Efffects of High Altitude on HP and Torque

[NewMexicoCobra]

I just tested my Cobra and it is amazing how much power is lost to altitude (5600'). Only mod so far is the air silencer removed and a 0945 K&N filter.

Run#1 was immediately after driving 70 miles to the dyno in 75 degree weather and Run#2 was done 22 minutes later with the shop fan on.

RUN #1 HP TORQUE
Actual 306.7 308.9
STD 371.6 374.4
SAE 373.2 376.0

RUN #2
Actual 310.1 314.2
STD 376.2 381.3
SAE 378.0 383.0

 

[Randee of the Redwoods]

I still hate you, high altitude or not!

 

[ArizonaSnake]

When Ford posts their figures... what do they use....

SAE or STD?

 

[Blue03Cobra]

Originally posted by ArizonaSnake
When Ford posts their figures... what do they use....

SAE or STD?

SAE, but at the flywheel, not the wheels...NMCobra's flywheel number (better run) is 444 BHP (SAE)

 

[Z06_2002]

What was your correction factor on your dyno sheet? Like 1.15 or something?

 

[MacMan]

Yeah, I used to live in Utah.

Where I was, a little over 6000 ft, the expected HP loss was 25%.

 

[Got Incon?]

A positive displacement blower is the worst type of blower to have at altitude in regards to maintaing power output. I can explain this later if anyone cares but a good turbo setup will not loose nearly the percentage power as a postive displacement type setup at altitude.

 

[Reelman]

I just got back from a trip from home(5800 ft) to Dallas with the new Flowmaster catback installed. What felt somewhat sluggish at home was amazing at near sea level. The first WOT run (on the street) pinned me back in the seat, and when it hit 4000 rpm in first gear, the tires just lit up. This with 500 pounds of passengers and two sets of golf clubs in the trunk Me likee.

 

[Smrgol]

Originally posted by Z06_2002
What was your correction factor on your dyno sheet? Like 1.15 or something?

Hah ! We dream of 1.15 SAE correction. 1.22 (on a great day) to 1.25 is about the range we can expect up here. The only thing we lack is real humidity, then we'd really get some big correction factors .

NewMexicoCobra:

Nice numbers. Just to relate your numbers to something else, the last Z06 I saw dyno'd in Abluquerque was tuning to get 300 rwhp actual. The previous Z06 that particular gentleman owned measured as high as 305 rwhp actual, I believe.

The only downside is that the Z06 is much lighter .

 

[NewMexicoCobra]

Originally posted by Z06_2002
What was your correction factor on your dyno sheet? Like 1.15 or something?

Correction Factor SAE was 1.22
STD was 1.21

I hope to get my UPS shipment of Paul's High Performance CAI on Friday. It is a large cone K&N filter, with shroud, in the engine bay. After I drive the car for a week, I will get another dyno test and post the results.

 

[Randee of the Redwoods]

Originally posted by NewMexicoCobra
Correction Factor SAE was 1.22
STD was 1.21

I hope to get my UPS shipment of Paul's High Performance CAI on Friday. It is a large cone K&N filter, with shroud, in the engine bay. After I drive the car for a week, I will get another dyno test and post the results.

I think the opened up intake will help greatly and ANY extra air you can get in the motor will help in the end. Just beware: if you ever come down to sea level, you may not be able to handle it.

 

[NewMexicoCobra]

Originally posted by Randee of the Redwoods
I think the opened up intake will help greatly and ANY extra air you can get in the motor will help in the end. Just beware: if you ever come down to sea level, you may not be able to handle it.

As you know, I live at 7000' above sea level and it's great fun to go mountain driving. My car needs all the help it can get. With the new air intake, it should be interesting to see how HP and Torque are affected at high altitude. I am hoping for across the board improvement, not just higher max numbers.

Randee: Thanks for your advice in the last few weeks. If I get to your neck of the woods, watch out!

 

[byevette]

What effect would 20 feet below sea-level have on a DYNO run? The DYNO was done on a day with 93 degree temp. and 80% humidity. Numbers: 358.4 RWHP 356.5 RWTQ.

NewMexicoCobra,
Man you are way up there compared to me. I bet you could get some great pictures of your car with a snowy mountain background...It would be a great screensaver for those of us who live below the Mason-Dixon Line and NEVER get to see snow. Just a thought.

:beer:

 

[Smrgol]

Originally posted by NewMexicoCobra
As you know, I live at 7000' above sea level and it's great fun to go mountain driving. My car needs all the help it can get. With the new air intake, it should be interesting to see how HP and Torque are affected at high altitude. I am hoping for across the board improvement, not just higher max numbers.

Randee: Thanks for your advice in the last few weeks. If I get to your neck of the woods, watch out!

You've got great numbers there and you'll see a little more with an exhaust too, the stock unit is a real cork. I didn't get a stock run on my car but with a K&N, no snorkle, and an FR500 cat-back my car put down (SAE) 384 rwhp / 376 rwtq (I'm in Albuquerque, btw). I'd bet your car is putting out 10 to 20 more rwhp than mine did and I'm gonna guess you'll see at least 5 to 10 rwhp with the cool air kit.

 

[Smrgol]

Originally posted by byevette
What effect would 20 feet below sea-level have on a DYNO run? The DYNO was done on a day with 93 degree temp. and 80% humidity. Numbers: 358.4 RWHP 356.5 RWTQ.

Do you remember your barometric pressure? If I assume 29.23, and use you other parameters, that gives an SAE correction factor of 1.07. The altitude doesn't factor too much in this case, the temperature and humidity have a much bigger contribution.

 

[byevette]

Originally posted by dwtalso
Do you remember your barometric pressure? If I assume 29.23, and use you other parameters, that gives an SAE correction factor of 1.07. The altitude doesn't factor too much in this case, the temperature and humidity have a much bigger contribution.

dwtalso,
Thanks for the info. Generally, during the summer months (when the car was DYNOed), the pressure is above 30...30.00-30.10 range.

Educate me: 1)what is the correction factor and how would SAE of 1.07 be used\applied?

2) Would this change my HP, if so what would it be (how to calculate?)?

They might seem like basic questions to some of you, but I have to start somewhere. Thanks in advance.

:beer:

 

[Smrgol]

Originally posted by byevette
dwtalso,
Thanks for the info. Generally, during the summer months (when the car was DYNOed), the pressure is above 30...30.00-30.10 range.

A barometric pressure of 30 inHg would put the correction factor at 1.04.

Educate me: 1)what is the correction factor and how would SAE of 1.07 be used\applied?

2) Would this change my HP, if so what would it be (how to calculate?)?

You mulitply your specific output measurement by the correction factor (CF). So, if your measured power is 358.4 rwhp, the the corrected power would be 358.4 * 1.04 = 372.7. You do the same thing with the torque value.

The correction factor adjusts the output to a fixed reference temperature, pressure, altitude, and humidity. For the SAE correction those values are 77 degrees F, 29.23 inHg, 0 feet altitude, 0% humidity. In other words, you car made 358.4 rwhp at 93 degrees F, 30 inHg, -20 feet, 80% humidity and should make 372.7 rwhp if it were running at a location with the reference values.

STD correction is another CF you'll see mentioned. It's the same process as the SAE correction but it uses different reference values.

They might seem like basic questions to some of you, but I have to start somewhere. Thanks in advance.

No problem .

 

[byevette]

dwtalso,
Thank you, that was very informative. Your help is greatly appreciated.

I do have one final question: Now that the corrected RWHP stands at 372.7, how would the 15% driveline loss be calculated into the car's hp? Would it be 428.6?

Again, thanks in advance,

Chris

:beer: