Effects of humidity?

**Stav** · 10-08-2006, 09:01 PM

What are the effects of humidity on a 1/4 mile run?

CAMS290 · 10-08-2006, 09:19 PM

Quote:

Originally Posted by useless

What are the effects of humidity on a 1/4 mile run?

Sweaty crotch.lol

gurujosh · 10-08-2006, 09:22 PM

i dont think there is alot.i did my quickest run at 98% humidity

Walkinshaw · 11-08-2006, 11:11 AM

Free water injection

brenx · 11-08-2006, 11:37 AM

Humidity if higher in my experience makes for faster 1/4 times ;)

Hardtopxb · 11-08-2006, 12:04 PM

Townsville. Humidity alwasy high up here.I run drags and track,and find if I venture down south with the same set up I always run better times..(ie, less humidity)IMO.

Quadcams · 11-08-2006, 06:34 PM

Stav realy hot days with very high humidity like the AFF day (36c 100% rh) in January most people were about .4 off there best which had a RA of about 3500ft and for every 1000ft drop in RA you should gain roughly about .15

Quadcams · 11-08-2006, 06:37 PM

Stav play around with this density altitude calculator and you will see the differences humitiy, air temp and ABS will affect air quality.density altitude calculator
Rembering WSID is at 230ft and take into account good air is below 1000 RA (relative altitude)

marcuss · 12-08-2006, 08:37 PM

higher humidity = less horsepower. basically, water displaces oxygen

brenx · 12-08-2006, 09:31 PM

Quote:

Originally Posted by marcuss

higher humidity = less horsepower. basically, water displaces oxygen

My timeslips @ Heathcote show otherwise. Humidity increases and the times start falling quite rapidly. In low humidity I run slower.

Quadcams · 12-08-2006, 10:38 PM

Quote:

Originally Posted by brenx

My timeslips @ Heathcote show otherwise. Humidity increases and the times start falling quite rapidly. In low humidity I run slower.

Brenx did you look at the difference in the RA on those occasions as I have noticed in cooler temps the humidity doesnt play a big factor but in high temps high humidity (muggy conditions) will kill power big time.

brenx · 12-08-2006, 10:52 PM

Whats RA?

I've only ran the XB once during the day. I'd have to check my track data but I'm sure my fastest time for the day was set on a high 20's deg day. Our meets are usually night meets.

Quadcams · 12-08-2006, 11:19 PM

Quote:

Originally Posted by brenx

Whats RA?

I've only ran the XB once during the day. I'd have to check my track data but I'm sure my fastest time for the day was set on a high 20's deg day. Our meets are usually night meets.

RA = relative altitude is where the air quality is measured in a scalce (in feet) of how good the air is, its worked out by taking in account the air temp, humidity, barometric pressure and the height at which the reading the was taken (for example WSID is at 230ft above sea level), air quality only starts to get good when the RA drop below 1000ft as the closer to sea level the denser the air but will vary with different air temps,humidity and barometric pressures for example WSID might be at 230ft above sea level but the air quality might be only equivilant to say 1250ft above sea level when the RA takes into account the varing conditions. If you find out what the height calder or Heathcote is above sea level you can use the RA calculator I put up a few posts earlier to work out how good the air is you raced in, some tracks will have the RA on your time slip like willowbank does but WSID only has air temp, humidity and barometric pressure but if you have those 3 you can work out the RA with the calculator. Also I have noticed for every 1000ft drop in RA you should gain about .15 in your ET. RA is the only thing you need to check to see how good the air is where 0ft is awsome air to say 3500ft which is total crap air.

brenx · 12-08-2006, 11:25 PM

Heathcote doesn't have the RA data on their slips. They only have barometer, temp, humidity, wind speed and wind direction.

Quadcams · 13-08-2006, 12:10 AM

Quote:

Originally Posted by brenx

Heathcote doesn't have the RA data on their slips. They only have barometer, temp, humidity, wind speed and wind direction.

Yeh brenx I have some heathcote slips in front of me, they only read the air pressure in millibars (mb) where WSID is in ABS (absolute pressure in hg). I will find out how to convert mb into ABS then you will be able to use the calculator.

