Any easy way to detect the engine's "null point" when driving?

[basjoos]

One instrument I wish I could find is one that would tell me when the engine hits the "null point", the point where it switches over from propelling the car to engine braking the car. Right now I have to memorize or keep a chart of the fuel consumption when reving the engine to various rpms when unloaded and either pop the clutch and freewheel or go to "N" whenever my fuel consumption drops below that point while driving.

[RobertISaar]

i imagine an accelerometer would do the job.

i mean, all you need to do is measure G forces from the front to rear of a vehicle to know if it is accelerating, decelerating or neither.

unless i'm misunderstanding the question?

[pgfpro]

I can see where that would be a issue on your car. Because of your excellent aero cd you have very little aero-drag to overcome. So there would be a very fine line between engine braking and engine power. So the smallest change in the road from flat to a very,very small decline would cause engine braking.

The only thing I can think that would work without in depth building something would be a management system with the fuel table displayed at dash level or even above the dash.

Here's a example off my car going a dip in the road.
Fuel table - YouTube

[Daox]

A vacuum gauge should do this.

[H-Man]

A force meter on the motor mounts would do it. I can feel it on my car because the CV joints are loose.

[freebeard]

Instrumentation - Fuel Economy, Hypermiling, EcoModding News and Forum - EcoModder.com

Right now I have to memorize or keep a chart of the fuel consumption when reving the engine to various rpms when unloaded and either pop the clutch and freewheel or go to "N" whenever my fuel consumption drops below that point while driving.

With all respect, this confuses me and makes my head hurt. Wouldn't the chart show 1/∞mpg at all rpms? If it has a clutch and "N" it's a 1950 Dodge with Fluid Drive, right?

[RedDevil]

I used to give short taps on the clutch pedal to see/hear/feel which way the revs would go.
Nowadays I can only tap a plastic foot rest but now I have an UG.

[basjoos]

Originally Posted by freebeard

Instrumentation - Fuel Economy, Hypermiling, EcoModding News and Forum - EcoModder.com



With all respect, this confuses me and makes my head hurt. Wouldn't the chart show 1/∞mpg at all rpms? If it has a clutch and "N" it's a 1950 Dodge with Fluid Drive, right?

This refers to different cars, using the clutch when driving a manual, shifting to "N" when driving an automatic.

I'm normally using the injector pulse width display on the SuperMID. but it also works with the gph display on the Scangauge. As an example, if the SuperMID shows 2.3 usec pulse width when reving the unloaded engine at 2K rpm while sitting motionless in my driveway, then when I am driving at 2k rpm in any gear and the pulse width drops below 2.3 usec, I assume the engine is dragging rather than propelling.

[Mcgiiver]

Originally Posted by Daox

A vacuum gauge should do this.

I think most are overthinking this question. A vacuum gauge gives an instantaneous and accurate indication of changing load.

[UltArc]

I know what you mean, it is difficult for myself. In the Mustang, right above 77 mpg by SCii is when engine braking starts. On the highway, that's EOC time.