Boost Control Updates - EWG (Electronic Wastegate), Boost By Gear, Pressure Limiter Adjustment - bootmod3 CustomROM V2
Overview
In CustomROM V2, boost control has gotten a couple of major updates that help fine tuning a boost target as well remove limitations in boost ceiling. These changes apply across the board, not just OEM EWG (Electronic Wastegate) stock and hybrid turbo setups, but also to big turbo upgrades using pneumatic style wastegates such as those from Tial, Turbosmart, Garrett, etc.
Raising the boost target on these DMEs requires many changes to DME tables including Load limits, Torque limiters, Boost Limiters, Pressure Ratio Limiters, etc. However, even when all of these limiters are raised out of the way, you get to max values for some tables that still limit how far up in boost you can go on the DME without jumping through hoops, doing funny things with MAP sensor rescaling, etc to get a few pounds of boost more out of it.
The first issue comes from the Pressure Ratio Limitation table. OEM values go to a max value of 4.0. Not being able to go past that max value you’d be capped to tuning up to 4 bar absolute pressure (3bar of boost, i.e. about 43.5psi) with the factory EWG (Electronic Wastegate) setup. While that boost level certainly isn’t low for some standards, these cars have been needing to push to much higher pressure ratios than that. We lifted that limit and now you can take that max value to 8.0 absolute (or 101.5psi of boost). Shown below for illustration is the Flex Fuel version of the Pressure Ratio Limitation table.
In addition to the above, we’ve often received requests for Boost By Gear. Torque by gear is possible through OEM tables but for a tuner that is used to more conventional boost by gear setup, this was not possible until now. Shown below for illustration is the original Boost Ceiling 1D table where a tuner could set up maximum Boost Ceiling the tune could request once various Load, Torque, Pressure Ratio limiters, and other associated tables were looked up and calculated against.
That’s now been expanded to a 3D Boost Ceiling table which has Gear and Engine Speed axis for a boost by gear and engine rpm mapping of the Boost Ceiling allowing for a really simple approach to tuning a desired boost curve. In this approach, all load, torque, compressor/turbine limit, pressure ratio tables could be raised to some higher value and by simply setting up the new Boost Ceiling By Gear table you can set your desired boost target in a more conventional way. Its available across all 4 map slots and as shown above in Flex Fuel with its blend factor logic.
OEM EWG or Mac Solenoid control Switch
The above table can be used to not only set how the Mac Solenoid is to be controlled for duty cycle, but also, in the case of OEM EWG turbos, the value can be left at 0 to leave the OEM EWG (Electronic Wastegate) operation unmodified for stock/hybrid turbo use.
In case a Mac Solenoid is being used for boost control this table sets how the mac solenoid is controlled through the REV2 board. REV2 has a dedicated output (EBCS - Electronic Boost Control Solenoid) for the Mac Solenoid.
Using value of 0 in the above table, DME will use FlexRay’s static segment to send a message to REV2 indicating what duty cycle to run the Mac Solenoid at.
Otherwise, using a value of 1 will have the DME repurpose the bank 1 OEM EWG connector and it will be pulsed at duty cycle required which REV2 directly replicates at the EBCS output to the Mac Solenoid.
For those vehicles running factory electronic wastegate actuators, this setting should be left at 0.