Formula?

LX5liter · 08-23-2003, 09:51 AM

Can anybody tell me the formula to correct ET's to sea level?

StangFlyer · 08-23-2003, 01:48 PM

To convert your timeslip ET and MPH to sea level. Multiply applicable factor times your ET or MPH.

(Example: You ran a 14.4 @ 103 MPH at 5000' elevation track. The correction factors are .9367 and 1.0661 for 5000'. (14.4 * .9367) = 13.50 , (103 * 1.0661) = 109.80 MPH. So the correct timeslip would be 13.50 @ 109.80 MPH at sea level)

FT above Sea Level | Elapsed Time | Trap Speed (MPH)

1200 .9874 1.0129
1300 .9861 1.0143
1400 .9848 1.0157
1500 .9835 1.0171
1600 .9822 1.0185
1700 .9809 1.0199
1800 .9796 1.0213
1900 .9783 1.0227
2000 .9770 1.0241
2100 .9757 1.0255
2200 .9744 1.0269
2300 .9731 1.0283
2400 .9718 1.0297
2500 .9705 1.0311
2600 .9692 1.0325
2700 .9679 1.0339
2800 .9666 1.0353
2900 .9653 1.0367
3000 .9640 1.0381
3100 .9627 1.0395
3200 .9614 1.0409
3300 .9601 1.0423
3400 .9588 1.0437
3500 .9575 1.0451
3600 .9562 1.0465
3700 .9549 1.0479
3800 .9536 1.0493
3900 .9523 1.0507
4000 .9510 1.0521
4100 .9497 1.0535
4200 .9484 1.0549
4300 .9471 1.0563
4400 .9458 1.0577
4500 .9445 1.0591
4600 .9432 1.0605
4700 .9419 1.0619
4800 .9406 1.0633
4900 .9393 1.0647
5000 .9380 1.0661
5100 .9367 1.0675
5200 .9354 1.0689
5300 .9341 1.0703
5400 .9328 1.0717
5500 .9315 1.0731

The differences are .0013 per 100ft on the time and .0026 per 100ft on the mph.

Jeff Chambers · 08-25-2003, 06:27 AM

Was the 2000' the physical altitude or the density altitude? More times than not, the density altitude far outweighs the correction required for the physical altitude. For example, Norwalk (my home track) is only at 742' physical altitude but during the summer months its pretty common for the density altitude on any given day to be in excess of 2500'. This is because of the combined effects of barometric pressure, humidity and temperature. The last two times I've been out for TnT, the barometric pressure has been in the mud at less than 28.9 in-Hg. That's a killer for an N/A car....the density altitiude was at more than 3800' both times. That's why you'll see the serious racers with a weather station; to help them really tune to the conditions. Being a carbureted car, I can usually tune more than two-tenths of a second based on weather alone. That's huge when you're racing heads-up.

LX5liter · 08-25-2003, 07:28 PM

the Physical altitude was 2100 ft. I have no idea what the density altitude was. Next time I'll have to ask the guys with the weather stations. Thanks guys!

08-23-2003, 09:51 AM	#1
LX5liter dude5l Join Date: May 2001 Location: Grande Prairie, Alberta, Canada Posts: 603	Formula? Can anybody tell me the formula to correct ET's to sea level? __________________ Good luck! Brad R. 1992 L.X. 5.0 coupe MODS: A few little bolt ons New Best time ...11.60 @ 128 mph @ 2000+ ft altitude. Rice Haters Club member #39 Users rides #2542

08-23-2003, 01:48 PM	#2
StangFlyer Founder Join Date: Jun 1995 Location: Michigan Posts: 19,326	To convert your timeslip ET and MPH to sea level. Multiply applicable factor times your ET or MPH. (Example: You ran a 14.4 @ 103 MPH at 5000' elevation track. The correction factors are .9367 and 1.0661 for 5000'. (14.4 * .9367) = 13.50 , (103 * 1.0661) = 109.80 MPH. So the correct timeslip would be 13.50 @ 109.80 MPH at sea level) FT above Sea Level \| Elapsed Time \| Trap Speed (MPH) 1200 .9874 1.0129 1300 .9861 1.0143 1400 .9848 1.0157 1500 .9835 1.0171 1600 .9822 1.0185 1700 .9809 1.0199 1800 .9796 1.0213 1900 .9783 1.0227 2000 .9770 1.0241 2100 .9757 1.0255 2200 .9744 1.0269 2300 .9731 1.0283 2400 .9718 1.0297 2500 .9705 1.0311 2600 .9692 1.0325 2700 .9679 1.0339 2800 .9666 1.0353 2900 .9653 1.0367 3000 .9640 1.0381 3100 .9627 1.0395 3200 .9614 1.0409 3300 .9601 1.0423 3400 .9588 1.0437 3500 .9575 1.0451 3600 .9562 1.0465 3700 .9549 1.0479 3800 .9536 1.0493 3900 .9523 1.0507 4000 .9510 1.0521 4100 .9497 1.0535 4200 .9484 1.0549 4300 .9471 1.0563 4400 .9458 1.0577 4500 .9445 1.0591 4600 .9432 1.0605 4700 .9419 1.0619 4800 .9406 1.0633 4900 .9393 1.0647 5000 .9380 1.0661 5100 .9367 1.0675 5200 .9354 1.0689 5300 .9341 1.0703 5400 .9328 1.0717 5500 .9315 1.0731 The differences are .0013 per 100ft on the time and .0026 per 100ft on the mph. __________________ StangFlyer 1991 Mustang GT - Supercharged 377 Stroker 2000 Ford Lightning - Project Lightning Hauler Media Center Gallery - View my member photos

08-25-2003, 06:27 AM	#3
Jeff Chambers Moderator Join Date: Aug 2000 Location: Milan, OH Posts: 2,699	Was the 2000' the physical altitude or the density altitude? More times than not, the density altitude far outweighs the correction required for the physical altitude. For example, Norwalk (my home track) is only at 742' physical altitude but during the summer months its pretty common for the density altitude on any given day to be in excess of 2500'. This is because of the combined effects of barometric pressure, humidity and temperature. The last two times I've been out for TnT, the barometric pressure has been in the mud at less than 28.9 in-Hg. That's a killer for an N/A car....the density altitiude was at more than 3800' both times. That's why you'll see the serious racers with a weather station; to help them really tune to the conditions. Being a carbureted car, I can usually tune more than two-tenths of a second based on weather alone. That's huge when you're racing heads-up. __________________ Jeff Chambers 1990 Mustang GT 10.032 Seconds / 137.5 MPH 14-time Street Warrior World Record Setter CRT Performance 2001 Tropic Green Mustang GT - 12.181 / 113.2 MPH 2002 Ford F-250 Crew Cab 7.3l Power Stroke - 17.41@77.2 "There's nothing boring about a small block automatic shifting gears at 9400 rpm!"

08-25-2003, 07:28 PM	#4
LX5liter dude5l Join Date: May 2001 Location: Grande Prairie, Alberta, Canada Posts: 603	the Physical altitude was 2100 ft. I have no idea what the density altitude was. Next time I'll have to ask the guys with the weather stations. Thanks guys! __________________ Good luck! Brad R. 1992 L.X. 5.0 coupe MODS: A few little bolt ons New Best time ...11.60 @ 128 mph @ 2000+ ft altitude. Rice Haters Club member #39 Users rides #2542

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