Death of the Hemi

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Originally Posted By: turtlevette
Yep, I see it. It's more of an oblong chamber so the piston will come real close to the head on both sides. The dual spark plugs must help too. With valves that big you'd think they would out power the ls engines.



As has always been the issue with the design, even with a quench area, meeting power targets whilst maintaining acceptable emissions and drivability is a serious juggling act. The dual-ignition is part of that formula but I would hazard camshaft design is more of a compromise in this platform than it is for a wedge. The huge valve area and ports probably have poor velocity characteristics at lower speeds which hamper emissions performance and I know historically did, due to poor low-speed swirl, for both Ford and Chrysler back in the day with their fully hemispherical chambers, cause serious low-speed performance issues. That was the primary reason the street version of the BOSS 429 had a small quench area on one side of the chamber.

I would posit that Ford has similar issues with the big 6.2L "cammer" which shares a very similar chamber design. The BMW DOHC mill on the other hand, with the 4 smaller valves and full pent-roof style chamber would have superior low speed fill and velocity characteristics. Also, with the ability to manipulate both intake and exhaust camshaft profiles independently, can be more finely tuned throughout the power band when compared with a cam-in-block setup.

Now, you add boost to it and all of a sudden you seriously change things. Hence the 840HP Demon. I have no idea what the stock ceiling is on that mill but an honest 840HP emissions-legal engine is wild.
 
AFAIK, the car ersions of the 5.7 Hemi have always been clean. My 2007 Magnum was a Tier II ULEV...and at its last emission test, it blew zero across the board.
 
What a moron would drive these behemoths - the video towards the end tells if you want one of these badassss V8 get it now. What a joke?
Every time I see one of those suped up vehicles, I really feel sad for the insane buyer - idoiotic American buyer
 
Originally Posted By: MaximaGuy
What a moron would drive these behemoths - the video towards the end tells if you want one of these badassss V8 get it now. What a joke?
Every time I see one of those suped up vehicles, I really feel sad for the insane buyer - idoiotic American buyer


Well us guys that drive the "behemoths" could really give a flying [censored] what you think. I would not drive the junk cars you do under any circumstances. I would rather walk.
 
Originally Posted By: SilverSnake
Originally Posted By: MaximaGuy
What a moron would drive these behemoths - the video towards the end tells if you want one of these badassss V8 get it now. What a joke?
Every time I see one of those suped up vehicles, I really feel sad for the insane buyer - idoiotic American buyer


Well us guys that drive the "behemoths" could really give a flying [censored] what you think.


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Originally Posted By: jeepman3071

The tick is annoying, yes, but it doesn't make the engine any less reliable. It is usually from poor maintenance. Chrysler thinks going 10,000 miles on conventional oil per the OLM is perfectly fine, while many of these engines see abuse and heavy towing. My father's 2013 Grand Cherokee with the 5.7L is approaching 95k miles and the engine has no ticks of any kind. He tows almost every weekend with it. I use Pennzoil Platinum synthetic and change it every 8,000 miles.

The first few oil changes were with conventional, but that was because the dealer told us they were using synthetic when the work order showed conventional.
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What issues did you have with your 2016?


Some engines with the "tick" develop issues while some dont. My tick was pretty prominent. I bought her with 10 miles, brand new. The tick was barely audible at first, but at around 500 miles it got much louder.

At around 800 miles, she started to develop a bottom end noise coming off throttle, the service writer heard it, but couldnt explain why or where the noise was coming from. The mechanic pretended not to hear it, telling me to come back another time when the "hemi specialist" was gonna be around.

I thought maybe the 1000 mile oil change would help. I bought the special SRT oem filter (better than the stock one) and the Penzoil SRT spec oil from dodge, but it didnt help quiet anything.

Ohh... and all this time, the trans (6 speed manual), would howl in 4th and 5th gear like an old mustang I used to have, but she had 150,000 HARD miles by the time I started hearing anything, NOT 1000! Apparently the manual trans in these cars are known for issues.

All this and I started to hear reports of body rusting issues behind the back doors, something about the way they stuffed foam in the body thus allowing water and dirt to get trapped. I wasnt gonna wait around for that!

