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      07-15-2013, 12:45 PM   #23
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Quote:
Originally Posted by regular guy View Post
The weather station on this dyno is broken. If you look at the ambient pressure for your stock and 614whp runs, the dyno weather station shows 915mBar and 848mBar respectively. Both of those numbers are not possible on planet earth without being inside a tornado. So that's a sign that the dyno weather station is broken. Typical numbers will be 990 - 1030 mBar.

Because of the bogus weather station, your horsepower correction is way off too. The dyno calculated 24% correction, which is far outside of the 7% allowable specification. It looks like the real pressure at your location that day was about 1008 mBar. That would put your dyno correction factor at 4.61%, and your corrected horsepower around 517whp (assuming 494whp uncorrected is accurate).

See if there's another dyno in the area. If your uncorrected numbers are the same, then in order to use results from this shop, you'll need to get your own weather data from another source and calculate the horsepower correction by hand (or web sites will do it for you).
You are arguing a 23whp correction to SAE on a 90 degree day at 5000 ft?

C'mon, you know better than that.
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      07-15-2013, 01:13 PM   #24
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Quote:
Originally Posted by SYZ
You are arguing a 23whp correction to SAE on a 90
degree day at 5000 ft?

C'mon, you know better than that.
Please check your math. 613 - 494 = 119whp. As the correction factor is stated as 1.24 (124%), you can do the math a different way from 494 * 1.24 = 613. So we're clearly talking about 119whp of correction and I'm not even sure where you got 23 from.

HP correction formula used by the dyno uses temperature, barometer, and humdity. Altitude is not in the equation.
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      07-15-2013, 01:30 PM   #25
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Quote:
Originally Posted by regular guy
That would put your dyno correction factor at 4.61%, and your corrected horsepower around 517whp (assuming 494whp uncorrected is accurate).

Quote:
Originally Posted by SYZ View Post
You are arguing a 23whp correction to SAE on a 90 degree day at 5000 ft?

C'mon, you know better than that.
Quote:
Originally Posted by img View Post
Please check your math. 613 - 494 = 119whp. As the correction factor is stated as 1.24 (124%), you can do the math a different way from 494 * 1.24 = 613. So we're clearly talking about 119whp of correction and I'm not even sure where you got 23 from.

HP correction formula used by the dyno uses temperature, barometer, and humdity. Altitude is not in the equation.
see highlighted portion of where I got the number. I didn't realize altitude is not in the equation. Seem like it should be however, since SAE is supposed to be at sea level. Why have that as a standard if you don't compensate for it?

Edit: did a little research, amazing

Quote:
Originally Posted by Shelquist Engineering

Additional Information:

Originally, all of the major US auto manufacturers were in or around Detroit Michigan, and the dyno reading taken in Detroit were considered to be the standard. However, as the auto industry spread both across the country and around the globe, the auto manufacturers needed a way to correlate the horsepower/torque data taken at those "non-standard" locations with the data taken at the "standard" location. Therefore, the SAE created J1349 in order to convert (or "correct") the dyno data taken in, for example, California or in Tokyo to be as if the data had been taken at standard conditions in Detroit.

For example, at 85 deg F, 24.71 in-Hg absolute pressure and 0.121 in-Hg vapor pressure, the engine only produces about 81.1% of the SAE rated power so that the required dyno correction factor is 1.233. Therefore, when dyno testing under these conditions, it is necessary to multiply the measured torque and horsepower values by the correction factor of 1.233 to determine the SAE corrected readings. The dyno correction factor takes into account all of the effects of temperature, altitude, atmospheric pressure and humidity to arrive at corrected horsepower and torque values.

The air temperature should ideally be the temperature of the air that is going into your engine.

The absolute pressure is the actual atmospheric pressure, also called station pressure. This is not the barometric pressure or altimeter setting as is typically reported on the local weather report.

The vapor pressure is the partial pressure of the water vapor in the air.

