This time for sure: 2012 Wrangler gets Pentastar V6, 5 speed auto

[JPK]

I found the overlaid torque and HP curves of the 3.8 and the 4.0.

As I recalled, the differences are all but non-existant until 3000rpms, when the 3.8 climb away on the torque curve and begins to climb away on HP too.

I think I figured out how to post the graph, here goes:

Here's a graph of the Hemi torque and HP, its SAE corrected and the engine was run with all accessories and exhaust. But its the pre-VVT Hemi, the 2009 and later VVT has more HP and more torque along with a flatter torque curve, the LX/Grand Cherokee version has 375HP max, can't recall the torque, at least 375lbs'; the truck version has ~395HP and 425lbs' torque, iirc. I have the LX/GC vesion.

Here it is resized, it get blurry, still readable though.

Write up goes wih he Hemi graph:
Fig 1This power curve showing 345hp and 375 lbs.-ft. of torque is impressive enough as is, but consider this: it is SAE corrected which shows numbers some 2 percent less and this is the output with the accessories and a full exhaust. In our estimate, this compares with a standard corrected motor of about 395 lbs.-ft. and 365hp.

Just to have all of the graphs in one post for comparison, here's the 3.6 graph:

The 3.6 doesn't look to shabby compared to the 4.0 or the 3.8, eh? And talking about a flat torque curve..., wow.

JPK

 

[Pskhaat]

JPK, yes (and quite surprisingly) the 3.8 has very similar curves. My personal opinion on the 4.0 is just that: opinion and worth not much. The bigger point though is the 3.6 with said flat curve, what I'm arguing is inappropriate for the Jeep, but maybe will satisfy the Costco-goers.

 

[JPK]

Surely it will please the soccer moms and commuter dads, any HP or toque improvement would, but with 40 or 50lbs' more torque - read ~20% more - in a useable range than either the 4.0 or the 3.8, it will please those who drive their Jeeps off road as well. Torque is everything, whether gotten through gears or through a more powerful engine. This engine is more powerful, and it will respond well to lower gears.

A flat torque curve is not a negative, its a huge possitive. The only reason a Hemi is better than any of the 4.0, 3.8 or 3.6 is because it has more torque at every rpm off idle.

JPK

 

[Pskhaat]

A flat torque curve is not a negative, its a huge possitive

Genuinely curious, why do you think that?

 

[JPK]

Your question makes me wonder if you understand the relationship between torque and HP. Here's an interesting explanation: http://www.houseofthud.com/cartech/torqueversushorsepower.htm Here's one that, if you think "wide and flat torque curve" when reading will probably help even more: http://www.allpar.com/eek/hp-vs-torque.html

A flat torque curve gives more control since similar torque is available over a wider rpm range. No need for more throttle or rpms to produce the torque required for the task at hand.

Off road a flat torque curve - which means more torque at lower rpms, will enhance the Jeeps potential to crawl at low rpm's. It gives the driver greater control when climbing as well.

On road a flat toque curve means an easier drive and, if you wish, a more spirited drive. No gear hunt for autos, no sifting through the gears for manuals trying to keep the engine speed within the top of the torque curve. The engine with the wider flatter torque curve is within its power band longer, more frequently and it is more often ready to provide the work required at the mear depression of the throttle.

An engine with a peaky torque curve can be a pita to drive, on road or off.

Wide, flat torque curves think diesels, think small block V8, think Jaguar 3.8's and 4.2's of the past, their long gone 5.3 V12, their recent 4.0 V8 and their current 4.2 V8. Peaky torque, think Lotus Elite Turbo, Formula 1 cars, two cycle bikes...

More later, gotta go.

 

[Pskhaat]

Your question makes me wonder if you understand the relationship between torque and HP

Ummm, I think we may need to close up the topic in this thread and call it a difference of opinion. Give me a peaky torque engine way down low any day off-highway

 

[Dan Grec]

I think Ford is the only ones who have made an improvement considering their 300hp 30mpg stang.

I find it so interesting to see a comment like this. I agree with you 100% that Ford seem like the only US auto maker doing anything about power and gas mileage - the interesting question is how did they do it?

