NHRA Altitude Compensation Chart

[Sherwin@xcede]

So the NHRA know a little about drag racing. Just a little. Been doing this for what 60 years at different locations all over the USA. They have many divisions, leagues, etc. In order to neutralise the effect of running at different altitudes they have designed a correction factor for the times & exit speeds. Remember I Sherwin did not do this. Little men in white coats with multiple PhD's did this. IF anyone doesn't agree with it, I suggest you mail the NHRA and put in a strongly worded disagreement.

http://www.nhra.com/competition/altitude.aspx?AspxAutoDetectCookieSupport=1

Johannesburg is between 5500-6000ft above sea-level depending where you are. Tarlton is actually just on 6000ft. So we shall use Denver Colorado as our reference:


Division 5 - West Central
Convert to Sea Level

Convert to Altitude
City Name Denver, CO
Altitude
5800

To convert to sea-level you mutiply

Also to note:

Supercharged, turbocharged, or nitrous-oxide Comp Eliminator vehicles (i.e. AA/A, AA/AM, AA/AT, BB/A, BB/AM, BB/AT, CC/A, CC/AT, DD/AT, AA/AF, BB/AF, H/D, and I/D) use half factor.

Ok so the best N54 we have run to date up here ran 12.2 @ 191 with s/w & DP's. That's it. Let's use the NHRA factor to compensate that to sea-level.

To get sea-level ET you multiply ET by 0.9405. But you use a half factor for FI cars. So that's 0.97025

12.2 x .97025 = 11.837

To get sea-level exit speed you multiply trap by 1.0563. But you use a half factor for FI cars. So that's 1.02815.

191km/h x 1.02815 = 196.37km/h

11.837 @ 197.37 is the corrected time for a car with DP & software and it ran on runflats.

Drag times has a calculator where you enter the DA & it calculates the corrected ET for this and even has different times for NA & FI cars. Here's what it corrects:

http://www.dragtimes.com/da-density...=12.2&mph=119&correctetmph=Correct+ET+and+MPH

Also 11.8 @ 196.

So Dean, Kish & other guys that want to compare times. Just be sure to factor in that there is a half a second & 4-5km/h difference in sea-level to altitude for the N54. And that's not the world according to Sherwin. That's from the NHRA.

Thank you for your time.

 

[Sleeper135i]

Thanks for this. very interesting, always wondered what my car would run on a proper track at sea level.

Although I feel if we ran on a properly set up track as they do in the States, our times would be lower.

 

[Sherwin@xcede]

Thanks for this. very interesting, always wondered what my car would run on a proper track at sea level.

Although I feel if we ran on a properly set up track as they do in the States, our times would be lower.

YEah bud you would be deep in the 11's. On a fast american track it would be even faster as they have unbelievable traction.

---

BTW, in certain NHRA leagues, the board doesn't even who your real time. IT shows the corrected time.

 

[Gunner-Win]

Rather interesting. Thanks for the read. :coolShake:

 

[Kish2604]

I see you have calmed down now....

thank you for this interesting post :clapper:

 

[Le Clue]

And that's why I say Mathuba times will always be faster than Tarlton.

 

[UpNcOmiNg!]

isn't mathuba also quite the downhill?

 

[S1NGH 911]

isn't mathuba also quite the downhill?

Nope, Isithebe is

 

[Dean ///M]

It makes sense in theory but not so easy cos of our track conditions. I calculated that my car could run a 11.75 even before I ran my 11.9. Rather do the time first speed can vary as much as 5km/h if there is head wind. A 2014 M135 Auto FBO should easily run 11's and capable of mid 11's. To run those calculated times everything has to be perfect. Cos if we carry on like this we all can go dyno at KAR and input our values in the above and it's settled without wasting any money at an event. So cool!!! We forget about the man behind the wheel.

 

[dvst8]

It makes sense in theory but not so easy cos of our track conditions. I calculated that my car could run a 11.75 even before I ran my 11.9. Rather do the time first speed can vary as much as 5km/h if there is head wind. A 2014 M135 Auto FBO should easily run 11's and capable of mid 11's. To run those calculated times everything has to be perfect. Cos if we carry on like this we all can go dyno at KAR and input our values in the above and it's settled without wasting any money at an event. So cool!!! We forget about the man behind the wheel.

Where do you see dyno figures being put into the calculation above ?

 

[Sherwin@xcede]

It makes sense in theory but not so easy cos of our track conditions. I calculated that my car could run a 11.75 even before I ran my 11.9. Rather do the time first speed can vary as much as 5km/h if there is head wind. A 2014 M135 Auto FBO should easily run 11's and capable of mid 11's. To run those calculated times everything has to be perfect. Cos if we carry on like this we all can go dyno at KAR and input our values in the above and it's settled without wasting any money at an event. So cool!!! We forget about the man behind the wheel.

Dean, you 1st need to actually run an actual time in your local conditions before you can apply correction. The NHRA says that in the same conditions at sea-level that is the corrected time. And actually they very conservative. The VAG's like the K04's GOlf R's etc run at Tarlton and then Matuba and they run half a second and 10km/f faster. Sameeer, Avashen, all of them. All the K04's exit 10km/h higher at MAtuba vs Tarlton.

And so do the N54s. But the NHRA say 0.4 sec ET & 5km/h. So we will use that. If you have a problem maybe call the NHRA hotline & lay a complaint but I have seen all the VAG's run a lot faster at MAtuba vs Tarlton & it makes total sense when I log airflow and see them flowing 50g/s more at sea-level.