A visit to the Chrysler Technical Center in Auburn Hills
Category
🚗
MotorTranscript
00:00 Hi guys, this is Johnny Hunkins with the Hot Rod Network and we've got something really
00:16 special for you today.
00:18 We're actually at Chrysler in Auburn Hills, Michigan at the Chrysler Tech Center, CTC
00:26 as we like to call it.
00:27 Yes, and we are here with Greg Black and he is the Chief Engineer for the Hellcat Engine
00:33 Program and that's exactly what we have right here.
00:37 I've got to tell you Greg, we've just had a great time today photographing this engine
00:42 and finding out all kinds of great things about it.
00:46 I think this is one of the deepest dives we've ever done on any engine, let alone a Chrysler
00:51 engine.
00:52 Excellent.
00:53 You can tell I think from our interactions Johnny that we're real excited about it.
00:58 It's got some really interesting technical features and it's a really neat product.
01:04 Well you know what, let's take a look at it and give people an idea for what's under the
01:08 hood here.
01:09 Be glad to.
01:13 Well what we've got here is a very interesting display of a real Hellcat engine, Greg, and
01:19 it's been cut away.
01:22 What do we got up here on the top?
01:24 Well yeah, I think you're right.
01:26 The top is where we probably ought to start talking.
01:29 Certainly the blower is the source of the air.
01:31 Without the air we can't make the power because we can't burn the fuel.
01:34 So the throttle body, we'll start right there.
01:37 Air flows into the throttle body obviously.
01:39 This is a 92mm throttle body.
01:41 That's the biggest throttle body you've ever had in a Chrysler?
01:43 It is.
01:44 It's the largest diameter that we've ever utilized in a product.
01:49 And then from there we go into the internal inlet to the supercharger.
01:53 And then if you come around this way you'll get a good look at the screws.
01:57 This is a screw compressor.
01:59 The unit is actually made by our partner IHI.
02:04 This unit actually is manufactured in the United States, which is exciting stuff.
02:09 But the air flows into the screws and then up to the top part of the supercharger.
02:14 You can actually kind of make out the outlet port of the supercharger in this area of the
02:20 supercharger.
02:21 Yeah, let's show people that.
02:22 We actually have one here.
02:25 So here's a separate supercharger, Johnny.
02:27 Let me pull the top off and get a pretty good look inside.
02:31 So this is some seriously heavy duty hardware here.
02:35 It does the job.
02:36 It does a great job.
02:38 So this is the inlet we were looking at before.
02:41 So the air flow is in through the throttle body, into the underside, into the screws.
02:45 And this is our outlet.
02:46 And then as you saw, this is a plenum area up on top.
02:49 Right, and that's the lid right there.
02:51 That's where the pressurized charge is going to be.
02:54 Absolutely.
02:55 And then the air flows down and through the two intercoolers that you see mounted on either
02:59 side directly over the intake ports and fuel injectors.
03:02 Right.
03:03 Now those heat exchangers are on a separate coolant loop that's actually a low temperature
03:08 loop.
03:09 It does not work on engine coolant, right?
03:10 That's correct.
03:11 The coolant itself is the same fluid, but it's a separate cooling loop.
03:15 It has its own heat exchangers at the front of the vehicle and its own separate water
03:19 pump that we can control with the calibration.
03:22 Well that actually is the key to all the horsepower you're making, isn't it, Greg?
03:26 It's a big part of it.
03:27 As you know, you can boost things till the cows come home, but if you can't deal with
03:31 the fact that you are going to get into a knock problem, you're not going to be able
03:35 to utilize it.
03:36 So getting the air cooled off is really key to being able to make the power that we wanted
03:40 to make.
03:41 Yes, the Delta T.
03:42 One other thing I'll point out, this opening here that you're looking at is the bypass
03:48 opening actually.
03:50 It works in conjunction with the electronic bypass valve that you see here mounted to
03:53 the lid.
03:54 Interestingly, this part is actually one of our four cylinder throttle bodies, a little
03:58 bit different gearing, so it's normally open as opposed to normally closed.
04:04 But having an electronic bypass valve really gives the engine the ability to have a super
04:09 quick response.
04:10 We don't have any kind of vacuum lag or anything like that to get that bypass valve closed
04:15 up.
