Density altitude and 1/4 mile how it affect to our engine!

[kennis827]

Hi Folks,

I have been researching how the density altitude (DA, involving altitude, humidity, temperature) can affect our cars performance such as 1/4 miles, trap speed...etc.

The only website i found is from dragtimes, http://www.dragtimes.com/da-density-...calculator.php

I live in a place that has almost 10000 ft(edited) of density altitude , using vbox(the most accurate tool around), i am hitting 12.8s-12.9s @ 119mph (0-60 at 4.7-5.0s), using the link calculator, i got these results after corrected data by dragtimes:

"stock naturally aspirated engine" 12.0s @ 126mph
"extensively modified turbocharged engine" 12.46 @ 122mph

I am not sure if our stock twinturbo engine can consider as "stock NA engine" or "extensively modified turbocharged engine"?

As it's a simple calculator, it takes consideration to all type of cars, but how close it compares to our cars? As for what i know, Less DA=more dense air, which is better for the engines, and if im not wrong, when the air pressure is not enough, our engine increases some boost to compensate the loosing air pressure... does somebody know if these corrected data can fit on our cars at sea level? If so, in which category correction it fits? Or my m5 cp 2014 is just under performance!

[gmd2003]

Originally Posted by kennis827

Hi Folks,

I have been researching how the density altitude (DA, involving altitude, humidity, temperature) can affect our cars performance such as 1/4 miles, trap speed...etc.

The only website i found is from dragtimes, http://www.dragtimes.com/da-density-...calculator.php

I live in a place that has almost 5000 ft of density altitude, using vbox(the most accurate tool around), i am hitting 12.8s-12.9s @ 119mph (0-60 at 4.7-5.0s), using the link calculator, i got these results after corrected data by dragtimes:

"stock naturally aspirated engine" 12.0s @ 126mph
"extensively modified turbocharged engine" 12.46 @ 122mph

I am not sure if our stock twinturbo engine can consider as "stock NA engine" or "extensively modified turbocharged engine"?

As it's a simple calculator, it takes consideration to all type of cars, but how close it compares to our cars? As for what i know, Less DA=more dense air, which is better for the engines, and if im not wrong, when the air pressure is not enough, our engine increases some boost to compensate the loosing air pressure... does somebody know if these corrected data can fit on our cars at sea level? If so, in which category correction it fits? Or my m5 cp 2014 is just under performance!

It doesn't apply to the S63 tu or any modern Turbo that can adapt for altitude . It's a very small delta on these cars over a wide range of conditions stock, I.e it will make the same power at 1000 DA as 3000 DA stock. 5000 is certainly thin air and will have an effect but no where near as much as that calculator states. Tuned is another story as you have already used up the excess capacity in the system for added power so you will see more of a drip on extreme conditions and altitudes .

[Northern X5M]

Originally Posted by gmd2003

It doesn't apply to the S63 tu or any modern Turbo that can adapt for altitude . It's a very small delta on these cars over a wide range of conditions stock, I.e it will make the same power at 1000 DA as 3000 DA stock. 5000 is certainly thin air and will have an effect but no where near as much as that calculator states. Tuned is another story as you have already used up the excess capacity in the system for added power so you will see more of a drip on extreme conditions and altitudes .

Yeah, even though these cars can mostly compensate for bad air, from experience up to about 2,000' DA there is negligible difference, +/- 2 MPH. I find that around 1,000-1,500' DA I can mostly achieve identical numbers as those posted at sea level. After 2,000 DA, my trap speed drops. It isn't uncommon here for the DA to hit +4,000'. My trap is probably off by at least 4 MPH around 4,000'. Even turbos and computer control just cannot completely compensate for crap air.

When my Trailblazer SS was N/A, I was running identical mods to another guy in California. He was running 12.9's vs my 13.5's and he was about 7-8 MPH faster.

I use the DragTimes calculator to mostly gauge mod gains at the track. I find the extensively modified turbo calculator gets me very close to reported times closer to sea level for the M5.

[BadGTR]

I too live at 5000+' and have had many cars over the years. N/A, supercharged, single turbo, twin turbo. Don't let anyone full you (most people that don't live at altitude will give you wrong information). Although the newer cars will try and compensate for altitude changes they still lose quite a bit. My car has been tuned and the tuner was commanding 20#s up top and the car would only make 15#s. First problem was the m5 computer has a built in 75% waste gate max, which at sea level will get you past 22+ psi. Not at 5000'. When adjusting that limit up, the stock turbos became the restriction. They are just not large enough to push enough air up here. Most factory turbos cars are very similar. From the factory they are detuned and you can retune for higher boost, but the stock turbos cannot keep up. My GTR stock spiked 18#s with 100% waste gates open, but only holds 11#s of boost at red line. At sea level it would hold 15#s at red line. So typically at 5000' I have seen about a 4#s difference in turbo boost to sea level. Most N/A cars at the track lose about 1 second and 8-10mph in the quarter. Turbo cars tend to do better losing about .6 and 6-8mph. But they still lose quite a bit.

