I purchased a Beltronics "Vehicle Performance Computer" FX-2. It measures G forces using a 2-axis accelerometer. It also can give you a 1/4 mile time and speed. You can get times by 10's MPH (10, 20, 30, ....., 60,.., 100,etc). It can also give you Horsepower. To do this, I need some information, to set up the unit.

Vehicle Weight
HP drivetrain loss
Rolling resistance
Drag CDA= Drag coefficient X Frontal area

-Vehicle Weight I can figure out. It is labeled in the car.
-HP drivetrain loss is suggested in the product manual to be 0.15 for a 2 wheel drive with Manual Transmission. 0.20 for a 2 wheel drive with Automatic Transmission.
-Rolling resistance is suggested to be 0.013 for most passanger vehicles.
-Drag CDA is the multiplication of Draq Coeffieicent x Frontal Area

I am trying to determined these figures. I would like to know if you, the gurus in NAM, agree with the numbers that are been suggested or that I have found. I found a pdf file at NOLOGY that had information on the MINI S' Frontal Area, but the number provided by this pdf (0.33) for the drag coeficient was not the same that is posted most everywhere (0.36). This has shaken my trust on the Frontal Area number the pdf provides. To make things more complicated, I found a website of a group of guys that did some wind tunnel experiments with MINI models. They indicate that drag increase significantly with a spoiler. By spoiler, I assume they mean a stock rear wing. So is the 0.36 drag Coefficient that is published with or without a spoiler? A look at the picture of the team that did the experiments also raises some questions . Anyone can help?

Vehicle Weight? I have to figure out this one with my mods
HP drivetrain loss? 0.15
Rolling resistance? 0.013
Drag CDA? 0.36x21.30 sq.ft.=7.67 CDA

I added some links below for your own investigation. enjoy !


http://www.nology.com/pdfandzipfiles/carsdata.pdf

http://www.sjbaker.org/telamom/speed_math.html

http://www.vu.union.edu/~stroudj/Conclusions.htm

Bomboasy

 

That's a great list of sites you've found. Everything looks good but you might want to increase your rolling resistance a little bit as the MINI uses some sticky tires (especially if you have aftermarket).

My other car is a Honda Insight so Cd and rolling resistance are in my vocabulary. Some Insight drivers who have gone with aftermarket tires (even just 10mm wider) have experienced 5-10 mpg drop in mileage due to the higher rolling resistance.

 

I, and some others have the Auterra Palm Dynoscanner. It uses similar data. I quote the popular settings:

Weight: 2760 w/sunroof (I run 2980 which includes my weight, amps and a pretty large sub)
Gear Ratio: 7.181 in second gear for 2004 and older MCS
CW: .34 w/roof rack
Frontal area: 20sqft even
My tire diameter: 23.9 (will effect gear ratio)

The Auterra will calculate the gear ratio if you have accurate tire diameter measurements.

hope that helps,
Ciao,

 

BluMiniMe,

Thanks for the settings update. I recall that you were one of the first people to get the OBX header, that I also installed. I also recall that you had some dyno runs done. Do you see a reasonable corralation between your Dynos and the Dynoscanner? How much of a difference? If there was a lot of difference, was the delta between mods close enough between both? Thanks for your insights.

kapps,

Thanks for you comments. I am running with 17 " runflats right now, but will eventually change to wider and smaller. I will keep that in mind. The question is if there is a way to determine the real number with any setup?

Bomboasy

 

Most use 12%. Does it have a coast-down feature to measure the combined effect of drag and friction?

Matt

 

I have a related question (well, related to CD).
In April, I had to remove my rally lights to swap out my grille. Before I had a chance to re-rivet the mounting brackets, the Sin City MINI Club had a weekend run to Sedona. The milage I got on that trip was about 4-5 mpg better than my average on similar roads since I've had the car. Would rally lights on the front make THAT much difference in mpg?

 

The pop up corvette headlights degrade MPG 1-2. 4-5 might make sense if you were doing 100! That seems high, but it's possible.

Matt

 

No problem, Bomb. I've actually never had any true dyno runs done. The OBX header dyno numbers were done by a fella living in Germany on his MCS, and I was posting on that thread soon thereafter with my own thoughts and experiences with the install. I can't find a dyno here in Naples, Italy, and wanted a way to measure and assure myself that my mods were indeed improving performance, hense the Dynoscanner.

Provided that one inputs accurate data, and weather variables, the results are claimed by Auterra to be true SAE measurements at the wheel. I'm nearly certain that Ryan from Detroit Tuned has compared the results of his Dynoscanner with a true dyno and found them to report very close numbers.... certainly within less than 10% error, and I'd wager closer to less than 5% delta between the two.

I have documented a 13whp increase in peak HP and substantial increase througout the upper 1/2 of the rpm band by adding a GRS Intercooler, by doing before/after runs and updating the weather variables between the two. Bummer that these dyno plots aren't exportable though... one can only read them off the Palm.
Ciao!