[pbp1]

Dear Gump, I get it that you prefer to tune in Alpha-n, but you are completely mis-understanding how speed density works. I also zero out all air temp corrections in my tuneups. I am not talking about making corrections for changes in air temperature. In speed density, the ECU uses air temperature to determine the density of the air. Please go back and read my post again. Speed Density does not make the engine richer or leaner because of changes in air temp or barometric pressure, it just calculates the fueling, taking these things into account, and gives you consistent air/fuel ratios, even as pressure and temperature change. It is just doing the same thing you do with your tune when the weather changes, or you go to a different track with a different elevation, it just does it automatically and perfectly (if setup and calibrated correctly). If you read my example about icing the manifold, I pointed out that when the air temp sensor was in the manifold where it belongs, the speed density setup produced the exact same actual A/F ratio with the manifold iced as it did with the manifold not iced. It perfectly calculated the increased density of the cooled air even in open loop and the Air/Fuel ratio stayed exactly the same. I can send you the datalogs from these two runs showing air temp. Air/Fuel ratio, and pulsewidth. If you prefer to use Alpha-n, I wouldn't try to change your mind, but I started this thread because there is so much false and incorrect information that is passed on from racer to racer, I just wanted to put out the true facts about how Speed Density works. Based on your last post, you have clearly had some of this mis-information passed on to you. The fact is, the air is always changing, if you don't change your fueling to match these changes in air density, your engine will run leaner when you get in better air and richer when you get in worse air. These changes in air fuel ratio WILL cause unpredictable changes in performance. You are correct that Alpha-n is easier or quicker to dial in your desired air fuel ratio, but the problem is, when the atmosphere or elevation change, you have to manually change your fueling to match, and if you are really experienced at it, you can do a very good job. At the end of the day, the engine doesn't know or care what strategy you use as long as it is getting the amount of fuel it wants. But if your experience showed you that Alpha-n was more consistent than Speed Density, then you were doing something wrong. It definitely is a completely different process and takes a different approach. Anyway, I'm not trying to down your tuning, just correct the mis-information.