Thread: Why do diesel tuners use EGTs and nor widebands

Joe,

The single biggest difference between petrol and diesel engines is that excess fuel in a petrol engine can COOL combustion, in a Diesel it can and does heat up combustion and therefore the temperatures within the cylinders can actually melt piston crowns, turbocharger vanes etc etc, whereas a petrol engine can do the opposite- melt pistons with LOWER fuel to air ratios.

More fuel = more heat energy and power in a diesel, but can be brought to destructive levels and still be running fine,

JC

In addition to what JC said, diesels do not meter Air. So air (and therefore O2) levels will vary between 50% and 250%+++ excess depending on rpm and how much fuel you are injecting (i.e. accelerator position).

O2 levels are irrelevant as long as your EGTs are within spec.

Thanks for the replies. Makes a lot of sense really. If something ignites with compression, then putting more of it in will only add more compression and so more power, more heat and the circle keeps going.
Thanks again.
Joe

its not quite that simple, especially if you're going to deal with a turbo'd engine.