High Torque Starter Motor Tests

martinr · Post by **martinr** » Sun Mar 17, 2019 7:04 am

I wonder if anyone has used the PicoScope to look at the performance of a high-torque starter motor? The advertising hype states these starters use less current and put less strain on the battery as well as spinning the engine over faster. The first claim didn't make sense as the electrical power required to crank the engine is determined by the engine and not the starter. But spinning the engine over faster was conceivable, but then that struck me as requiring more electrical power not less. So I put it to the test when I replaced the standard starter on a 1991 Opel Kadett with a high-torque starter. I cranked the engine over first on the standard starter and used Reference Waveforms to display the battery voltage and starter current (and power, in black, using Maths Channels Volts x Amps). So these waveform are paler than those taken after the high-torque starter was fitted. (The battery was not charged after the first cranking session, which lasted some 3 seconds. So here is the screenshot comparing battery voltage, starter current, and power consumed by both starters.

The tests show that the current drawn and power consumed by the 2 starters are practically the same, and the high-torque starter cranks the engine no faster than the standard starter; if anything, it cranks slightly slower, but that could have been due to the battery having less reserve after the initial cranking of the standard starter. (And the average power consumed appears slightly higher with the high-torque starter.)

There are a few interesting discussions on the Internet about these high-torque starter motors, and there are, naturally, some differing opinions. Certainly, listening to the car start with the new starter, one is easily convinced it has more "umph", but until Pico get round to adding an "umph" button in Maths Channels, I can only look at my objective results and conclude the advertising hype does not stack up.

I wonder has anyone done similar tests and come to any conclusions or perhaps sees flaws in my tests?

Technician · Post by **Technician** » Sun Mar 17, 2019 12:32 pm

You probably are already well aware of this, but thought it might give interesting insight about motors.

https://www.youtube.com/watch?v=gpesDF6hzn4

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