Hybrid question

"and 100 more" (nth256) 05/18/2016 at 13:40 • Filed to: None

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What would be the accepted designation of an AWD hybrid where the front wheels are powered by a conventional I.C.E., and the rear is powered by an electric motor?

And are there any current examples of this design?

IIRC, the last Mitsu Eclipse concept had a setup like this, but that’s the only example i can think of.

AndyG_UK > and 100 more 05/18/2016 at 13:45

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Isn’t the hybrid XC90 like that, plus maybe the Mitsubishi Outlander hybrid?

Sampsonite24-Earth's Least Likeliest Hero > and 100 more 05/18/2016 at 13:49

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I thought Honda used a system like that for their hybrid all wheel drive models

RamblinRover Luxury-Yacht > and 100 more 05/18/2016 at 13:50

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In the interests of clarity, we are talking about a hybrid FWD drivetrain, correct? I can think of at least one really good reason for the front drivetrain to be hybridized rather than pure ICE, and that is that throwing away the 70% of braking energy in front on an FWD platform would be dumb, dumb, dumb. Once that’s taken into account, having fully separated electric AWD drive in back as part of the overall picture isn’t a terrible idea. Probably.

BvdV - The Dutch Engineer > and 100 more 05/18/2016 at 13:50

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Volvo and Peugeot/Citroën currently are making such cars, Volvo calls them Twin Engine and Peugeot calls it Hybrid4. An official designation would Through The Road (Parallel) Hybrid or TTR Hybrid, since the systems are connected through the road, instead of at the gearbox.

and 100 more > BvdV - The Dutch Engineer 05/18/2016 at 13:55

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Bam! Thank you!

JustAnotherG6 > and 100 more 05/18/2016 at 13:56

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I would be interested in setting up the G6 as such... If only.

and 100 more > RamblinRover Luxury-Yacht 05/18/2016 at 13:57

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For my purposes, I was considering a conventional I.C.E. propelling the front wheels, and an electric system powering the rear wheels, and of course then hardware/software to control the whole system.

To me, it just seems like a simple, no-brainer solution to AWD hybridization of existing FWD platforms.

and 100 more > JustAnotherG6 05/18/2016 at 14:01

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I think this is an idea ripe for the aftermarket.

RamblinRover Luxury-Yacht > and 100 more 05/18/2016 at 14:01

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Well, then my remark would stand. That makes for a hybrid system that is nowhere near as effective as it should be for city driving, but might be okay over-the-road.

and 100 more > Sampsonite24-Earth's Least Likeliest Hero 05/18/2016 at 14:02

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I don’t believe so, but I’ll look into it.

RallyWrench > and 100 more 05/18/2016 at 14:04

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Lexus has done that in the RX400h.

JustAnotherG6 > and 100 more 05/18/2016 at 14:06

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Agreed.

and 100 more > RamblinRover Luxury-Yacht 05/18/2016 at 14:10

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Are you referring to braking due to engine compression (DFCO)?

I see your reasoning in this regard, but your point is making the assumption that the I.C.E. is completely inactive when the (electric) rear drive is engaged.

On the contrary, something like GM’s mild-hybrid solution (an oversized alternator/generator/starter motor) could be run by the gas engine to supply power in a series-parallel setup (not unlike the Volt) and simply disconnected from the front transaxle by means of a clutch system. This would offset the need for some of the battery requirements. <—- Sorry, I got off the point here...

The engine could still be used for compression braking in this regard, as all you would need to do it engage a clutch between the engine and transaxle.

That being said, for my money, I’m assuming a system that would be less focused on hybrid efficiency, and more focused on providing AWD to an existing FWD platform... and also a slight efficiency boost.

and 100 more > RallyWrench 05/18/2016 at 14:13

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Awesome, I’ll look into that. Thank you!

and 100 more > AndyG_UK 05/18/2016 at 14:14

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Pretty sure the Outlander is not, but other people have said that this is how Volvo does it.

