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Discussion Starter · #1 ·
Since my recent dyno run I haven't been paying much attention to old videos. I eventually realized something however, I have a perfect opportunity to figure out hp lost to wind resistance! I have dyno figures, and a good video with a stopwatch. Perfect! ... or so I thought ...

The calculations started out ok. I made sure to do each estimation twice. One conservative guess, and one not so conservative guess, each within 1-2 hp of eachother in the end. The line in the picture represents actual loss due to wind, and *REAR* wheel rolling resistance. The front wheels are on rollers on the dyno, so there is of course about 2/3's of the rolling resistance right there.

The 50,60, and 70 mph figures seemed ok, with slightly increasing resistance each time, then suddenly at 80 mph there was a large jump in hp loss. It spiked at about 5,000 rpm, and then went back down, then I shift in the video and in fourth gear suddenly I'm losing even MORE hp.

The yellow line represents a "good estimate" of what it should have looked like given the 50-70 figures. You can see how far off the blue line is. At 105 mph I'm losing 50 or so hp somewhere. This did not seem at all reasonable given that I have a beat up '74 Beetle with roughly that at the *crank* and it goes about 100 mph with at least as much resistance as the nice new waxed Saab. Something was amiss.

I eventually decided that the ECU must have cut back on boost and/or ignition during the latter parts of the run. I had already done the run once, but my friend pushed the wrong button and didn't record it, so it was a second run and could have been heat soaked.

It's interesting to see the effects of having the ECU tamper with the power, and now I'm getting curious about how to stop it ...

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