The Jeep Wrangler 4xe Two-Motor Hybrid System

Hello, I'm Professor John Kelly and this is the Weber Auto YouTube channel. In this episode, we will be looking at the hybrid components of the Jeep 4XE system that is used in the Wrangler and the Grand Cherokee. The Wrangler has used it since 2021 and the Grand Cherokee since 2022. There are two electric motors used in this hybrid system. The first motor is this one right here called a motor generator. And it's bolted to the front of the 2 L turbocharged uh internal combustion engine. And this is the starter motor. It also can recharge the battery. It also can assist the internal combustion engine, give it more power, specifically during the turbocharger spool up to get rid of the turbo lag. So this motor right here is not the exact motor that's on the Jeep. This is one that's very similar from a different car manufacturer. But if you look at this photograph right here, you can see the one from Jeep and it's liquid cooled. This is a high voltage motor generator. This is not to be confused with the e torque system that was 48 volts. This is a 400vt system. We've got the first motor that's bolted to the front of the crankshaft. Technically, that's called a P0 parallel hybrid position. uh we start at the front of the engine with P 0 and then P1 2 3 and four as we head towards the back of the vehicle in the position of electric motors that help the internal combustion engine propel the vehicle down the road. So this would be considered P 0. Okay. The other electric motor is inside of this big bell housing section that you see right here uh of this 8-speed ZF transmission. The model number is the 8P75PH. I shot a video on how the 8-speed ZF transmission works 10 years ago. You can see the link to it right here. And although this transmission has an electric motor in the front of it, the rest of the transmission is the regular 8-speed transmission that we've had all of these years. However, it does have a few additional components for dealing with this electric motor that's behind this cover here that we'll take a look at here. The transmission has an electric oil pump that's there to supply oil to the electric motor stator windings that are in here to keep them cool and to keep the clutch pack supplied that are all throughout the transmission when you're at an idle stop position. It also has an additional solenoid as you can see here in this photo uh to turn on and off a special engine disconnect clutch that's inside of the electric motor. uh that you'll see here. All right. Right here in front of me is the flywheel. And this is a dual mass flywheel. It's a big heavy dual mass flywheel that bolts to the back of the engine crankshaft. So, we've got the P 0 electric motor with a serpentine belt driving the front side of the crankshaft. And as it rotates, this dual mass flywheel rotates. you can see it's has some splines right here that will cause this input shaft for the automatic transmission to rotate. So, let's take this front cover off and take a look at what's inside of this transmission. Okay, with the front cover removed and the second rotor as part of the second electric motor also removed. Uh we can see inside of here the stator windings. You can see the kind of uh copper colored wires in there. That is the stator windings. This is a 24 slot uh delta wound stator uh with concentrated windings. Uh it's a pretty big one. This rotor that spins inside of that is pretty powerful. Uh this has let's see 80 kilowatt which is 107 horsepower. Uh it has a peak torque rating of 248 newton meters which is 182 pound- feet of torque and continuous torque of about half that. And so this is an internal permanent magnet rotor. Um, if you look closely at the rotor itself, you can see the internal permanent magnets in sort of a V-shaped groove right there underneath the layers there on the laminations. Okay. So, this rotor fits inside of that stator and it has splines right here to where if this rotor rotates, it will turn the input shaft of the automatic transmission, which is just the 8-speed automatic transmission that we've had for years. But inside of this rotor, there's a clutch housing. You can see

all these little slots right here. There is what's called the K0 clutch pack that fits inside of here. It has five fiber discs. So, alternating steel fiber uh clutch discs. Um the uh the clutch discs are fairly large. You see I got stuck to the per permanent magnet rotor. So, here's our clutch discs. Uh, and then we have alternating steel fiber, uh, steel plates and fiber plates. The steel plates spline to the inside of the rotor here, and the fiber plates spline to an in the input shaft that we had on the inside of this cover right here. So, here's the input shaft, and it has a torsional damper in it. On the back side of it, it has all these little notches for the fiber clutch plates to slide onto and lock. So, we've got this input shaft that is going to connect to the rotor. But notice the input shaft just free spins without spinning the rotor. And that's because the clutch clutches in this case aren't even in there. But if they were in there and they weren't applied hydraulically, these are wet clutches. They're applied hydraulically. It has an apply piston with molded one in place lip seals, a return spring, a balance piston, and a snap ring. Uh there it's applied hydraulically. There's a separate solenoid on the valve body that I showed