New Guy with Two Hemi's

[HemiX2]

Hi all!! Everyone says why do you buy gas guzzlers and expect half way decent economy? For me, I've always loved the power, but loved a little economy too. Sometimes it's kind of difficult to get to that point though. I have taken it as a challenge, and that is one reason I signed up here. I am hoping to get some pointers to further my quest. About 95+% of my driving is at ~2400-5000 feet elevation. A quick summary of what I have, and I am up against, especially for highway driving:

--Hemi (w/Multi-Displacement System) Dodge Magnum bought new and got 24 mpg at best with 87 fuel. Weighs ~4200 lbs. Now, on a day without headwinds and mountains, it gets no less than 27 mpg, and usually 28-30 mpg using 85, 87, 89, and/or 91 fuel, depending on the type driving and altitude I'll be driving at.

--Hemi (w/MDS) Jeep Grand Cherokee Overland bought used and got 18 mpg with 87 fuel when I bought it. Weighs ~4800 lbs. Now, on a day without headwinds and mountains, it gets no less than 20 mpg, and usually 22-23 mpg using 85, 87, 89 and/or 91 fuel, again depending on the type driving and altitude I'll be driving at.

I am looking forward to hearing suggestions from forum members on how to improve these numbers. Thanks for allowing me to become a member.

[Cd]

Take out the Hemi and use the proceeds to install a diesel ?
Build the diesel up for power like you have with the hemi, but you get the economy as icing on the cake.

Or ....you could just do what most of us here would do and buy another cheap old Civic and garage your toys for the weekend.

You would end up "win win" with that.
Low miles on the hemi cars , no supermarket dents , etc. ,and money at the end of the month to put into your toys versus gas.

[JRMichler]

Welcome to the site. Start with the 100+ tips button on the home page. Here's the link: 100+ Hypermiling / ecodriving tips & tactics for better mpg - EcoModder.com

The biggies are DWL (driving at a steady throttle opening) and DWB (driving so as to not use your brakes).

[ncnealncn]

I just traded my 07 Dodge Magnum for an 08 Toyota Yaris Manual. I get much better mileage, but I miss my Hemi. My wife, and I cannot afford three cars, but that is a great suggestion. Get a small beater for the day to day driving, and Keep the Hemi's for the weekends.

[Sporty Modder]

I had a 04Lincoln Towncar, not the most eco friendly. I went from getting epa numbers, 16/23- to 20-28 with an air dam under the nose and a lower grill block,and inflateing the tires to 40psi.
There was an air scoop for the rad and i built the air dam off. The airdam went to the front tires.

[UltArc]

I know exactly what you are saying with having the potential with performance, and still see a decent amount of power.

I don't know if I would suggest a hemi, but I've never had a good encounter with a chrysler, regarding engines or any other aspects, to be honest. I don't mean any offense by this, I just am not familiar with anything really to for it.

It appears you are not really interested in getting rid of a vehicle, and it seems like you enjoy your vehicles, ie, you want to drive them.

So what to do?
A more efficient air intake can help with power, and efficiency. Also, a cold air model will help direct incoming air, cold, rather hen engince compartment air, hot, which will be more efficient.

Coldair molecules are supposedly more dense, more air it, I don't really know the science.

Pizza pan wheel covers.

Close off some of your air intakes.

Over inflate tires.

Fill up the gaps between panels.

Keep your vehicle clean.

And a bit more extreme, you can

Close off your rear wheel arches.

Extend your arches to help the air flow around the tires.

More aero dynamic mirrors, or no mirrors at all.

Engine tuning.

Sorry for the length, I just tried to make it more checklist style. If you don't want to buy another vehicle, switch to ecoboost or better VT, andlike your cars, this is a great way to start. You can find way more in the section of 65+ mods, which most of these are included in.

[HemiX2]

Ncneal, I won't be getting rid of either of them anytime soon. Fortunately, I don't have to drive too much around town, and most of my driving (for economy anyway) is focused on highway economy. It's kind of tough, no matter what you do, to increase in town mileage when you're hauling around a 4200+ lb. barn door. Maggie has a Cd of .358 and the Jeep (with SRT front bumper) has a Cd of .39. IMO, the only saving salvation for the late model Hemi engines is the Multi-Displacement System (MDS) which shuts of 4 cylinders when cruising under light (~30%<) load. The way mine are set up, I can keep the MDS on for ~90-95% of the time on the highway. I also installed a light that tells me when the system is active. I've tried running them without the MDS active and they lose about 2-3 mpg without it.

