By: Dave

Dave — Sat, 18 Jun 2011 07:01:40 +0000

Diesels actually have worse engine braking ability than equivalent petrol engines, unless they’ve been fitted with an exhaust brake of some kind. In a petrol engine, when the engine is spinning at high rpm with the throttle body closed, it creates vacuum in the manifold which the engine must overcome and is what actually allows braking. A diesel on the other hand has no throttle other than the injector pump, and no vacuum in the manifolds – this is why many diesels use a separate vacuum pump to run brake boosters. Compression in the cylinders themselves essentially acts as a spring in a diesel, providing very little braking. An exhaust brake can close a valve in the exhaust creating backpressure for the engine to work against, and big rigs often have “Jake brakes” which are an extra set of valves in the cylinder head which release pressure at the top of the compression stroke to eliminate the spring effect, at the expense of complexity and lots of extra noise. For a small diesel like a 4 cylinder Land Rover though, neither is a very practical option.

By: Pclay

Pclay — Mon, 14 Mar 2011 18:01:34 +0000

While I agree with many of the favorable attributes about diesel engines, modern diesel engines are also susceptible to electronic failure. Like their petrol cousins, modern diesel engines also rely upon electronic engine management systems to achieve improved fuel economy, power and reduced emissions. The choice between engine types should not be based upon a fallacy of reduced electronics, at least for engines that are less than 15 years old or so.

Comments on: Engines on Expedition – Why is Diesel best?

By: Dave

By: Pclay