Hondata

I have to change to OBD II for smog reasons and have an easily accessible switch on J1 to switch back to stock if necessary. Also, I am using all the inputs available for switching for their stock functions and want to keep it that way.

So it seems that best input to use is the brake switch input. This allows me to keep the most functions under all conditions.

The help section states that the brake switch input is used to idle the car up. How much does it idle up? Under what conditions does it idle up? I have never seen or felt this happen. I can see this being the case for an automatic equipped vehicle, but not a manual. Is this the only thing the brake switch input does? I am specifically asking about an OBD I & OBD II USDM P72 ECU.

I just want to make sure of exactly what will change by elimination of the brake switch input to the stock ECU.

It idles up slightly depending on temperature and load. It is not much. The bottom line is that you can disconnect the brake switch input without noticing any difference.

Thank you.

All I have been able to notice by datalogging is that when not moving or at very low speeds and at hot idle conditions, the timing will advance around a couple of degrees when the brake pedal is depressed. I do not notice that the idle speed increased.

When you said idles up did you mean idles up due to timing increase?

Mine actually idles at little lower and worse when the timing is advanced due to the brake switch input.

Why did Honda do this? It seems like a lot to add simply to get a change that appears to make basically no difference. I am assuming that all the brake switch input does is slightly raise the timing at idle. I have not seen any other effect.

I disconnected the brake switch input and found that the timing increase is still there with the brake switch input fixed either high or low.

I eliminated the ELD and the timing increase is still there.

So it is either the field return input or internal battery voltage monitoring that is causing the timing increase.

I might later try tricking the field return input to see if this is the cause.

Any comments?