Ugly Duck wrote:
What else would give you an intermittant 80 ft-lb jump in torque besides a sticky wastegate?
I know...I'm just trying to make this wastegate thing make sense. I'm in sponge-mode right now, so fire away.
Here's what I've come up with...the only difference between the pulls is ΔRPM/ΔT related. If the wastegate in the second gear pull went from closed to open quickly and was controlling the boost pressure properly while we get the same TDO4 look to the plot (it's building very quickly (looking at the torque curve) - all in by 3.5K rpm. It looks to me like we're rapidly building boost from 3 to 3.5K (pink line) then the engine is seeing a pretty steady boost past that point.
On the graph that has the blue and the pink lines, we see a similar shape to the blue curve, it's just happening more rapidly and starts sooner. It's almost the same shape, but happening 300 rpm sooner and it's going up faster (Δtorque/ΔRPM). The first sign of something wrong is around 3300 rpm (blue line). Then over the next 200 rpm, then the power goes (spark pull) and AFR's go to 9.
When we have the mechanical advantage of second gear and can spin the wheel faster (ΔRPM/ΔT) the wastegate may be opening more quickly (as we spin up the dyno) vs. when we're in a higher gear and can't move the drum that fast and perhaps if the wastegate was sticking and then building too much boost, then the MAF/LH sense knock, it then pulls timing and goes pig rich?
What I really don't understand is why the wastegate would be sticky. When I was adjusting it last week, it moved freely (even loose) and when I put pressure to the wastegate it opened every time as it should. But all the evidence points to something MECHANICAL not computer related (though, Jim...start looking please. I've got Philski looking as well).
Maybe I should ditch this 15G for a Cossy T3 over the winter? They at least have a reasonable wastegate.