42 mph

[ukrkoz]

anyone knows what is THE BIG SCIENCE behind HSD cutting off at 42mph? well, not completely, but ICE kicks in.

i am really curious, why do we have to lose all the idling ICE gas $$, when we are simply rolling down the frway or hill? what is it that just MUST HAVE ICE ON to roll at speeds over 42mph? doing nothing but wasting idle gas?

esp here, in Pacific NW, where we have abundance of long downhills that are just screaming to roll down with no engine.

why, or why??

[ukrkoz]

well, was told that ICE kicks in at >42mph to prevent MG from going over its rpm limit.
also, that in "free roll" mode, >42mph, if power is not needed, ICE turns off and does not take any gas.

ok.

[ukrkoz]

OK, here's the science:

However, from equation 1 in The Power Split Device, we know that MG1 spins backwards 2.6 times faster than the ring gear and MG2 spin forwards. This situation isn't safe when the car is travelling at high speed. At 42 m.p.h. and above, keeping the planet carrier still would result in MG1 spinning backwards at more that 6500 r.p.m. So that this doesn't happen, the computer configures MG1 as a generator and begins to draw off power. The generator drag created prevents MG1 from overspinning and instead the planet carrier begins to turn forwards. By spinning the planet carrier and the ICE at 1000 r.p.m., MG1 is protected at speeds of up to 65 m.p.h. At higher speeds, the planet carrier and ICE must spin faster. The electrical power produced by MG1 in this process can be used to charge the battery.

[andym1978]

Originally Posted by ukrkoz

OK, here's the science:

However, from equation 1 in The Power Split Device, we know that MG1 spins backwards 2.6 times faster than the ring gear and MG2 spin forwards. This situation isn't safe when the car is travelling at high speed. At 42 m.p.h. and above, keeping the planet carrier still would result in MG1 spinning backwards at more that 6500 r.p.m. So that this doesn't happen, the computer configures MG1 as a generator and begins to draw off power. The generator drag created prevents MG1 from overspinning and instead the planet carrier begins to turn forwards. By spinning the planet carrier and the ICE at 1000 r.p.m., MG1 is protected at speeds of up to 65 m.p.h. At higher speeds, the planet carrier and ICE must spin faster. The electrical power produced by MG1 in this process can be used to charge the battery.

Very interesting info. If I remember correctly, power generated by MG1 will be directed to MG2 for propulsion if the battery is fully charged. Is that correct?

[ukrkoz]

http://www.ecrostech.com/prius/original/PriusFrames.htm