After all of this, I got fed up and traded her in with 1200 miles for my 2017 WRX, 6 speed. Sure, not as fast, but a better all around car in general.... besides, I drove like an idiot with the Chally, it was only a matter of time before I got myself into major trouble.

The 6.4 is a great car to track, but not so much for legal street driving. A waste not to get to stretch its legs I think.

Originally Posted By: SilverSnake
Originally Posted By: babyivan
You guys are swooning over these Hemis. They are not so reliable with their infamous "TICK". I had a 2016 Challenger Scat Pack 6.4 six speed and it was nothing but trouble. Fast and fun, but a basket case otherwise


Every car line has their issues. Neither of my current Hemis tick and both vehicles have been flawless. However, there are those that do have their problems. I had a 2015 Challenger R/T that never had a tick but the start up clatter on the 5.7L was terrible. Sounded like it had no oil in the engine for about 20 seconds. Could not stand it and dumped the car at 1300 miles.

I guess I coulda had a lemon, but it seems that other 6.4 guys were having similar issues.
 
Dang it sounds like the dealer was just ignoring the issue. I would've tried to find another dealer or done the same thing you did. Chrysler dealers can either be okay, or really terrible. I haven't found any who have spectacular service unfortunately. We have a few really terrible ones around here, and one decent one that is a bit further away.
 
Dealers in general suck, some more than others though.

All in all I'm happy with the decision I made, the WRX is a fantastic car and I prefer nimble over brute power, but I will surely miss what that 6.4 can do in a straight line!!!!
 
Originally Posted By: MaximaGuy
What a moron would drive these behemoths - the video towards the end tells if you want one of these badassss V8 get it now. What a joke?
Every time I see one of those suped up vehicles, I really feel sad for the insane buyer - idoiotic American buyer


When do you replace your Highlander with a Smartcar?

Hypocrite.
 
Originally Posted By: Jarlaxle
When do you replace your Highlander with a Smartcar? Hypocrite.


Soon once you send me the check. Enjoy the V8s and keep feeding it!!!
 
Originally Posted By: SilverSnake
Originally Posted By: MaximaGuy
What a moron would drive these behemoths - the video towards the end tells if you want one of these badassss V8 get it now. What a joke?
Every time I see one of those suped up vehicles, I really feel sad for the insane buyer - idoiotic American buyer


Well us guys that drive the "behemoths" could really give a flying [censored] what you think. I would not drive the junk cars you do under any circumstances. I would rather walk.


Likewise. Great thing is he can drive his junk and we can drive ours! I like something with a bit of excitement, and that is precisely what SRT delivers...
 
Originally Posted By: MaximaGuy
Originally Posted By: Jarlaxle
When do you replace your Highlander with a Smartcar? Hypocrite.


Soon once you send me the check. Enjoy the V8s and keep feeding it!!!


Not much difference in gas mileage And if you have the V-6 Highlander, your mileage is the same (actually less on the highway)
 
Originally Posted By: Silverado12
Originally Posted By: MaximaGuy
Originally Posted By: Jarlaxle
When do you replace your Highlander with a Smartcar? Hypocrite.


Soon once you send me the check. Enjoy the V8s and keep feeding it!!!


Not much difference in gas mileage And if you have the V-6 Highlander, your mileage is the same (actually less on the highway)


Don't try to confuse this guy with the facts. His mind is made up.
 
In mostly city driving, I was getting 11 mpg with my 6 speed scat, driving with an oh so HEAVY foot of course. On pure highway, I got as high as 19-21, but that was in 6th and talking it easy. There's no way to defend this car's mpg if it's being driven the way it's meant to... but hey, I didnt buy it to save on gas, and anybody who expects otherwise is imo, a dope.

MaximaGuy is obviously trying to ruffle some feathers, I believe the youngsters call it "Trolling". It's not the first time, nor will it be the last. It is entertaining to some extent as well as annoying, haha.
 
The 215HP 3.3L V6 4x4 Highlander is rated 16/22 with a curb weight of 3,935lbs. The i4 is rated 18/23.

The 360HP 5.7L V8 4x4 Grand Cherokee is rated 14/22 with a curb weight of 5,135lbs. The 470HP SRT-trim is rated 13/19.