04:18 This is the Hellcat Hemi under the hood of the 2015 Hellcat Challenger, and I wanted
04:25 to show you the low temperature cooling loop, which starts at the front of the car behind
04:32 the grill.
04:34 Right behind the grill, you will notice that there is a heat exchanger, and we like how
04:42 Chrysler got their priorities straight because that's the first point of contact with the
04:47 air.
04:48 It actually, we've taken away the covering here, and I hope we don't get in trouble for
04:53 it, but that very first heat exchanger there is the one for the low temperature cooling
04:58 loop, and it does not mix at all with the high temperature engine cooling loop.
05:03 And that is the secret to the Hellcat Hemi's huge amount of power.
05:07 You got that large delta T that allows you to get that very dense air charge going into
05:14 the engine.
05:17 Well, as every tuner knows that you can change the pulley and make more boost, but that may
05:25 not be the easiest thing to do on this motor because of a very interesting device that,
05:31 as it turns out, is a piece of genius in my mind.
05:35 What do we got there, Greg?
05:36 Well, what you're talking about, Johnny, is the input pulley for the supercharger is actually
05:43 a decoupler, and we've done that for a couple of different reasons.
05:48 One is to prevent shock loading from positive and negative torques from going into the supercharger,
05:55 but that also helps us keep things a little bit quieter from an NVH perspective, noise,
05:59 vibration, and harshness.
06:00 So I've just got a part here, a development piece, but I can show you the way this works.
06:04 There's a coil spring on the inside of this that when the outer pulley tries to rotate,
06:10 this spring actually expands because of the direction of rotation.
06:12 It locks it in place.
06:13 It locks it down, and then that's providing the driving torque for the supercharger.
06:17 Yeah, the torque only goes through one way.
06:19 You got it.
06:20 Conversely, when it goes the other direction, the spring will wind down and it allows the
06:24 supercharger actually to freewheel down.
06:26 So for instance, at a shift point, which is pretty aggressive speed change for the engine,
06:31 we're not driving a bunch of negative torque into the supercharger, which really helps
06:35 from a durability perspective and a noise perspective both.
06:38 Well, we've got two different cylinder heads here, Greg.
06:42 We actually have the new cylinder head for the Hellcat, and we also have what we know
06:47 as the Apache head, which is the 392 6.4 liter.
06:52 They look remarkably the same.
06:54 However, there's some very important differences here that allow this engine to live at very
06:59 high horsepower levels and temperature.
07:02 Yeah, absolutely, Johnny.
07:04 We couldn't just take the Apache head and apply this kind of boost and power output
07:09 to it.
07:10 So what we did is we took a lot of the basic architecture from this head, but we've actually
07:15 added quite a bit of structure and stiffness.
07:17 We've done that a number of different ways.
07:20 Just by looking at the deck faces of the heads, you can see we've got quite a bit of ribbing
07:23 added on the induction side of the cylinder head.
07:27 The other thing that you can't necessarily see just by looking at the parts is that the
07:31 alloy of this is a 356 T6.
07:35 It's a premium aluminum alloy that is heat treated for additional strength.
07:41 The other thing that you really can't see is that the 356 alloy has a little bit better
07:45 heat transfer coefficient to try and keep those valves and chambers a little bit cooler
07:48 as well under those high loads.
07:50 And speaking of the valves, we've got quite a lot of work in the valves in order to manage
07:56 the heat, right?
07:58 Absolutely.
07:59 When you're dealing with this kind of power output, getting the heat out is paramount.
08:04 And what we have is a sodium-filled exhaust valve.
08:08 So again, the sodium turns to liquid in the stem and allows heat transfer to go up into
08:15 the stem and guide area from the head, which helps cool the head of the valve.
08:20 The intake valve is a hollow stem intake to try and reduce the mass and allow for better
08:25 valve train dynamics.
08:27 Right on.
08:28 Now the intake ports, not necessarily any difference in terms of the flow.
08:33 Mostly this is designed to handle the heat and do it with a 100,000 mile warranty as
08:39 well.
08:40 Absolutely.
08:41 In fact, you can see in the pictures here that the chambers between the Apache and the
08:45 Hellcat are the same chamber and the ports are the same geometry.
08:48 So we get really great flow characteristics for both engines.
08:52 Well, when all that air and fuel goes into the combustion chamber, it ends up dealing
08:59 with pistons.
