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Old 02-20-2007, 08:55 AM   #51
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CO ZX2 -

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Originally Posted by CO ZX2 View Post
I always drop into the next lowest gear. I don't very often go lower than 4th. In the past, if I let my car pull way down 5th, it was also too slow for 4th to pull strong. Then I would use 3rd to bring it back up. I do not skip shifts often.

Keep in mind that I have a 130 HP 2.0 liter engine. But it may not be as different as it seems. At my 10,000 ft. altitude, I may be losing 35% of HP and torque. Actual barometer readings here are in the 21-23 in. Hg area, vs 29-31 in. Hg at altitudes of 0-2000 ft. What this means is that I have about one third less atmospheric pressure pushing air into the engine. Like a supercharger in reverse.
Is there a way you can measure your "effective HP" at your altitude? I was using a tangential "Colorado Rockies" metaphor where, in Denver, a baseball can travel 10% farther in the thin air of Coors Field, 5280 feet above sea level.

Ok, maybe I can answer my own question. I just googled "engine horsepower elevation" and got these results :

Engine Tuner's Calculator
http://wahiduddin.net/calc/calc_hp_dp.htm

Using this in conjunction with weather.com, I got current "relative horsepower" assumptions for Denver to be 83% of rated HP, a 17% reverse supercharger in Denver.

Density Altitude Calculator - selectable units
http://wahiduddin.net/calc/calc_da_em.htm

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Old 02-20-2007, 11:29 AM   #52
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CO ZX2 -



Is there a way you can measure your "effective HP" at your altitude? I was using a tangential "Colorado Rockies" metaphor where, in Denver, a baseball can travel 10% farther in the thin air of Coors Field, 5280 feet above sea level.

Ok, maybe I can answer my own question. I just googled "engine horsepower elevation" and got these results :

Engine Tuner's Calculator
http://wahiduddin.net/calc/calc_hp_dp.htm

Using this in conjunction with weather.com, I got current "relative horsepower" assumptions for Denver to be 83% of rated HP, a 17% reverse supercharger in Denver.

Density Altitude Calculator - selectable units
http://wahiduddin.net/calc/calc_da_em.htm

CarloSW2
Carlo, Here I am trying to help anyone who wants help and you seem to have made it your life's work to repeatedly dispute anything I say. Review the responses you have made on my posts since I have been on GasSavers. What is the deal?

You are literally and actually a mile off on this one. Denver(5280) is near half of my altitude. I gave you my altitude (10,000feet). All you would really have to have done was enter my altitude (10,000 feet) into the calculator. For a guy obsessed with figures, how could you not have seen that in my post? Even so 10,000 feet may be a low average figure. I regularly drive over mountain passes 11,000-12,000+ feet elevation. I do drive to Denver occasionally but overall a small percentage of my driving.

Answering your own questions with careless factfinding is not very scientific. I raced in Denver many years and used NHRA altitude correction factors so am very familiar with them. I have spent endless hours running engines on dynamometers using altitude and weather correction factors for HP and torque.

I am not very sure of the validity of the baseball travel statement. I have heard it many times but have no idea where it got started. It stands to reason that thinner air would have some effect but I've never worried about it much. If you can make it into something that will produce more FE for me, I'll take it. CO ZX2
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Old 02-20-2007, 12:27 PM   #53
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CO ZX2 -

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Originally Posted by CO ZX2 View Post
Carlo, Here I am trying to help anyone who wants help and you seem to have made it your life's work to repeatedly dispute anything I say. Review the responses you have made on my posts since I have been on GasSavers. What is the deal?

You are literally and actually a mile off on this one. Denver(5280) is near half of my altitude. I gave you my altitude (10,000feet). All you would really have to have done was enter my altitude (10,000 feet) into the calculator. For a guy obsessed with figures, how could you not have seen that in my post? Even so 10,000 feet may be a low average figure. I regularly drive over mountain passes 11,000-12,000+ feet elevation. I do drive to Denver occasionally but overall a small percentage of my driving.
I am not disputing anything you say. I already know that you are at 10,000 feet. You are reacting to this :

... for Denver to be 83% of rated HP, a 17% reverse supercharger in Denver

I am saying it is in Denver. I am not claiming it to be your location. Sorry for not making that clear in my post .

The reason I did not enter your altitude is that there are 4 inputs to the calculation. I did not want to make the assumption that the weather conditions in Denver are identical to yours, especially with a 1 mile altitude differential. Wouldn't you agree?

If I had plugged in your altitude, your estimate of 35% is inline with a doubling of altitude, aka 17%*2 = 34% reverse supercharger.

