The reason for targeting 13.0 by default is safety mostley. Also room for changes in wheather, altitude, barometric pressure, humidity. If you tune for 16.5AFRs on a 95deg day then are cruising on a 70degree day you will lean out excessivly and probably start to encounter lean missfires. The other issue with mapping a lean cruise area is that with no control over tip in throttle acceleration enrichment being at a lean cruise then bliping the throttle can cause alot of hesistation if not done correctly. Another thing you must remeber is that when you lean out your mixture flame propagation slows WAY down increasing the amount of heat absorbed by the piston and head. To full optimise for lean cruise you need to jack a bunch of timing in it to make up for the slower flame speed, and to reduce your chance for lean missfire.. This again will increase total heat in the cylinder though so you have to keep an eye on that. So yes it can be done and does work very well, but your risk factor is increased a great deal when doing this due to the limitations of the tuning parameters available on PCs and Bazzaz units. If your running a full standalone or fully programable ecu (like alot of the cars I tune) and have access to all the proper corrections needed to stabilise lean cruise at any air temps, air density, or air quality, and the ability to make fuel corrections in the event that engien temps start to climb too high, as well as massage tip in enrichment, then I would say go for it cause your risk factor of having any issues would be very minimal.
Last edited by Bugermass; 04-11-2010 at 12:55 PM.