How to over-ride computer RPM while coasting?
 

My 2012 Toyota FJ Cruiser has a 6 speed manual. The vehicles computer adjusts the RPM's based upon the mph. For example, if I am going downhill (45 mph) and put the tranny in neutral and foot off the gas, the computer idles up to 1,500 rpm. The faster the mph, the faster the rpm. Typical manual trannys allow the vehicle to idle as normal at 6-700 rpm.

Has anybody on this forum been able to over-ride their car computer to adjust the idle as it should be?

Until I get around to proper wiring for my kill switch, I just use the key.

Does the vehicle have some kind of active rev matching?

Lots of cars do this. My Toyota Matrix did it as does my Metro. Until you're stopped, it won't idle down all the way. IMO its a pretty minor thing and I don't intend on trying to mod anything to 'fix' it. I'm not even sure you can. Even if you faked the signal, I think you'd create other issues with ABS and other stuff.

If I turned the car off, it would impact the power steering and possibly brakes...right?

Yes. I have heard it does this for two reasons....emissions and allow for easier shifting. I don't need it though.

I'm interested, as such a mod would roughly 1/2 the gas use while coasting.

Turning the car on and off is not always efficient, and has it's own issues.

Generally the brake system stores enough vacuum for three full presses. If you need anything close to that, your engine should be running.

Once you're moving, especially at driving (not parking lot) speeds, power steering doesn't add too much. Cars with electric steering have it come right back. I'd be concerned about whether an automatic transmission car would treat things like locking the column, but I can't really speak to that.

But shutting it off does override the computer's desire to keep the revs up. ;)

I doubt you'd ever pull off a swerve and recover without PS on an FJ Cruiser, I know my Wrangler won't.

The aerodynamics of these 4x4's is such that EOC isn't very practical anyway. If I do EOC occasionally, it's with the gearbox in gear and foot on the clutch ready to bump start at short notice.

EOnC is probably the preferred method, the only solution I can see to the problem is to spoof the ECU's speed input while in neutral. An ECU tuner might be able to help.

As far as the engine revving while coasting in neutral, i would start by measuring the fuel consumption when idling (stopped) and when coasting.