How A Diesel Engine Works

Jeeps and Diesel

Alright - this is the Holy Grail of fuel economy and torque. Diesels typically aren't your first choice for horsepower, but if you want economy, power to tow and a reliable, long-life engine, diesel's are for you.

You will have to live with a noisier motor, exhaust smell and, in some areas, it's harder to find the fuel. In the end, though, it's worth it.

The biggest differences between gasoline engines and diesels engines are these:

  • A gasoline engine intakes a mixture of gas and air, compresses it and ignites the mixture with a spark. A diesel engine takes in just air, compresses it and then injects fuel into the compressed air. The heat of the compressed air lights the fuel spontaneously.

  • A gasoline engine compresses at a ratio of 8:1 to 12:1, while a diesel engine compresses at a ratio of 14:1 to as high as 25:1. The higher compression ratio of the diesel engine leads to better efficiency.

  • Gasoline engines generally use either carburetion, in which the air and fuel is mixed long before the air enters the cylinder, or port fuel injection, in which the fuel is injected just prior to the intake stroke (outside the cylinder). Diesel engines use direct fuel injection -- the diesel fuel is injected directly into the cylinder.
  • It's been just about 20 years since Jeep last really offered a diesel in a Jeep. Back in the mid-80's, the Cherokee came with the option of an underpowered, but very economical, 4 cyl diesel. Available with either the five speed manual, four speed manual or three speed automatic, the diesel engine was the Renault 2.1 Litre Turbo-Diesel. Most of the Diesel Cherokees were sold in Canada and Europe. If you could live with the lackluster acceleration that less than 100 hp provided, you'd be very happy with the 31+ MPG the motor provided in your 4WD SUV.

    Jeep Liberty Diesel

    Today, it's easy to find a Jeep Liberty diesel - provided you have a deep wallet and are patient. There's precious few of these great trucks riding around right now. Given the fickle public's aversion to diesels (created by the crap products GM turned out in the early 80's), Jeep was aiming low with production runs of well under 10,000 units allocated to Canada, for example.

    Add in the fact that this option, the Liberty 2.8 CRD (Common Rail Diesel) is only avialable in the up-line Limited model, and you have the reason for that low number - exclusivity guaranteed. At almost $40,000 Canadian, before taxes, etc., that's one mighty expensive Libby.

    If you were lucky, and lived in Europe, you'd have a hand full of diesel motor options to choose from - units designed for everything from top fuel economy to top torque and towing. Alas, North America is slow to this dance. At least, the manufacturers are...


    Let's say you want to be a bit different. Let's say you want to swap that tired old 2.5 4 cyl in your YJ for something different. Sure, you could drop a 5 litre in there, or maybe a Dodge 318. Lot's of power and lots of fuel, too.

    If you've got some money (more than a normal V8 swap, less than stuffing a Hemi in a TJ), maybe you should condsider a diesel for your swap. We don't mean go out and find on of the old, ratty Renault 2.1 litre units - you'd probably never find one anyway.

    Look to newer technology. Borrow from the Suzuki guys - VW's 1.9L TDI motor is the hot swap for Samaurias, so why not in your MB, Willys or YJ? It's not going to make it a drag machine, but it offers plenty of torque for daily driving and offroading, plus it'll still net you over 30 MPG.

    Not convinced - how about this. The VW TDI's came with 90 HP & 177 lb/ft of torque stock (the 1998 - 2003 models). With only a few cheap mods, these motors can reliably put out 125 hp and 270 lb/ft of torque - that's V8 territory for torque! Diesels are, as many now know, easy to make power with. They're built tough enough to handle it, too. AND, the low-rev nature of them ensures the torque is available down low, right where you want it.

    At this point, though, you'll be pretty much on your own. We know of no one who's done such a swap, so everything would be custom. But, that's what building your Jeep is all about anyway, right? If you've got the skills, the time and the money, the parts are avialable. This is definitely not for novices.

    If you've just got to have one of the OEM motors supplied to the European marketplace, start with these guys - VM Diesel Specialists. They're in the UK, but no one knows Jeep diesels like they do.

    Mitsubishi Jeeps - Diesel

    Way back in 1953, Mitsubishi secured the rights to produce a branded version of the Willys.

    Knowing they had a good thing going, production carried on until 1998 for this version.

    Very few changes, other than to the engine, were made during this time.

    Jeep Diesel

    The guys over at are a wealth of knowledge on these, and other, diesel rigs. Drop them a line and they'd be happy to get you into a new-to-you Mitsubishi Jeep or Toyota Land Cruiser.

    Here are the specs of the rig in the pic above. For a historical overview, more model specs and driver's impressions, spend some time here.


    Specifications (1983 model year- J54)
    Dimensions Engine
    Overall Length: 3975 mm Model: 4DR5
    Overall width: 1690 mm Type: Normally aspirated diesel
    Overall height: 1865 mm Design: Inline 4 Cyl.
    Wheel base: 2310 mm Bore and Stroke: 92.0mm x 100.0mm
    Tread front/rear: 1425 mm / 1420 mm Displacement: 2659cc
    Ground clearance: 205 mm Compression ratio:
    Turning radius: 5.3 m Max net power: 55 HP @ 3300rpm
    Max net torque: 130 ft/lbs @ 2200/rpm
    Transmission (4spd Manual): Transfer:
    1st: 3.300 High: 0.903
    2nd: 1.795 Low: 2.306
    3rd: 1.354 Axle: 4.777
    4th: 1.000
    Reverse : 3.157 Suspension
    Front: Semi-elliptic leaf spring
    Brake Rear: Semi-elliptic leaf spring
    Front: Drum
    Rear: Drum J54 specs the same, except engine is Turbo Diesel