For these calculations, the standard reference conditions are: Air temp 77 deg F (25 deg C), 29.235 Inches- Hg (990 mb) altitude-corrected barometric pressure, 0 ft ( 0 m) altitude, 0% relative humidity.
http://wahiduddin.net/calc/calc_cf.htm

Last edited by SYZ; 07-15-2013 at 02:26 PM.
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      07-15-2013, 02:40 PM   #26
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Quote:
Originally Posted by img View Post
Please check your math. 613 - 494 = 119whp. As the correction factor is stated as 1.24 (124%), you can do the math a different way from 494 * 1.24 = 613. So we're clearly talking about 119whp of correction and I'm not even sure where you got 23 from.

HP correction formula used by the dyno uses temperature, barometer, and humdity. Altitude is not in the equation.
Altitude isn't considered for SAE corrections??? Has it always been this way? I was under the impression that altitude was definitely part of the correction factor....
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      07-15-2013, 03:20 PM   #27
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Originally Posted by Skooterbrah View Post
Altitude isn't considered for SAE corrections??? Has it always been this way? I was under the impression that altitude was definitely part of the correction factor....
It is.. indirectly. Absolute pressure is affected by altitude. (990 mb) altitude-corrected barometric pressure, 0 ft ( 0 m) altitude, 0% relative humidity.

So your 848mBar is not far fetched at all.. lower absolute pressure at a higher elevation.
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      07-15-2013, 03:23 PM   #28
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Quote:
Originally Posted by SYZ View Post
It is.. indirectly. Absolute pressure is affected by altitude. (990 mb) altitude-corrected barometric pressure, 0 ft ( 0 m) altitude, 0% relative humidity.

So your 848mBar is not far fetched at all.. lower absolute pressure at a higher elevation.
Gotcha, that's what I figured as well. Thanks!
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      07-15-2013, 03:27 PM   #29
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Quote:
Originally Posted by SYZ
see highlighted portion of where I got the number. I didn't realize altitude is not in the equation. Seem like it should be however, since SAE is supposed to be at sea level. Why have that as a standard if you don't compensate for it?

Edit: did a little research, amazing
Yes, that is a great web site and the one I reference most often. If you want even more information, you can purchase and download SAE-J1349 horsepower and correction specification, although that's probably unecessary because that web site shows the actual formula (see link below).

Quote:
Originally Posted by Skooterbrah
Altitude isn't considered for SAE corrections???
Not directly, no. Air pressure is affected by altitude. So altitude is compensated, but only by virtue of it's effects on absolute air pressure. I hope that makes sense.

Quote:
Has it always been this way?
Yes.

Quote:
I was under the impression that altitude was definitely part of the correction factor....
Not directly, no. Altitude is compensated indirectly through it's effects on absolute air pressure. This page shows the actual SAE formula:
http://wahiduddin.net/calc/cf.htm

You can see that Altitude is not in that equation. The equation shows the use of absolute air pressure "Pd" and does not include altitude. If you don't have Pd measurements, then there's ways to calculate it. One way of calculating Pd is with dew point and altitude. So altitude is in there...but only as a means to calculate absolute air pressure.

Other ways to calculate Pd are with humidity and barometer -- just like the dyno. If you want to use the same formula the dyno uses, then use this page and type in your numbers.
http://wahiduddin.net/calc/calc_hp_abs.htm

If you type in your numbers of 90.62F, 1008hPa, and 36% humidity, then you get a correction factor of 1.5% -- which is far different than what I said yesterday. Yesterday I made a mistake and calculated "STD" correction, not SAE correction. The SAE correction for those settings would be about 1.5%.

You might want to compare the barometer on the dyno with a valid weather station in the area. I'm sure you will find the dyno barometer is not close to accurate.

Anyways, I hope this helps.

