openinverter forum

If you were to weld the PSD in the L110 as in the prius would this alow MG1 to run at the same speed as the MG2 thereby allowing you to rev MG2 higher without over reving MG1? Also would this then cause the internal oil pump to drive?
Just asking. Cheers

PSD welded means that the input shaft (carrier), MG1 (sungear) and output shaft (ring gear) are locked together. So yes you lose the MG1 reduction, it would spin alot slower then MG2.

Yes the oil pump would de driven as it is geared to the carrier. Note you would thus now also be spinning it at MG1 speeds but also output shaft speeds. So zero prop speed is zero oil pump speed. and the speed range will be very low, and thus useless.

Big question is, what are you trying to achieve?

So my understanding the the MG1 spins faster than MG2 is wrong and for them both to spin at the same speed you would be advised to leave the PSD alone and lock the input shaft and rely on the external oil pump.
I'm wanting to use both motors to there best ability in a project.

Caddy2Spark wrote: ↑Mon Oct 06, 2025 12:21 pm So my understanding the the MG1 spins faster than MG2 is wrong

Did I say that? You asked about welding the PSD.

My assumption was that if the PSD was welded the two motors would run together at the same speed.
I will go back to Damien's early videos and recap.
Thanks for the help.

Have a review of the diagrams linked and provided to try and understand the gearing and gear ratios.

tom91 wrote: ↑Mon Oct 06, 2025 8:47 am image.png

PSD welded means that the input shaft (carrier), MG1 (sungear) and output shaft (ring gear) are locked together. So yes you lose the MG1 reduction, it would spin alot slower then MG2.

Yes the oil pump would de driven as it is geared to the carrier. Note you would thus now also be spinning it at MG1 speeds but also output shaft speeds. So zero prop speed is zero oil pump speed. and the speed range will be very low, and thus useless.

Big question is, what are you trying to achieve?

This would also mean that MG1 spins in the opposite direction than when used with the input shaft locked.
Provided the direction is taken into account, it could make MG1's torque more useful at higher road speeds, as it appears to be designed as a lower speed motor (an assumption from the dimensions, I admit).

As far as making the oil pump useless is concerned, I don't see why, as it's designed to run at output shaft speed in the OEM setting and, if it were useless at that speed, what would be the point of it?
I guess it takes over pumping duty above a certain road speed.

If the two speed gear at the rear were to be locked in high (as several people have done) high oil pressure wouldn't be required from 0 mph and the oil pump would be responsible only for lubrication, not hydraulic pressure.
In this setting, it's possible that the internal pump would be sufficient on its own.

nino500 wrote: ↑Sat Apr 04, 2026 2:27 pm As far as making the oil pump useless is concerned, I don't see why, as it's designed to run at output shaft speed in the OEM setting and, if it were useless at that speed, what would be the point of it?
I guess it takes over pumping duty above a certain road speed.

I can see I made an error there, as the planet carrier spins with the input shaft and is therefore designed to run at ICE speed in the original car.
So, on accelerating gently, it wouldn't be much above 1500rpm and, at a cruising speed, not much over 2500rpm (obviously the pump itself runs around twice the carrier speed due to the pump gear being around half the size of the carrier gear).

So, with the PSD welded, the carrier gear would be locked to the output shaft which, depending on the final drive ratio would be pretty similar, once up to around 30mph.

That wouldn't engage the clutches in the two speed gear as there'd be no pressure until moving and there'd be no drive w/o pressure so this would only work with the 2-speed gear locked (as I suggested above).

Thanks for the revision will looking into this further .

nino500 wrote: ↑Thu Apr 23, 2026 8:15 pm That wouldn't engage the clutches in the two speed gear as there'd be no pressure until moving and there'd be no drive w/o pressure so this would only work with the 2-speed gear locked (as I suggested above).

A further revision is that there would still be drive to the output shaft, directly from MG1, as it's locked to the carrier and ring gear in this format (it's just MG2 that needs one of the 2-speed clutches engaged in order to transmit drive) so you could start off on (a very tall geared) MG1 until pump pressure rises enough to engage one of the clutches.

Personally, if using this setup, I think I'd lock the 2-speed in high, then the question of hyd pressure is moot.