Recording mileage with engine off?

[vrmilionzx]

Hey Guys,

I've been browsing at work, so I'll just apologize in advance if I've missed where this is discussed - I searched, but not too in depth.

Both of my cars calculate mileage based on the speedometer. The speedo only runs when the engine is running - so when I shut the car down for long coasts up to longer lights, I'm effectively not capturing mileage traveled. This may seem like nitpicking, but I've been working on modifying my driving style to get the most from every tank of gas, and traveling "free" distance like this should count towards my total.

Assuming that I've run into something that most people here have as well, how do those of you (without hybrid engines that do this automagically) capture distance traveled with the engine off?

[mikehallbackhoe]

my 95 nissan pickup speedometer only registers with the key on, but the engine doesn't have to be running. If your engine has to be running, you might see if a gps would calculate miles for you

[MetroMPG]

I'd also want to confirm your key is switched back to the "on" position after you kill the engine - speedometer/odometer should work.

I haven't seen a vehicle where the speedo/odo relies on the engine running to register. (I suppose there's a first time for everything, though...)

[HilseeJ]

I have the same problem, but only when the key is turned to off.

However, you could look on the bright side. If your odometer isn't going up, it literally is "free" miles. As in, your mileage is LOWER than reality and your car will resell for MORE money.

[ksa8907]

Install a kill switch, it will cut the injectors and allow the computer to run.

[Piwoslaw]

Originally Posted by ksa8907

Install a kill switch, it will cut the injectors and allow the computer to run.

+1
I noticed that when I keyed off, then turned the ignition to ON, the computer went through the reset cycle and didn't always register the coasting distance. With a kill switch the comp is always on and thinks the engine is running, so all of my milage is accounted for. I can even watch the trip fuel economy on the OBC change as I EOC

[JRMichler]

Originally Posted by ksa8907

Install a kill switch, it will cut the injectors and allow the computer to run.

+2
And you do not take the risk of inadvertently locking the steering.

[ecomodded]

+3 no make that +10
I really want to do it to my car, It is a pain to flip the key off then on and a distraction.
I think having it on the steering wheel for my left hand to control would be convenient and safe & fast. A simple button that once pressed turns the motor off and when released puts the ignition back to on.

[ksa8907]

i have an automatic transmission, so im not too interested in the idea and haven't read any threads on the idea. i assume all you would need is a push switch(like a push button start), a relay and some wire. most cars keep a constant voltage to the injectors and modulate the ground, use the button to control a relay that would eliminate a ground for the injectors. as soon as the engine dies, let off the button.

[vrmilionzx]

Awesome input - I don't think I had the key in the on position. I'll double check, and see about an injector kill switch. I was never worried about steering locking, because I tend to only coast with the car off on long straightaways before stopping. I suppose if I had to swerve, this would become a rather immediate concern.

RPMs aren't necessary (for monitoring), as when you're decelerating in gear, many cars don't add any more fuel at full decel. Mine doesn't, so it's running fuel free - I was using this more as a replacement for coasting in N - N still fires the injectors to keep the engine turning as you coast - I want zero consumption.