As I struggle to find simple ways of interpreting the data obtained from my car there has been one thing that has puzzled me. (In reality there are many more than one!) The question is, where is the throttle on my diesel? All the other engines I have experience of (all petrol) have a butterfly valve controlling the airflow into the engine. Where is it on my diesel? Well the answer provided by Denbury Diesels is that there isn't one!
The explanation is that petrol and diesel engines operate in two different ways. Whereas a petrol engine maintains a constant air to fuel ratio the diesel just alters the amount of fuel. Using a fire as a crude analogy the petrol engine controls the air vent to vary the heat output where the diesel is equivalent to getting more heat by adding another log. This basic information answers many questions raised by articles on volumetric efficiency etc that assumed the reader knew the engine was petrol.
So looking back at the volumetric efficiency graphs it could be expected that the efficiency is flat until the turbo kicks in. The really interesting work will be to see how the graphs looks when the new MAF is installed.