It's not a secret - Overhead cams, 4 valves a cylinder, sophisticated VVT, variable exhaust timing, lighter materials, finer internal tolerances, better internal balancing etc. etc. **

In short, they are moving away from "Great hunking V8's" and moving towards much lighter, sophisticated engines. (I applaud this)
And yet, as soon as Jeep try to do this (first with the 3.8, soon the more sophisticated 3.6) time and time again we see people raving along the lines of
"The 4.0 wasWAY better. bring it back!"
or
"Jeep need to put a Hemi in there or it's going to be crap"

I can't imagine how a person in the year 2011 actualy wants a gas-guzzling, noisy, high emission engine with technology from the 70's. It's pure madness.

** NOTE: While you guys in the US might think these are "new technologies" and that a 300hp 30mpg engine is revolutionary or in any way cutting edge, I can assure you these are nothing new. German and Japanese autos have had all this and more since the early 80's.

-Dan

 

[Dan Grec]

Ummm, I think we may need to close up the topic in this thread and call it a difference of opinion. Give me a peaky torque engine way down low any day off-highway

Do some googling on "area under torque curve" until you find an article that speaks to you.
I think what you are trying to say is you want an engine that produces lots of torque early-on in the rev range (low down). You absolutely don't want an engine that "peaks" down low, because it will drop off sharply as the revs climb.

Aside from insane applications (Forumla 1 cars, Honda S2000, or a GSX-R 1000) the goal of every auto maker is a flat torque curve, with as much area under it as possible.

-Dan

 

[Pskhaat]

You absolutely don't want an engine that "peaks" down low, because it will drop off sharply as the revs climb.

Incorrect. That's exactly what I want. Called "torque rise."

the goal of every auto maker is a flat torque curve, with as much area under it as possible.

Which brings us back to the beginning of this topic. Not trying to be obtuse here, I just like my engines with old-school truck characteristics.

 

[JPK]

I read your link and I can tell you that it is out of date wrt automobiles and non-commercial boats. The HP and torque figures given are the max's just as in gas engines. Torque rise doesn't exist in these applications because they do not even meet the "intermittent" definitions, which can vary by manufacturer, and the engines are not intended to run at a constant rpm. If you doubt me, take a look at the Caterpillar or Cummins light truck or recreational marine sites, the VM or Mercedes vehicle sites. Recreational also applies to some relatively light duty commercial applications as well.

But in any event, if you are willing to live with the substantial penalties of a diesel vs. a modern gas engine, especially within the US and soon the EU due to the ridiculously stringent current (US) and forthcoming (EU) emissions requirements, then you can enjoy torque in the relatively low rpm range for a few more model years - all good off road. But you will be giving up on road performance that many others want or require, like acceleration.

And you will live with the modern diesel penalties vs. the modern gas engine benefits. Those penalties include more frequent maintenance requirements at higher costs, the lack of acceleration compared to the typical gas engine alternative offered in the same model vehicle, higher fuel costs offsetting better mpg, and much, much higher acquisition costs.

Modern gas engines do not share the awful maintenance schedule of their ancestors - no points, no rotors, no coils, no plug wire changes, 100k+ miles plug life, avg of 6000 mile recomended oil change intervals or better - some 10k miles, and they beat the heck out of a modern diesel. I oversee a mixed fleet, and truly, the diesels are an expensive pita, only justified when a gas engine isn't up to the task, like frequent heavy loads, frequent heavy towing or massive annual milage. Furthermore, the modern diesels often lack some of the reliability of the old diesels, the "git home" features, like the ability to run w/o the alternator, the ability to run on only the mechanical pump, the ability to run witout the turbo... Now its computers, particulate filters, urea tanks, BlueDot (something like that,) egr sensors, in tank pumps, high pressure fuel rails all eating into the once renowned diesel relability though some also making diesels easier to live with, cutting noise, smoke and grit, flattening early but peaky torque curves, adding higher rpm capability and HP....

