Electronically switch from FWD to AWD?
1 - 20 of 22 Posts
the 2024 Range numbers are still estimates, won't know officially until an AWD is actually produced.
Joined
·
872 Posts
I have the same question, daisy. At the moment, no one knows.
Joined
·
248 Posts
In the past, GM used an "AWD on demand" concept. Their old Versatrack AWD system was absolutely fabulous. Versatrack stayed FWD unless the front wheels lost traction. Then power would be routed almost instantly to any of the four wheels. The only real issue is you couldn't get a satisfying burnout from a standing start because Versatrack routed power that fast. You did get a good launch, even on sheets of ice.
The vehicle is likely always in FWD with AWD on demand as @obermd noted with previous concepts. VW does this on the ID.4. I have the ID.4 AWD and it's always utilizing the RWD motor. The larger of the two motors in the RWD giving the 201 HP and then the AWD kicks in either: 1) automatically due to detection of terrain changes (i.e.slippage); 2) changing the mode to Traction mode (puts it in AWD automatically); 3) you have the car charged up enough and are looking to overtake vehicles or test out the car's max speed (in this one it can reach maximum power between 80-100% but then slowly derates maximum power capability below that to conserve energy [still very easy to overtake vehicles at lower SOC]). My guess is that the Equinox EV will be exactly the same but flipped with FWD with eAWD under certain conditions (which I actually like more, because I'd prefer the larger motor in the front living in the Northeast of the U.S.(although all EVs are very heavy and have a very low center of gravity with the battery, so they have that going for them), and I don't really need a sports-car RWD handling...not necessary.
With that said: it's unlikely that it's "choosing" FWD that might give you extra range. It's the added weight of the second motor that mostly decreases range (I'm sure there are some range decreases in efficiencies that I don't really understand when energy is distributed between the two motors). The Lyriq question, though? I have no clue. I wonder if in the AWD they actually decrease motor size/weight with single motor resulting in less weight added but still having the capability of AWD. Either that or they've lost weight or added efficiencies elsewhere. That's a mystery to me!
With that said: it's unlikely that it's "choosing" FWD that might give you extra range. It's the added weight of the second motor that mostly decreases range (I'm sure there are some range decreases in efficiencies that I don't really understand when energy is distributed between the two motors). The Lyriq question, though? I have no clue. I wonder if in the AWD they actually decrease motor size/weight with single motor resulting in less weight added but still having the capability of AWD. Either that or they've lost weight or added efficiencies elsewhere. That's a mystery to me!
Joined
·
11 Posts
Speculation....maybe they will have a larger primary motor for FWD and a smaller, lighter, secondary motor for "on demand" eAWD in the rear. I just want that extra traction on steep gravel roads in moist conditions on an as needed basis. Primarily want the most efficient situation and that would be FWD for highway speeds, getting the most miles per kWh, and having a lightweight motor in the rear that won't affect efficiency so much due to weight.
That is my best guess of what will occur. That’s been the case for pretty much all single vs dual motor EVs in this segment
Joined
·
486 Posts
A disconnect would be nice but perhaps expensive to engineer. If I was living in a warmer climate year-round like sunny Florida, FWD or RWD would be on the table. And from what I remember Florida has long exits from each other which would be a great benefit with FWD.
Joined
·
248 Posts
I can't find it now but I saw a comparison of the various Ultium electric motors and the rear AWD motors are about 40% the size of the front motors.
Joined
·
872 Posts
Five drive units, three motors. Two will be permanent magnet motors – one with 180 kW power for front installation, the other with 255 kW for front and/or rear installation. The third motor in the bunch is a smaller 62 kW induction motor to assist with four-wheel drives. Depending on the positioning of the drive units the motors are in, they will be able to deliver front-, rear- or all-wheel-drive configurations. One of the drive units has been described as an all-wheel-drive assist unit, i.e. it will add traction when slip is detected. This particular setup is expected to feature on an all-wheel-drive Corvette, among other vehicles.
GM:
"The GM Ultium Drive family covers front-wheel drive, rear-wheel drive and all-wheel drive propulsion combinations, including high-performance and off-road capabilities.
All five drive units are expected to be powered by one or more of three motors including a primary front-wheel drive motor, which can be configured for front- or rear-wheel drive, and an all-wheel drive assist motor."
Rather than a single unit, Ultium Drive will be a small family, all based on the same technologies but offering combinations that make the various systems work in a wide range of vehicle shapes, sizes, and use cases.
![Flash photography Jewellery Automotive lighting Body jewelry Rectangle]()
GM:
"The GM Ultium Drive family covers front-wheel drive, rear-wheel drive and all-wheel drive propulsion combinations, including high-performance and off-road capabilities.
All five drive units are expected to be powered by one or more of three motors including a primary front-wheel drive motor, which can be configured for front- or rear-wheel drive, and an all-wheel drive assist motor."
Rather than a single unit, Ultium Drive will be a small family, all based on the same technologies but offering combinations that make the various systems work in a wide range of vehicle shapes, sizes, and use cases.
Edit: Looks like I was just beat.
