Bluewaterrider

This is straignt from the man Dave Hagy at AEV:

Lets see if I can get this straightened out:

The current software that is out there to put a HEMI into a JK is the same regardless of who is doing the conversion. Its a cal that someone at Chrysler did for the aftermarket. This cal does not have EGR or MDS functioning and its not a great cal, its OK but not perfect and will never be truly "legal" for on road use.

Our goal is to be able to use the factory calibrations, meaning cals that are in production vehicles and are available at the dealer. The major reasons are:
Dealer servicing will be easier with factory cals
If you use a production cal (along with the rest of the kit and production parts), the conversion will then be of a "previously certified configuration" meaning they are eligable to go through CARB and be legal federally. The cal that is currently out there is not legal federally and is for off-road use only.
The 6.1L will benefit from getting the A580 trans which is what comes behind it in an SRT8. The 545 is a great transmission but is not suited for the 6.1 nor is the cal which is why the 6.1L does not perform very well in a JK, with the A580, the performance should be what one would expect from the 6.1L.
It gets rid of a high priced computer from the conversion
It will allow a true manual HEMI conversion. Currently all manual HEMI conversions use the automatic cal which means that the installer has to go into the cluster and cut traces as well as wire up the lights aftermarket style in order to make everything work OK, but its still not a true manual cal so the performance is not what should be there.
MDS and EGR will function in the automatics
This will allow the new VVT (really VCT) engines to be used in the JK. (!) which are great motors, the VVT really wakens them up.

All manual cals do not have MDS, MDS is an automatic only thing. That being said, the manual will still get better MPG than the auto with the MDS.

dh

So I guess I will have to wait a while for correct working 5.7L Manual Transmission MDS software......it's OK good things come to thoes who wait.

thissideup

Wish I could get that kind of gpm out of the hemi in my Dodge Ram(1500)!!!! I only get 14-15...Sure is fun to drive

bigbluejk

I think 16mpg is pretty good. I didn't mean 30. lol. This is my 5th Jeep, and one had a V8. I am ok with 16... right now I am getting 12-13 sometimes 14.... o well. It is a jeep.

OP...
If I was trying to increase my MPG a hemi is the last thing I would want. I understand how this guy is thinking lower rpm, at 70 the engine is just at idle almost... BUT the design of the Hemi is not as efficient as other engines of the same displacement. The Hemi is not and never has been made for MPG, it is a design for power. Ya, it has MDS and can shut off a couple cylinders which helps it a little at cruise, but if I had that system all 8 would be on all the time. I bet cash money if this dinky V6 had 2 more cylinders and 5.7l displacement I bet it would smoke the hemi on fuel consumption, but 100(+) horsepower less. The hemi was always made for power not mpg. I really doubt you will set your cruise at 65 and never pass anyone with that type of power there. I could very well be wrong, and I am sure someone that knows everything will correct me as I know close to nothing.

If I was willing/ able to spend hemi level cash... and I was doing it for MPG? I would only consider one option: turbo/vortech style supercharger. They increase mileage by a good bit and power. Hemi will give you the extra power but not the MPG increase. The magnum is a heavy car like the Jeep, yes... but it is much better aerodynamically.

All said. If I could afford to upgrade my rig with one... I would go Hemi hands down. But I would never expect better mpg from it. If you can afford a hemi, you are not a broke student like me. Gas here is only 1.74 a gallon right now. Who cares if it burns some gas??? It is a freakin fire breathing, growling, left lane driving, mustang passing monster.

dsy

Can anyone who has had the manual conversion done, verify the MDS system is working on their rig? My understanding from conversations with Dave is the same as quoted above. All of the different shops are using the same computer programming for the JK Hemi swaps, and none have the MDS working. I know it is not working on mine yet. I was also told that the MDS system was a function of the motor, computer and "auto transmission". Does anyone know if there are any other vehicles running the 5.7 hemi with a manual trans that also advertise running the MDS?

eDiveBuddy

[quote=dsy;988990]Can anyone who has had the manual conversion done, verify the MDS system is working on their rig?[quote]

Heck, I'd like to find out how anyones got MDS to work with the auto. I'd try it for a while atleast. But then I don't know how much it would come on. I almost never get it into 5th.

DarthBauer

There is no way that a Wrangler with a hemi is going to get over 20mpg. My wife used to drive a Honda Element, it was a 4cyl , and got way under 20mpg. Beware the box factor. One of my cousins has been fleet sales for Dodge for longer than 10 years and he even said the MDS is pointless cause it's only getting 1 or 2 MPG better than engines without MDS. Maybe you should look at going to a smaller engine than the 5.7, like the 4.7. Probably better mpg that the hemi and will probably also cost a lot less and still give you more power than the stock V6.

JKlad

I have to agree with those who point out that the Hemi motor was originally designed for power, not minimal fuel use; this is why MDS was deemed necessary in the first place to make the re-introduction of the Hemi palatable in todays gas-price senstive world.

The hemispherical cylinder head was developed back in the 60's (when gas prices were so cheap as to be irrelevant) to provide the perfect shape of combustion chamber for maximum power output relative to cubic capacity when compared with conventional cylinder heads, and are also noted for awesome low-down torque production.

These Hemi heads however are limited to two valves per cylinder and cannot be reconfigured to four valves per cylinder due to their hemispherical shape. Modern 4 valve per cylinder heads allow for better fuel economy and better performance higher up on the RPM range with higher and freer revving due to the engine's better "breathing" abilities and smaller valve components (and thus lighter valve mass allowing greater engine speeds while retaining operating smoothness). But then again, multi-valve engines require multiple overhead camshafts and timing belts, so are more complex in some ways than the simpler pushrod Hemis.

noot

There's more to fuel economy than it seems... power/economy/emissions are engine tradeoffs, and vehicle aerodynamics also help.

The speed you drive also plays a huge factor, as wind resistance really kicks up at higher speeds. I see a 20%+ difference in mileage when I drive 100 instead of 110 km/h.

In my mind, the reason the hemi could potentially get better mileage is that it's not working hard to move the jeep.

The displacement of the engine makes a difference, however a 2.85L engine pumping twice the gas into the cylinders as a 5.7L really isn't burning any less fuel is it?

It comes down to engine efficiency, and you'll never ever get proper numbers (you'd need the RPM vs throttle position maps with dyno information).