Acceleration:
Don completed four acceleration runs but no power runs since the RPM signal was total hash. As we mentioned, he wanted to test and see if varying the throttle changed the transmission behavior and also if his fan would engage differently. His first run was a standing, full throttle launch which yielded a 16.7 second quarter-mile at 83mph. His second and four runs were both using some brake-torquing, and as expected they gave better results: a 16.4 and a 16.5, both at 86mph. They also four-tenths of a second on the 0-60mph mark, taking only 8.9 seconds. His third run was the slowest, since he was using less-than-full throttle to see how the tranny and fan would behave. The transmission shifted identically, and the lighter pedal gave us a 17.1 second quarter-mile at 82mph.
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Power:
The 323's rated power is 170bhp @ 5500rpm, and 181lb-ft of torque at 3500rpm. Unfortunately, we had some difficulty getting RPM readings. Apparently Don's BMW had even more filtering than Damian's, because the G-Tech could not make heads or tails of the signal. We tried turning on the headlights, foglights, etc. to draw more juice -- no good. After a quick post on Tesla's forum, the consensus from a couple BMW owners is that if you can't get a clear signal try turning on the rear defroster! That does suck quite a bit of power, so we're going to try a quick re-test for a power run later. Until then, I do have a good solid pair of 124bhp readings from the acceleration runs. Given a calculated 12bhp aero drag and 20-22% driveline losses, the adjusted output is 163-166 bhp -- very close to the published 170bhp!
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Technique:
Due to the 323's moderate output, RWD driveline, and upgraded tires traction was never a problem. Even hammering the throttle from a dead stop did not give any wheelspin. Since the 323 is an automatic we can't control the RPMs before engaging the driveline, so brake-torquing to raise the RPMs up towards the 3500rpm torque peak was the plan. As you can see from the launches, the brake-torquing increased the launch acceleration significantly, if temporarily, and gave the fastest runs. Once the run was under way there wasn't any significant difference between the runs, although Don's throttle experiment did slow things down slightly on the third run.
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So, in summary the brake-torque launches were quite a bit faster, and if Don could get some more RPM by laying on it longer before launching it should get faster still. However, it seemed like the 2.5 liter V-6 was not going to get any more RPMs if we waited, so we're probably at the optimum now. Since we don't have any RPM data I can't verify the automatic shifted at the optimum points, but given that it's a BMW I would expect them to have done their homework. When we re-test later I will hopefully be able to fill this bit in.
More Info:
No skidmarks were left on these runs! Hmm... I think I have some bleach somewhere... :)
Adjustments made to the run data include:
- I'm not sure if there are any clear optimizations to be had from the 323i as it stands. Perhaps given that Dinan supercharger kit...
- After removing my weight from the vehicle, the corrected quarter-mile drops to 16.1 seconds at 88mph!
Oooh, that sound you just heard was Jon's ES300 hitting the mat after a clear KO from the BMW. This contest confirms that old email's prediction of which vehicle is faster. However, if Jon can cure his helium-infected throttle foot there might be hope in a rematch... :)