Na mbt to boosted mbt

hello all.

i was wondering about mbt for a boosted vs na engine.

Considering this is a non knock limited turbocharged engine and we use same fuel.

for example, i disconnect a coupler to do some mbt tuning on na.

lets say i found 26° of timing, works best and gives best results (like shown in mbt tuning lesson)

Does the mbt during boosted application will be the same as NA then ? for example, this time i reconnect coupler and do a 0.5bar run with the same 26° i found earlier during mbt NA tuning...

Will there be variables like the fact that now there is a richer mixture with boost or more pressure in the cylinder that change mbt ?

same question for 1bar and more..

or does mbt isnt much dependant on boosted or na but more on engine specs like bore, stroke, fuel, cr etc if case of a non knock limited engine.

thanks a lot !

Required timing will reduce with increased charge density as the flame front moves faster in denser charge. You should have reduced timing with increased charge density. Something like 1 degree per pound to the first bar of boost is probably a safe starting point you can work from. I definitely wouldn't run flat timing based on 1 bar absolute.

found out after reading tech articles

"Secondly, moving further into positive boost also affects the ignition timing and the trend we see here is that more boost requires us to retard the timing, or in other words, start the spark event later in the engine cycle. You might be assuming that we need to retard the timing to prevent knock, and while that can be a consideration, even before the engine starts suffering from knock we will see this trend in our timing table. The reason for this is that all other things being equal, as we combust more fuel and air in the cylinder, the combustion process happens faster. This means we don't need as much ignition advance to reach MBT."

There is usually a higher temperature reached from the compression, which further increases the burn speed.