Alpha-N
[[Manual: Detailed.Control.Alpha.Operate]] If something is not clear on this page, please check and understand GenBoard/UnderDevelopment/AlphaN and try to make this page clearer from what you have learnt.
Tuning
[[Manual: Detailed.Control.Alpha.Config]]
Tuning is definitely more difficult than pure MAP based speed density.
Note that it is highly recommended to place an RPM bin (r table) on both hybrid_rpm_a and hybrid_rpm_m (3200 and 4800 RPM in the example) because the tables will look strange (and possibly steep) between these columns. The reason is the smooth, continuous change. The function that selects relevant table-lines blends smoothly from TPS to MAP as the RPM goes up from hybrid_rpm_a to hybrid_rpm_m.
Otherwise the TPS is highly nonlinear at low RPM, as an example, TPS=6% can result in 70% of the available power at 1000 RPM. Also note that any changes in the TPS sensor position will affect the VE table heavily in the alpha-n region.
Notes
- VE_learn currently works for speed-density only, not for Alpha-N
- make sure to adjust VE learning not to learn under hybrid_rpm_m (if using VE learning at all)
- MegaTune theoretically moves the dot according to kpa_tps_blend below hybrid_rpm_m (and according to high-resolution MAP above that RPM). However, be suspicious until you find it acting right.
- The highest "kpa" (which in fact load, not kpa under 2000 RPM) bin recommenended value is 200..255 because 255 means 100% TPS in the alpha-n low-RPM range. All the other load bins can be as normal, eg. from 10..100 in case of an NA)
- could it be changed so 0-100 kpa would mean 0..100% TPS?
- theoretically possible, but I don't see it justified:
- there are many bins, remaining 11 is more than enough (only those ECM-s need more kpa bins that have broken injector-opening model)
- the TPS -> MAP is not linear at low RPM anyway. There are only 2 points where TPS and load bins are equal (one is 0, of course). If the second point is MAP=40 kpa (40/256=16% TPS) or MAP=100kpa as you suggest: matters little. Actually, at TPS=39% (100/256) at low RPM the load is above 90%, so the current approach is better.
Who uses it?
I only know a racing team with ITB-s that uses VEMS with alpha-n on a 4-cyl. Unfortunately they don't publish their stuff (to protect their" work" ). I know they blend from alphan to MAP from 2000 to 3000 RPM.
Single throttle-bodys should not be a big problem either.
GRM team has ITBs and will be trying it. as always we'll post our configs and tables. 4 clyn, 16v, 2.0L huge cams.. nitrous.. if it ever works.
[[Manual: Detailed.Control.Alpha.Operate]]
See also