you earlier that turns the fluid passage on and off to allow fluid to come to apply this clutch pack. So this engine disconnect clutch when it's off allows the engine crankshaft to rotate without spinning the rotor. When it's on, this whole thing spins as an assembly and turns the input shaft of the automatic transmission. Okay, so let's put all the pieces together that fit here in the front of this extra long bell housing of this 8-speed transmission. We've got our dual mass flywheel that is bolted to the crankshaft. So if the engine is running, this part is rotating the dual mass flywheel that's spins in front of this stationary cover that fits right here. And so that sits right there. And then we have the input shaft to the whole transmission right here with a another torsional damper. And so it splines to our dual mass flywheel. Notice our cover is free. But if we turn the dual mass flywheel, the input shaft turns. And then we have our clutch plates and piston that applies it. And then the electric motor rotor right here that fits just like that. So this entire assembly fits in there. These are very strong permanent magnets. It's very difficult to get out of that stator. So I'm not going to put it back in to show you. This is the second electric motor that is used to propel this vehicle. So, we've got that motor generator that's connected to the crankshaft through the serpentine belt at the front of the engine and this one that can be connected to the crankshaft if the clutch pack is applied. But if it's not applied, then this can just free spin or it can run in electric vehicle mode. Okay. Okay, the Jeep 4xe hybrid system in these vehicles have four major modes of operation. Uh the first mode that it defaults to if you've plugged in and charged your high voltage battery is electric vehicle mode. And so in electric vehicle mode, we use our 17. 1 kWh battery uh in the Wrangler to provide power to the inverter. And the inverter drives the three-phase electric motor. this one right here. And we run down the road on electric power only. Remember, if this rotor rotates, it spins the input shaft of the automatic transmission. And then just the regular 8-speed automatic transmission will take you through all eight gears as required as you drive down the road or reverse. Um, then when your battery state of charge gets down low enough that we can't drive on electric power alone, then we can go into what's called series

hybrid mode. In series hybrid mode, we use the internal combustion engine to rotate the front motor generator to provide energy to the battery and simultaneously or exclusively to the the rear motor here to propel the vehicle. Once again, a series hybrid is one where an internal combustion engine turns a generator like this one that provides power to a motor to propel the vehicle. there's no mechanical connection between the internal combustion engine crankshaft and the electric motor that's propelling the vehicle down the road. So that's series hybrid mode. The second mode, uh the third mode is called parallel hybrid mode. In parallel hybrid mode, we can have if your battery state of charge is high enough, we can have the front electric motor through the drive belt helping the crankshaft rotate. We can have the internal combustion engine crankshaft rotating providing power and we can apply the clutch pack back here. Uh the K0 clutch pack, the engine disconnect clutch. We can connect the rear motor to the crankshaft also and have it helping the internal combustion engine crankshaft rotate. So that means we have three sources of power giving you maximum torque or acceleration, whatever you're after at that particular moment, which is quite incredible. And if you're in first gear of this automatic transmission, which has about a 4. 7 to1 uh first gear ratio, and you put your transfer case in four-wheel drive low, which can be as low as 4:1, uh, and then your rear axle is right around 4. 1:1. If you multiply all those together, you get about a 77 to1 gear reduction, which is also a 77 to1 torque multiplication minus frictional losses and so on, which provides a tremendous amount of torque uh to the drive wheels to get you to wherever you need to be uh fast or slow depending on what gears you're in. All right. Well, that's a that's an impressive parallel hybrid system uh that we have there. Okay. Then we have uh the another mode that is when you're stopped with the engine idling. You're at a stop sign or you're it stopped with the gear in your gear selector in park. Uh with the engine idling, if your battery needs to be charged, the belt driven generator here at the front of the motor will be used to recharge uh the battery. Once the battery state of charge gets up to a certain point, this won't fully recharge the battery, but it'll bring it up enough for hybrid operation. Once it gets to that point, then the engine will shut off and there'll be no power flow uh at all. These vehicles do not have a 12volt starter motor. It they do have a 12volt battery and that's just to keep your 12volt uh systems on the vehicle operating, your power windows, your radio, and your air conditioning and everything else. lighting and so on. Uh, as I mentioned before, this motor generator at the front of the engine is a 400volt generator, but it's also the starter motor. This 400vt motor generator, the motor portion of it when the engine is off through the drive belt can start the engine. And