Best drag racing/track racing weather...

[B00STDZ]

Curious what you guy's opinions are on this subject... Does Density Altitude play a role? Temperature? Humidity?

 

Also lets assume the track has been properly prepped so lets just focus on weather conditions...

 

 

Im not sure about DA playing a role but my opinion on temp and humidity is..

-60's-70's degrees F (in my opinion anything colder than say 50 degrees is detrimintal to a cars performance as it uses more energy to keep things that are suppose to stay hot.... hot[like the turbo manifold])

-between 0-50% humidity (less water in the air the better... more air less water better explosion)

 

 

 

These are my opinions... let me hear yours.

[turboHLS30]

High 60's to low 70's are the best to get really good grip.

[B00STDZ]

High 60's to low 70's are the best to get really good grip.

Yup that too forgot to add that in my post...

 

What ive figured out about DA

 

people say the more DA the better... what plays into DA is altitude, temperature, baramotic pressure, and humidity.

 

To have more DA is mainly dependent on a Higher altitude paired with a very very low humidity and a mild temperature.

 

 

so like maybe Colorodo, Tucson Arizona, or El Paso Texas (I would say california but does cali have a strip on a place with high elevation? I though cali was mostly low elevation) having optimum conditions most of the year? Or just live elsewhere at high elevation and wait for the optimum day to race?

 

Would track racing be the same? Better performance with a higher DA? Or just with street/strip?

 

 

Ive always assumed high speed track racing or "topping out" and drag racing it is optimum to have a dry extremely hot pavement I guess characteristics of a desert environment...

 

But as far as what an engine performs optimumly at would probably be a milder temperature...

[zgeezer]

Yup that too forgot to add that in my post...

 

What ive figured out about DA

 

people say the more DA the better... what plays into DA is altitude, temperature, baramotic pressure, and humidity.

 

To have more DA is mainly dependent on a Higher altitude paired with a very very low humidity and a mild temperature.

 

 

so like maybe Colorodo, Tucson Arizona, or El Paso Texas (I would say california but does cali have a strip on a place with high elevation? I though cali was mostly low elevation) having optimum conditions most of the year? Or just live elsewhere at high elevation and wait for the optimum day to race?

 

Would track racing be the same? Better performance with a higher DA? Or just with street/strip?

 

 

Ive always assumed high speed track racing or "topping out" and drag racing it is optimum to have a dry extremely hot pavement I guess characteristics of a desert environment...

 

But as far as what an engine performs optimumly at would probably be a milder temperature...

 

No, I think you have it backwards. All other things being equal, you will not generate the same HP at 5,000 feet as you do at sea level or lower. Any pilot will tell you that taking off at 5,000 feet is not the same experience as at sea level. Cooler is generally better than hotter and a little fog helps too.

 

"Back in the Day" when we were running 1/4 mile drag races in at the Carson City, NV airport (right at 5,000 feet above sea level) a '57 tripower Pontiac would turn trap speeds in the high 80s. The same car at Half Moon Bay or Lodi, was always turning in the low 90's. About 5 mph faster in the 1/4 mile. It was a real treat for us to convoy down to Half Moon Bay because we could feel the difference in horsepower as we dropped altitude. Generally night drags under the lights produced faster times all the way around than in the heat of the day.

 

G

[B00STDZ]

Maybe lower altitudes are better for NA and higher are better for turbos...

 

Because dont turbos hit their efficiency range better at a high altitude?

[m4xwellmurd3r]

It shouldn't matter. A turbo car and an N/A car should hit better numbers the lower the altitude. Lower altitude=higher air density. more air into the engine=more power. N/A or Turbo, they'll both make better numbers at lower alt. than higher.

 

From what our little weather meter said that my dad got back in teh days of him running his bug out here in Phoenix, lower temps+drier air=faster times.

[B00STDZ]

Did more research I stand corrected...

 

So i guess low altitude, very very low humidity, High UV rating from sun to heat pavement, temperature in the 60's or 70's...