No Jeep sees any of the justifications for a modern diesel. But Jeeps still do best with torque down low off and on road. So a flat toque curve is a huge advantage. A flat torque curve plus appropriate lower, non-mpg gears will make up for the diesels' typical abundance of torque on the low end. And a gas engine will give all around driveablity, better acceleration, less frequent and less expensive maintenance.

The other way to get an abundance of torque down low without going diesel and sacrificing is to start with an engine that produces a ton of torque. That's where the Hemi shines. While the later VVT 5.7 Hemi has more torque and a much flatter torque curve than the one shown in the graph I posted, that pre-VVT engine still has a strong peak at about 4500rpms. However, it produces ~300lbs' right off idle. The abundant torque of eother the pre-VVT or the VVT, peaking at 375lbs' at relatively high revs ensures drivability and that is confirmed by the respective 355 and 375HP at ~5200rpm.

If you compare the available-everywhere-but-the-US 2.8l VM diesel in the Wrangler, it makes 295lbs' torque at 2000rpms. 15% more than the forthcoming 3.6l engine with its flat torque curve, a nice improvement off road (but it weighs more too, though not a lot more.) About 15% less torque than the earlier non-VVT a Hemi. Its drawback is that it only puts out 161HP at 3800rpm, so day to day acceleration, drivability compared to the 3.6 will suffer, and it won't compare on the road with the Hemi. Going to the 3.0 Mercedes engine, once available in the GC is a big step up, with ~390lbs' torque, a relatively flat torque curve and ~240HP. But that engine hasn't been in a Wrangler, and almost surely never will be.

BTW, I have ran in Moab with a 2.8 powered JK on 35's. Reported real world milage was 26mpg, on road performance was said to be ok. It handled the trail with the same ease that the Hemi Jeeps did, no better, and both the Hemis and the diesel seemed to struggle less than the 3.8 powered Jeeps, which you would expect with the abundance of torque down low from the Hemis and the diesel. I also ran with a 3.0 Mercedes powered GC. The GC struggled over the same trail my Hemi cruised through, but that might be the difference between an Unlimited Rubicon with the Hemi, 4.5" of lift, 4.88'd and 37's and the more limited suspension modifications of the GC and its smaller tires.

What Grecy wrote is true of gas engine manufacturers, but it is equally if not more true with diesel manufacturers. They are working hard to flatten torque curves and bring peak torque up in the rpm range to improve drivability.

JPK

 

[Dan Grec]

Awesome info JPK, thanks.

Going to the 3.0 Mercedes engine, once available in the GC is a big step up, with ~390lbs' torque, a relatively flat torque curve and ~240HP. But that engine hasn't been in a Wrangler, and almost surely never will be.

Fingers are crossed for the newer VM 3.0 in the Wrangler that is confirmed to be coming for the GC in a few years.

-Dan

 

[JPK]

Awesome info JPK, thanks.



Fingers are crossed for the newer VM 3.0 in the Wrangler that is confirmed to be coming for the GC in a few years.

-Dan

I hope so for the diesel lovers!

But the damned funny thing is that the diesels everyone raves about, including the 3.0 Mercedes engine and the larger VM diesels are all engines that the manufacterers have spent a tremendous amount of time and money making more gas engine like!

JPK

 

[Dan Grec]

I hope so for the diesel lovers!

But the damned funny thing is that the diesels everyone raves about, including the 3.0 Mercedes engine and the larger VM diesels are all engines that the manufacterers have spent a tremendous amount of time and money making more gas engine like!

JPK

Agree 100%. I think so far, VW is the only company to do this well enough for "normal" people to want to buy in for regular passenger cars.
For me, diesel is about gobs of torque, better mileage, and cheaper re-fuel costs (at least in a lot of countries, diesel is subsidised more than gas, and is cheaper)

-Dan

 

[Plannerman]

How long has the Pentastar been in use in other vehicles? Is it pretty well proven or will 2012 Wrangler owners be cutting their teeth on a new engine?

 

[haven]

The 3.6L V6 was introduced in late Summer 2010 for the 2011 model year. So they have a year's worth of experience building the engine.