Quote:
Originally Posted by NoDOHC
I wish you would post AFR on the graph (or are you not logging it to the dyno?)
I am curious what more experienced Turbo engine tuners run, as a lot of people I talk to say nothing lean of 11:1 and I think that is leaving a lot of power on the table.
Peak power (for pump gas) is 13.3:1 (0.9 lambda). There is not much gain to be had lean of 13.0:1. As far as I know, this holds true for any chamber pressure - it is definately true for naturally aspirated applications.
Your VE must be relatively high if you are running 11:1 AFR.
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Yeah when tuning a turbo engine, I do not use the dyno wideband. The internal dampening is too slow for quick decisions if things get out of hand. AFR for a turbo rotary strictly depends on how much generated heat is entering the engine. For example, I see ALOT of people running a turbine housing that is 1 inch away from the intake manifold with no heat shield at all! Hmmmm blown engine anyone?? But typically a nice safe tune will be in the 11.1-11.2 range. In a controlled environment or on a very well insulated/ well cooled turbo rotary setup, 12.0- 12.5 can be done. But that tune is not safe in my opinion in the real world at the track.
Now with that said, do not get too hung up on a 13.3 afr number. Yes n/a two rotors seem to enjoy 12.8-13.4 in the testing I have done as well. But remember not each rotor is burning EXACTLY the same as the other. And we typically are using only one wideband. So if you ever get into n/a 3 rotors, trying to tune for 13.3 might actually hurt power. Simply the variance and heat difference from the front of the engine all the way to the rear can cause this. When I tune N/a piston engines like the Honda b16 and b18, they actually made the best power at 14.0 afr. So dont cling too hard on values, and always let the dyno do most of the talking.