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August 2005

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Feature > New Vehicle Reviews

August 2005 Issue

2005 Jeep Liberty

Jeep Goes Diesel: The Diminutive Liberty Takes a Big Step Towards Raising SUV Fuel Economy

text and photography by Rob Reaser

Seeking to replace their aging Cherokee mid-size SUV while providing a more compact, stylish model to entice the growing ranks of urban sport utility vehicle buyers, Jeep released its all-new Liberty for the 2002 model year. Now, a scant three model years later, the popular Liberty has been treated to several updates — not the least of which is the first use of a diesel engine in a mid-size SUV.

Diesel engines are gaining a more prominent position in the minds of the consuming public, as everyone looks to improve fuel efficiency and reduced operating costs. For Jeep, the timing for the introduction of its high-tech Common Rail Diesel (CRD) could not be better.

In America, traditionally, diesel engines have meant chuggy powerplants best suited for over-the-road semi and fleet trucks rather than urban daily drivers. Yes, certain European import sedans and wagons have found a small market here, but loathe as we are to follow any lead from the continent across the pond, traditional small Diesels have never enjoyed the popularity here that they do in Europe. Now, however, in the case of the new generation common rail diesel engines, the wine-and-cheese contingent may indeed show us a better way.

The CRD engine found in the Jeep Liberty Diesel is one of those powerplants that pleases just about anyone looking into the mid-size SUV market. Although its 2.8L displacement may seem wimpy at first blush, its numbers quickly dispel such notions. Horsepower is a smart 160 at 3,800 rpm — comparable in performance to most V6 engines in this class. Torque output is where the CRD truly shines brightest. Coming in at a whopping 295 lb/ft at 1,800 rpm, this number places the Liberty Diesel in the same ring as V8s which power full-size pickups. Consider the CRD’s stablemate, the Dodge 4.7L Magnum SOHC. That powerplant has a solid 1.9L displacement advantage over the CRD, yet its torque rating is the same at 295 lb/ft. However, it doesn’t hit that peak until 3,600 rpm. For its size, the Liberty Diesel is a powder keg of muscle — and it does most of its grunt work way down in its rpm range, right where you want it.

You can’t see much of the 2.8L CRD I4 due to the noise-dampening cover, but when in operation there’s no mistaking the peculiar “tinkle” of a diesel engine at work.

To pick back up on the European connection, many of you may know the Europeans have been ahead of the curve in advancing diesel technology in the passenger car market. Most of the best diesel engines (Cummins notwithstanding) are rolling off that continent’s assembly lines. Such is the case for the CRD found in the refreshed Liberty. It’s built by VM Motori of Cento, Italy — a company owned since 1995 by Detroit Diesel, a DaimlerChrysler company, which we all know is in the hands of the Germans.

(The increasingly incestuous nature of this industry continues to amaze...)

You’re not going to stuff a whole lot of gear in the back of the Liberty with the rear seats in the up position, but the cargo capacity is good enough for most grocery hauls (note the grocery bag hooks incorporated in the seatbacks).

Anyway, VM Motori has been a leading diesel technology manufacturer for over half a century, and has supplied engines for the Jeep Cherokee in Europe since 1994.The CRD powerplant went into production in 2001. So, in reality, this is nothing new to Jeep from a global perspective. It’s just new to the North American Jeep marketplace.

The CRD’s hook, if you will, is its common rail direct injection fuel system. To better understand how it works, let’s run through a quick primer on the mechanics of diesel engines.

For 2005 the rear seats fold flatter to make for a more level cargo floor. In this configuration, cargo capacity goes from 29 to 69 cubic feet.

As you know, gasoline engines (electronic ignition) utilize a combination of air, fuel and electrical spark to provide combustion. On its downstroke, a piston simultaneously draws air and atomized fuel into its combustion chamber. On the piston’s upstroke this mixture is compressed and ignited by the spark plug to provide the power stroke. Diesel engines, by contrast, do not use an electric spark for ignition. Instead, the piston draws only air into the cylinder, which is squeezed on the compression stroke to the point where the air is extremely hot. At some point in the compression stroke, atomized fuel is delivered into the system. When the fuel hits the hot, compressed air, the mixture ignites and the power stroke is initiated. This is why diesels are also referred to as “compression ignition” engines.

The window switches are relocated on the center console for 2005 for a more ergonomic placement.

This may sound a bit crude to those schooled in the EFI arts. In reality, however, current diesel engines have a whole lot going for them. For example, they excel in fuel efficiency, in part because they allow for high compression ratios (compare Jeep’s 2.8L CRD compression of 17.5:1 to its sibling 2.4L EFI engine with 9.5:1 compression). Higher compression ratios usually mean better fuel efficiency in terms of power output and consumption. Additionally, diesel fuel contains more energy per unit than does conventional automotive-grade gasoline. It’s also less (should be) expensive because it does not require as much refinement as pump gas.