this will always start the engine anytime the outside temperature is approximately -10 Celsius, 14° F. uh and above. So below those temperatures, the larger electric motor back here will kick in and be the starter motor through the clutch pack. And if the engine crankshaft is turning at zero RPM, we just bring this motor to zero RPM. We apply the clutch pack and then we crank this motor up to 1,000 RPM and get the engine uh started. Okay, there's one additional thing that you may or may not have noticed with this automatic transmission, and that it took me a little while to notice this. This also, I'm kind of embarrassed to admit it, but I had this transmission for 2 weeks before I it finally occurred to me, and this was back in 2021. There's very little information about it, but this transmission does not have a torque converter. There is no torque converter. So, a week or so ago, I shot a video on a Toyota um let's see, they call it the I Force Max system, and it uses an electric motor with a disconnect clutch like this in a parallel hybrid system in the Toyota uh products that are uh trucks and large SUVs. Um, but it uses a torque converter and a torque converter has some advantages and some disadvantages. Uh one of the advantages of a torque converter is it can multiply

engine torque. So it's like an additional gear reduction uh through the slipping in the torque converter. Uh but another thing that it does that is nice at certain times is it has a fluid coupling which means there's not a direct connection between the engine crankshaft and the input shaft of the automatic transmission. It allows for some slippage uh to occur, especially uh sitting there at idle. You don't have to step on a clutch pedal or anything. It allows for a slip up to a certain RPM, the stall speed as it's called. Well, turns out u torque converters also are the number one source of heat in automatic transmission. So, one thing that I noticed on this um transmission is that here on the side of the transmission, you can see right here, this piece right here, that's your transmission cooler. That's it. That's your transmission fluid lines right here coming into this heat exchanger. And then you've got your engine coolant lines that go out to the radiator right there. This doesn't have the massive heat generation that you would get with a torque converter, but because it doesn't have a torque converter, it has the disadvantage of not having the fluid coupling to allow for slippage. So, inside of this 8-speed automatic transmission, there are multiple clutch packs. Um, here's one from another transmission. and it's not from this one, but it's just a larger uh set of fiber and steel fiber steel plates. And inside of this 8-speed transmission, there's a clutch pack that sits right here in this big bump housing right there. It's called the B-clutch, and it's also called the integrated launch element. So, it's the B-clutch. If it's just a regular 8-speed automatic transmission, but when it's used in this hybrid design, then it they call it the integrated launch element, the IL clutch. And what they do is they purposely let it slip under certain conditions. Now, this clutch, this B clutch or the IL clutch is used in first gear, second gear, and reverse. So, it has to come on and be squished and applied anyway. It's a brake. it stops the B-clutch housing from rotating. Um, but as it's applying, it can allow for some slippage. And it's large enough. It's a large set of clutch plates like these here. They're they're pretty large. It's large enough and has good enough lubrication apparently that uh it can handle some slip. It's built to slip. Okay. There are times where we would want that B-clutch or the IL clutch to slip just a little bit and it it's most likely going to be during an event where the internal combustion engine is off but we're propelling the vehicle down the road with this motor right here, the second motor. U if the engine is off, the engine crankshaft RPM is zero and this motor RPM will not be zero. So in order to start the engine, we will use the front belt driven uh motor generator to start the engine and then bring the engine up to about the same speed as the electric motor here. It's called rev matching and then apply the K0 clutch to connect the engine crankshaft to the automatic transmission input shaft. If it gets off just a little bit in the timing there, it could be a rough engagement and you could notice that. So, if you're in first or second gear when this happens and this IL clutch uh was only on or off and didn't allow for some slipping, it could possibly cause a rough engagement to be noticed. And so, they used that clutch to make up for not having the slipping in the torque converter. So, these are the components and the basic operation of the Jeep 4xe hybrid system. We teach this technology in our automotive technology uh program here at Weber State University in Northern Utah. I also offer some online and face-to-face electric vehicle training if you're interested. There's a sign up in this link right here above me. We have two online classes that you take and then come and spend five days with me here in the shop. Uh but we also have full twoyear and fouryear degrees in these technologies. And if you go to this link right here, you can get information on how to register for our college classes on these topics and others. Well, thank you for watching. Have a good day.