I was thinking that the best way to figure out what's going on is with live sensor data.

When a modern engine is idling high, for example when it's cold, how does it do that? Does the throttle get opened, or does it run rich, or something else? I suspect high idle in neutral at speed would be done the same way. What sensor should I watch? I'll order my ELM327 tonight, I think...

I know on my protege I have about a dozen ecu "triggers" that tell the ecu to enrichen the mix, ie more fuel. This bumps the idle up slightly. Headlights, rear defog, rad and interior fan, wipers, etc are all triggers. I would assume most vehicles have some sort of trigger. At idle the Protege is nearly 15:1 for mix, but if I kick a few of these triggers on it increases to about 13.7:1. Small increase, more fuel, bigger bang, more air drawn in, idle increases to compensate against the alternators increased drag. Currently all these triggers are just bare wires, and I can increase my rpm manually without the alternator drag.

Okay, small sidetrack there. But yes, the ecu injects more fuel, leaves the injector open longer, wala, higher idle/rpms. You should be able to see it with your fuel rate monitor. You should see a higher value when you first fire it up in the morning.

i'm mean there isn't 0 zero friction,,,,,have you ever been it a car sitting engine off,then start it in neutral and it slowly roll ??? i have tons off times

Yes I have actually. On top of a hill, with me holding the brakes pointed downhill.

You didn't read what I said did you?

i re-read it ,,and yes i wouldn't be surprised it a rpm increase as it rolls down a hill ,,,,,,,,,my truck idles at 8-850,, at 50mph in N i see about 950-1000 rpm and its old school ,,77 chevy 350/350 ,,,and itstalls at 1200 rpm flashs to 1800

I thought of that, but it won't tell me what's causing it. If neutral was still putting some power through to the input shaft (I can't imagine how, but let's say it is) then it would force the engine to turn a little faster and therefore use more fuel (yes, it does use more fuel for faster RPM even with my foot off the gas, unless it goes into DFCO). The fuel rate monitor won't tell me what the cause is, just the amount of fuel that's being used.

It should suffice to monitor O2 sensor readings via OBDII; I'd compare triggered fast idle and normal low idle to the neutral-at-speed fast idle.

You know, you've got a point there.

Put a car up on jack stands and start it. In N the wheels will start turning. Damn. How does that work?

the internal friction,,thats the easest way i can explain,,,which i have a hard time at

input shaft spins, fluids move, primary and secondary shafts move. When loaded (ie on level ground) the car doesn't move, but in the air, the friction is close to nothing, therefore shafts spin. Does this mean there is no neutral? no, it just means the tranny is built solid and with tight tolerances. Neutral still exists. The engine has no direct mechanical connection with the tires.

Ok, so the question is...is that fluid connection enough to increase engine RPM by 10% when the driveshaft is spinning at highway speed?