Quote:
Originally Posted by thejeremyman9
Now this log is very interesting and highlights a couple of more 'advanced' concepts i would say... didnt even think about these factors until looking at this logs compared with the previous ones.
At a basic level, timing is for lack of a better word pretty awful. In 3rd it goes negative on all cylinders and generally speaking there is a ton of timing being pulled across the board in both gears.
This is there is gets interesting...
This logs shows you making more boost than in the other 4th gear logs, up to 20psi in 3rd and ~20psi and even a little more throughout most of 4th. At the same time, WGDC is lower than in the other 4th gear pulls... which at the surface seems to make no sense if these were on the same day with the same hardware, etc.
But the plot thickens when you look at timing. During the 4th gear pull right before 4k rpm a massive amount of timing gets pulled and cylinders go negative. At the same time boost starts to rise and WGDC falls simultaneously. Seem counter intuitive unless you realize that EGTs are going to skyrocket when you pull timing (especially when it goes negative). I am almost certain that this is a cascading effect of timing getting pulled causing EGTs to increase, then all that extra heat/energy from the high EGTs is causing the turbo to spool up even more, which causes the overboost and a decrease in WGDC at the same time.
Boost starts to fall back down as timing is fed back in, but then you shift into 4th and timing has not fully recovered. It starts to recover a little but then gets pulled again (especially cyl 3) and boost creeps back up before falling back down slightly as timing becomes positive again after about 4300 rpm.
Bottom line is this logs shows the very interesting effect that timing has on EGTs and in turn WGDC and boost. There are no EGT sensors on these cars so its not in the log, but i imagine they had to be through the roof (think glowing manifold during a long pull). MHD has a calculated EGT value that would have been very interesting to see.
I would also note that there is no throttle closure from the overboost, which is characteristic of a BM3-ish tune (and unlike MHD and load based tunes).
I would be very interested to see what your tuner says about this log.
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Great post.
Can you explain a bit on why/how timing drops effect EGTs and why increased EGT causes higher boost?