The stock ECU uses manifold pressure and RPM to determine fuel and ignition timing. At full throttle, manifold pressure is directly related to atmospheric pressure. At high altitudes, the manifold pressure at full throttle will be lower than it would be at low altitudes. This means that the ECU will provide less fuel and more ignition advance at high altitudes.

 

So the part of the tune below full throttle/manifold pressure should have more ignition advance?

Also, Jake's OBD2 logged stock AP1 ignition curve may appear more advanced than normal due to the lower manifold pressure, but is there any reason to think the shape of the curve itself is inaccurate? Would a lower elevation/full manifold pressure curve look the same, just with less advance?

 

So the part of the tune below full throttle/manifold pressure should have more ignition advance?

Also, Jake's OBD2 logged stock AP1 ignition curve may appear more advanced than normal due to the lower manifold pressure, but is there any reason to think the shape of the curve itself is inaccurate? Would a lower elevation/full manifold pressure curve look the same, just with less advance?
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Ignition advance will increase as manifold pressure decreases, so there is an inverse relationship between fuel and ignition advance. On average, the shape of the IGN curve will be similar at different MAP levels, but the knock tables will cause it to deviate at high MAP levels.

 

I agree with both of you on most Dynojets. You can't get a good tune on most Dynojets unless your idea of a good tune only involves WOT. (Mine doesn't.) To me, load bearing dynos are awesome because they're a one stop shop and you can fully tune a car in a couple of hours or maybe half a day at the most. Note that Dynojet does make load bearing dynos and they're said to be fairly decent.

Tim