Quadcams · 13-08-2006, 12:15 PM

Brenx heres a weather conversion calculator which will convert millibars to hg (mercury), then all you need to know is the altitude of heathcote from sea level then you will be able to use the densisty altitude calculator to work out the RA.weather conversion calculator

northey · 13-08-2006, 01:33 PM

The fact is, as stated above, dense air contains more oxygen. High humidity is not conducive to making good horsepower. Engines make more power in cold air.
If you need proof on the track have a look at how many records are set at the Winternationals at Willowbank. It's always cold, the air is usually very dense. I believe last Winters though the air was 1000 ft above sea level which is not very good for that track.

If a car goes better in humid conditions than it does in cold air it may need a set up change. Remember that as the sun goes down and the air cools the track can get a mild to heavy dew on it as well. Some cars won't adapt well to the change in grip levels.

It doesn't matter what opinions are here. A correctly tuned engine makes more power in cold air. Whether that can be applied to the track is a different story.

Hardtopxb · 13-08-2006, 01:44 PM

Quote:

Originally Posted by northey

The fact is, as stated above, dense air contains more oxygen. High humidity is not conducive to making good horsepower. Engines make more power in cold air.
If you need proof on the track have a look at how many records are set at the Winternationals at Willowbank. It's always cold, the air is usually very dense. I believe last Winters though the air was 1000 ft above sea level which is not very good for that track.

If a car goes better in humid conditions than it does in cold air it may need a set up change. Remember that as the sun goes down and the air cools the track can get a mild to heavy dew on it as well. Some cars won't adapt well to the change in grip levels.

It doesn't matter what opinions are here. A correctly tuned engine makes more power in cold air. Whether that can be applied to the track is a different story.

Absolutely correct..From experience..

xdclevo · 13-08-2006, 04:17 PM

Quote:

Originally Posted by brenx

Humidity if higher in my experience makes for faster 1/4 times ;)

Thats why turbos boys like winter, as the air is cooler and dryer. If you went faster in humid weather, maybe your jetting is too lean. I find in winter with the "good air", i have to richen the jetting a bit to compensate for the denser air supplied, and increases effeciancy. When humid, the extra moisture in the air makes for less oxygen to burn, hence not needing as much fuel, which drops power off some.

brenx · 13-08-2006, 04:19 PM

Quote:

Originally Posted by xdclevo

Thats why turbos boys like winter, as the air is cooler and dryer. If you went faster in humid weather, maybe your jetting is too lean. I find in winter with the "good air", i have to richen the jetting a bit to compensate for the denser air supplied, and increases effeciancy. When humid, the extra moisture in the air makes for less oxygen to burn, hence not needing as much fuel, which drops power off some.

12.7AFR and 1320deg F exhaust gas temp is spot on.

Check the air temp and humidity -> http://www.users.on.net/~brenx/images/Timeslip_20_05_06.jpg

Prior pbs 393 - 11.14@121.92, Air temp 25.9, humidity 31%, barameter 987

351 - 11.85@115.83 Airtemp 9.8, humidity 92%, barometer 994

xdclevo · 13-08-2006, 05:17 PM

Quote:

Originally Posted by brenx

12.7AFR and 1320deg F exhaust gas temp is spot on.

Check the air temp and humidity -> http://www.users.on.net/~brenx/images/Timeslip_20_05_06.jpg

Prior pbs 393 - 11.14@121.92, Air temp 25.9, humidity 31%, barameter 987

351 - 11.85@115.83 Airtemp 9.8, humidity 92%, barometer 994

How do you know the tune was spot on with the better air? And when you had your motor dynoed is a different story than when you race a year on, with different extractors etc.
But if you think humidity is better for power, no one is probably going to convince you different, so good luck!

brenx · 13-08-2006, 05:21 PM

Quote:

Originally Posted by xdclevo

How do you know the tune was spot on with the better air? And when you had your motor dynoed is a different story than when you race a year on, with different extractors etc.
But if you think humidity is better for power, no one is probably going to convince you different, so good luck!

I've done plenty of R&D with my engine/car. I know where it's at.

I also stated before the last AFF drag meet the humidity would increase and the pb's would roll on. Humidity increased and the barage of pb's went through the roof. It's not just one racer. Plenty went faster with the high humidity.

Hardtopxb · 13-08-2006, 05:41 PM

Quote:

Originally Posted by brenx

I've done plenty of R&D with my engine/car. I know where it's at.

I also stated before the last AFF drag meet the humidity would increase and the pb's would roll on. Humidity increased and the barage of pb's went through the roof. It's not just one racer. Plenty went faster with the high humidity.

