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flame speed, injector timing and load

Diesel Tuning Fundamentals

Discussion and questions related to the course Diesel Tuning Fundamentals


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hi,

im trying to understand what happens to timing when boost increase,

from what i understood the timing increase with rpm and load(fuel) which is the opposite in gas engine timing decrease with load.

now let say the timing mbt is 6degree at 18psi and 16.5afr,

scenario 1 we increased boost to 23psi while we maintained the afr 16.5 would timing mbt increase?

scenario 2 we increased boost to 23 psi and didnt add more fuel would the timing maintain mbt or retard abit,

im thinking of tuning timing before adjusting boost/fuel/pressure or should i do it last?

on the stock timing map there was -4 degree of timing in the cruising area i think that is for emission? can i interpolate low load from 500rpm (3 degree) to 4000 rpm (5-7 degree) and then interpolate for high load from 500 rpm (5degree) to 4000 rpm (8 degree) to build a base map or is there a purpose for the retard either performance or fuel economy

is two-four degrees over advance an issue in the low load area? or would it be safe cylinder pressure wise

I think its important to understand that boost in and of itself has very little to do with it. Charge temperature increases from compression and combustion chamber pressure increases due to oxygen density (these are byproducts of boost, yes) are the issue.

You wont be able to mitigate CCP and still make power but you can decrease charge temp in various ways to make informed decisions on timing decreases (or increases in some cases)