Back seat passengers don’t fare too poorly in the Liberty. Forward-opening doors, mildly bolstered seats, integral headrests and 37.2 inches of legroom make rear occupancy tolerable.

Diesel engines have been around for a while (since 1892, to be exact), and to American minds they’ve always been viewed as loud, clunky, dirty and low on vicarious performance. So what’s the excitement about now?

It all has to do with ever-improving technology and the incorporation of the common rail direct injection system. Traditionally, diesel engines used what is called indirect injection, where a pre-chamber in the cylinder head mixes air and fuel, and begins the combustion process before the full fuel charge is sent into the combustion chamber. This was necessary in order to optimize the air/fuel mixture prior to it entering the combustion chamber. The result was a loss of some fuel efficiencies, noise, heat loss and relatively high particulate emissions, to name a few of its detractions.

Enter the common-rail direct injection system, such as is found on the new Jeep Liberty Diesel. The CRD relies on high pressure fuel delivery (rated to 23,000 psi) to send highly atomized fuel directly into the combustion chamber. All of the cylinder injectors are linked to a single, or common, high-pressure fuel rail (hence the name) that is fed by a cam-driven high-pressure pump. The whole operation is run by an electronic control system that is quite similar in operation to conventional EFI systems. Performance is computer-controlled to deliver the optimal fuel pressure, injection duration and injection timing to achieve an acceptable balance of power output and fuel economy. Compared to the indirect injection pre-chamber system, noise is down, fuel consumption is down, power output is up, and emissions quality is significantly improved. The 2.8L Liberty engine actually uses two pilot injections, which come on before the main injection, to further reduce the “edgy” nature of diesels and smooth idle noise. Furthermore, the Liberty incorporates an electronically controlled turbocharger. This unit uses moveable vanes to optimize power output and fuel efficiency across the power band.

The next best thing to drop-top off-road adventure is a sunroof, and for $700 you can have one in the Liberty.

So, that’s what all the hype is about. The question is, how does it feel?

Prior to field testing, we had picked up on some Internet chatter about how the Liberty Diesel was noisy. What a bunch of brie-and-cognac whiners! Yeah, the CRD is no purring kitten, but then...IT’S A DIESEL! One thing’s for sure...it’s the quietest diesel in a domestic 4x4 we’ve ever tested. Actually, it’s not bad at all. By tweaking the timing and fuel delivery events, placing the engine on hydro mounts, adding damping material here and there, stuffing a resonator into the air induction tract, and dropping a massive engine cover over the four-cylinder, the CRD doesn’t sound loud to us, just neat...like it’s got some real character going on.

Get over it, already.

On the road the Liberty Diesel isn’t going to win you any streetlight jousting tournaments, but on the other hand it has a pretty fancy snap for a four-cylinder once the turbo kicks in. Acceleration, however, isn’t this 4x4’s bag — rather, it’s torque. And torque it has. The max trailer weight is 5,000 pounds. We can almost see a Liberty Diesel hauling butt to the coast with a 20-foot runabout in tow, causing gawking passersby to remark something like...“What?”

There’s certainly nothing fancy about the Liberty’s interior décor, but for most off-highway adventurers, that is as it should be — functional, without being overbearing. New seats and fresh fabric choices are part of the 2005 changes.

The 2.8L turbo diesel option is not available on the Liberty Renegade, only the Sport and Limited models, and it comes only with a five-speed automatic transmission. ABS is also part of the diesel package.

After only three model years since its introduction, the Liberty receives some minor body updating for 2005. The Sport model seen here benefits from higher fog lamp and park/turn lamp placement, a new front fascia, new body-color grille with fog lamp provisions, and new rocker panel protection.

Do we like the Liberty Diesel? You bet. In fact, given its 22/27 city/highway fuel economy, pleasing diesel hum, and stump-ripping, rock-rolling torque, our money goes here. After all, while the Renegade and Limited’s 3.7L V6 may have it in the horsepower department, let’s face it, the Liberty is no corner-carving SUV. It does a fine job under moderate road driving, but its real deal is its dual on-/off-road credentials.

If high-end horsepower and slot car handling is what you crave, get a Corvette Z06. If, instead, you want a maneuverable trail rig that’s got the beef where it counts, the Liberty Diesel is waiting for your test drive.

What Else Is New?

The CRD engine is not the only new balloon floating at the Jeep Liberty party this year. Inside and out the Liberty gets a bit of a facelift. Changes include: