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 Post subject: Spreadsheet Dyno?
PostPosted: August 17, 2011, 10:19 pm 
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Joined: February 28, 2009, 11:09 pm
Posts: 1307
Location: Connersville, Indiana
I have logged performance data of my Duratec 2.3. I have the following:
RPM's posted every 1/4 second in 2nd and third (2k to 6.8K)
RPM's posted every quarter second in 4th and 5th (to 80 mph)
Weight of the car during the logging
RPM's/mph for each gear
Road gradient (flat and level)

I feel this is everything I need to know to calculate HP and Torque as well as make acceleration comparisons in each gear to determine shift points. Problem: I am a mathematical dunce. Could someone give me guidance as to the arithmatic involved and how to best set up the comparisons?

I titled this "Spreadsheet", but in reality, it will be probably be done by hand, the only thing worse than my math skills are my computer skills.

Bill


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 Post subject: Re: Spreadsheet Dyno?
PostPosted: September 15, 2012, 8:38 am 
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Joined: February 28, 2009, 11:09 pm
Posts: 1307
Location: Connersville, Indiana
Bringing this one back from the dead. Found the program last year, but it was usually screwed up and spewed nothing but garbage. Currently, it seems to be working, here are the results.

Bowling's Highway Dynamometer Calculator
Input Parameters Are the Following:

Transmission Ratio One = 1.50 to 1
Transmission Ratio Two = 3.80 to 1
Vehicle Weight = 2650 Lbs.
Coefficient of Drag = 0.350
Frontal Area = 18.00 Square Feet
Tire Pressure = 30 psi
Tire Diameter = 23.6 inches
Engine CID = 140
Engine Stroke = 3.700 inches
Carburetor Air Temp = 70 inches
Barometric Pressure = 30 inches Hg
Altitude = 800 feet
Percent Humidity = 50
MPH = 20 at 0.00 Seconds
MPH = 30 at 1.70 Seconds
MPH = 40 at 3.30 Seconds
MPH = 50 at 5.00 Seconds
MPH = 60 at 6.80 Seconds
MPH = 70 at 8.80 Seconds
MPH = 80 at 11.80 Seconds

Computation Results:

- - - - - - - - G - - - Road - Flywheel - Corrected Corrected
MPH RPM - Force - Horse - Horse - Horse - - - - -Torque
-------------------------------------------------------
20 1624 - 0.25 - - 35 - - - - 37 - - - -39 - - - - 126.4
25 2030 - 0.27 - - 48 - - - - 50 - - - -53 - - - - 137.3
30 2436 - 0.28 - - 60 - - - - 64 - - - -67 - - - - 144.9
35 2841 - 0.29 - - 71 - - - - 76 - - - -80 - - - - 147.7
40 3247 - 0.28 - - 79 - - - - 85 - - - -90 - - - - 145.5
45 3653 - 0.27 - - 85 - - - - 93 - - - -99 - - - - 141.7
50 4059 - 0.26 - - 91 - - - -102 - - - 108 - - - -139.2
55 4465 - 0.25 - - 98 - - - -111- - - -118 - - - -138.3
60 4871 - 0.25 - -106 - - - 122 - - - -129 - - - -139.1
65 5277 - 0.23 - -107 - - - 126 - - - -134 - - - -133.4
70 5683 - 0.20 - - 96 - - - -120 - - - -128 - - - -118.0
75 6089 - 0.15 - - 82 - - - -110 - - - -117 - - - -101.2
80 6495 - 0.11 - - 61 - - - -95 - - - - -102 - - - -82.4

Bruce Bowling
bowling@cebaf.gov
Bowling Superior

I liftred the above from the SAOCA site. A guy there feels the corrections are not right, that the corrected hp should be close to 160. The car is a Sunbeam Alpine. Any comments?

Bill


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 Post subject: Re: Spreadsheet Dyno?
PostPosted: September 17, 2012, 1:00 am 
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Joined: April 26, 2008, 6:06 pm
Posts: 3268
Location: Under the weather. (Seattle)
That's pretty cool, but how certain are you on all the inputs? Remember I have minimal background when it comes to Alpines, but the only data I've found online puts the frontal area slightly higher at 18.5 ft^2. More importantly .35 sounds a bit slippery for the drag coefficient on one of those. I would guess, and again the only number I've found online appears to corroborate, that .5 might be more realistic. So I would be interested to see how changing those inputs affects the outputs from the calculation.

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 Post subject: Re: Spreadsheet Dyno?
PostPosted: September 17, 2012, 8:13 am 
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Joined: February 28, 2009, 11:09 pm
Posts: 1307
Location: Connersville, Indiana
My certainty of the inputs your mention is zero. The term, "Wild Ass Guess" is appropriate. Bruce posted a link to guidelines to estimate these criteria and I followed them. I am willing to rerun the numbers based on more accurate numbers. Is the .5 CD based on top up or top down? The runs were made with the top up. Well, not quite accurate, the fiberglass top was on. Can't see the computer screen with the top down. I will run the numbers again using different CD's and post the results.

I have a lot of confidence in the times. The runs were very consistent, most of the incremental incremental differences are probably due to rounding errors in the timing system. In the four runs, there were only two 10 mph increments that were different and they were within .1 seconds of the others. Every run had an E.T. of 11.8 seconds.

Bill


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 Post subject: Re: Spreadsheet Dyno?
PostPosted: September 17, 2012, 5:14 pm 
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Joined: February 28, 2009, 11:09 pm
Posts: 1307
Location: Connersville, Indiana
Reran the program with these changes:
Tire inflation 25 psi (actual pressure) instead of 30
Frontal area 19 sq.ft. The hard top sticks up more than the soft top.
CD of .55

Max hp went to 144 @5277 with torque of 142.9
Max torque of 150.8 @ 2841

Total gain of 10 hp.

Bill


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 Post subject: Re: Spreadsheet Dyno?
PostPosted: September 18, 2012, 12:08 am 
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Joined: July 17, 2008, 9:11 am
Posts: 6414
Location: West Chicago,IL
Quote:
Vehicle Weight = 2650 Lbs.
????

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 Post subject: Re: Spreadsheet Dyno?
PostPosted: September 18, 2012, 12:52 am 
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Joined: January 10, 2008, 4:47 pm
Posts: 7652
Location: Massachusetts
Quote:
The car is a Sunbeam Alpine.

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