External boost controller

Hi everyone,

i have a car with aftermarket garrett bigger turbo, which keeps creating me issues with the stock boost controller,

so i put a separate MAC valve with an external boost controller and works fine, leaving the duty cycle table stock in the ecu maps, keeping the stock boost controller plugged in but with no vacuum lines connected

- only issues i have now the car throws randomly the engine light telling boost controller error, and other limiters then cut power when CEL on

- ecu is bosch Me17.3, my question is, how can i prevent this happen? should i put max values in the oem duty cycle table?

(with the complete damos file i tried to deactivate or to increase some thresholds around the wastegate but seems same issue)

(if i delete DTCs, doesn't show the DTC then but make the same behaviour without the engine light)

thanks in advance

I don't know the details of your system, but this often happens when desired/expected manifold pressure does not match actual pressure. By removing the ECU's ability to manage pressure, you've created conditions where actual pressure likely deviate from what the ECU is attempting to achieve by a significant margin.

This can be avoided by tuning with the stock controller and working with the system until it offers the desired result. Doing so can be more challenging until you figure out all the load targeting and limiting functions, but in the end the result is worth it.

hi, problem is with the stock boost controller there is no way to handle over than 1.5-1.55 bar, and having it with "slower" spool, more than that it starts having weird behaviour on turbo pressure, floating or dropping (and this boost controller is already an improved one than stock, from another stock car)

with the external valve no issues at 1.85 bar which is our target... everything smooth

I certainly understand your want to proceed with the external controller as it is much easier to tune than figuring out how to tune the stock ECU systems which are more complex, but you will face the ECU continuing to respond with codes, possibly unwanted throttle closures, etc. as long as you're externally altering boost so engine load, airflow, manifold pressure do not match ECU expectation.

100% agree with Mike McGinnis. The ECU logic requires that it has control of the charge pressure. Using big turbos and upgraded MAC valves does require a significant amount of time and effort to get the feedforward values correct.

hi, first of all thank you for your answers,

for the external controller yes, it would be "faster" in a way, but i would not go for it if i had no issues with the oem one... so it is a battle between codes it seems...

i'll try to figure out a way to use the oem one or some compatible to be managed from the ecu then

Sounds good! I know it seems like more work, and it is more work in terms of getting boost where you want it, but in the end allowing the ECU to control boost will allow all the other systems to work properly, and ultimately help you get you the result you're looking for. Please keep us posted on your progress and have a great day!