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07152013, 12:45 PM  #23  
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C'mon, you know better than that. 

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07152013, 01:13 PM  #24  
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HP correction formula used by the dyno uses temperature, barometer, and humdity. Altitude is not in the equation. 

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07152013, 01:30 PM  #25  
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Edit: did a little research, amazing Quote:
Last edited by SYZ; 07152013 at 02:26 PM. 

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07152013, 02:40 PM  #26  
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07152013, 03:20 PM  #27  
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So your 848mBar is not far fetched at all.. lower absolute pressure at a higher elevation. 

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07152013, 03:23 PM  #28 
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Gotcha, that's what I figured as well. Thanks!
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07152013, 03:27 PM  #29  
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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; 07152013 at 03:36 PM. 

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07152013, 03:35 PM  #30 
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Here's a link to weather data in that area for July12. Lowest pressure that day was 1008 hPa. Pressure around 12 PM (hottest part of the day) was 10091010 hPa (mBar). DA was 9510.
http://www.wunderground.com/history/...q_statename=NA I hope this helps. 
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07152013, 03:52 PM  #31  
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07152013, 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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07152013, 04:42 PM  #33  
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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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07152013, 04:48 PM  #34  
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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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07152013, 04:54 PM  #35  
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07152013, 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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07152013, 05:59 PM  #37  
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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 sealevel 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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07162013, 12:58 AM  #38  
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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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07162013, 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. Quote:
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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05152017, 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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05162017, 01:17 PM  #44  
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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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