Engine Safety Features

[esso]

I have tuned a numerous subaru's ecu and other manufacturers , i see that the knock protection function on subaru's are very effective and i see the link lack one of the important features which is 

if excessive knock occur the boost controller should pull down to the lowest boost , as this will protect the engine more , this feature can be also if lambda is enabled for closed loop , any failure in a target AFR should disable the boost control algorithm which will bring down the boost to the minimum .

 

 

[Scott]

Thanks for the suggestion, I will pass it on to the engineering team. How would you see this working? If the ECU sees knock at any level it should reduce wastegate duty cycle to 0.0? or should it introduce a boost cut to cause no boost at all? Would the system then stay like this, or would it do this temporarily and then try and increase the boost again?

Scott

[esso]

lets say a street car is tuned for 95ron and pushing 1.5 bar of boost and the customer then put 93ron and the engine will start to knock and the knock protection function then will pull timing , but sometimes pre ignition occurs which is not timing dependent ,  the best case is if the knock count exceed certain amount of knock through a period of time (excessive knock) then the boost control should apply 0% duty cycle which will make the engine run on the lowest boost , by this the engine is protected from running on bad fuel with high boost for a longer time 

[mapper]

Good suggestion! Was something i was thinking about too for some time. I would suggest a table that with the follow axis option:  one axis knock/time period vs free choise (boost target rpm,  WG DC. This way user can set it up depending on his other settings and needs in boost control.

Another posibility would be to add 4D and and 5D maps for boost control and add a parameter knock/time period. Time constant for this parameter should be set under knock control settings.

Target boost(closed loop boost control) or WGDC (open loop boost) can be modified based on the knock parameter. The advantage of this solution is that 4D and 5D boost tables can be used for alot of other functions. As an example: main boost table axis are spaned RPM vs driver rotary boost switch.  4D is set for boost baro corection or an overboost function can be added there as a overlay. Finally you can set up knock control safety future in the 5D table. 

 

Edited November 2, 2016 by mapper

[Scott]

Thanks for sharing your thoughts guys.

Scott.