598 big block chevy
07-23-2015 | 07:53 PM
#11
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From: On A Dirt Floor
BTW: be careful with news' reported baramoteric pressure. Alot of the time, they report corrected pressure, not absolute.
Air pressure corrections
When you read a barometer the reading directly from it is the "station pressure."
Two things affect the barometer's reading, the high or low air pressure caused by weather, and the air pressure caused by the station's elevation, or how high it is above sea level.
No matter what weather systems are doing, the air's pressure decreases with height. If you're trying to draw a weather map of air pressure patterns, you need a way to remove the effects of the station's elevation. That is, you want to see what the pressure would be at the station if it were at sea level. Otherwise, all high-elevation locations would be mapped as having low pressure.
You need to calculate, sea-level pressure, which is defined as: "A pressure value obtained by the theoretical reduction of barometric pressure to sea level. Where the Earth's surface is above sea level, it is assumed that the atmosphere extends to sea level below the station and that the properties of that hypothetical atmosphere are related to conditions observed at the station."
To do this, you have to take into account the barometric reading at the station, the elevation above sea level, and the temperature.
Another kind of barometric reading is the altimeter setting, which aircraft use. It's defined as: "The pressure value to which an aircraft altimeter scale is set so that it will indicate the altitude above mean sea level of an aircraft on the ground at the location for which the value was determined." For it, all you need is the station pressure and the elevation, you can ignore the temperature. (Related: Calculate altimeter setting).
How pressure decreases with altitude
As you go higher in the air, the atmospheric pressure decreases.
The exact pressure at a particular altitude depends of weather conditions, but a couple of approximations and a formula can give you a general idea of how pressure decreases with altitude.
A rule of thumb for the altimeter correction is that the pressure drops about 1 inch of mercury for each 1,000 foot altitude gain. If you're using millibars, the correction is 1 millibar for each 8 meters of altitude gain. These rules work quite well for elevations or altitudes of less than two or three thousand feet.
The standard atmosphere is a table giving values of air pressure, temperature and air density for various altitudes from the ground up. You can think of these values as averages for the entire Earth over the course of a year. (Related: Standard atmosphere tables).
When you read a barometer the reading directly from it is the "station pressure."
Two things affect the barometer's reading, the high or low air pressure caused by weather, and the air pressure caused by the station's elevation, or how high it is above sea level.
No matter what weather systems are doing, the air's pressure decreases with height. If you're trying to draw a weather map of air pressure patterns, you need a way to remove the effects of the station's elevation. That is, you want to see what the pressure would be at the station if it were at sea level. Otherwise, all high-elevation locations would be mapped as having low pressure.
You need to calculate, sea-level pressure, which is defined as: "A pressure value obtained by the theoretical reduction of barometric pressure to sea level. Where the Earth's surface is above sea level, it is assumed that the atmosphere extends to sea level below the station and that the properties of that hypothetical atmosphere are related to conditions observed at the station."
To do this, you have to take into account the barometric reading at the station, the elevation above sea level, and the temperature.
Another kind of barometric reading is the altimeter setting, which aircraft use. It's defined as: "The pressure value to which an aircraft altimeter scale is set so that it will indicate the altitude above mean sea level of an aircraft on the ground at the location for which the value was determined." For it, all you need is the station pressure and the elevation, you can ignore the temperature. (Related: Calculate altimeter setting).
How pressure decreases with altitude
As you go higher in the air, the atmospheric pressure decreases.
The exact pressure at a particular altitude depends of weather conditions, but a couple of approximations and a formula can give you a general idea of how pressure decreases with altitude.
A rule of thumb for the altimeter correction is that the pressure drops about 1 inch of mercury for each 1,000 foot altitude gain. If you're using millibars, the correction is 1 millibar for each 8 meters of altitude gain. These rules work quite well for elevations or altitudes of less than two or three thousand feet.
The standard atmosphere is a table giving values of air pressure, temperature and air density for various altitudes from the ground up. You can think of these values as averages for the entire Earth over the course of a year. (Related: Standard atmosphere tables).
07-23-2015 | 09:06 PM
#12
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Joined: Apr 2005
Posts: 2,150
Likes: 15
From: Northport N.Y.
It, and most all performance engine dyno's, is correcting to 29.29 and 60* dry air. This is SAE Standard J607.
If it was 30.1 actual at dyno time, then the dyno computer would actually be correcting (power) down for air pressure.The standard is lower at 29.29 But, heat, humidity, etc, could, and did, raise the correction back up.
Lower elevation, more air pressure, more power.
Higher elevation, less air pressure, less power.
Given the same heat, humidity, etc,etc
I've raced and dyno'd in weather many times below the SAE J607 standard numbers. 1200ft below sea level conditions once. Mine shaft air. Many people broke schit. LOL.
If it was 30.1 actual at dyno time, then the dyno computer would actually be correcting (power) down for air pressure.The standard is lower at 29.29 But, heat, humidity, etc, could, and did, raise the correction back up.
Lower elevation, more air pressure, more power.
Higher elevation, less air pressure, less power.
Given the same heat, humidity, etc,etc
I've raced and dyno'd in weather many times below the SAE J607 standard numbers. 1200ft below sea level conditions once. Mine shaft air. Many people broke schit. LOL.
07-23-2015 | 09:24 PM
#13
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Joined: Nov 2004
Posts: 14,154
Likes: 3,714
From: On A Dirt Floor
That's cool. Figured I'd enter some dyno chat. LOL.
A lot of people read them, not all understand them.
There are a lot of pos dyno charts out there. These do not do any favors to the engine owner..in fact, can be a major detriment by throwing major curve balls when trying to set up the boat - props, tune, rigging , etc.
BTW; BobM helped WetteVette some years ago who'm ended up going well into the 120's with a pump gas single NA 598" Bravo drive cat. You can bet that put out more than 800hp. LOL.
A lot of people read them, not all understand them.
There are a lot of pos dyno charts out there. These do not do any favors to the engine owner..in fact, can be a major detriment by throwing major curve balls when trying to set up the boat - props, tune, rigging , etc.
BTW; BobM helped WetteVette some years ago who'm ended up going well into the 120's with a pump gas single NA 598" Bravo drive cat. You can bet that put out more than 800hp. LOL.
07-23-2015 | 09:26 PM
#14
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Joined: Jan 2001
Posts: 1,098
Likes: 4
From: cedar springs mi
It is a solid roller and I'm here to Tell you Dave does not fudge numbers to get a good number on the Dyno this motor has a very good set of heads and the header where only 1 7/8 primary this motor will make some one a great motor this would cost $40000 if you were to buy this out west
07-24-2015 | 05:59 AM
#15
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Joined: Aug 2011
Posts: 2,733
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From: bel air, md
The power numbers sound very realistic to me. Actually for the amount of effort that went into that motor if it didn't put up those kind of numbers I would think there was something wrong with the motor. 691ft lb @3000rpm the thing has a power curve like a 4x4... It's always making power. Do you want torque or do you want horsepower? Take your pic it's always there.
