Measure fuel consumption from injector signal?

I need to measure relative fuel consumption.
Backstory...
I have friends interested in energy efficiency.
"Something-for-nothing" transportation is a favorite
topic (of theirs).
I was asked to go look at a car with a gizmo
added to improve fuel efficiency.
The guy was all bubbly about his modifications.
I asked to see some data.
His answer was typical:
"I filled her up, drove her 80 miles, filled her
up again at a different station. WOW, I got
60MPG."
I asked why he didn't use a fuel flow meter.
Answer was again typical, "what's a flow meter?"

I firmly embrace "conservation of energy", but
everything ever invented was impossible before
it was invented. I'd like to keep an open mind
(and keep my friends happy)
that there might be some as-yet undiscovered synergistic effects
that improve overall efficiency without violating
the basic principles of thermodynamics we know today.

Since most claims are bogus, a quick means to debunk
them is in order.

Adding a fuel flow meter is rather invasive, so
I'm looking at ways to measure RELATIVE fuel flow
non-invasively.

I know nothing about the technology past what I learned
in a few hours of googling.

In steady state, the rate of fuel flow should be linearly
proportional to the open-time of an injector times the number
of injection events/unit time.

But it's an electromechanical system with short time elements.
It takes time for the magnetic field to build/collapse and more
time for the mechanical parts to move.

In a symmetrical system, this would make the fuel flow time
approximately equal to the pulse width, shifted by the delay.

I don't understand the terminology, but I'm reading about
a 1ms time that needs to be added to the pulse width, on average.
I'm leaving out all the complexity of voltage corrections and
assuming the fuel pressure regulator is working.

If I measure the pulse width and subtract 1ms, will I get a reasonable
measure of relative fuel flow? I don't need ultimate precision.
Any claim worth debunking claims BIG reductions in fuel consumption.

There's also an issue of pulse-width modulation to reduce injector
heating. Sounds like this just reduces average current, but the
mechanical parts don't move during this interval. I can deal with
sorting that out in software.

What am I missing? Tips to improve accuracy without huge additional
complexity appreciated.

Remember, I'm not controlling anything or tuning an engine.
All I want to do is say, "turn on your gizmo and show me the
fuel flow drops to half," so I can get excited about your innovation.

I don't even own a vehicle new enough to have fuel injection
and the test car is not close to me. I'd like to start out
pretty close to right.

In article >, mike > wrote:
>In steady state, the rate of fuel flow should be linearly
>proportional to the open-time of an injector times the number
>of injection events/unit time.
>
>But it's an electromechanical system with short time elements.
>It takes time for the magnetic field to build/collapse and more
>time for the mechanical parts to move.
>
>In a symmetrical system, this would make the fuel flow time
>approximately equal to the pulse width, shifted by the delay.
>
>I don't understand the terminology, but I'm reading about
>a 1ms time that needs to be added to the pulse width, on average.
>I'm leaving out all the complexity of voltage corrections and
>assuming the fuel pressure regulator is working.

Assuming the fuel pressure regulator is working PERFECTLY. Which in the
real world it doesn't; fuel pressure varies substantially between idle
and highway driving.

>If I measure the pulse width and subtract 1ms, will I get a reasonable
>measure of relative fuel flow? I don't need ultimate precision.
>Any claim worth debunking claims BIG reductions in fuel consumption.

Under similar driving conditions, yes.

>There's also an issue of pulse-width modulation to reduce injector
>heating. Sounds like this just reduces average current, but the
>mechanical parts don't move during this interval. I can deal with
>sorting that out in software.

Right, you can still tell where the thing opens and closes.

>Remember, I'm not controlling anything or tuning an engine.
>All I want to do is say, "turn on your gizmo and show me the
>fuel flow drops to half," so I can get excited about your innovation.
>
>I don't even own a vehicle new enough to have fuel injection
>and the test car is not close to me. I'd like to start out
>pretty close to right.

If you have a carb, you can just stick a flow sensor in the fuel line and
be done with it. That's even easier... one sensor and a meter movement.
--scott
--
"C'est un Nagra. C'est suisse, et tres, tres precis."

