Help with MG1 and MG2 specifications for All Prii (and G3)

Been searching a bit, and not found anything more concrete than this thread here.

What's the primary source or evidence that the MG1 rpm limit was increased above 10000rpm?

I'm a bit doubtful, suspecting that someone somewhere has just assumed that it increased at the same time as MG2.

I can see various people across the net, including Professor Kelly at Weber Auto, asserting 13500rpm (G3) and 17000rpm (G4), but I can't see where they got that from.

You can compute from the geometry that MG2 must be capable of those speeds in G3/G4 (and 17000rpm for G5 too), but I can't see any reason to think that MG1 would go that fast.

MG1 being 10000rpm would mechanically permit maximum engine-off speeds of 136km/h-162km/h (85mph-101mph) in the various G3-G5 drive ratios, and the G4/G5 PHEV manuals do quote "approximately 135km/h (84mph)" as being the (software) EV Mode limit. You would only need >10000rpm to drive >135km/h with the engine off.

So I reckon MG1 is still at 10000rpm in G3-G5, unless someone can find me a Toyota source or instrumentation evidence of it ever running faster (which could be evidence of the engine stopping at very high speeds). Anyone got any?

 

Pretty sure those rpm Ratings are the maximum turn rate not maximum driven/Powered rates

So a more accurate test would be to bring the car up to 160km/h and release the throttle and see wen the engine shots off

 

I think you're maybe misunderstanding what was written, as you think you're disagreeing by restating the situation. Yes, they are maximum turn rates, and the discussion is on that basis.

MG2 is linked to the wheels, so its maximum turn rate is linked to the speed limiter - you can clearly see across all generations of Priuses when you compare the specs that the speed limiter is set to a few percent below the speed derived from the MG2 limit (unless that would put it above 180km/h). PHEV versions have lower speed limits because of their lower gearing.

MG1's maximum turn rate determines the maximum engine off speed, as MG1 spins fastest when the engine is off. 10000rpm would still be consistent with the speed given for that in the latest manuals. Yes, it would be interesting to check that in practice, but I don't see a reason to suppose the manuals are wrong.

 

For at least the third generation, the maximum car speed allowed with engine stopped is about 46 mph, which corresponds to about -5420 RPM of MG1. (The negative sign means "backward" rotation, opposite the direction the ring gear is spinning and the direction the engine runs.) That looks like they allowed a very generous safety margin vs. the 10,000 RPM mechanical limit on MG1, but the limiting factor may instead have been potentially dangerous back voltage generated by spinning MG1 backward too fast with zero current. It may turn faster in the forward direction during hard acceleration.

 

I think there's an issue in that they've never bothered to give "forwards" and "backwards" maximums, and people have tended to think they apply symmetrically.

G1 seems to have had the limit as 6500 both forwards and backwards, so it was originally symmetrical.
G2 raised the forward limit to 10000 to allow the engine to rev higher, but the engine-off speed still seems to correspond to -6500, unchanged from G1.
G3 seems to have kept roughly the same engine off road speed as G2, even though that now means an even lower MG1 rpm.

Thinking about it, I suspect that the symmetrical MG1 limit was planned into the original PSD 78/23/30 ratio.

They knew what road speed they wanted to achieve EV in, and what engine rpm they were going to use, and that PSD ratio gave a symmetrical MG1 speed range of ±6500rpm in G1.

As the cars evolved, they never changed the PSD ratio (why not is another question).

And the desired EV road speed - bearing in mind considerations like battery welfare - remained the same for G2 and G3, so the actual used MG1 speed range became asymmetrical. MG1 was no longer a limiting factor on EV speed. But then it never was. It was the battery + inverter that they were worried about. It's just that the original G1 6500rpm MG1 was designed for the battery technology.

And later on they did finally take advantage of the -10000rpm MG1 possibility in the PHEVs with Li-Ion batteries that were able to sustain high-speed cruise.