Simple question for you Guys................

[FreddyG]

My car is tuned using the COS3 OS in open loop speed density.

My question is that I heard that if I put the car back into closed loop, that there's a chance that my mileage will go up. How do I set it to go into the "Semi Closed Loop" mode?

Is this true and what would be the advantage or disadvantage of doing this?

Thanks for your help!

[5.7ute]

Semi closed loop is enabled wherever you are commanding stoich in {B3647} in a custom OS. This can be an advantage in a vehicle with a large cam overlap, where lower engine speeds have a lot of unburnt gases in the exhaust stream.
Set up properly I cant envision any major increase in fuel milage.

[FreddyG]

Thanks for your help Mick!

[5.7ute]

Thanks for your help Mick!

No worries Rob.
After rereading the little I posted I realised that there wasnt much of an explanation given, but I gather you got the gist of it. By not commanding stoich at low engine speeds where there is unburnt fuel in the exhaust due to cam etc you will not enter semi closed loop & wont get erronous fuel trims. These inaccurate trims will cause your milage to escalate.
The O2 switch points can be fine tuned to match your wideband readings & keep the economy consistant with what you already have where stoich is commanded.