I currently have it setup 15 degrees initial 32 total at WOT 1 degree pulled per pound of boost.
Sure, you want something in there to fill the timing curve, but I don't go there until I can prove what the engine will like, before I push it there. You may already have a system in-place for tuning boost on det-limited fuel (pump gas), so this is just to cover one method I use for comparison, and for others reading and wondering how we tune boost without risk of melting stuff. The last thing we want to do is give it some guessed numbers, then cross our fingers and hope it's not too much or too little (both can be bad), before just hitting the throttle and hanging on.
I dislike anxiety, so I tune in a way I don't have any.
A tuning method I use is to limit throttle (clamps or linkage limiters), or boost by pulley, wastegate, or bypass, in order to tune for roughly NA max. The tuning is "bottom-up" so it begins at idle and works it's way through part-throttle and continues up to WOT. What this gives me is a foundation of a developed timing table showing what
this fuel and
this engine like for most efficient timing (peak torque), while building the table, without risk of damaging detonation.
From this I can clearly see timing regression with increasing manifold pressure. The engine does not know or care what boost is, as to it, it's just a higher level of manifold pressure. Nothing magic. The timing reduction from, say, 50 kPa part-throttle to 100 kPa wide-open will be effectively continued when boosted to 150 kPa and beyond. Bingo - a predictive timing table that this engine with this fuel should like to run best. With that mapped, it is a simple matter to run harder and harder incrementally, repeating and checking the results for best timing, watching multiple telltales for onset of minimal detonation. I
always use more than one det detection method, and bend the timing curve approaching that point to delay cylinder pressure. It makes creation of boost timing a much quicker, more accurate, and yet safer process.
AFR is setup at 14.0 idle 12.8 WOT 10.5 under full boost estimating full boost is 15 pounds.
Just a note to take care with very rich mixtures, as they conceal the timing the engine
should have at peak power Lambda (AFRs). Both reduced timing and enriched fuel work to delay cylinder pressure, so if tuned sloppy rich at 10.5 AFR, and for any reason it flashes lean, you're in-trouble. However, if it's tuned at peak torque AFR, the timing is optimal there, and leaning will have far less effect ā and you also won't leave power on the table unless you really need to.
We don't begin rich and retarded, we begin at peak efficiency, and retard or enrich when it's needed at det limit. Whenever possible I also continue the peak torque AFR found in the lower tuning, and carry it through to max boost. Peak torque is peak torque, and we do not know if we need sloppy rich fuel, yet. This gives a reserve capability to suppress det if and where it's needed, as an additional tool, layered-on in coordination with timing. Hope that helps!