[BadGTR]

Originally Posted by kennis827

Hi Folks,

I have been researching how the density altitude (DA, involving altitude, humidity, temperature) can affect our cars performance such as 1/4 miles, trap speed...etc.

The only website i found is from dragtimes, http://www.dragtimes.com/da-density-...calculator.php

I live in a place that has almost 5000 ft of density altitude, using vbox(the most accurate tool around), i am hitting 12.8s-12.9s @ 119mph (0-60 at 4.7-5.0s), using the link calculator, i got these results after corrected data by dragtimes:

"stock naturally aspirated engine" 12.0s @ 126mph
"extensively modified turbocharged engine" 12.46 @ 122mph

I am not sure if our stock twinturbo engine can consider as "stock NA engine" or "extensively modified turbocharged engine"?

As it's a simple calculator, it takes consideration to all type of cars, but how close it compares to our cars? As for what i know, Less DA=more dense air, which is better for the engines, and if im not wrong, when the air pressure is not enough, our engine increases some boost to compensate the loosing air pressure... does somebody know if these corrected data can fit on our cars at sea level? If so, in which category correction it fits? Or my m5 cp 2014 is just under performance!

So you used a vbox (which is very accurate) and then you plugged those numbers into the drag times calculator and got 12.8@119?

[kennis827]

Originally Posted by BadGTR

So you used a vbox (which is very accurate) and then you plugged those numbers into the drag times calculator and got 12.8@119?

Hey BadGTR! thanks for your reply and helping here! my real time before dragtimes correction is 12.8@119 and after correction i have these 3 results: (not sure which to use at 5000 DA, my car has no fault codes, maybe its under performance?)

"Stock and Mildly Modified Naturally Aspirated Engines" 12.0s @ 126mph

"Extensively Modified Naturally Aspirated Engines" 12.2s @ 124mph

"Extensively Modified Supercharged and Turbocharged Engines" 12.46 @ 122mph

Originally Posted by BadGTR

I too live at 5000+' and have had many cars over the years. N/A, supercharged, single turbo, twin turbo. Don't let anyone full you (most people that don't live at altitude will give you wrong information). Although the newer cars will try and compensate for altitude changes they still lose quite a bit. My car has been tuned and the tuner was commanding 20#s up top and the car would only make 15#s. First problem was the m5 computer has a built in 75% waste gate max, which at sea level will get you past 22+ psi. Not at 5000'. When adjusting that limit up, the stock turbos became the restriction. They are just not large enough to push enough air up here. Most factory turbos cars are very similar. From the factory they are detuned and you can retune for higher boost, but the stock turbos cannot keep up. My GTR stock spiked 18#s with 100% waste gates open, but only holds 11#s of boost at red line. At sea level it would hold 15#s at red line. So typically at 5000' I have seen about a 4#s difference in turbo boost to sea level. Most N/A cars at the track lose about 1 second and 8-10mph in the quarter. Turbo cars tend to do better losing about .6 and 6-8mph. But they still lose quite a bit.

hey btw what times did you achieve with your M5 f10 and GTR R35 on 0-60mph and 1/4mile times at 5000 DA? i would like to compare your results to my m5 and friend's R35.

[BadGTR]

Originally Posted by kennis827

Hey BadGTR! thanks for your reply and helping here! my real time before dragtimes correction is 12.8@119 and after correction i have these 3 results: (not sure which to use at 5000 DA, my car has no fault codes, maybe its under performance?)

"Stock and Mildly Modified Naturally Aspirated Engines" 12.0s @ 126mph

"Extensively Modified Naturally Aspirated Engines" 12.2s @ 124mph

"Extensively Modified Supercharged and Turbocharged Engines" 12.46 @ 122mph




hey btw what times did you achieve with your M5 f10 and GTR R35 on 0-60mph and 1/4mile times at 5000 DA? i would like to compare your results to my m5 and friend's R35.

On my vbox I showed 115-117 traps on the m5. But I am over 5000' elevation and air density is typically no lower then 7500'. A stock GTR up here will trap about 117 stock and with full bolt ons plus e85 will trap 125-127mph.

[Northern X5M]

Originally Posted by kennis827

Hey BadGTR! thanks for your reply and helping here! my real time before dragtimes correction is 12.8@119 and after correction i have these 3 results: (not sure which to use at 5000 DA, my car has no fault codes, maybe its under performance?)