The fact that the 1,100lb heavier Grand Cherokee gets the same highway mileage is amusing. However, even in town, starting and stopping that weight with 145 more HP on tap only yields a 2MPG penalty.
 
Originally Posted By: OVERKILL
Originally Posted By: turtlevette
I've had arguments with people about this before. There is nothing that magical about a hemispherical combustion chamber. It's archaic and less efficient. A modern head should create quench as the GM engines do. It acts to create turbulence to get a better homogeneous mixture to burn. So the head should be flat and be within 40 thousands of the piston top at tdc.

GMs LS engines create plenty of power without being hemis. It just sounds macho. There are usually 20 of these in challengers at the show with their hoods open. I just walk right by as there is nothing to look at other than a huge plastic piece covering the whole thing.





The modern "HEMI" moreso resembles a pent-roof than a hemisphere. It has two quench areas (even the ones that "don't have a quench area" by nature of the shape of the chamber relative to the bore actually do) and canted valves that oppose each other. Unlike your GM LSx example, which is a traditional wedge, the HEMI and pent-roof designs offer more valve area. This was also the logic behind the Cleveland and BBC heads, which both feature canted valves, to allow for more area.

A quick look at the chambers of each:

6.4L Chrysler "HEMI":


Ford 6.2L SOHC head:


BMW M62 DOHC head:


GM LS3 "CNC" head:


Like with the SBF and venerable SBC, on the LSx both valves are on the same angle on the same side of the chamber, which limits valve area relative to bore diameter. The valves on opposing angles opposite each other like seen in the HEMI, SOHC and DOHC configurations offer more room for larger or more valves.

This doesn't make a huge difference in stock engines, but does, generally, facilitate greater flow for a given bore diameter in high performance applications. This becomes particularly relevant when dealing with engines that are bore-diameter limited and was evident with the Chevrolet 305 that could not accommodate larger valve heads like its 4" bore sibling the 350 and was subsequently of limited potential when compared to GM's previous 302 (4" bore) or its Ford counterpart (302HO).



There's a lot to like about the dual-squish, dual-plug Chrysler Hemi combustion chamber, and I don't get hung up on worrying about whether the surface of the combustion chamber is really a section of a sphere or a collection of conic sections, revolved surfaces, planes, and fillets. It is the squish pads, dual plugs, and the direction of air flow out of the intake ports that contributes to fast combustion. That is the ultimate goal that makes possible complete combustion, low emissions, and high power output.

I think the GM LS3 has a larger intake valve than the 6.4 Hemi. 2.165 vs 2.13, the last time I checked. But GM has a smaller exhaust valve, which they compensate for by putting longer duration on the exhaust lobes. When GM designed the DI Gen V LT1, they actually decreased the intake valve size to 2.125. The Gen V head also has canted valves, whereas the Gen III and IV don't. GM had to make more room in the chamber to put in the injector, and move the spark plug closer to the center of the chamber to get into the spray zone of the injector. The LS3 head actually flows better than the Gen V LT1, and the LT1 only makes more power because it has a longer duration cam, and higher compression ratio.

If it came down to an ultimate HP contest, I think the Hemi could be built to beat the LSx.
 
Originally Posted By: Jarlaxle
Just BATHE in that hypocrisy, dude.



He is just jealous, sad part is these new Hemis get decent mileage if you keep your foot out of the Throtle.

Just picked up my 2nd hemi, my 17 SRT Challenger came in last week. anyone calling owners of these morons doesnt have a clue nor have they driven one.

Got more thumbs up driving it and a neighbors 10 yr old nephew came over and told me my car was the coolest car he had ever scene, loved the Gomango orange, although he did think it was a Hellcat, told him I choose the 392 for the fuel economy
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sidetrack - it's amazing to me that we can get real HP and size at a greatly shrinking mpg penalty. This engine is a great example of extremely disciplined engineering. It demonstrates a 50% improvement in mpg over my 06 'yota. There was an EPA-bashing happening in another thread last week. Me--- I'm tickled that we have the option to buy all that power and yet not give away money at the pump, especially considering all of the dry sandy places we send our money to. I like it.
 
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