Why does a car’s engine dip while on a dyno.

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Like what parts move to make the engine dip. Like in [this](https://www.instagram.com/reel/CONyYFZp4VM/?igshid=krf7sw1o8q3a) video?

In: Engineering
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The engine and transmission are on semi-rubber mounts. When the engine is making big power against the resistance of the dyno the engine/tranny will twist in the mounts. This twist is against the driveshaft(s) connected to the wheels running on the dyno

It’s compression/extension of the suspension.

There’s some motion of the motor within the mounts, like /u/drewathome mentions, but the bulk motion when it gets up to full power is compression of the rear suspension (and matching extension of the front suspension).

This is happening because of the torque against the dyno. The engine is twisting the dyno shaft, that reaction torque comes back through the wheels into the transmission, then into the frame. So the entire car is getting torqued counterclockwise (from the angle we’re looking in the video). That compresses the rear and extends the front suspension.

It’s trying to flip over the axle. If it was in neutral or if there was less resistance on the dyno, it wouldn’t do that. Same thing happens in your car.

I suppose, because I don’t know enough about these types of cars, it could also have an active suspension that lowers the car when it gets up to a certain speed.