What happens at 43 MPH?

It is the ICE and there is a small injection of fuel at that time.

In a French forum we're still speculating over what this injection is for though... The latest hypothesis is for a smooth restart of the ICE..

 

Note: Your terninology is not up to speed with what most are using here. Glide refers to ICE off operation. You will only know that if you have a gauge that will read RPM.

Here is what is happening in your case.

Assuming the engine is warmed up, and you are in the Gen III equilelant of Stage 4.

When slowing from above 46 MPH through 43 MPH the ICE (Internal Combustion Engive) will shut off at 43 MPG. It gives a slight bump when this happens. The only way to know this for sure is to moniter the RPM. A SG II (Scan Guage 2) is what I use.

Interestingly, going the opposite direction (Example, going down a hill with the ICE off). When starting at 40 MPH with the ICE off, The ICE will come on (continuously spinning mode) at 46 MPH. Above 46 MPH, the ICE will always be turning under normal operation.

When doing pulse and glide, the area 43 MPH to 46 MPH is an area where sometimes you can get the Gen III to glide and sometimes you can't.

To answer your question, it is 100% certain, the vibration or bump your are feeling is the ICE stopping rotation.

 

Actually my speedometer is both types. Just push the KM/Hr // MPH button. I suspect all are both types.

 

If you have a Scangauge II running, you can see the RPM's drop off when you feel this sensation. As many others have said, it's the ICE stopping. Similarly, you can see (on the SGII) and feel the RPM's jump when you are gliding down a hill with the ICE off and the speedo passes 46MPH, forcing the ICE to start spinning.

 

I think when you hit 43 the car spits out a small rainbow and flowers from the tailpipe, thus causing the slight bump you feel.

 

Here is a link to explain exactly what you're talking about.
Tony Renier

Toyota Prius - Power Split Device