Lean tuning myths

If overall power and engine saftey is decreased with a leaner mixture, then why do you say that some endurance race cars run up to a .950 Lambda value? I know that you stated they will build the engine to withstand the increased heat but wouldn't they also suffer in power running that lean?

They run a leaner mixture to increase the time between fill ups. You can see from the attached "generic lambda efficiency curve" that you can still make power at 0.95 lambda. Of course more passing power is good, but being able to overtake doesn't help you if you have to fill up many more times than your competitors. From a safety perspective, they are running racing fuel so the concern about knock is less. Also, those engines run in a very narrow operating range (not like a street car). They put them on an engine dyno and tune the spark and fuel and measure all the temperatures to make sure it will be ok.

Also think that most of these teams have the resources to rebuild engines between races or whenever they need.

what is power if you constantly stop?