Motivation Equation

by Imad Ali

1KZ or 2LT, 3B or 13BT, 1C and 2L, confusing numbers and alphabet game or engine designations, who knows... it might as well be Greek for those who aren't engine savvy. If you are even considering building a Jeep in Pakistan, you should know the various engine choices available to you. Read on and enlighten yourself.

Choosing the right engine is the most important decision for those of us lucky enough to own a real Jeep. As we all know, almost all Jeeps to be found in Pakistan, came outfitted with petrol engines from the factory, even though Jeep has offered diesels in the European market for years now. Why these vehicles never made it the Pakistani market is a story for another column. Anyone who has lived in Pakistan for any length of time can tell that the prohibitive price of petrol has created a diesel conversion craze. The diesel advantage in Pakistan is clear: You get an engine that is at least 30% more efficient than its petrol counterpart and it runs on fuel that costs less than two thirds as much. This economic advantage totally overshadows the facts that the majority of diesels available to choose from are antiquated designs that are noisy and rough, terribly underpowered for their size and weight, and gross polluters. The unfortunate motorcyclists and pedestrians of our country know the last fact all too well.

However, all is not lost. The diesels available to us may be antiquated and underpowered, but there are some tried and true performers amongst them that have withstood the test of time and the trail. In the course of building a Jeep, the mechanic will usually suggest which engine to go with. Opinions on the best engine for the job differ between mechanics, depending on their technical expertise and the ruggedness of the Jeeps they build. That makes it all the more important for the owner to be educated about the engines available. For instance if your mechanic is adamant about dropping a Hilux 2.4 litre engine into your project CJ-7, you may seriously want to reconsider your choice of mechanic. The following list can be used as a reference guide to selecting the ideal engine for different kinds of Jeeps.

1951-52 Willy's M38, CJ2A, Ford MB

These are the most commonly found flat-fender Jeeps. Their engine bay is by far the smallest, calling for smaller, lighter engines than those required for other Jeeps.

Early model CJ-5, M38A1 and M170 ambulance

These Jeeps have a shorter length engine bay than the later model CJs but have more vertical room than the flat fenders.

Late model CJ-5, CJ-6, CJ-7, CJ-8 Scrambler, and Wagoneer/Cherokee

This group of Jeeps can be called the heavyweights. They have the largest engine bays of all Jeeps. Redesigned suspension and chassis on these Jeeps make's them capable of higher highway speeds, calling for more powerful engines.

Starting with the B at 2.8 liters, the 1B, 2B, and 3B displace 3.0, 3.2, and 3.4 liters respectively. With its ever abundant torque and power, the 3B is the most favoured engine of the lot. It's rated power is 90hp@3500rpm. The 3B also boasts the best oiling system of all the B series engines. Unlike other naturally aspirated diesels, it has oil injectors at the bottom of the cylinder skirts for better cylinder wall lubrication. Toyota replaced the 3B with the 13B-T. This is basically a technically updated and turbocharged version of the 3B and produces 120hp@3400rpm. It can also be found as the 13B in local markets. After much research, I have come to the conclusion that this is simply a 13B-T engine stripped of its turbo setup and outfitted with intake and exhaust manifolds off a regular B series engine. All commonly available B series engines can also be found with plunger or rotary fuel pumps. The plunger pump is slightly noisier, but it is also completely rebuildable and seems to have far more torque throughout the RPM range.

Other B series engines not so commonly available are the 11B, 14B, 14B-T, and 15B. With the 14B at 3.7 liters and 15B at 4.1 liters, these are probably the largest 4-cylinder engines in use today. While B series engines are by far the most popular choice for CJs, they also have their drawbacks. The weight of the huge cast iron block and cylinder head adversely affect the Jeep's already marginal handling characteristics and require beefed up front suspension.

Common Rail Diesels

Almost all new diesels are common rail - which is significantly different from the older designs. A common rail engine uses a high presuure pump to maintain 26,000 to 30,000 pounds pressure in a fuel rail which feeds the injectors. That means at any engine speed, every injector gets the same maximum pressure. The higher the pressure, the smaller the injector nozzle openings can be, producing smaller pulses that provide better fuel atomization. Combine that with more frequent, strategically timed pulses during each compression-stroke injection, and the result is more complete combustion.

The majority of current common-rail systems employ solenoid injectors - these are actuated by a magnetic field generated by electric current. However, newer injectors use piezoelectric technology.

CRD diesels are quieter, pollute less and more powerful. A win-win situation, except for one drawback - they require regular maintanence and clean fuel, both of which are in short supply in Pakistan. Common rail engines are asssembed in 'clean rooms', which means they cannot be opened up in any local workshop. A 28,000 psi encounter with a bit of dirt is not going to be pretty!

Whenever any work is done in the fuel system, like changing the fuel filter or an injector or just about anything else, the technique here to get the air out of the system is to loosen the injectors one by one and let them squirt out the air. With a common rail, that technique is obviously not going to work - or if it does it won't be too healthy for the mechanic tightening the injectors. This is not to even mention the often dodgy diesel outside the big cities.

As of April 2005, common rail engines aren't available in the local market. Once they are, more will follow.

Related Links:

Please post engine/tech related questions at the forums.

Posted in Tech, October 15, 2003, by Imad Ali

You are reading Motivation Equation, an entry made on January 16, 2010 by Imad Ali, filed under Tech. This entry is part of

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