IDI Diesel FAQ

Frequently Asked Questions about IDI Diesels

 

What are the differences between IDI and DI diesel engines?

IDI: Indirect injection diesel. Fuel is injected into a pre-combustion chamber, sometimes referred to as a swirl chamber, where ignition starts and then spreads to the combustion chamber. IDI diesels do not have the necessary fuel injection pressures to atomize the fuel completely, therefore making the pre-chamber necessary for efficient operation. IDI diesels use mechanical injection systems (not computer controlled), therefore making them reliable and easier/cheaper to repair. They are also typically quieter than a DI diesel engine.

DI: Direct injection diesel. Fuel is injected directly into combustion chamber. Due to high injection pressures, fuel is atomized (vaporized) and therefore rapidly diffuses with the air in the cylinder as combustion occurs. Since the fuel is highly atomized, a pre-chamber is not required.

What benefits do diesel engines provide over gasoline engines?

Diesel has several large advantages over gasoline. First and foremost, diesel engines are much more efficient. This translates into better fuel economy. Diesel engines also use much stronger components than gasoline engines and the diesel combustion process generates more torque than gasoline. This allows diesel engines to handle much higher loads, and gives them a longer life (diesel engines typically last beyond 300,000 miles before needing major repairs). These are only the basic advantages...

Which is better, a V-8 or I-6 diesel?

Different engine configurations each have their benefits. An I-6 (inline 6 cylinder design) generally provides peak torque at very low engine speeds. Though this is good for getting a heavy load going, their powerband typically drops off fast and they have a limited operating range. A V-8 diesel does not always provide peak torque as low as an I-6, but they have a much broader operating range in which they generate peak or near peak torque. One can not be said to be better than the other. It all depends on the application & the drivers preference. A V-8 diesel is preferred in a light duty application, where the truck may see frequent towing, but also used for daily activities. Inline-6 diesel engine designs dominate the heavy duty market, where trucks are rarely driven without a trailer. It should be noted that many variables of an engine design affect its characteristics, not just cylinder configuration.

If diesel engines are so great, why arn't they more popular?

In the past, diesel engines have been given a poor reputation. However, the popularity of diesel engines has been rapidly increasing and their benefits are being utilized more than ever. They may not be "popular", but they sure are gaining in popularity. Many 1/2 ton diesel trucks & commuter cars will recieve diesel engine options in the near future.

Should I purchase a new diesel, or an older model?

Several factors come into play when making this decision. Shopping for a diesel truck is not like shopping for a gasoline one. The life expectancy of diesel engines is often double that of gasoline engines. The biggest factor is cost. An older model is going to be much cheaper, but will not perform like a new truck. The performance of new diesel vehicles far surpasses that of previous generations. Another factor is what the truck will be used for. A 6.2 L GMC truck that gets 20 MPG city sure seems better than the expected 10-13 city from a new 6.6 L Duramax, provided you do not need the truck for towing purposes. If payload is critical, you will most likely look for a turbocharged diesel, between the mid-90s to present. No matter what, you can not go wrong with a diesel...