09:00 And in the particular case of the Hellcat, we actually have stepped up to a forged piston
09:07 right here.
09:08 The Apache piston was a hyper-eutectic casting.
09:12 A great piston, but we have some additional needs thermally.
09:16 Why don't you address those for us, Greg?
09:18 Yeah, the forging gives higher strength and as you're dealing with the kind of cylinder
09:23 pressures that we are dealing with, you really need a premium piston.
09:27 So we went with the forged alloy.
09:29 The increased radii in the center as well as the continuity and the flow characteristic
09:34 of the metal gives a much more sound piece.
09:38 In addition, you can kind of see the two different piston pins.
09:40 They look similar, but this one's obviously darker.
09:43 This has got a DLC or a diamond-like coating on it.
09:46 It allows us to run much higher contact pressures without having any kind of a piston pin scuff
09:52 issue.
09:53 Well, I noticed that when I put that pin in there that it had incredibly tight clearance.
09:58 And I want to say well under a thou.
10:00 It just fits in like a glove.
10:03 If I can get this to go together, they are very tight.
10:06 You've only got a couple of ten thousandths of an inch in the system.
10:10 And you've got to get things just right, but they slip in there and provide a nice quiet
10:15 power supply.
10:16 And I can show folks there's a slight dish in that piston as opposed to the slight dome
10:20 on the Apache.
10:22 Very subtle, but we did lower the compression ratio to nine and a half.
10:26 So because in order to do that, you obviously have to change the piston crown in our case.
10:30 So we pulled a little bit of stock off the top of the piston to make that happen.
10:36 Right down from the piston is the connecting rod.
10:39 And in this case, we do have a forged powder connecting rod, which is quite a bit stronger
10:45 than prior, right?
10:46 Yeah, it is.
10:48 It's a higher strength alloy and definitely a premium piece.
10:52 You can see that we've got the taper on the small end of the rod that provides more bearing
10:57 area on the bottom part of the bushing for the firing loads that we're trying to deal
11:03 with.
11:04 Now the crankshaft is a really amazing piece.
11:07 This is a forging.
11:09 And I noticed that you have the micro polished races for the main and the rod journals.
11:15 Yeah, absolutely.
11:17 In a way, really kind of standard stuff for a crankshaft, but it's a-
11:21 Yeah, at this horsepower level, you really have to be in this forging.
11:24 Absolutely, rolled fillets.
11:25 But the interesting thing about this crank is all of the main and pin journal surfaces
11:31 are actually heat treated prior to polishing.
11:35 So that's an additional step that we took to provide the durability that we required.
11:39 Now tell us about what we have down here.
11:41 I noticed this is QR code and then there's some letters that says ABBA and it's not because
11:46 you like Swedish rock bands.
11:48 No, this is graded so that when the crank is manufactured, we measure the mains and
11:56 then it could be of an A, B, or a C level and then we select fit the main bearings to
12:02 provide quiet power supply.
12:04 Yeah folks, what I understand is that when this crankshaft is made, it is measured and
12:09 spec'd out and when they actually do the measuring, it actually keys to specific bearings that
12:16 are pulled when it's manufactured.
12:18 There's less than a thou difference between all of those bearings.
12:21 That's all part of our manufacturing process when we put the engine together and do the
12:26 assembly work.
12:27 Great, well let's take a look at the block now.
12:30 Well the Hellcat block is a thing of beauty.
12:32 There's a lot of beefcake in this thing.
12:35 It looks pretty much like a Hemi architecture block, Greg, but it's not exactly the same
12:41 that you would get in an Apache or even a 5.7.
12:44 No, not at all.
12:46 First and foremost, it's got to be Hemi orange, right?
12:48 So that's the first thing we did.
12:49 But the things you really can't see just by looking at it on a cursory glance is that
12:55 the water jackets in the block are slightly deeper so they're a little bit longer and
13:02 that provides us, again, a way to get more heat out of those pistons because we're dealing
13:06 with the thermal issues that come along with power generation.
13:09 And then the second area that's significantly beefed up is in the web sections by the main
13:16 bulkheads.
13:17 Yeah, I noticed that.
13:19 There's a lot of beefcake in there, if you can see, next to the bore and it's all tied
13:25 together really good.
13:27 I think you said at full rated power, there's a force of 22,000 pounds coming down on that.
