Dec 7, 2014 and later, Holidays, New Year...: Exhaust Valve Revisions and TuningBeen busy with holidays and needed time anyhow to get things all dialed in. For starters, those el-cheap-o eBay China special MAP sensors are A COMPLETE PILE OF CRAP. No wonder they were only half price and no wonder I was getting sporadic reading as reported back at
reply #349, THEY ARE JUNK. Fortunately I had a real genuine GM sensor, the new type ACDelco P/N 12615136, that I had bought prior to the eBay sensors and hadn't returned to the dealer yet. So on it went.
Because I'm posting this now 2 months old, it's sort of foggy as to when I made the change, but I have to report that the exhaust back pressure monitoring is not the way to go and I plugged off the line at the exhaust and moved the MAP sensor to the intake.
Looking back I can't say for sure what the exact issue was, but between unknown factors of how hot the exhaust is (in real time) and loosing pressure through that dang TRD balljoint, I could never get a steady, reliable, and meaningful reading from the exhaust itself to base calculations off of. I decided to switch to the real MAP, the actual Manifold Pressure instead and man oh man has it been wonderful.

I've since done 12 revisions to my program and it is pretty much all dialed in now. The difference this has made has BEEN AWESOME! The car is much quieter while cruising on the freeway but also comes FULLY alive whenever you put your foot in it!
The biggest thing I've had to troubleshoot and work with is what happens between full and no throttle. As I'm now basing exhaust throttle adjustments on intake pressure, these things change quite rapidly with a mechanically driven Supercharger

Switching over to MAP readings actually hasn't been as shortcoming or as negative as anticipated. Because I'm not likely to run full throttle at lower RPMs (as I'd rather downshift than kill my engine), concern about low RPM backpressure is kept in check.
One last thing to note is that after some testing I've found that my peak boost is somewhere around 11.75 PSI. Earlier on
reply #347 I claimed peak boost was "11.25 PSI" but it's certainly closer to 12 PSI now with proof from a digital MAP sensor. There is a bit more to discuss regarding peak boost and I'll mention it below...
Here is a list of revisions I've done so far:
v1.0
Initial Release
v1.1 (Dec 6, 2014)
Bug Fixes:
Throttle % vaules were displaying outside of 0-100%
New Features:
High Boost mode using a less restrictive Line EQ to prevent throttle
from slamming shut between shifts
Display Boost in PSI
Display Peak Boost and reset on each gear change
Changes:
Minimum throttle is now 10% at < 0.8 volts (observed warm idle vdd)
Maximum throttle now occurs at > 4.5 volts (11.75 PSI)
v1.11 (Dec 7, 2014)
New Feature:
Now displaying Absolute Throttle Angle
Now displaying Throttle Angle along with Peak Boost per shift
v1.12 (Dec 7, 2014)
Changes:
Main Line EQ reverted back to 720 baseline to have an Absolute Throttle Angle value
Minimum throttle is now 20%
High Boost Line EQ now comes in at 2.25v
Rewrote psipeak section
v1.13 (Dec 7, 2014)
Bug Fix:
High Boost mode was not using it's conservative Line EQ under vacuum (the exact reason why it's needed!)
Changes:
Changed "highboost" to "boost": Highboost mode is now simply Boost mode
Cleaned up some code
Lowered Boost mode to 10 iterations
v1.14 (Dec 8, 2014)
Changes:
Drastically reworked and optimized LCD Display code
Got rid of Text Refresh code since LCD code is improved
New Integer Math to display numbers to two decimal points
Moved Boost Mode up above servoabsolute to get accurate throttle angle reading
Changed Boost mode from 2.55 to 2.5
Added asterix to Throttle reading when in Boost Mode
Changed Initial to count down rather than count up
Added Initial checking to prevent Boost and Peak displays from activating during cranking
Changed Initial vdd detection level from 2 to 1.25
v1.15 (Dec 10, 2014)
Changes:
Removed unused "angle" variable and related functions
Returned to 0.5v|720 Line EQ
Cleaned up more comments
Raised Boost mode from 15 to 20 iterations
Added code for a 25% minimum mode while not idling
There are now three modes: Idle (20%), Cruise (25%), and 25%+
v1.155 (Dec 11, 2014)
Bug Fixes:
Corrected possible IF statement error concerning 25% throttle cruising mode
Replaced all <= and >= with <,> and moved numbers up/down in an attempt to correct possible IF statement errors
Boost Mode Asterix was set to come on at the old 15 rather than the new 20
Added an extra space to the Peak display to prevent lingering '0' from appearing
Changes:
Reduced main loop pause from 150 to 100 to try to combat quick changes in vdd (55ms is about as fast as it can go)
Also increased LCD pauses from 5ms to 10ms to be nice to LCD. Overall refresh is still improved
Removed Terminal debugging code. Just pull from previous versions if needed
Changed PSI conversion from 14.69 to 14.6959 due to accuracy concerns
v1.156 (Dec 14, 2014)
Bug Fix:
Added extra blank space to the end of MAP display
Changes:
Reduced refresh rate from 100 to 125ms
Increased Idle to 25% and Cruise to 30% throttle
v1.157 (Dec 15, 2014)
Bug Fix:
Changed subsequent servo IF statements to ELSE IF since servo only needs to be set once
Changes:
Added ignition in ACC position triggering for Initial mode (when vdd=0)
Attempting to widen the range of 30% by shifting the trigger for 25%|924 to be 1.1v|843
Experimenting with 35% Cruise instead of 30%
v1.158 (Dec 24, 2014)
Bug Fix:
35% Cruise displayed 34.1 instead of 35%. Now it's gonna be 35.1% I think
Changes:
Idle circuit is now 27.5% instead of 25% and also now activates below 1.0v (instead of 1.1v)
v1.159 (Dec 28, 2014)
Changes:
Sending initial 100% Servo command before the 4sec LCD delay so I don't have to wait for it anymore
servo float variable is now an integer before being sent to the servo
Now we can do anything we like with servo, so adjusted to get just the right thr% display for idle/cruise modes
Lowered idle mode activation to below 0.9v (instead of 1.0v)
Basically with all the driving I do I get a lot of time to test out and consider how to improve the code. I'll make notes on my cell phone and when I get back home I'll pull out the laptop and USB cable and update code.
Here is an explanation of the display:
Throttle -- This is the actual % open of the exhaust throttle.
MAP -- This is the actual voltage reading from the MAP sensor now installed to the intake system
PSI -- This is the voltage signal converted to pounds per square inch. Negative means it's operating under vacuum.
Peak -- This is the highest registered PSI in between boost and no-boost conditions (ie. a gear change).
And here come some shots of various displays throughout my progression:
Pic 1: One of the earliest pics I took. This is from code version 1.1 with alllll the digits showing and overall had a clunky and slow refresh rate.
Pic 2: This is after version 1.11 where I added the Throttle Angle that was occuring at the time of (that particular) peak boost. You can see that after a while I would get random characters on the first row overwritten by numbers. It took me a while to figure this one out
Pic 3: Same sort of text getting messed up on the first row of characters. Peak boost here is nearly what I have the throttle set for for 100%, or 11.75 PSI. So at 11.6 PSI the throttle is only opened 99.71% of the way.
Pic 4: This is at version 1.14 where I "Drastically reworked and optimized LCD Display code". This was the first milestone release, fixing multiple rendering bugs including the number overlay error mentioned in pics 2 & 3 allowing for a more responsive refresh rate.