No worries Brenx, your car just goes against the laws of thermodynamics.Good on you mate..

brenx · 13-08-2006, 05:52 PM

Quote:

Originally Posted by Hardtopxb

No worries Brenx, your car just goes against the laws of thermodynamics.Good on you mate..

Sometimes things just work. Things look like they shouldn't work just do ;)

Quadcams · 13-08-2006, 06:58 PM

Quote:

Originally Posted by brenx

12.7AFR and 1320deg F exhaust gas temp is spot on.

Check the air temp and humidity -> http://www.users.on.net/~brenx/images/Timeslip_20_05_06.jpg

Prior pbs 393 - 11.14@121.92, Air temp 25.9, humidity 31%, barameter 987

351 - 11.85@115.83 Airtemp 9.8, humidity 92%, barometer 994

The 11.14 run the RA was 2561ft (crap air)

The 11.85 run the air was 467ft (awsome air worth about .3 off ET )

Mate there was something going on with the 11.85 run also what was your 60ft for both runs as the air on that run was excellent.
Out of the 3 the biggest factor is air temp to improving air density/quality dont just look at humidity, I have raced a WSID in 100% rh but the air was 15c and with a RA of 650ft quiet good air but because the humidity was so high the track was getting slipery from dew.

brenx · 13-08-2006, 07:02 PM

Quote:

Originally Posted by Quadcams

The 11.14 run the RA was 2561ft (crap air)

The 11.85 run the air was 467ft (awsome air worth about .3 off ET )

Mate there was something going on with the 11.85 run also what was your 60ft for both runs as the air on that run was excellent.
Out of the 3 the biggest factor is air temp to improving air density/quality.

Different engines ;)

Quadcams · 13-08-2006, 07:07 PM

Quote:

Originally Posted by brenx

Different engines ;)

Well you cant even compare the 2 times then ;)

troppo · 13-08-2006, 10:01 PM

Guys, you need to remember that humidity is a relative thing. 100% humidity is the maximum amount of moisture the air can absorb, but how much water it takes to reach that maximum varies significantly depending on temperature.

In a nutshell, humidity has very little effect at low temperatures. As temperatures increase, the effects of humidity increase exponentially.

Imagine a room full of air at 0 deg. The amount of moisture in the air would only be a few drops. It's because :a) the air at that temperature can absorb bugger all moisture and b) any moisture at that temperature is likely to be liquid and difficult to be absorbed.
If you increase the temp and add steam, you would maintain 100% humidity. At 5 degrees you would have added a cupful of water. At 10 degrees you'd need a litre. 20 degrees would need a bucket full of steam, 30 a large drum, a 44 gallon drum at 40 and so on.
De-humidifiers work in reverse. They take hot, wet air and cool it down, which forces out the moisture as condensate. You end up with cold air thats still 100% humidity and a big puddle. Remove the puddle and allow the air to warm up again and you have warm, dry air. Cold air at 100% humidity can still be drier than hot air at 50%.

RA is way a way of relating changing air pressure to a fixed scale between sea level and the the outer atmosphere.

Imagine standing inside a huge column at sea level. The air pressure you feel is the result of gravity acting on the mass of air inside the column above you. The higher you go in the column, the less mass there is and therefore less pressure at that point. If you know your altitude, you can theoretically calculate the air pressure and vise versa. This is how plane altimeters work. If you took one to the dragstrip on day when there was a high pressure system in the area, it would read a certain altitude. Same place on a day with low pressure system in the area would make it read a lot higher altitude.

Ideal conditions are low temperatures, low humidity, low altitude and high air pressure.

brenx · 13-08-2006, 10:09 PM

Quote:

Originally Posted by Quadcams

Well you cant even compare the 2 times then ;)

I'm not comparing the 11.85 time to the low 11's The car was running 12.1/12.2's all night. As soon as the humidity went up the times dropped. On average I do 5-10 pass's per meet.

I've done quite a lot of racing at Heathcote raceway. I know at Heathcote as soon as the humidity rose the times fall.

troppo · 13-08-2006, 10:14 PM

Check your slips. I have a hunch the increase in humidity coincides with a decrease in temperatures. Cooling air means relative percentage will go up, although actual volume of moisture doesn't change much at all, unless it cools enough too reach 100%, then moisture starts getting forced out of the air as dew or condensate.