Hi All,

Im new to diesel tuning and would like if possible to go through a few basics and a few questions.

If people could check would be greatly appreciated:

- Running richer on diesel results in higher EGT
- Tune richer until limited by smoke/EGT/power e.g. 17:1
- Max boost like petrol determined by compressor maps/power goals
- Max EGT should be 680-850 deg c ?


Questions:

- When tuning "leaner" for cruise what happens if you tune "too lean" or is that not possible ?
- Why do people talk about SOI for MBT. I thought ignition always occurs at TDC in diesel so is not like adjusting a spark map in petrol? I can understand adjusting SOI for larger requested fuel.


Thank you for all help on the forum have already learnt a lot! will post up build & experience of mapping when I start.

Just a very quick post as a pointer (im sure more advice will follow)

on your first bulletpoint, that is true broadly speaking, regarding the second that once again is largely true, cylinder pressures should be considered too and many other things, you've got the gist though.

Third point, max boost depends on a load of factors, compressor maps, power goals, what sort of fuel to air ratio you want as well, but you should always be aware of shaft speed being too much (for example higher boost at low rpm can be quite safe, but as rpm goes up the shaft speed goes up too), also the relationship between boost and emp should be considered too to ensure that the boosted air is actually flowing well

On your fourth point it depends on a lot of things, the turbo is quite sensitive to egt, the exact max depends on what the engine you are tuning can tolerate and the technology and materials/design of the turbocharger.

Some cars stock i've seen 800, so its not easy to give a fixed answer to. But tuning is a lot about careful and skilled use of judgement, another reason not to get too hung up on having the highest figures, aim for a nice drive.

The good thing about diesels is there's little consequence for running lean, in fact if you log one they will spend a lot of their time in the mid and upper twenties, you don't have to worry about this, modern diesel engines are no way simple things but the principle is very simple in that there is no throttle and you more or less just add the required fuel.