 

 

EDIT* Also wanted to add, ive researched that the effects of high altitude on performance is considerably less on a turbocharged engine vs NA...

Edited October 8, 2010 by B00STDZ

[BRAAP]

HybridZ Rules

4. There is no Best! No best tires. No best engine. No best shock. No best big chrome foot gas pedal. Every car builder and driver is in a different situation. What's good for one might suck for another. The decision on what is "best" for you and your car is completely up to you. As with any decision time, effort, and research is needed by the decision maker - you! Instead of asking what is "best", do some research, explain your situation in excruciating detail, and describe what alternatives you're considering in your decision. Posting a thread with "What's the best..." in the title it is a sure way to get that post tossed into the Tool Shed.

 

I wont shed this so long as the topic remains on the path it appears to be headed, not so much a "what's best" discussion but a technical discussion as to the affect of Air temp, pressure and density altitude, humidity, etc on engine performance and/or temperature and humidity effects on available traction for various tires and tire compounds.

 

 

For power production! As cold and dry at the lowest possible elevation as possible. Scenario, death valley during a high pressure front moving through, -20 degree F, 0% humidity, you'll make big power. Problem with that is depending on the tire type, compound etc, available grip might not be ideal, but that's what tire warmers and burnouts are for, right? Not to mention the discomfort of trying to perform pre-race chores in that enviroment.

[B00STDZ]

Im going to throw this out there...

 

The turbocharger also helps at high altitudes, where the air is less dense. Normal engines will experience reduced power at high altitudes because for each stroke of the piston, the engine will get a smaller mass of air. A turbocharged engine may also have reduced power, but the reduction will be less dramatic because the thinner air is easier for the turbocharger to pump.

 

TURBO EFFICIENCY

Pressure ratios play a large role in how efficient a turbo can sustain airflow (power). The higher the pressure ratio, the faster the fans must spin, which requires more pressure differential across the turbine, thus more exhaust manifold back pressure and a hotter, less efficient charge temp from the increased fan speed (friction). Pressure ratio's are generally on the Y-axis of a compressor map, and as you move higher, you move away from the ideal efficiency islands. Here are 2 calculated pressure ratios to give you an idea of how altitude affects turbo performance.

 

Pressure ratio = (boost + baro) / (baro).

 

- 14psi at sea level: (14psi boost + 14.7psi baro) / (14.7psi baro) = 1.952

- 14psi at 5500 ft: (14psi boost + 12psi baro) / (12psi baro) = 2.167

 

That is an increase of 0.215 PR, not huge, but still significant depending on the turbo used.

 

Let's look at 30psi next, and show how the difference becomes worst at higher boost levels

 

- 30psi at sea level: (30psi boost + 14.7psi baro) / (14.7psi baro) = 3.041

- 30psi at 5500 ft: (30psi boost + 12psi baro) / (12psi baro) = 3.5

 

That's an increase of 0.46 PR, which is significant on most any turbo.

 

This shows why a turbo must work much harder to sustain a given boost pressure at altitude.

 

In summary, there are 2 primary affects that elevation has on a boosted cars performance, and they are inversely related.

 

- As boost pressure increases, the losses due to elevation are decreased. This is a good thing.

- As boost pressure increases, the turbo efficiency at elevation becomes worse. This is a bad thing.

 

The effect of high altitude on a turbocharged diesel at full power shows that although the absolute inlet manifold pressure reduces with high altitude, the fall-off is slower than that of ambient temperature. Turbocharger speed increases due to the increase in turbine inlet temperature and expansion ratio up to a point. This point is limited by the thermal limits and the maximum permissible turbocharger speed, especially the latter. The movement toward surge on the compressor map will be greatest for a non-intercooled engine, since the post boost air mass density will be reduced considerably due to higher temperatures.

 

 

Some good reads. But as far as altitude making a big difference? It appears it only makes a big difference when comparing with a difference of 5000 ft between elevations.

 

Edited November 13, 2010 by B00STDZ

[stony]

I think the only reason Alaska raceway park isnt visited more is because its 6000 miles away BUT.

