Jeep Wrangler SRT8 Under Consideration

A new report is indicating Jeep is considering a Wrangler SRT8.

Citing a "well-placed and trustworthy tipster," MSN Autos is reporting American Expedition Vehicles (AEV) built a HEMI-powered Wrangler for Jeep CEO Mike Manley. While this sounds like an excellent executive toy, the website goes onto say that the SUV was built for evaluation purposes which implies the company is considering a production model.

Nothing is official, but the Wrangler was reportedly outfitted with the 6.4-liter HEMI V8 that produces 470 hp (350 kW / 477 PS) and 470 lb-ft (637 Nm) of torque. This, as you're probably aware, is the same engine that will be used in the Jeep Grand Cherokee SRT8 which is slated to be unveiled at the New York Auto Show - [url="http://www.worldcarfans.com"]Worldcarfans[/url]

If this was to happen I would camp out at my Jeep dealership to test drive it because sometimes combinations of car and engine come along that you just can't ignore. I can only imagine this car would be EPIC if it was to happen. However I concede that, even if it was to happen, the chances of it coming to Australia are extremely low to say the least.

well i've seen vids of people dropping big engines in wrangles so a factory option would be nice right?

I know this has nothing to do with the car, but how can Americans struggle to get so much power out of a HUGE engine. I mean 470 HP out of a 6.4 litre V8? British engineers manged to get 400 HP in an 2.0 litre, inline-4 Evo VIII with simple tuning and an upgraded turbocharger.

We have been down this road many times.

The 6.4 L is OHV, which means it can't rev as high. However, an OHV engine is more compact. The LSX engines I believe are also rather light, and have a good power to weight ratio.

culver can explain better. Specific power is a fairly useless statistic.

Interesting but meh. It's still got high ground clearance so it won't work as a sports car, which is generally what I equate the SRT designation with. However, it makes sense for people who would otherwise drop a V8 into their Wrangler to go mudding or rock climbing or whatever.

Would be interesting I think, like the Brawler sort of way....though Wrangler doesn't really strike me as the open terrain off roader to suit that kind of powertrain...

Very interesting!
___________________________________

EDIT: SPAM deleted

[quote=I NEED NAWZZZ;963711]I know this has nothing to do with the car, but how can Americans struggle to get so much power out of a HUGE engine. I mean 470 HP out of a 6.4 litre V8? British engineers manged to get 400 HP in an 2.0 litre, inline-4 Evo VIII with simple tuning and an upgraded turbocharger.[/quote]

This is an oft discussed point. Here are some highlights:

1. WHY is smaller displacement better? What are we trying to optimize? Is it weight, cost, size, mileage? In the US we have no displacement based taxes so there is no financial reason to limit displacement as there is in much of Europe.

2. Don't assume that less displacement=smaller engine. The GM LSx engine is light and small for it's delivered power. The motor weighs about the same as the 3.5L Nissan VQ V6 yet produces more power and is physically smaller. The LSx motor is hardly bigger than the 1.8L I4 in my Miata.

3. Don't assume that hp=hp. Drive a ~215hp older SAAB turbo I4 then drive a 3L 220hp BMW I6. There is a BIG difference in how the engines behave even though their peak power (and torque for that mater) isn't that much different.

Small displacement turbo I4s often don't pair well with large, heavy vehicles such as this Jeep.

If you do a search for my user name and HP/L we have had this discussion before.