Edit 2:
That was later proven incorrect as the E-Ray doesn't use any of the Ultium motors. So it may be used for a future compact CUV.
Joined
·
24 Posts
Based on the power ratings, it appears as if the AWD Lyric uses the same front motor as the hybrid Corvette (160hp). Given the low AWD penalty on the Lyric, I assume it is an induction motor like the 62kw motor. If I understand correctly the induction motors have the benefit of being able to draw little to no power and created little resistance when power is not needed. The drawback is that the motor cannot be used for regenerative braking. But I could be wrong.
Joined
·
248 Posts
I'm not sure the inability of a rear motor when it comes to regenerative braking is an issue. Remember, over two thirds of braking forces come from the front wheels even on an ICEV.
Joined
·
309 Posts
Well, none of us have found any interior photos for an AWD button\switch, so my guess would be it's an auto AWD. And we're pretty good here at finding these things. We already found the memory seats and the voice activation, and many other features before they were announced.
Joined
·
11 Posts
My Rivian R1T has 4 motors, all same size and weight as far as I know, and all the changes in configuration from FWD to AWD are on the touchscreen...no buttons or knobs. Changing from all purpose mode (all motors engaged, typical for usual around town or highway driving) to Conserve Mode (FWD, 2 front motors active, best for long trips) changes range on full charge from 316 to 347. Pretty significant difference with absolutely no changes in weight. Still makes me wonder why a simple software change on the touchscreen might have a similar effect on the range of the AWD Equinox EV for better range on long trips.
These vehicles are simply large computers on wheels. Have had the Rivian R1T since last May 2022, and am receiving, on average, an over the air software update monthly. Numerous tweaks have been added that have improved comfort and functionality, and improved range. If I remember correctly, GM has said that over the air software updates would be possible with the Equinox EV, so there is always hope! All speculation, will find out in the months ahead.
These vehicles are simply large computers on wheels. Have had the Rivian R1T since last May 2022, and am receiving, on average, an over the air software update monthly. Numerous tweaks have been added that have improved comfort and functionality, and improved range. If I remember correctly, GM has said that over the air software updates would be possible with the Equinox EV, so there is always hope! All speculation, will find out in the months ahead.
The Rivian is also a more expensive vehicle with a larger battery. I'm positive that all versions of the Equinox will be FWD 95% of the time unless you change to some type of traction/terrain mode. I could see there being some kind of conserve mode on the Silverado EV or other future off-road vehicles. Equinox EV use case is not supposed to be a mainly off-road vehicle. It's a city/road trip vehicle that has some AWD capability to use in various cases. But I'm 99.99% certain that there's no "conserve mode" on the Equinox that will extend the range beyond 300 miles. It will likely be that putting it in AWD mode likely will decrease the efficiency below 300 miles. Equinox EV (and Blazer EV - minus the SS) even though they're slightly different sizes and slightly different price points are in the same class as ID.4, MachE, Ioniq 5, and EV6 all of which are not in AWD mode most of the time.
For the Rivian, it’s not just software. Rivian incorporated axle clutches in the rear drive units half-shafts that, when commanded by conserve mode, physically disconnects the drive units from the outboard portion of the shafts. This allows the rear wheels to free-wheel. The drive unit inverter can then turn “off” completely and the motor/reduction gears stop rotating. magnetic rotor/stator losses are eliminated, as well as all mechanical windage and reduction-gear/bearing friction losses. Hyundai/Kia also do that on the front drives of their e-GMP platform EVs, and Tesla incorporated axle clutches on their Semi’s rear driver axle set.
For the Equinox rear assist drive unit with an induction rotor, it likely will turn off the inverter in FWD-only mode and save energy there. But axle clutches are $$ and outside the price/value box the Equinox is designed for. There will still be windage and friction losses as the rotor and gears idly spin, plus the rear unit’s always-present extra weight. An Equinox EV will likely replace both my 2013 Volt and my wife’s 2013 Subaru Outback, so a cost-effective AWD version w/ towing capacity (and blue paint
) is a necessity.
Joined
·
309 Posts
+1 for the blue paint!For the Rivian, it’s not just software. Rivian incorporated axle clutches in the rear drive units half-shafts that, when commanded by conserve mode, physically disconnects the drive units from the outboard portion of the shafts. This allows the rear wheels to free-wheel. The drive unit inverter can then turn “off” completely and the motor/reduction gears stop rotating. magnetic rotor/stator losses are eliminated, as well as all mechanical windage and reduction-gear/bearing friction losses. Hyundai/Kia also do that on the front drives of their e-GMP platform EVs, and Tesla incorporated axle clutches on their Semi’s rear driver axle set.
For the Equinox rear assist drive unit with an induction rotor, it likely will turn off the inverter in FWD-only mode and save energy there. But axle clutches are $$ and outside the price/value box the Equinox is designed for. There will still be windage and friction losses as the rotor and gears idly spin, plus the rear unit’s always-present extra weight. An Equinox EV will likely replace both my 2013 Volt and my wife’s 2013 Subaru Outback, so a cost-effective AWD version w/ towing capacity (and blue paint
1 - 20 of 22 Posts
