Acceleration:
The day's testing included a total of eight acceleration runs and one power run. The four most consistent acceleration runs gave 0-60mph times between 5.8 and 6.1 seconds, with the quarter mile passing by in 14.0 to 14.2 seconds at 100-101mph. Unadjusted these times are slightly slower than the previous runs, however since I did not have the instrumentation or calculations to correct for atmospheric conditions and aero drag we can't compare them directly. At least now we do have corrected figures so they can be compared between other corrected runs...
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A few runs didn't turn out the best due to various reasons. The first run was very slow since we forgot to turn off the traction control and Brian short-shifted -- whoops! Another run was thrown out due to a missed shift, and yet another didn't make it due to Brian restriping the road for 20 feet. Unlike Chad, however, he only spun it through one gear <vbg>. Nice job Brian -- you've finally made it into the Burnout Gallery!
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Power:
For 2004 the Mustang Mach 1 is rated at 310bhp @ 6000rpm, and 335lb-ft of torque @ 4200 rpm. From the last season's runs I'd calculated 274bhp and 306lb-ft of torque. However, this year I brought along my new testing gear and can finally correct for aero drag and atmospheric conditions. The power run yielded a recorded peak of 224 bhp @ 5500rpm, and 246 lb-ft of torque at 4300rpm. After corrections the reverse-calculated power is 299-304bhp -- right on top of the rated power! Excellent...
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You might wonder why there was such a difference between the previous season's measurements and the current ones. While the atmospheric corrections allow us to more actually compare one run to another, the real reason the aerodynamic drag. After researching Brian's Mach 1 I found the coefficient of drag (Cd) for his car is 0.36, which is pretty high. This is mainly due to the hood power bulge and shaker air intake. Based on the power run, my correction spreadsheet shows that Brian was losing 29bhp to aero drag at 82mph (his measured power peak.)
As a comparison, my G35 with aero kit only has a Cd of 0.26, which means at the same speed I would lose approximately 20bhp. This gives my car a slight advantage at higher speeds, equalizing our true net power -- something Brian and I had noticed while, err... excercising our cars from a stoplight last year. :)
However, Brian's shaker hood does have one other effect, and this one is very cool -- literally. I noticed that according to my ODB2 data logger Brian's intake air temperature was exactly the ambient air temperature! While we've all heard about "cold air" intakes, "ram air" hoods, etc. his is both functional and effective. By keeping his intake air temp at ambient his engine can put out 1.5-2% more power than it otherwise could. By comparison, my G35 usually has a 7-9 degree increase in temperature under the hood for the air intake, and my buddy's M3 had a 14 degree difference!
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Finally, last time we were a bit confused by the power curve shown in the power run. Brian's engine is rated at 310bhp @ 6000rpm, yet we were seeing a power peak at about 5200rpm. Some research indicated that Ford was playing a bit loose with their dyno charts -- other dyno shots showed a very flat power peak from 5000-6000rpm. With the new beta firmware I'm running on the G-Tech the RPM detection has improved for marginal cases like Brian's Mustang, so we can see that his actual power peak is around 5500-5700rpm and that at 6000rpm the power has only dropped off by perhaps 10bhp.
Technique:
Well, after smoking off 20 feet of rubber Brian was reluctant to heat up his tires again. His launch RPMs were about 2300-2700rpm, which was enough to get a hard launch, but not enough to make any significant wheelspin. He should be able to drop his 0-60mph time by a few tenths with some modulated wheelspin at launch if he desired.
Now that we have some better power and RPM figures, we can more accurately predict what different shift points would affect. From the RPM levels we recorded, the 1st-2nd and 2nd-3rd shifts at 6000rpm drop the engine right on top of the torque peak -- the optimal result. However, a 3rd-4th shift at 6000rpm puts the engine at about 4600rpm, where there is another 10-15 bhp but about 10 less lb-ft of torque. When combined with the 10bhp or so loss from 5500rpm to 6000rpm, it looks like the best 3rd-4th shift should be at 5500rpm or so.
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Corrections and Other Factors:
Once again I've corrected the quarter mile results to the weight of a single person, quarter tank of fuel, and SAE J1349 standards. Check out the correction spreadsheet for the best run data, including the new power and aero drag figures:
| Recorded Data | Corrected Data | |
|---|---|---|
| Best Run | 0-1/4 mile in 14.0 secs @ 101mph | 0-1/4 mile in 13.7 secs @ 103mph |