How much does cold weather boost Power/Torque?

[Gosling1]

Your on the right track oldman....If you engine runs better cold then its tune is out of whack.
Cooler means more air which means leaner mixture. Your bike is leaning out a little when cold.
For those with EFI bikes, the computer will always punch more fuel in when cold.
That doesnt happen with carbs......

what are you talking about Steve ? The engine responds better to a colder intake temperature not because its *out of tune*, but for *exactly* the reason you then stated - it runs leaner ! When you tune carbies for maximum response, which way do you tune them ? I would suggest that if a bike runs better when its cold, and its a carbie bike - then the state of tune is probably pretty good.......if the bike ran *worse* in cold temps, then yes, the tune could be out of whack....

This is exactly the same effect when you ride in the rain. The fact that the air coming into your motor is saturated and 'wet', results in better and more complete combustion due to the lower temperature. For those old farts out there who used to run carbied V8's back in the 70's and 80's........how many remember that your Sandman panelvan ran *heaps* better in the rain ??

I actually fitted a water-injection kit to my old HQ308 with a 600 vac.sec Holley back in the 80's - the difference in response and even fuel economy was very noticeable, especially in hotter weather.

[jonoZRX]

Either my bike was running better in the cold weather on the weekend, or I'm finally learning how to do a half-decent race start

[Blurr]

Last winter i smashed the throttle hard one night in first gear at 60kph and it just broke traction and started wheelspinning.. So much for kawasaki's traction control system on the 08-09m, did fark all.. It kept spinning hardcore until i backed off

The Bug doesnt have traction control, never did.

It have KIMS which is an electronic rev accidental rev spike inhibitor. Doesnt work when you "smash the throttle" at 60kms, thats not exactly accidental.

KIMS Ignition
- Kawasaki Ignition Management System (KIMS) helps curtail sudden spikes in engine speed, enhancing the rider's control of power delivery
- In addition to standard fuel injection system inputs (engine speed, throttle position, vehicle speed, gear position, intake air temperature, intake air pressure, engine temperature and O2 sensors), KIMS monitors the rate of rpm change every 0.02 seconds
- Designed not to interfere with the rider's intentions, the complex ECU program assumes all rider inputs are intentional. However, when a change in engine speed exceeds the predicted response for given parameters, KIMS will slow the ignition timing to reduce power
- Adjustment of KIMS parameters is possible with an accessory racing (circuit-use only) kit installed

[oldman]

Cold weather causes both the oxygen and the gasoline to become more dense, (unlike water gasoline expands and contracts with the temperature) so the carb mixture should remain at approximately the same air/fuel ratio just more fuel/air molecules in the combustion chamber. Kind of like a low boost super charger. The more fuel/air in the combustion chamber at the proper ratio, the more HP. Pretty obvious even to a moron like me. If you don't understand this concept you should switch to pedal bikes, and you can ride them after a Jim Beam.

[Kawawog]

Last winter i smashed the throttle hard one night in first gear at 60kph and it just broke traction and started wheelspinning.. So much for kawasaki's traction control system on the 08-09m, did fark all.. It kept spinning hardcore until i backed off

The Bug doesnt have traction control, never did.

It have KIMS which is an electronic rev accidental rev spike inhibitor. Doesnt work when you "smash the throttle" at 60kms, thats not exactly accidental.

KIMS Ignition
- Kawasaki Ignition Management System (KIMS) helps curtail sudden spikes in engine speed, enhancing the rider's control of power delivery
- In addition to standard fuel injection system inputs (engine speed, throttle position, vehicle speed, gear position, intake air temperature, intake air pressure, engine temperature and O2 sensors), KIMS monitors the rate of rpm change every 0.02 seconds
- Designed not to interfere with the rider's intentions, the complex ECU program assumes all rider inputs are intentional. However, when a change in engine speed exceeds the predicted response for given parameters, KIMS will slow the ignition timing to reduce power
- Adjustment of KIMS parameters is possible with an accessory racing (circuit-use only) kit installed

I guess i was expecting it to work differently..I assummed that if it broke traction at any time it would retard the timing massively and you would see a very noticable decrease in power.. I can tell you know i felt nothing, it continued to wheelspin strong until i backed the throttle right off

[DaveGPz]

Have a JIm Beam and a cold brew and even the most mentally challenged will understand.

I keep my Jim Beam in the freezer. Makes me go way faster.

[MickLC]

....This is exactly the same effect when you ride in the rain. The fact that the air coming into your motor is saturated and 'wet', results in better and more complete combustion due to the lower temperature....

Unless the same rain has been pouring onto your pod filters all day, then it runs like a dog

....

[Wattie]

I think the rev spike feature would only cut in, say when you were gassing is in the rain and your wheel hit a bit of white paint in the road and spun up suddenly?

[tim]

QUICK VERSION:
To cut to the chase I've calculated that between June6 at 3pm, and June 14 at 9am in Richmond Sydney you would have expected to see a real world rear wheel difference of 7% of your Maximum bike power, or for me close enough to 7kw (10hp) difference between riding your bike at those times.

