Taming the HEMI, a new project for PowerTV, Part 1

The Chrysler Corporation surprised America back in 2005 by re-introducing the HEMI, which is now a modern day monster displacement engine that takes it’s roots from the old muscle car era as being one of the most powerful engines on the street. Staying true to it’s name, the HEMI still packs a punch most engines can’t compare to.

Chrysler has placed this American icon engine in several semi-high performance vehicle models including the Chrysler 300, Chrysler Aspen, Dodge Magnum, Dodge Charger, Dodge Ram, Dodge Durango, Jeep Grand Cherokee, Jeep Commander, and the up coming Dodge Challenger. Dodge also offers a high-performance line known as the SRT8 model available in the Magnum, Charger, Cherokee, and 300.

2007 Dodge Magnum RT

So, what do you get when you combine a legendary historic engine platform and modern technology? You get the best of both worlds, but with technology comes complexity. Practically all newer vehicles today are equipped with sophisticated computer controlled engine management systems. Somewhere there is something electronic controlling even the basic operations of your modern vehicle. Chrysler engineered the HEMI and it’s hosts in the same manner. For you old Mopar fans, you can’t just lift up the hood and take a wrench to the engine to tune these vehicles. Enter the Predator.

5.7 HEMI Engine with 350 HP Stock

Being a fairly new Mopar owner, I can’t take full credit for being a die-hard fan. I do love performance and since I’m somewhat of a techie, I enjoy the fact that today technology and performance can go hand in hand. Back in February I picked up a 2007 Dodge Magnum R/T (Road and Track edition). I’ve had my eye on the Magnum ever since it came out. With it’s bold lines and unique muscle car inspired look, I hardly see it as a station wagon. For a grocery getterthough, it is the fastest in the sub $30,000 price tag. The R/T comes standard with a 5.7 HEMI engine that pushes out 350 horsepower to the crank. The Magnum weighs over 4000 pounds and still has great get-up-n-go power. It drives nicely with nimble steering and has a smooth tip-tronic enhanced (known as Autostick) five speed automatic transmission. But like most OEM performance based vehicles, it just wasn’t up to par with what the enthusiast-inside-of-me wanted.

What do we do first to solve the lack of excitement? The folks atDiablosport recently finished up production on their tuner (deemed the Predator) for the Hemi. I was lucky enough to get my hands on one since these have been sell outs. The Predator is a full featured hand held tuner smart enough to decode the German inspired ECU on board my Magnum. It’s exactly what the doctor ordered for immediate power. This little box of circuits also opens the door for future mods I have planned. The HEMI version still has the same tuning features as other Predators, but offers a unique advantage for HEMI owners due to the complexity of the HEMI’s ECU.

We here at PowerTV like to show proven performance, so we put the Diablosport Predator to the test. We set the Magnum up on the Dynojet to get some base numbers. We pulled 287 horsepower and 322 foot pounds of torque for our stock baseline numbers. One of the challenges in dynoing the Magnum was the Autostick (and the automatic transmission in general). During a dyno run, the car automatically shifts to the next gear right in it’s peak power which can be a bit annoying. Diablosport recognizes this and the Predator has an option to remove the auto-shifting function while in Autostick mode. This allows us to take the Magnum into redline.

Predator tuning options.

The Predator is full featured with all kinds of options. The best feature has got to be the preset tunes available depending on your application and fuel. These presets have been R&D’d by Diablosport and are probably your most reliable bet for a plug-and-play tune. You can also hook the Predator up to your laptop to create completely custom CMR tunes using Diablosport’s tuning software (I’ll be using this feature a little later on when Vortech puts a supercharger system on, but shhhh… no one’s supposed to know that yet!). Diablosport keeps the menu selections fairly simple but still effective with RPM based fuel and spark trim adjustments.

To take full advantage of the Predators tuning capabilities and to get the most power out of my first mod, we decided to install a AFE Stage II Cold Air Intake to accompany the 91 octane CAI Predator preset tune. The Predator has other presets for 93 and 91 octane performance tunes without a CAI. You can also use it to modify the tunes even farther. The adjustability includes spark advance, fuel trim levels, WOT spark, rev limiter, axle ratio, idle RPM, ESP enable/disable, and even tire and wheel size adjustments. Can it get any more specific? It also removes the speed limiter, clears codes, resets the adaptive TCM, and adjusts transmission settings for shift firmness and shift points. Since I want the works, I went for it all.

AFE CAI installation.

The AFE CAI took less than an hour to install and was extremely simple, even for an old fogey like our shop manager BJ. It replaces the stock intake perfectly and takes up no extra space in the the engine compartment. It has a conical style filter that fits on the heat dissipating intake pipe and mounts up using the existing factory mounting points, so you don’t have to take a drill to your brand new car.

91 Octane performance tune with AFE CAI.

Once BJ was finished installing the AFE CAI, it was time to move on to the tuning process (although calling it a process seems a bit excessive). It took less than five minutes to tune the Magnum with the Predator. The tuner fits right up to the ODB2 port and immediately boots up. The first step is downloading the stock tune so when I take it to the dealer for warranty work, I can easily upload the stock tune back into the vehicle. Once it’s finished you are free to choose your path towards performance! I anxiously selected the 91 octane performance tune with CAI preset. Just press “I accept” on the ol disclaimer screen and the installation begins. A few minutes later the car chirped and the Predator was finished uploading the tune. I adjusted the wheel and tire size to accommodate my twenty inch rims and I also adjusted the shift firmness to give me a little more pickup when banging through the gears.

After tuning the vehicle, BJ and I put the car back up on the Dynojet to get our performance numbers. Since the tuner allows you to remove the auto-shifting while in Autostick mode, our numbers maybe be a bit higher due to the higher RPM limit, or so I thought. The true power band for the HEMI was at about 4500 RPM which was just before the car auto-shifted on our first dyno run. Even though we could take it all the way to the red line thanks to our Predator tune, the HEMI’s highest horsepower showed up again at about 4500 RPM’s. We picked up a substantial amount of power with the tune and cold air intake. Coming in at 324 horsepower and 351 ft. lbs. of torque, this HEMI was significantly more powerful than ever before. Thats a 37 horsepower gain!

Proud to be a Magnum Owner.

It didn’t take long for me to get the car off the Dynojet and hit the streets with my hot rod wagon. It was a night and day difference when driving the car. The Magnum shifted much more aggressively and the extra horsepower was easily felt through the butt dyno. I wasn’t quiet ready to take on a SRT8, but I was pretty close.

The Diablosport Predator and AFE CAI certainly proved itself to be a very cost effect performance mod and because the Predator is universal to the other HEMI vehicles, you can expect the Predator to show performance across the board. The Predator will stick with me where ever I go in my Magnum. It will prove itself over and over again as I use it to continuously tune with each additional modification I have in store for the fastest grocery getter in town.

~ Kevin McIntosh, Digital Technology Manager

DYNO SHEETS:

Stock Run

Predator Tuned Run

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