Fuel Flow Rate Gauge in Instrument Panel 2

[olynyk]

Hello all.

So as I was riding to see War of the Worlds last night in a friends 1998 extended-cab extended-box 5.4L V8 F150, I got thinking about fuel economy and conservation (surprise, eh?). It's an interest of mine, and one of my strong beliefs is that technology can only take us so far on conservation issues; people must learn to adapt as well.

Anyway my story ends with a decent movie, but also an idea similar to the smart power meters currently being installed in Ontario. Why not install a fuel rate gauge in the instrument panel of new cars? I thought about it for a while, but I can't see anything particularily wrong with the idea. It's been proven with the smart-meter study that when people can see the energy they're using, they will adapt to use less of it. "Out of sight, out of mind" really does apply to the electricity bill, and there's no reason to believe it wouldn't apply to the gas tank. (How many here really pay attention to their fuel bill every week? Of everyone I know, not more than a quarter of them do this...)

Some thoughts I had:

(1) It seems like it would be incredibly cheap to add -- on a digital instrument panel there'd be no cost for extra gauges, only the cost of adding any required sensors or logic to the fuel-injection or fuel-pump system to calculate the rate of use. On an analog instrument panel there'd be the cost of one extra display gauge plus added labour time at the factory to install it.

(2) I'm pretty sure on Buicks at least, it already tells you your rate of use, though it's not updated as quickly as I'm imagining. I'm thinking something that when you step on the gas and the tach spikes up, so does this "fuel rate" gauge. If I had to express it as a response time, I'd say, maybe 50 ms? I could be way off-base there.

(3) The actual fuel savings, of course, come from the behaviour change -- when you see that gauge shooting up as you floor it, you take it easier on the gas. Obviously the whole idea is useless if people can only watch helplessly as their fuel rate stays "in the red", but in this case they can do something about it -- and "eco-driving" (driving less aggressively) is supposed to save somewhere between 5% and 33% of fuel economy.

Anyway, being an engineering physicist by training and a valve designer by (current) employment, and someone who bikes to work, I know very little of current automotive systems. So I ask you, automotive eng-tips members:

- Has this been done hundreds of times before?
- How much would it really cost?
- Do you have any tips on where else to start looking or asking questions on how this could be done? Would this kind of thing be made by Tier 2 or 3 manufacturers?
- If I want to pursue this, do you think it's better to approach my MP to try to get legislation, or better to go to a PR person at an auto company and say "this'll look really good if you guys do this, here's how much it'll cost, let's talk"
- Am I totally off base here?

 

[Hydroformer]

A simple method is to just use a vacuum gauge. Less vacuum means more fuel (throttle open).

My '02 Intrepid has "instant MPG" as well as "average MPG" in the overhead unit, so yes, it IS being done. I'm in Canada so I keep it set to L/100km.



*Without data, you're just another person with an opinion.*

Hydroformer

 

[olynyk]

Thanks hydroformer, I hadn't thought of a vacuum sensor. Is that information already on the data bus? That'd reduce the costs of this proposed idea.

I should have mentioned that I have seen what you're talking about on your Intrepid -- it's on my mother's '01 Buick Park Avenue as well. But from what I understand, the "instant" fuel economy is not really that "instant", i.e. it seems to have about a 5 or 10-second response time, not quick enough to change people's behaviour.

In addition, at least in the Buick, that option is hidden in one of the digital sub-menus (you have to push the "fuel gauge" button three or four times). I was more thinking of a gauge that is always there. Just a small one, next to the fuel tank level display, perhaps. A major part of the smart metering program for electricity is that the display of the smart meter must be installed somewhere highly visible (usually the kitchen). The impact of this will only be realized if people get used to seeing their fuel rate usage all the time.

 

[NickE]

The use of the manifold vacuum gauge as an indicator of fuel economy has been around for a very long time. Several friends in college had caprice/parisenne's and other large boats, they had instant reading fuel economy (qualitative not quantitative) indicators on the dash. my mom's prius computes fuel economy two ways also instant (or xx.xx samples but still realtively quick) and trip.

 

[Hydroformer]

Yeah NickE,
Manifold pressure is the best 'immediate' indicator. Many moons ago I put a vacuum gauge on my '72 Nova. I was young, I loved watching the needle move as I stepped into it.

*Without data, you're just another person with an opinion.*

Hydroformer

 

[IRstuff]

But to carry your analogy further; "out of sight, out of mind"

It's unclear whether the average driver even looks at their instruments, so adding this instrument is probably irrelevant.



TTFN

 

[Hydroformer]

You gotta put it "in their face", maybe a HUD set-up. A warning tone/light at a preset pressure ? Or for habitual abusers, a set of pins in the seat to jab the driver off the throttle.

*Without data, you're just another person with an opinion.*

Hydroformer

 

[NickE]

hydroformer- what about those of us with forced induction? There you could use the boost pressure to push the pins, more boost deeper stab.

 

[olynyk]

Alright, laugh it up guys

I think it'd really work -- and there can be no objection to the idea really, you're not forcing people to do anything except be conscious of the data. Anything beyond that is up to them.

 

[GregLocock]

Manifold pressure is a pretty awful way of displaying fuel consumption - after all, at full throttle at 2000 rpm you are going to be a damn sight more efficient than 4000 rpm 50% throttle.

The information you really need is already present in the EEC, since both the volumetric fuel rate (via the injector pulse width/ fuel rail pressure) and the vehicle speed are available internally.

I don't know how you'd decide on the time constant, or a display. BMW have had fuel consumption displays for at least 25 years, can't say I've noticed that having much effect.

Cheers

Greg Locock

Please see FAQ731-376 for tips on how to make the best use of Eng-Tips.

 

[jons999]

A lot of vehicles now have an instant mpg display on the instrument panel, and even on vehicles that don't have it you can still access it with a dealers scan tool. All OBD2 vehicles have an injection duration PID that will show you injection duration in milliseconds, assuming that fuel pressure stays constant you just have to know how much fuel goes through the injector in a millisecond and multiply it by your number of injectors.

I know that on Toyota's the scan tool has a fuel consumption program that calculates this for you. This way we can drive the car for a few minutes to verify a customers complaint that the car is getting poor gas milage. (99 times out of a hundred the customer is calculating it wrong, or their gas milage expectations are unrealistic for the type of driving they do).

-Jon