Question : Can you go to the website and plug in your zipcode/location and tell me the numbers you get? Also, can you go to the website and interpret the numbers for accuracy for me?

Quote:
Answering your own questions with careless factfinding is not very scientific. I raced in Denver many years and used NHRA altitude correction factors so am very familiar with them. I have spent endless hours running engines on dynamometers using altitude and weather correction factors for HP and torque.
You know this stuff off the top of your head, but other people do not. The level of car smarts in this forum is great. That ain't me. I am just "Joe car owner". I have to do "unscientifical research" to find stuff out. I have to go "somewhere else" to learn and understand information that you know by rote.

I never knew the existance of "NHRA altitude correction factors" until you just posted them.

Quote:
I am not very sure of the validity of the baseball travel statement. I have heard it many times but have no idea where it got started. It stands to reason that thinner air would have some effect but I've never worried about it much. If you can make it into something that will produce more FE for me, I'll take it. CO ZX2
Thinner air implies less oxygen (to me) which implies lean-engine running (to me) "up thar" in the Rockies, but I can't prove it because I haven't done this stuff all my life. You have.

Dammit, Jim, I'm a programmer, not a race engine builder !!!!!!

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Old 02-20-2007, 12:45 PM   #54
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Thinner air implies less oxygen (to me) which implies lean-engine running (to me) "up thar" in the Rockies, but I can't prove it because I haven't done this stuff all my life. You have.
The a/f mixture will be corrected by the ECU via the O2 sensor - a modern engine won't run leaner in thinner air.

What it IS doing though is running at a wider throttle opening to generate a given amount of power (relative to a car at lower elevation), which reduces throttle/pumping losses.

Add to that the reduction in aero drag in the less dense air...

Add to that the mountainous terrain, likely forcing the engine into an even better BSFC zone under higher loads on the ascents...

And you have the makings for better than average FE, when driven correctly (which CO clearly knows how to do!).
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Old 02-20-2007, 12:45 PM   #55
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Dammit, Jim, I'm a programmer, not a race engine builder !!!!!!
Good one!
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Old 02-20-2007, 02:29 PM   #56
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Good one!
More silliness. And mistakes. Do you know Jim? I do not.
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Old 02-20-2007, 02:37 PM   #57
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Dammit, Jim, I'm a programmer, not a race engine builder !!!!!!

CarloSW2
I have a sneaking suspicion that the above was a reference to Captain Kirk.
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Old 02-20-2007, 02:48 PM   #58
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10,000 ft . I wish I lived that high up!. I suppose, it shows the value of 3 things for good fuel economy:

(1) Driving style
(2) Aero mods (if you can't thin the air, at least you can reduce the resistance!)
(3) Reducing pumping losses (again if you can't thin the air). Unless you can get new cams made, this will have to be be increasing the throttle load.

By the way, a simple way to think about the engine on + idling or 'coasting in gear' argument would be...

- The engine uses a certain amount of fuel to idle at 750rpm
- If you coast in gear at 1500rpm, the engine will be 'wasting' more energy
in the form of engine braking. This energy originally came from petrol, so, by coasting in gear at 1500rpm, you are wasting more energy than by idling in gear.

The only real reason to coast in gear would be to slow your car down, without using the brakes, because there is a red light / junction etc up ahead. This is more efficient than idling + using brakes.

Something I have noticed with my new lambda sensor - the brakes run on vacuum, so, at idle (with the car not moving), if I press the brakes 3 times in a row, the mixture goes to 20:1 briefly (because the brakes are using the vacuum by letting air flow from the environment into the inlet manifold). When this happens, the engine runs OK, maybe *slightly* unevenly. I know that you do get a lot of NOx emissions with lean running, but would this be the case at idle?. If not, it might be possible to modify the mapping so that, at idle, the car runs lean and uses a lot less petrol (noting that diesel engines run very lean at idle).
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Old 02-20-2007, 03:49 PM   #59
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I have a sneaking suspicion that the above was a reference to Captain Kirk.
NO NO NO!!!! My reference is to that guy from priceline that keeps trying to book your vacations for you! He also played the police chief on TJ Hooker back in the 1980's, and was in that Black and White Twilight Zone episode where the gremlin/monster was trying to destroy the engine and crash the passenger plane.



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Old 02-20-2007, 04:17 PM   #60
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NO NO NO!!!! My reference is to that guy from priceline that keeps trying to book your vacations for you! He also played the police chief on TJ Hooker back in the 1980's, and was in that Black and White Twilight Zone episode where the gremlin/monster was trying to destroy the engine and crash the passenger plane.



CarloSW2
Oh yeah, now I remember.
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