13:32 And that creates a lot of vibration, that creates a lot of shock loading through that
13:38 juncture right there.
13:39 Indeed.
13:41 The bottom end of the block's got to be stout and I think the Hemi architecture has proven
13:46 itself over a lot of years and it can handle the loads we're generating.
13:51 Now on our model engine here, you can actually see the deeper water jackets.
13:55 Why don't you point those out, Greg?
13:57 Absolutely.
13:58 What you see is here in the inner bore region, this green area, the water jackets coming
14:02 all the way down to what we call 100% of stroke.
14:04 If you watch closely, the lower ring reversal point is down at the water jacket level.
14:10 So the entire time that the ring is traveling, we're able to pull heat out of it and get
14:15 it into the water jacket to take it away from the piston and combustion chamber.
14:19 Now folks, when you typically build an engine that's this high output, you usually see manufacturers
14:24 go to dry sumps or they're going to all kinds of measures to get the oil and air separated
14:31 from each other because when you're accelerating or turning, the oil is just basically a froth
14:40 and getting the air out of the oil before it goes back into the lube system, it's a
14:45 problem that has to be dealt with, right Greg?
14:47 Absolutely, Johnny.
14:48 Kind of like what you and I were talking about earlier, if you have oil entrained in the
14:52 induction air, it really can become a real knock problem for the engine.
14:58 It provides, in essence, an additional spark plug that you just don't want in the combustion
15:02 air.
15:03 Yeah, oil injection in an internal combustion engine equals a diesel engine.
15:07 We don't want that.
15:08 Exactly, not desirable.
15:09 So these are unique valve covers, as you've noted, they're die cast components.
15:15 And this upper volume here that you see cut away is, in essence, basically a labyrinth
15:21 that allows us to get good separation of the oil that's entrained with the air that we're
15:25 pulling through the positive crankcase ventilation system.
15:28 So we make sure we get all the oil out before we pull it back into the induction system.
15:33 Right on.
15:34 Well we actually have one last special piece of video that we want to show folks from when
15:39 we were earlier today, we saw, what do you call that?
15:42 A cold cycle test?
15:44 Oh yeah, the deep thermal shock test.
15:48 And let me tell you folks, if you've never seen an engine covered in frost, you're going
15:53 to see it now.
15:55 Let's go to what we saw earlier today and we'll give you a taste of exactly some of
16:00 the harsh tests that the folks here at Chrysler put through the Hellcat.
16:04 Well here we are in the dyno wing at Chrysler and we're getting ready to do a deep thermal
16:11 shock test on the Hellcat engine.
16:14 What I wanted to point out to you is that this is minus 40 degrees centigrade water
16:21 coolant that's coming through this engine and you can see that the water pump is completely
16:28 frosted over, as are the cylinder heads.
16:31 And they're going to hit this thing, they're going to fire it up and run this thing and
16:35 put the maximum delta T on this motor for a durability test.
16:41 Well now it's time to put a hurt into this bad boy.
17:05 So Johnny, you've seen the Hellcat inside and out today.
17:08 Glad to show it off a little bit.
17:10 I'm very impressed with what you guys have done.
17:13 I mean when you think about it, a 700 horsepower car that anybody can buy with a 100,000 mile
17:20 warranty and by the way, fuel economy too, you can't beat that.
17:24 I mean nobody else can bring that.
17:26 It's just an amazingly fun vehicle and can't give enough kudos to the team that made it
17:32 happen.
17:33 You know it's a lot more than just this one person that makes an engine like this.
17:36 So it's been a fun part of my last few months here and I think that when folks get into
17:44 this car and have a chance to experience it first hand, they'll be pretty excited about
17:48 it.
17:49 Let me tell you, you guys are going to love this car and you're going to love the story
17:52 which is going to be in the February 2015 issue of Mopar Muscle.
17:56 Don't miss it.
17:57 Well guys, you're just going to love the Hellcat, the way it drives.
18:04 When you're going down the road, it's quiet, it's luxurious, it's confidence inspiring
18:11 and it's just a very comfortable car.
18:14 But the second you let unleash those 707 horsepower, oh geez, everything gets really close in the
18:28 windscreen.
18:28 It's just a great car.
18:31 It's a great car.
18:32 It's a great car.
18:33 It's a great car.
18:34 It's a great car.
18:34 [BLANK_AUDIO]