Fuel Computers

[ColinBarber]

When the system is in closed loop then the information from the O2 sensors will reverse the setting. However when it's in open loop mode (under load/full throttle etc) the fuel computer should make a difference.

[Fargo]

can you explain the closed loop colin,, do you mean when the car is simply driven under normal conditions as opposed to puting the boot down...

[ColinBarber]

This will explain better than I could:

http://www.autoshop101.com/forms/h44.pdf

http://www.autoshop101.com/autoshop15.html

[Fargo]

hmm information overload colin..lol.. give it me in laymans terms

[ColinBarber]

The ECU has various sensors and a pre-programmed map in the software. Using the values of the sensors it looks up the correct timing and fuel to use at any one time.

In closed loop mode it uses the information from the O2 sensors to adjust the fuel mixture to achieve the best air/fuel ratio. It does this many times a second so if you modify the MAF sensor signal, for example, it won't make much difference.

In certain conditions closed loop mode is not used because a different air/fuel ratio is required - e.g. when the engine is cold or when accelerating. Then the ECU just uses the input sensors and its pre-programmed map. If you alter an input sensor in this mode it will make a difference.

This is why you see better fuel consumption when you fit a Unichip/fuel computer because Toyota normally over fuel at high revs under acceleration.

[Fargo]

so what were saying here is that a fuel/air computer will work.

[ColinBarber]

so what were saying here is that a fuel/air computer will work.

Best to speak with TDI or another tuning company. But I believe there have been people who have UniChip/HKS/Apex fuel computers installed and they have made a difference.

[Fargo]

thanks for your help colin..

Mark (tdi) what are your thoughts on the Apexi SAFC II, with its additional funtions.

and also this issue with the oem ecu coutneracting piggyback ecu's

[tdiplc]

Colin has already said it: Under closed loop conditions (cruising etc) the ecu is self correcting. Under open loop conditions (accelerating etc) the fuel and ignition parameters can be modified :)

[Fargo]

so that is true to apply on the f-con S.. how does the f-con pro get around this..

[tdiplc]

The only way to get around this is to turn off the lamdas inside the standard ecu ( I don't know anyone that can do this), or use the fcon Pro as a stand alone ecu.

[Fargo]

ah right so the fcon pro is a stand alone unit,, much like the

Haltec, Autronic and Motec..