RallyWrench > and 100 more 05/18/2016 at 14:20

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No problem. I’ve had a couple in the shop, the diff units look like this:

RamblinRover Luxury-Yacht > and 100 more 05/18/2016 at 14:26

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I was mostly saying that while engine braking is useful, actual braking at the wheels or through driveline engagement for regenerative purposes is *more* useful, and a driveline with no electric components up front cannot, by definition, harness any of the front end braking effort productively in an electrical sense. That’s a huge throwaway for an in-town hybrid, but matters very little on the highway. Then again, if you don’t need acceleration assist more than % of braking at the rear times efficiency losses in storage and drive, it’s not that much of a thing. Never practical to go on full electric drive in such a setup, I wasn’t saying that - this is purely a mild hybrid “enhancement” sufficient to more than make up for AWD weight increases, etc.

and 100 more > RallyWrench 05/18/2016 at 14:27

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Awesome! It seems Honda has a similar setup, as well as Volvo and Peugeot.

and 100 more > RamblinRover Luxury-Yacht 05/18/2016 at 14:29

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Gotcha, and on that point, i totally agree - regen braking is basically free energy (or rather, otherwise-wasted energy), and if you’re only using the rears for that purpose, you’re not collecting much energy during those braking cycles.

RamblinRover Luxury-Yacht > and 100 more 05/18/2016 at 14:33

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Assuming that the FWD drivetrain has at a minimum a big alternator to help recharge the batteries while in dynamic balance, you get a *little bit* back on the engine end, through the drive wheels driving the engine driving the alternator. Peanuts compared to a big old motor ring/whatever, though.

and 100 more > RamblinRover Luxury-Yacht 05/18/2016 at 14:43

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Then again, on a modern DCT, you could simple disengage the engine/transaxle during all-electric driving, and simply re-engage once the brake pedal is pressed.

Might be more tricky w/ a conventional auto or CVT.

bhtooefr > RallyWrench 05/18/2016 at 15:06

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The RX/Highlander (and NX/RAV4) hybrids do have a rear electric motor, but they’re not through-the-road hybrids like the OP is describing. A through-the-road hybrid ONLY has the rear electric motor, and has a completely conventional front engine and transmission (or vice versa), and that’s what Peugeot is doing on some stuff.

The Toyota AWD hybrids (well, not the LS 600h - that’s just a mechanical AWD system) are using their FWD two-motor hybrid system, but with a third electric motor in the rear to add AWD.

bhtooefr > and 100 more 05/18/2016 at 15:09

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Honda puts their electric motor between the engine and a conventional transmission in their older systems, and in their new systems, either uses it to directly drive the wheels (with the engine also engaged to a generator, and the wheels with a single-speed gearbox and a clutch to disengage it from the wheels (instead using the generator to send power to the electric motor) for when it’s below, I believe, 42 MPH, or power demand and vehicle speed don’t match up), or on one system on foreign Fits, integrates the electric motor into a dual-clutch transmission.

Volvo’s integrating the motor into a DCT, and I think putting a second motor in the back.

Really, AFAIK, the only major automaker using a TTR hybrid system is PSA (Peugeot/Citroen).

Cé hé sin > and 100 more 05/18/2016 at 15:34

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Peugeot used to do it but gave up.

415s30 W123TSXWaggoIIIIIIo ( •_•))°) > and 100 more 05/18/2016 at 15:55

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Isn’t the Ferrari FF something like that.

and 100 more > bhtooefr 05/18/2016 at 16:04

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Nope, I did a little digging, and Honda has a TTR system as well: http://world.honda.com/automobile-tec…

However, for their more efficiency-focused models, they do exactly as you mentioned above.

and 100 more > 415s30 W123TSXWaggoIIIIIIo ( •_•))°) 05/18/2016 at 16:05

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I’m not sure, but it gives me an avenue to research. Thank you!

bhtooefr > and 100 more 05/18/2016 at 16:36

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That’s not what I would consider a through-the-road hybrid, as the front still has an electric motor, for what it’s worth.