Here's an old post
[quote=culver;276347]This comparison is for V block motors. Many of the pushrod benefits are less significant on an in line motor

The general advantages of a pushrod motor over an OHC motor are:
-For a given displacement the pushrod motor is more compact (smaller height and width)
[url]http://www.vorshlag.com/pictures/motor-4.6-4V-004.jpg[/url] (Ford 4.6L mod next to the old 5.0)
[url]http://www.vorshlag.com/pictures/BothRight.jpg[/url] (GM LS1 next to a Mazda Miata 1.8)
-For a given number of cylinders a pushrod motor is cheaper to construct
-For a given displacement a pushrod motor will be lighter assuming similar construction (ie all alloy or iron block and alloy heads)

The general disadvantages of a pushrod motor over an OHC motor are:
-Extra valve train mass limits high RPM work
-Generally limited to two valves per head which tends to limit high RPM breathing.
-This is not always true as shown by GM’s XV8 concept motor
[url]http://www.carcraft.com/techarticles/0303_GM/index3.html[/url]
-Generally limited to a single cam shaft thus cam phasing must be applied to both intake and exhaust profiles. Twin cam can be done as shown in GM’s XV8 motor.
-Perception

[b]Hp/L, why should we care?[/b]

Compared to an OHC motor, the fewer valves and heavier valve train mass of the pushrod motor limit it’s ability to work at high RPM. High RPM is the way to get the most power out of a given displacement without forced induction. Basically pushrod motors are at a real disadvantage in the HP/L game.

But why do we care about it? Some racing series like F1 run displacement limits. In that case they don’t care about HP/L, they care about getting the most power with in the rules. If they could get more total power by running a 2.0L motor instead of the 3.5L they would.

Production cars are different. Some countries have displacement based taxes. These taxes started way back at the dawn of automotive time when the French were trying to figure out how to apply taxes to cars. A standardized dyno (adjusted for temp, humidity, pressure etc) hadn’t been invented so the French government simply said displacement=power and applied taxes accordingly. We of course know this isn’t true but it has stuck. In countries with displacement based taxes it makes sense to get as much power out of a 1.6L motor because I don’t want the extra taxes of a similar power 1.8L.

However in the US and other countries that don’t have displacement based taxes we can just opt for the larger engine with more torque. A pushrod motor will allow me to get a lot more displacement into a given engine bay (note that a Mustang 5.0 fits under the hood of a 1.8l Miata quite nicely).

[b]BMW M5 V10 vs Corvette Z06 LS7[/b]
Both of these engines are 500hp monsters:
BMW 5.0L 500hp, 390lbft, 530lbs
GM LS7 7.0L 500hp, 475lbft, 485lbs
Yes, the LS7 displaces more but it weighs less. Should BMW be applauded for producing 100hp/L if the final engine weighs more than GM’s torquier 500hp motor?

[b]but aren’t smaller (displacement) engines more efficient?[/b]
Not really. Of course we should expect a small 1.6L Civic to be more efficient than a 6L Corvette. However when we start talking similar size and power smaller isn’t necessarily better.

Lets look at high Hp/L motors first. Generally the tricks used to get a motor to produce over 100hp/L are not the same tricks you need to maximize fuel economy. Notice that the high mileage HX Civics (ignoring the hybrid Civic) have lower Hp/L figures than the Si or even the more pedestrian Civics.

Smaller displacement also can sometimes hurt mileage. Larger engines typically can run at lower revs and still generate sufficient power to move the car. The last generation BMW 530 actually got better mileage than the 525 because the 3.0L was geared longer so it spun slower on the highway. The 2.5L could have been gear the same but then it would have very poor passing power. The Corvette’s impressive 28MPG highway figure comes from a very long 6th gear. The Corvette has the torque to drive it so why not use it.

Lets look at it from a more technical view. A large engine spinning slowly can be just as efficient as a small engine spinning quickly. At low RPM, part throttle conditions the extra breathing ability of a multi valve head really isn’t used. We have already choked the engine by having the throttle at less than wide open. The larger engine takes more force (well torque) to spin the crank but it spins slower.