Last edited by regular guy; 07-15-2013 at 03:36 PM.
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      07-15-2013, 03:35 PM   #30
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Here's a link to weather data in that area for July-12. Lowest pressure that day was 1008 hPa. Pressure around 1-2 PM (hottest part of the day) was 1009-1010 hPa (mBar). DA was 9510.
http://www.wunderground.com/history/...q_statename=NA


I hope this helps.
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      07-15-2013, 03:52 PM   #31
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Quote:
Originally Posted by regular guy View Post
Here's a link to weather data in that area for July-12. Lowest pressure that day was 1008 hPa. Pressure around 1-2 PM (hottest part of the day) was 1009-1010 hPa (mBar). DA was 9510.
http://www.wunderground.com/history/...q_statename=NA


I hope this helps.
The barometric pressure reported is adjusted to sea level... making your numbers way off. This is not the same as actual.
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      07-15-2013, 04:22 PM   #32
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Regular Guy,

Use this calculator to determine what I'm saying is true.

http://www.csgnetwork.com/barcorrecthcalc.html

Type in -5280 under the field for "Elevation of Barometer ASL"

Type in 848 milliBar under "Observed Barometric Readings"

Result?

Actual Barometer corrected: 1069.49 millibar... or pretty close to what you claim should be the imputed reading for the calculation. You see, it's a corrected value that you're trying to use for the correction, which is not the right way to do it!
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      07-15-2013, 04:42 PM   #33
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Quote:
Originally Posted by SYZ View Post
Regular Guy,

Use this calculator to determine what I'm saying is true.

http://www.csgnetwork.com/barcorrecthcalc.html

Type in -5280 under the field for "Elevation of Barometer ASL"

Type in 848 milliBar under "Observed Barometric Readings"

Result?

Actual Barometer corrected: 1069.49 millibar... or pretty close to what you claim should be the imputed reading for the calculation. You see, it's a corrected value that you're trying to use for the correction, which is not the right way to do it!
Interesting. I think what this means, is the Weather Underground site is using station pressure just as I thought. But it also means the dyno is using corrected pressure, which I didn't expect. I always thought the dyno used station pressure as well. I wonder if there's a setting in the dyno software to select between station pressure and corrected pressure. I didn't think there was, but I'm not a dyno operator. :-)

When you input the the weather underground values of 1008mBar and actual altitude of the dyno shop 5826ft, then you get adjusted pressure of 816mBar, which is very close to what the 848 mBar of the dyno. I definitely didn't expect that.

Might be helpful if the OP could post the dates/times, weather, and correction factors of all three dyno sessions to see if they all correlate with the adjusted values.

Thanks for the pointers and hints on this. I'll definitely keep digging into this to make better sense of what the dyno is doing.
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      07-15-2013, 04:48 PM   #34
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Quote:
Originally Posted by regular guy View Post
Interesting. I think what this means, is the Weather Underground site is using station pressure just as I thought. But it also means the dyno is using corrected pressure, which I didn't expect. I always thought the dyno used station pressure as well. I wonder if there's a setting in the dyno software to select between station pressure and corrected pressure. I didn't think there was, but I'm not a dyno operator. :-)

When you input the the weather underground values of 1008mBar and actual altitude of the dyno shop 5826ft, then you get adjusted pressure of 816mBar, which is very close to what the 848 mBar of the dyno. I definitely didn't expect that.

Might be helpful if the OP could post the dates/times, weather, and correction factors of all three dyno sessions to see if they all correlate with the adjusted values.

Thanks for the pointers and hints on this. I'll definitely keep digging into this to make better sense of what the dyno is doing.
Weather underground is posting corrected barometric pressure. Dyno is uncorrected... which makes perfect sense since it needs to be used for calculating a corrected (SAE) number!


Remember, it's the barometer AT SEA LEVEL. So in Denver, the barometer AT SEA LEVEL would be a NEGATIVE 5280.
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      07-15-2013, 04:54 PM   #35
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Quote:
Originally Posted by regular guy View Post
Interesting. I think what this means, is the Weather Underground site is using station pressure just as I thought. But it also means the dyno is using corrected pressure, which I didn't expect. I always thought the dyno used station pressure as well. I wonder if there's a setting in the dyno software to select between station pressure and corrected pressure. I didn't think there was, but I'm not a dyno operator. :-)

When you input the the weather underground values of 1008mBar and actual altitude of the dyno shop 5826ft, then you get adjusted pressure of 816mBar, which is very close to what the 848 mBar of the dyno. I definitely didn't expect that.

Might be helpful if the OP could post the dates/times, weather, and correction factors of all three dyno sessions to see if they all correlate with the adjusted values.

