Adding Lift Axle Cost

Many engines will have both valves open very slightly when a cylinder is between the exhaust and intake strokes to allow for scavenging.

https://m.youtube.com/shorts/JdOrK87u_BA

 

Casey Ladelle has videos on YouTube blasting air into an exhaust pipe showing that the turbos doesn’t spin.

 

Yes, but the truck he did that on was an emission truck. Appropriate for the topic of covering exhaust on new equipment, but not as helpful for the valve lap discussion unless it was done with every possible position of the valve train.

 

I will admit that I have often wondered why turbos don't fail while parked in a 70 mph wind, yet ostensibly can fail while being hauled at 70 mph.

That said, we still cover them.

 

I guess they do technically have slight overlap at the end of the exhaust stroke. I was thinking more of overlap where they are both closed and the only time they are both open would be if you were utilizing a Jake break or the overhead was way out of adjustment. But there is a brief period where they can both be slightly open. But there is no way that will flow enough mass of air to spin a turbo.