Comparing a C5 Z06 motor to a 2.0 Honda S2000:
The Honda turns about 4000 RPM at 75mph. The Corvette turns about 1800 at 75mph (these may be a bit off, I’m doing this from memory). Lets assume the parasitic friction in a motor is only due to moving the pistons up and down (there is more than that but for illustration’s sake). Lets assume the friction of a piston is equal to its circumference; ie each inch of cylinder wall imposes the same amount of drag on the piston regardless of bore. Thus it takes more force to move a large Corvette piston one inch and a small Honda piston 1 inch.
In physics terms, work equals force* distance. So it takes the same work to move a small force a long distance or a big force a short distance. The work it takes to turn the crank one rev will be circumference of the piston* stroke length *2 (up and down) * the number of pistons. Now the small S2000 motor clearly has the edge. It takes a lot less work to turn its crank one time.
In physics terms, power is work over time or work/time. The Honda has to turn it’s crank 4000 times a minute at highway speeds. The Vette turns its crank 1800 times. When I multiply out the work per rotation times RPM the Corvette ends up with a slight edge. In other words, given the speeds the engines are turning, the Corvette actually looses slightly less power to friction than the S2000. That is how a large slow turning engine can have lower frictional losses than a smaller faster turning engine.

It’s similar with pumping losses. The largest part of pumping losses come from choking the engine with the throttle. The closer you can run a motor to WOT the better. Infact BMW said the most fuel efficient way to accelerate in their cars is 80% throttle (most cars have a more aggressive, less fuel efficient fuel map at WOT) and shift at ~2500 RPM. At these low revs and open throttle conditions the motor is running in its most fuel efficient condition (that is power generated per fuel consumed). You might have the same rate of acceleration at 40% throttle and 5000RPM but you would have increased pumping losses and higher friction losses because the engine is spinning faster (see the Vette vs S2000 comparison above).

With a large displacement motor I can easily run it at these low revs and still have reasonable drivability. More so when the low cost of a pushrod motor allows me to add two extra cylinders (say a V8 for the price of a V6 or a V6 for the price of a I4). The extra power pulse of the extra cylinders help the engine stay smooth at low revs. A 2.5L V6 is smoother than a balance shaft equipped I4 under low RPM load. While the balance shafts make the I4 “inherently” balanced as a total system, there is no escaping the fact that the V6 fires 50% more, 3 times per revolution vs 2. According the Consumer Reports the Chevy Malibu V6 actually got better mileage than the Accord or Camry I4’s despite being significantly more powerful. A bit more embarrassing for GM is the V6 Malibu returned better mileage than the I4 Malibu.

So what we have is a valve train design that can allow us a lot more displacement with no weight or dimensional size penalty. We can maintain good mileage by taking advantage of the extra displacement and running the engine slower. With more advanced designs (XV8) we can get variable valve timing and more valves while still maintaining the size and weight advantages.
The drawbacks: Well many people know just enough about engines to have perception issues with pushrods. Lots of people mistake displacement for engine size and say, “only 200 hp out of 3.5L (or 400hp out of 6L or 500hp out of 7L), other companies are more efficient.” Finally, in my opinion, smaller engines can feel more sporty. The 2.5L SVT Contour motor is less powerful than Mazda’s 3.0L Duratec derived engine. I still think the 2.5L is more fun to drive.
[/quote]

I would much rather,

drive around in a low stressed 470hp big capacity V8 using a max of 6-6,500 rpm than a little 4-cylinder screamer that even made the same 470hp. If only for the sound! :)

There's nothing like grunt from a big engine. A V8 this size probably makes more torque at idle than most production 2-litre turbo-motors do at peak.

Add a decent after-market exhaust system c/w exhaust manifolds and a good re-map and it'll probably be comfortably over 500hp if it's anything like the LS V8's which only need a cam with less than 220 intake duration and re-tune to increase the torque and power numbers by 100.


Unsure what the poster means by "Americans struggling to make 470hp...."
Bit of a tactless comment; it's nothing to do with struggling or even ability, it's the car culture there. It'd probably be able to crank out 1000+ hp if it had the same treatment as the 4-cylinder engine mentioned.