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06-30-2017, 03:41 PM | #1 |
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Density altitude and 1/4 mile how it affect to our engine!
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! Last edited by kennis827; 07-04-2017 at 09:19 PM.. |
06-30-2017, 04:13 PM | #2 | |
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07-01-2017, 12:38 AM | #3 | |
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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.
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2014 ///M5 CP Tanzanite Blue/Cohiba - 11.15 @ 128.8 & 1.84 60' (2150' DA) - BPM Tune - MSR Intake - SSP DCT - SS DPs & HFC Mid Pipes/X-Over - E Race Muffs - 19" MT DRs... On to a new home.
Last edited by Northern X5M; 07-01-2017 at 12:43 AM.. |
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07-01-2017, 09:36 AM | #4 |
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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.
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07-01-2017, 09:41 AM | #5 | |
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07-01-2017, 11:53 AM | #6 | ||
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"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 Quote:
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07-03-2017, 11:36 AM | #7 | |
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07-03-2017, 12:53 PM | #8 | |
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2014 ///M5 CP Tanzanite Blue/Cohiba - 11.15 @ 128.8 & 1.84 60' (2150' DA) - BPM Tune - MSR Intake - SSP DCT - SS DPs & HFC Mid Pipes/X-Over - E Race Muffs - 19" MT DRs... On to a new home.
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07-03-2017, 01:11 PM | #9 |
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hey do you have the 0-60 or 1/4 mile times?
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07-03-2017, 01:20 PM | #10 | |
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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 |
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07-03-2017, 01:41 PM | #11 |
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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.
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07-04-2017, 06:36 PM | #12 | |
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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.
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2014 ///M5 CP Tanzanite Blue/Cohiba - 11.15 @ 128.8 & 1.84 60' (2150' DA) - BPM Tune - MSR Intake - SSP DCT - SS DPs & HFC Mid Pipes/X-Over - E Race Muffs - 19" MT DRs... On to a new home.
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07-04-2017, 09:19 PM | #13 | |
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also i dynoed my car with SAE correction is pulling 580whp stock without correction is pulling 520whp. |
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07-05-2017, 01:40 AM | #14 | |
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2014 ///M5 CP Tanzanite Blue/Cohiba - 11.15 @ 128.8 & 1.84 60' (2150' DA) - BPM Tune - MSR Intake - SSP DCT - SS DPs & HFC Mid Pipes/X-Over - E Race Muffs - 19" MT DRs... On to a new home.
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07-05-2017, 09:57 PM | #15 |
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