I should ask is it capable with the right jetting to make more or less horsepower. Enquiring minds want to know.

[Steve TLS]

I've seen water injection systems, can't remember what the real benefits were, cleaner engine, possibly a cooling effect on the incoming charge and thus increasing it's density?

Unlike NO2 which gives off it's oxygen molecules at a certain temperature, I'm sure the only way to seperate the hydrogen and oxygen molecules out of water is by an electric current (someone?) therefore the power increase if any from water injection isn't from the water itself.