Thanks for the pointers and hints on this. I'll definitely keep digging into this to make better sense of what the dyno is doing.
Ask and you shall receive

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      07-15-2013, 05:05 PM   #36
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just in case you didn't already know, if you just have them send you the runfiles you can download winpep free from dynojet yourself, then you can run any comparison or correction method you want without having to get them to send you screenshots
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      07-15-2013, 05:59 PM   #37
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Quote:
Originally Posted by SYZ View Post
Weather underground is posting corrected barometric pressure. Dyno is uncorrected... which makes perfect sense since it needs to be used for calculating a corrected (SAE) number!


Remember, it's the barometer AT SEA LEVEL. So in Denver, the barometer AT SEA LEVEL would be a NEGATIVE 5280.
So what you're saying is that my z-axis is upside down?

I confirmed all of the OP's weather station results do seem to match when I run them through the weather correction calculator. I still thought the weather stations all used "station pressure" because they had no way to know the value of sea-level perssure. I know I read that a while ago...but I'll definitely keep digging into it.

Thanks again for the info.
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      07-16-2013, 12:58 AM   #38
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Quote:
Originally Posted by Bmw135er View Post
Wow not only deleting my posts, but Roman's as well?
In that case...
Maybe you should at least put a secondary air filter on your recirc valve hose that's disconnected. Otherwise enjoy the power now, because all the road debris youre sucking into the supercharger from the engine bay will lower your compression in no time. The hacks at AR may not recommend it because they also think it sounds cool, but it'll kill that engine along with the inning issues you're creating.
Hacks? Really? No idea who you are, or why you would say that. But I'd certainly appreciate an explanation.

For what its worth, we never left that hose disconnected, I believe customer removed it on his own. I told him to plug or filter it the moment I saw it.
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      07-16-2013, 03:49 PM   #39
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Cool OP. So your engine now sees almost 21.5 psi, while at see level a 625 should see around the same amount of pressure. I don't think your engine is at risk or anything like that.
But perhaps you are off the efficiency islands and that's what costing you some HP.
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As you increase boost you often need to lower your timing and this is one of the things we do in our higher HP kits for proper safety margin. Without knowing exactly what your dynamic CR is at your altitude there is no way for you to know if the fuel you are running has high enough octane, if the software you are running has proper timing or if the motor is being exposed to CR levels that are unsafe.
Hey Roman. Wouldn't DME change timing on it's own because of increased boost? That's what the ion knock-detecting system should do, right?
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. Pulled plugs before pulley swap and they are spot on. Zero timing abberations on dyno.
Don't you have an E28 to finish? Fire up that beast of car man I have a E28 sitting here, just waiting for you to finish yours so i can copy what you did and paste it in my own.
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      07-16-2013, 06:04 PM   #40
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Ugh, I have 4 projects going on right now. Need to get a few others out of the way, then back to the E28!
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      05-15-2017, 09:43 AM   #41
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Bump form the dead, but im getting ready to install a 625 kit. Should be receing from ESS in the next week or two. Im curious if i need a different pulley to get the right power up here at elevation. Im in Denver as well.

Im afraid i might not be happy if im getting a low boost. As it might not feel significant enough for me.
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      05-16-2017, 11:44 AM   #42
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I have a ESS kit.

Hind sight is 20/20, I should have went with a Harrop set-up.
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      05-16-2017, 12:16 PM   #43
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Originally Posted by ASBSECU E93 View Post
I have a ESS kit.

Hind sight is 20/20, I should have went with a Harrop set-up.
Go on...
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      05-16-2017, 01:17 PM   #44
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Quote:
Originally Posted by Iyzmi View Post
Quote:
Originally Posted by ASBSECU E93 View Post
I have a ESS kit.

Hind sight is 20/20, I should have went with a Harrop set-up.
Go on...
My opinion and struggles with the customer service of a certain company are well documented.

I still have the kit on the car - and the car only has 23k total miles, 10k with the kit installed.

I'm selling the car now that I have a 335d that will outrun/outperform my Supercharged M3...and gets 45 mpg.
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