NHRA altitude correction factors

[Sin'sVr4]

NHRA altitude correction factors

Im Pueblo, CO

[R/T93]

Umm, they are correction factors.

Multiply your ET by .9508 and your MPH by 1.0466.....

[Sin'sVr4]

ya I figured it out lol saw this chart too...http://www.hardtail.com/techtips/altitude.html


so based on these, at 4900 ft compared to sea level, in Pueblo CO 4900 ft I ran 12.00 @ 113

the nhra says I ran a 11.40 @118 and the hard rail says 11.27 @120

Didn't realize its THAT huge difference

[J. Fast]

ya I figured it out lol saw this chart too...http://www.hardtail.com/techtips/altitude.html


so based on these, at 4900 ft compared to sea level, in Pueblo CO 4900 ft I ran 12.00 @ 113

the nhra says I ran a 11.40 @118 and the hard rail says 11.27 @120

Didn't realize its THAT huge difference

11.7 seconds in Denver and 11.5 seconds in Pueblo is a 10 sec car at altitude. 10.5 sea level quarter mile cars don't even break 10's at altitude... try like 11.2+ seconds. You need about 600 to the wheel here to crack off 10's in a 3700lb car. SAE corrected... that's somewhere in the 700whp range at sea level. Also, boost taper is huge here. Tiny hotsides just can't spin enough air out. You'll never see a TD-04 crack 10's they just can't produce the power here. The best 1/4 time I've ever documented on TD-04's was 11.4 @ 123.

The 0.7 added to ET is pretty standard.

In 2010 I ran 11.6@ 120mph and 11.4@ 123mph on 19T's. Here's the video's

11.6 run... Video_090910_002.mp4 Video by JFastMotorsports | Photobucket

11.4 run... Pump Gas 11.4 @123 Video by JFastMotorsports | Photobucket

According to the NHRA tables they would have likely translated to somewhere in the vicinity of 10.9@ 127mph and 10.7@ 130mph at sealevel. Mehh... I owned a 10 sec car 3 years ago... she's waaay faster now. Altitude sucks! If it makes you feel better no one on the board who owns a 10.5 second or over car could break-out of the 11's here. I'd actually bet a pretty hefty stack of cash on it.

[Chris@Rvengeperformance]

You guys realize that Matt set his records at 3600ft?

[J. Fast]

Hate to bust your bubble but the track in TX is still 0.4 faster than Denver IF the DA in Denver is actually 6000ft above sea level (which it never is). It's usually around 7500ft above sea level. In that case congrats you'll run atleast a half second slower. A 10.8 car in Amarillo, TX will run a 11.3 in Denver all day long without any changes. Hate to break it to you guys but DR750's would never break 600 uncorrected horsepower here. They wouldn't even crack 500 to the wheels.

Here's some results on what takes place here...


I posted this in feb of 2012. This is my NABR Co-Driver's car from Rally North America, Hal. This car was Dyno'd @ MAC Autosport in Denver on a Dynojet. It put down 600 uncorrected. The car was driven to sea level and put right back on a Dynojet and it made 750 uncorrected. NO changes were made to the setup.





Soo, Ray P makes 650 uncorrected at the wheels on DR750's with heads and a built motor and run's 10.6's at sea level. Here, according to real world data he would likely make 490 uncorrected and run an 11.3. I would wager $1000 dollars on that dial in and even pay with a breakout. More than likely with a 7500ft DA the numbers would be in the range of 11.5 seconds.

[Chris@Rvengeperformance]

well let's just say what you are saying flies in the fast of all of matt's drag racing actual experience and leave it at that.

If it makes you guys feel warm and fuzzy great, but I believe in actual timeslips.

[J. Fast]

I totally get the driver effect, Chris. The results depicted aren't about driver tho. It's all laws of physics. Ofcourse you can get that "X- Factor" out of a driver but a 750whp car and a 600whp car just don't drive the same if all else is equal. You can't expect the same 1/4 mile results with real world info out there like this.

I sometime wish DJ's had an altitude option wherein you could enter your "traveling to x elevation" information and they would spit out the net result. It would really help with turbo and cam selections on high and low altitude setups.

[R/T93]

Umm, the laws of physics say exactly what Sin's first link says.... thats from the given data over tens of thousands of runs over thousands of cars.

[RealMcCoy]

This same conversation is going on over on 3Si... Matt posted in it earlier.

There is a difference... Just not as big for turbo cars. The NHRA corrections are for N/A cars... look at the classes they correct. There are no forced induction cars there. Most real correction calculators have different factors for N/A and forced induction. But they include blowers in the same category as turbos. You don't just turn up the boost on a roots blower, you have to swap pulleys to change how much air it pumps.

An air density variation that would knock a second off an N/A motors time, would likely be less than half that on any forced induction motor, and maybe even less on a well set up turbo car.

Matt said he used to gain a couple tenths going to sea level with his old 11 second cars. That is pretty consistent with the more accurate calculators, and would likely equate to 4-5 tenths if he went from sea level to Mile High...

The OP has previously stated that the altitude density factor for his 12.00 runs was upwards of 8000ft. If that's so, it's very believable that he would run a mid 11 with sea level air... An N/A under the same circumstances would drop to 10.70's easily.