Sale ends todayGet 30% off any course (excluding packages)

Ends in --- --- ---

13bt BAC, Idle Control Valve

General Tuning Discussion

Forum Posts



Tech Articles

Discuss all things tuning in this section. News, products, problems and results. 

= Resolved threads


Good Day all,

i am attempting to improve my idle for the following;

S4 13BT rotors in S5BT block with S5 Intake system. Pretty aggressive street port.

TD07-25G Turbo

AWS is removed.

BAC is wired up

Adaptronic e440d with custom harness.

93 Octane RON Pump gas

now I have the base idle set at 850 and want the idle control valve to boost the idle to 1050. I love in a colder climate and want it to assist with startability.

13 degrees adavance with 10 degree split at idle

AFR of 13.2 at idle 850.

now I can not find setting that work with the OE BAC valve. When I do try to use it the idle surges hunts between 1000-1800.

anyone with any insight on this?


I'm not familiar with the idle control valve design on this engine. Can you provide more information around it? Is it a simple solenoid or a stepper? Either way you will need to ensure the Adaptronic is set up and wired to suit. If the porting is aggressive then I'd also suggest you may be attempting to make the engine idle too low. It's not uncommon for a ported rotary engine to need to idle at 1200 rpm or above. A serious bridge port will want even more rpm. You can also try retarding the timing as this will dull down the engine torque at idle and make the engine less prone to surging.

The BAC valve is just a simple 2 wire solenoid, I've never had to idle a street port with a worthwhile tune/ECU higher than 1050, so I can only assume that there's a configuration issue with the adaptronic or there's something wonky going on with the air bleed valve by the BAC.


As M:EP indicated it is a 2 wire solenoid that according to the factory manual runs at 244hz. It is wired to a PWM capable output on the adaptronic the other pin is 12V switched. As for the settings that is what I am attempting to fumble my way thru. Any insight or suggestions for me to try would be great!

You might find right on 12.7:1 and less ignition timing calms it down a bit.

I'd agree with less timing, making sure that you're not bleeding too much air via the bleed screw by the BAC, confirm injector characteristics of whatever injectors you're running et cetera. I forget what software the e440d runs (wari?) as adaptronics aren't really my jam but I'm sure if you post your map someone may find something, there's only so much that differs from ECU to ECU.

We usually reply within 12hrs (often sooner)

Need Help?

Need help choosing a course?

Experiencing website difficulties?

Or need to contact us for any other reason?