UltArc, I guess I shouldn't even be talking performance and economy in the same breath. The late model Chrysler Hemi is really quite nice, for what it is. They're relatively trouble free, like most engines, when properly maintained. They develop good power, and the 5.7's (and now the 6.4's) all have MDS, except for the manual transmission versions. There are also more and more aftermarket performance products available. Unfortunately, most are geared for just high RPM performance, and not economy. What I have done to both of mine (set up almost identical), among other things is install well proven high torque cams, Jeep with 2 degrees advance and Maggie with 6 degrees advance. This brings the torque/horsepower range to a more useable range and reduces the high RPM performance.

Thanks for all your suggestions. I've also read through the 100 suggestions someone had recommended. I've done quite a few already, and some are more than I want to get into. Here's what I've done, so far to both vehicles to increase volumetric efficiency, horsepower, torque and fuel economy:
--Home made modified SRT-8 Cold Air Kits and high flow filters....IAT is now at ambient all the time on highway, which allows for more timing.
--Custom tunes for the engines, and transmission up/down shift scheduling, and torque management.
--Siped (Sipers.com | Siping Tires, Sipe, Tire Traction, Tire Performance) over-inflated, nitrogen filled tires.
--Custom tubular headers and low restriction exhaust systems.
--Advanced cams, as mentioned above.
--DashHawk powertrain monitoring system.
--MDS "ON" light to maximize 4 cylinder operation.
--Debadged (both) and SRT front bumper (Jeep only) to improve Cd from .
--Airtab (Aerodynamic Fuel Economy Savers for Road Vehicles [Be sure to watch the video toward bottom]) vortex generators on top and under both chassis.
--Oil catch cans to prevent oil/condensation from entering and contaminating the combustion tract.
--Lowered vehicle (Jeep only)
--Electronic folding side mirrors (Jeep only)

With the mods. I've done I feel I am up a little more than 100 RWHP, and have improved the FE by ~3-5 mpg on both. As soon as I need tires on either/both, I'll be switching to larger (20 in.) alloy wheels. I'd also like to devote a little more attention to the "dirty air" on the underside of the vehicles. The Jeep, in particular has a huge crossmember that is like a small brick wall under the chassis. It would be nice to streamline both undersides a little. I usually keep both vehicles clean, so that is probably not an issue. I am also debating the pros/cons of removing the spare tires. I am a little reluctant to do it because I do a lot of highway driving and don't want to be stuck somewhere without a spare. Anyone's thoughts on how much difference ~50-75 lbs. would make on already heavy vehicles. My guess for "loaded for travel" vehicles, with us in them and a full tank of fuel is, ~5400 lbs. for the Jeep and ~4800 for the Maggie. Certainly not lightweights.

[larrybuck]

Smoothness in your driving will be key.

What is your differential gearing on the car? Would it be feasible for you to change that SINCE you seem to be more highway oriented ( a wonderful thing) than city?

Oh! By the way; a hearty WELCOME!!!!!!!!!!!!!

[UltArc]

Most of that is beyond me. I can do most simple things, but get a computer and electricity involved, and I back away. It seems like the computers and intake are well in place, maybe now to work on filling in gaps in your panels and frond end? I saw the SRT front end, but when I think of the SRT8 at the Detroit autoshow his year, it seemed more sporty than aero dynamic. Also, there may be people here who could improve your tune, if you check out the other threads or sections. I'm not too familiar, I haven't even bothered with enine tunes until I know the full extend of my warranty. (I don't have my vehicle to mod yet)

[HemiX2]

Larry, thanks for the welcome. I know that smoothness in driving is good, but unfortunately I like to have my foot to the floor too much. I know it kills the economy, but I am still just an old guy with a kid's hot rod mentality, LOL!! I doubt that I've ever gotten through a tank of gas, with either of my vehicles, without at least a half dozen WOT runs.

As far as the gearing goes, the Jeep has 3.73's and the Maggie has 2.82's. I don't know of any higher gears available, and most of the guys that do changes go for lower....4.11's and 3.26's respectively. They're solely after performance and off road enhancement though. The Jeep has 2 overdrive gears and the Maggie has one OD gear, so that helps a fair amount. Also, the 4 cylinder shutoff at cruise on both helps quite a bit too.