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Old 02-13-2008, 11:32 AM   #1 (permalink)
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Another Autospeed aero article: methods for measuring aero drag

http://autospeed.com/cms/A_109741/article.html

They describe a different method for measuring aero drag. Not bad, but I wonder how accurate it is. Its hard to say if a MAF sensor's voltage is directly proportional to engine load. For example, say you get 1 volt @ 60 mph and you are using 10 hp to maintain that speed. Does .5 volts mean you are now using 5 hp to maintain speed? I wouldn't be too sure. But, it is a way to measure improvements.

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Old 02-13-2008, 12:23 PM   #2 (permalink)
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I just can see that working unless you are on a dyno. Finding a perfectly flat road with no wind. That's a tough order to fill.
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Old 02-13-2008, 12:32 PM   #3 (permalink)
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I saw this yesterday also. I really like the DIY + empirical mindset at that publication.

Ideally, someone could calibrate direct sensor measurements against a SG or SuperMID, and post the information for others who don't have the $ to spend on the OBD2 computers, or whose cars are pre-obd2.
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Old 02-13-2008, 12:57 PM   #4 (permalink)
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Quote:
Originally Posted by Daox View Post
http://autospeed.com/cms/A_109741/article.html

They describe a different method for measuring aero drag. Not bad, but I wonder how accurate it is. Its hard to say if a MAF sensor's voltage is directly proportional to engine load. For example, say you get 1 volt @ 60 mph and you are using 10 hp to maintain that speed. Does .5 volts mean you are now using 5 hp to maintain speed? I wouldn't be too sure. But, it is a way to measure improvements.
For us - it would be better to consider a relative measurement (power is going to depend on a few other factors in addition to MAF readings and will vary from car to car). I think it would be pretty safe to say that given mostly consistent conditions - if ABA testing shows .5V - 1V - .5V... there's a benefit
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Old 02-14-2008, 12:34 AM   #5 (permalink)
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some of the error from wind and terrain can be canceled by driving both directions on the same road the same day.

another trick i mounted a TPS(throttle position sensor) on the linkage to my diesel injection a couple years ago, i read the ohms at a steady 55 both directions on the same day, change something, go run again, gives me a relative power level for the price of a TPS. would work for suspension travel also.

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