For a zx10r with 150kw this equates to 10.5kw.

What these figures represent is how much a correctly configured dyno/tuner would have to adjust the figures by under these conditions to find the SAE standard power reading, or, in reverse, how much extra power the bikes make because of the cold conditions.

Keep in mind what I've calculated is the difference between a moderate environment(actually turned out to be a "standard" environment as the correction factor is 1) and a cool environment.

The difference between a HOT environment (35degC assuming 1012hpa)and a cool environment calculates to a result of 14kw difference on my bike, 21kw on 150kW a zx10r!

Now completed and I'm pretty happy with my method and results, but I very likely made an error or fallacy so open to criticism etc.

LONG VERSION:
Revisiting this, the only actual evidence was from Glen saying the difference was around 10hp (7.5kw) on ZX10s between "cooler" and "bloody hot" temps.

I don't understand the "better response but that doesn't mean more power through the rev range" point of view, to me "response" = power.

It's annoying me enough that I've decided to work it out for myself.

I'll utilise the updated dyno correction factor calculation SAE J1349

Usually it's used to take variations in observed power due to environmental air temp and air pressure (on a dyno) and convert them into the "normalised" conditions by returning a factor to multiply with the observed power.

As discussed here: http://wahiduddin.net/calc/cf.htm

I'll be using it in reverse to take the real world rear wheel power of my bike, and then calculating in reverse to the boost in power from that due to colder denser air.

I'll use excel to apply the calculations to 2 different local real environment conditions from the day time last month in Richmond Sydney which is the closest weather station to me with air temp and pressure readings.
http://www.bom.gov.au/climate/dwo/201006/html/IDCJDW2119.201006.shtml

By working out the correction factors for 2 opposite weather conditions
(9am June14 - 5.6degC 1035hpa)
(3pm June6 - 19.8degC 1012hpa)

in the same local place within 8 days of each other last month I'm hoping to give a realistic picture of what numbers reflect the increase in power we feel in normal riding conditions this time of year.

Attached is a screen shot of my spreadsheet and the spreadsheet is attached.

NOTE: Pv is "saturation vapour pressure" dependent on temp as calculated here: http://wahiduddin.net/calc/density_altitude.htm which is subtracted from the air pressure and used in the formula (Pd)

[oldman]

Good job on the formula. There is not enough Jim Beam in the world for some people on this forum to understand what you are showing and there will still be arguments. It's kind of like religion no amount of common sense will convince some people that the earth is older than 8,000 years, (according to some interpretations of the bible). Some people think the TV show the Flintstones is a documentary. Cheers.

[Gosling1]

.... Some people think the TV show the Flintstones is a documentary. Cheers. .....

WHAT ?? You mean it's NOT ??

[Phantom]

As Tim has shown it is not just air temperature that affects inlet charge. Barometric pressure is in the game too; that is affected by the weather.... no doubt you have heard the weather girl on the news talking about highs and lows (of barometric pressure). Also altitude effects pressure to the tune of about 30 to perhaps 45 (less) millibars (or hectopascals if your less than 50 years old) per thousand feet (up). So, pressure and temperature are required to calculate air density........ However!!! if the algebra (adding and dividing the alphabet always gives me a headache) in Tims post is a bit much to have you noticing, there is another contributing factor. One that our cousins in the more Northern parts of this fair land especialy need to contend with! Percentage of humidity. Unlike water injection, that volume of water as invisible vapour excludes air in any given volume and decreases air in the inlet charge.

Just for the record Tim, its Vp not Pv...Good post though Bro.

[oldman]

Wow! there is intellegent life on the earth, just not in the U.S. especially Utah. A just cause for celebration, bring on the J.B.

[tim]

As Tim has shown it is not just air temperature that affects inlet charge. Barometric pressure is in the game too; that is affected by the weather.... no doubt you have heard the weather girl on the news talking about highs and lows (of barometric pressure). Also altitude effects pressure to the tune of about 30 to perhaps 45 (less) millibars (or hectopascals if your less than 50 years old) per thousand feet (up). So, pressure and temperature are required to calculate air density........ However!!! if the algebra (adding and dividing the alphabet always gives me a headache) in Tims post is a bit much to have you noticing, there is another contributing factor. One that our cousins in the more Northern parts of this fair land especialy need to contend with! Percentage of humidity. Unlike water injection, that volume of water as invisible vapour excludes air in any given volume and decreases air in the inlet charge.

Just for the record Tim, its Vp not Pv...Good post though Bro.

Wow! there is intellegent life on the earth, just not in the U.S. especially Utah. A just cause for celebration, bring on the J.B.

Phantom, I second guessed my memory with Vp/Pv I got it right in one section not in the other

Good post mate thanks. Don't seem to be getting a lot of interest since I proved it but I'm happy now I understand how it all works and that what I'm feeling is a significant increase in power.

Oldman, what's the weather like there now?

[kevindinho]

In conclusion TIMS A NERD!!!! hahaha