The reason why you can't find a balance on the DTEC is the source of the issue is the physics of the turbo, not the boost controller. You are right on the physical limits of that turbos ability to spool on your setup. When you cause it to spool later you are not riding up the surge line, so you do not hear any of it. Your best bet is to use the settings that get you the best spool, and then during normal driving down shift if you want to accelerate faster.

In general the spool threshold is the % of your target boost level at which the boost controller will switch from 99% duty cycle down to the values in your map. The duty cycle is how hard the DTEC is going to work initially to make your boost level. If the gain is anything other than 0 the DTEC will alter the duty cycle from the value in your map to a value that is more likely to produce the target boost in your boost map. Finally, the level of the gain determines how fast and how much the DTEC will alter the duty cycle to hit your target boost.

When we setup a DTEC I typically start with the spool threshold down at 35, and a gain of 4. From there I set a low duty cycle, like 20, and see how much boost you make. This will make only a small amount of boost over your wastegate boost level. Since we often do not know EXACTLY what spring is on a turbo this is a safe way to start tuning the boost and identify the actual spring rate. Depending on how much boost you get and how much duty cycle the DTEC actually ran you can start making adjustments. As an example, if you have 12 psi as the target and the DTEC ramped up the duty cycle from the starting 20% to 30% and made the 12 psi above 5500 rpm with a constant 30% duty cycle, you have a pretty good idea that 30% is a reasonable level to hit 12 psi. If I know that I want to run 18 psi, and the car is tuned to that boost level already, I will go ahead and set the boost target to 18 psi, and then increase the duty cycle until I have the same values in the duty cycle tables as the data logger shows produce 18 psi to redline.

This is the ideal situation. You know that in your current conditions the DTEC is going to make your target boost with minimal alterations to the duty cycle. That means that as you drive in varied conditions the DTEC is alreay close enough that it will compensate for altitude and temperature fluxuations and your boost should remain spot on through out the year.

Once you have the duty cycle set you can increase the spool threshold until you are making boost as fast as possible without a massive over shoot of your target upon spool up.

In the case of surge, like you are seeing, another option is to use the gear based boost control and set the lower gears more aggressive when surge is not possible due to limited load. And then in 4th and 5th run a little less duty cycle so that you are not surging the turbo.

Jarrad

No more DTEC, no more surging, hitting 17psi in first and 19 in all the other gears making 280whp on a not too agressive map (five less whp than when I was tuned with the DTEC).  Just running a simple MBC.  the DTEC me and the car did not get along I guess.