 

I have raced there before when there was very low humidity, 65 degres with a very bright sun heating the track and the track itself actually measured 100 feet below sea level!!!

 

they say it would be one of the fastest tracks in the world if it wasnt in alaska ;>

[Tony D]

' Scenario, death valley during a high pressure front moving through, -20 degree F, 0% humidity, you'll make big power. Problem with that is depending on the tire type, compound etc, available grip might not be ideal, but that's what tire warmers and burnouts are for, right?'

 

(Yes, this crossed my mind there, and made note to check things the next visit...been there, done that!)

 

Not -20, but it will get to 0 there on a cool night. And yes you can feel it. During the day, though, because of Death Valley's unique situation, the UV will heat macadam pavement considerably warmer than almost anyplace else in the USA. So your traction is considerably better than you THINK it should be for the recorded ambient.

 

Outside Trona, gateway to Death Valley in March:

 

As for 'what has been read' the basic premise is that altitude will affect turbo cars less than N/A because the turbo will 'equalize' WOT manifold pressures... at 12,000 feet, an N/A will have something less than 100kPa available for breathing, so it will make considerably less power.

The turbocharged car, since it doesn't open the wastegate until BOOST is reached will still have this same level of boost. You then have to figure turbo efficency loss due to operating at a different pressure ratio (the same thing happening to the N/A will now happen to the turbo, and it will have to 'pump harder' to reach the same psiG manifold pressure meaning operating in a different efficiency island) and then you have less dense air for cooling the intercooler so there is another loss there....meaning while in THEORY the turbo car should not be affected at all, in reality they ARE affected but nowhere near like an N/A would be because the turbo is helping the engine breathe.

 

20% psiA inlet pressure loss due to altitude, say similar loss in N/A horsepower, but only 8% loss on a turbo (example, not actual numbers, look at the Pike's Peak Race and see why guys run Turbos there!) I mean the OP seems to have stated 5K feet is required to make a difference---if you can tolerate a 16.7% loss in V.E. then I think you don't need to concern yourself with asking the question. I can't tolerate that kind of a loss and deem it not a "HUGE" difference. Even 1000 feet means a 3.5% loss, and that is significant, 10HP on an N/A car, and that's 10% by 3K feet. I could feel the difference between O.C. and Big Bear. Halfway up I could tell the N/A was loosing significant power.

 

AS TO THIS:

" A turbocharged engine may also have reduced power, but the reduction will be less dramatic because the thinner air is easier for the turbocharger to pump. "

 

Beware of wearing blinders and making absolute statements or generalizations based on writing like this, I don't know who wrote that, but it's as ignorant a statement and devoid of the realities of compression theory and practice that I think I could find engineers in some companies that would like to do the author physical harm for writing something so stupid.

Edited November 14, 2010 by Tony D

[proxlamus©]

Ill just share this..

 

In the aviation industry.. everything is based off "standard conditions" .. The ICAO (International Civil Aviation Organization) recognized the ISA (International Standard Atmosphere) which is 59* F at Sea Level with 14.7 psi (1013.25 hPa)and 0% humidity. These standard conditions yield the best results when rating aircraft performance and data interpretation.

 

In the Army Standard Metro atmosphere, now used only in ballistics, defines sea-level conditions as 29.5275 inHg of pressure (99.9916 kPa), 59°F (15°C), and 78% humidity.

 

In chemistry, the term standard temperature and pressure (abbreviated STP) denotes an exact reference temperature of 0°C (273.15 K) and pressure of 1 atm (defined as 101.325 kPa). These values approximate freezing temperature of water and atmospheric pressure at sea level. Also in chemistry, the term Standard Ambient Temperature and Pressure (abbreviated SATP) denotes a reference temperature of 25°C (298.15 K) and pressure of 100 kPa. Although there are many variations of the definition, the most accepted one is the temperature and pressure where the equilibrium constant for the autoionization of water is 1.0x10-14.

 

 

For practical uses? I would use the ICAO Aviation standard for ideal conditions.