question regarding difference of a mapped ECU and standard

[Whitesupraboy2]

Ok quick question. A standard ECU can adjust timing etc... to the fuel it runs therefore improve power and in theory MPG etc..

 

Can a mapped ECU also adjust itself to the fuel it is running or is it stuck rigid to the map. Probably a stupid question.

[JustGav]

It is a bit more complicated than that...

 

The ECU uses two different sorts of methods..

 

Namely : Open loop and closed loop

 

When it is in open loop, it uses a fixed map and the values from the stored map are fed directly into the various components.

 

When it is closed loop it uses the values from the lambda sensor and adjusts the map to suit the feedback it gets from the engine.

 

Most ECU's use a combination of these methods in order to function.

 

And most if not all ECU's use a feedback system, hence the reason for a lambda sensor.

 

Hope that helps.

[SimonB]

That only applies to fueling, which has nothing to do with adjusting to different fuel types. It is advancing the timing that allows more power with higher octane fuels. The stock ECU uses its knock sensors to retard the timing if det is detected. To some extent it will advance the timing to take advantage of higher octane fuel.

 

Most standalones don't use the knock sensors in this way, but then you just map them with the fuel you are going to use. If you want to use race fuel you just have a separate map for that. This is much more effective that relying on the ECUs limited ability to adjust itself based on knock detection.

[Whitesupraboy2]

ok thanks i just wanted to confirm what i thought

[JustGav]

Doh...in my eagerness to answer the post, I didn't read the question... Sorry....

 

But yeah, the knock sensors do a bit, I do seem to remember on a thread a while back it was mentioned that the knock sensors aren't any use with a modified engine.

 

Something to do with the fact that they only operate at a certain frequency and once you change components they aren't much good.