"Stock and Mildly Modified Naturally Aspirated Engines" 12.0s @ 126mph

"Extensively Modified Naturally Aspirated Engines" 12.2s @ 124mph

"Extensively Modified Supercharged and Turbocharged Engines" 12.46 @ 122mph

I would use the extensively modified calculation. But use it as a baseline only to gauge modifications to the car. If you are stock, your trap speed with that modifier is very close to stock at sea level. Your ETs are high but that is mostly driver dependent. Post your time slip, I would like to see your 60 foot times. What were the air temps during your run?

[kennis827]

Originally Posted by BadGTR

On my vbox I showed 115-117 traps on the m5. But I am over 5000' elevation and air density is typically no lower then 7500'. A stock GTR up here will trap about 117 stock and with full bolt ons plus e85 will trap 125-127mph.

hey do you have the 0-60 or 1/4 mile times?

[kennis827]

Originally Posted by Northern X5M

I would use the extensively modified calculation. But use it as a baseline only to gauge modifications to the car. If you are stock, your trap speed with that modifier is very close to stock at sea level. Your ETs are high but that is mostly driver dependent. Post your time slip, I would like to see your 60 foot times. What were the air temps during your run?

hey my 60foot times regarding vbox is between 2.5-2.6s (results from 50 runs with DCT or without) temp was 66F, altitude is about 3100 feet + 92% humidity and pressure... etc it pulls out 4500 density altitude (from the dragtimes calculator), what are your times at 2150 DA when your m5 was stock?

as i know the DA has big impacts for 60foot and 0-60 times, but wanted to figure out if my car is healthy on 12.8s @ 119mph at 4500DA

[BadGTR]

Originally Posted by kennis827

hey do you have the 0-60 or 1/4 mile times?

The quarter time is really dependent on that 60'. I was doing 12.4-12.5@115-117 with 295/35/20 tires. Try short shifting in 1st gear to second or half throttle thru first until you can go WOT. Also, for me not turning traction control completely off helps from a dig.

[Northern X5M]

Originally Posted by kennis827

hey my 60foot times regarding vbox is between 2.5-2.6s (results from 50 runs with DCT or without) temp was 66F, altitude is about 3100 feet + 92% humidity and pressure... etc it pulls out 4500 density altitude (from the dragtimes calculator), what are your times at 2150 DA when your m5 was stock?

as i know the DA has big impacts for 60foot and 0-60 times, but wanted to figure out if my car is healthy on 12.8s @ 119mph at 4500DA

Yeah, those are some pretty bad 60 times. Are you getting a lot of wheel hop and spinning? Even feathering the gas should net 2.0-2.1 60 foots.

That should get you into the low 12's

At my elevation I was running about 12.0 @ 121 stock, a few 11.9s and maybe one 11.8 I recall. Car was pretty consistent 120-121 MPH. Once it heat soaked, it would run 119's.

[kennis827]

Originally Posted by Northern X5M

Yeah, those are some pretty bad 60 times. Are you getting a lot of wheel hop and spinning? Even feathering the gas should net 2.0-2.1 60 foots.

That should get you into the low 12's

At my elevation I was running about 12.0 @ 121 stock, a few 11.9s and maybe one 11.8 I recall. Car was pretty consistent 120-121 MPH. Once it heat soaked, it would run 119's.

hey correction to my DA is not really 4500 its 10000 instead lol, i live in costa rica and the barometric pressure is 26 almost all the times, and i had calculated the hg base on 30, the real DA is 10000, is that the reason my car is doing 60ft: 2.5-2.6s // 0-60: 4.7-5.0s // 1/4 mile: 12.8s-12.9s @ 119mph?

also i dynoed my car with SAE correction is pulling 580whp stock without correction is pulling 520whp.

[Northern X5M]

Originally Posted by kennis827

hey correction to my DA is not really 4500 its 10000 instead lol, i live in costa rica and the barometric pressure is 26 almost all the times, and i had calculated the hg base on 30, the real DA is 10000, is that the reason my car is doing 60ft: 2.5-2.6s // 0-60: 4.7-5.0s // 1/4 mile: 12.8s-12.9s @ 119mph?

also i dynoed my car with SAE correction is pulling 580whp stock without correction is pulling 520whp.

Lol. Wow. I've been to CR and the weather there was pretty intense. I will stick to my 20C summers and -40C winters. No big bugs or spiders here either. Lol.

[BadGTR]

Originally Posted by kennis827

hey do you have the 0-60 or 1/4 mile times?

I did some testing tonight. Elevation is 5200', Air density is 8000'. Stage 2 tune, down pipes and new drag radials. 0-60 in 3.7, 1/4 in 11.7@125 with a 2.0 sixty foot.