Scott Dorsey wrote:
> In article >, mike > wrote:
>> In steady state, the rate of fuel flow should be linearly
>> proportional to the open-time of an injector times the number
>> of injection events/unit time.
>>
>> But it's an electromechanical system with short time elements.
>> It takes time for the magnetic field to build/collapse and more
>> time for the mechanical parts to move.
>>
>> In a symmetrical system, this would make the fuel flow time
>> approximately equal to the pulse width, shifted by the delay.
>>
>> I don't understand the terminology, but I'm reading about
>> a 1ms time that needs to be added to the pulse width, on average.
>> I'm leaving out all the complexity of voltage corrections and
>> assuming the fuel pressure regulator is working.
>
> Assuming the fuel pressure regulator is working PERFECTLY. Which in the
> real world it doesn't; fuel pressure varies substantially between idle
> and highway driving.
>
>> If I measure the pulse width and subtract 1ms, will I get a reasonable
>> measure of relative fuel flow? I don't need ultimate precision.
>> Any claim worth debunking claims BIG reductions in fuel consumption.
>
> Under similar driving conditions, yes.
>
>> There's also an issue of pulse-width modulation to reduce injector
>> heating. Sounds like this just reduces average current, but the
>> mechanical parts don't move during this interval. I can deal with
>> sorting that out in software.
>
> Right, you can still tell where the thing opens and closes.
>
>> Remember, I'm not controlling anything or tuning an engine.
>> All I want to do is say, "turn on your gizmo and show me the
>> fuel flow drops to half," so I can get excited about your innovation.
>>
>> I don't even own a vehicle new enough to have fuel injection
>> and the test car is not close to me. I'd like to start out
>> pretty close to right.
>
> If you have a carb, you can just stick a flow sensor in the fuel line and
> be done with it. That's even easier... one sensor and a meter movement.
> --scott
I don't think we're communicating.
It's NOT my car.
The fuel fittings on that Honda were non-standard. Obvious way to install
a flow meter is to cut the hose. And it's not my car.
Looked like hooking a wire to the injector would solve the problem
I have...If I get the algorithm approximately right.

Having said that, do you have a recommendation for a cheap
flow meter that works over the range of flows we have here...
and is gasoline and alcohol resistant?
Maybe I can talk the owner to installing one so he can calculate
actual MPG.
Thanks, mike

mike wrote:
>
> Scott Dorsey wrote:
> > In article >, mike > wrote:
> >> In steady state, the rate of fuel flow should be linearly
> >> proportional to the open-time of an injector times the number
> >> of injection events/unit time.
> >>
> >> But it's an electromechanical system with short time elements.
> >> It takes time for the magnetic field to build/collapse and more
> >> time for the mechanical parts to move.
> >>
> >> In a symmetrical system, this would make the fuel flow time
> >> approximately equal to the pulse width, shifted by the delay.
> >>
> >> I don't understand the terminology, but I'm reading about
> >> a 1ms time that needs to be added to the pulse width, on average.
> >> I'm leaving out all the complexity of voltage corrections and
> >> assuming the fuel pressure regulator is working.
> >
> > Assuming the fuel pressure regulator is working PERFECTLY. Which in the
> > real world it doesn't; fuel pressure varies substantially between idle
> > and highway driving.
> >
> >> If I measure the pulse width and subtract 1ms, will I get a reasonable
> >> measure of relative fuel flow? I don't need ultimate precision.
> >> Any claim worth debunking claims BIG reductions in fuel consumption.
> >
> > Under similar driving conditions, yes.
> >
> >> There's also an issue of pulse-width modulation to reduce injector
> >> heating. Sounds like this just reduces average current, but the
> >> mechanical parts don't move during this interval. I can deal with
> >> sorting that out in software.
> >
> > Right, you can still tell where the thing opens and closes.
> >
> >> Remember, I'm not controlling anything or tuning an engine.
> >> All I want to do is say, "turn on your gizmo and show me the
> >> fuel flow drops to half," so I can get excited about your innovation.
> >>
> >> I don't even own a vehicle new enough to have fuel injection
> >> and the test car is not close to me. I'd like to start out
> >> pretty close to right.
> >
> > If you have a carb, you can just stick a flow sensor in the fuel line and
> > be done with it. That's even easier... one sensor and a meter movement.
> > --scott
> I don't think we're communicating.
> It's NOT my car.
> The fuel fittings on that Honda were non-standard. Obvious way to install
> a flow meter is to cut the hose. And it's not my car.
> Looked like hooking a wire to the injector would solve the problem
> I have...If I get the algorithm approximately right.
>
> Having said that, do you have a recommendation for a cheap
> flow meter that works over the range of flows we have here...
> and is gasoline and alcohol resistant?
> Maybe I can talk the owner to installing one so he can calculate
> actual MPG.

What is a flow meter going to tell you? If you take your foot off the
gas the flow will decrease and if you step down on the gas the flow
will increase. What conclusions are you going to draw from that
information?

Accurately measuring the amount of fuel consumed in 80 miles of typical
driving would be a more meaningful way to determine mpg.

-jim

-jim


> Thanks, mike

mike wrote:
> I need to measure relative fuel consumption.
> Backstory...
> I have friends interested in energy efficiency.
> "Something-for-nothing" transportation is a favorite
> topic (of theirs).
> I was asked to go look at a car with a gizmo
> added to improve fuel efficiency.
> The guy was all bubbly about his modifications.
> I asked to see some data.
> His answer was typical:
> "I filled her up, drove her 80 miles, filled her
> up again at a different station. WOW, I got
> 60MPG."
> I asked why he didn't use a fuel flow meter.
> Answer was again typical, "what's a flow meter?"
>
> I firmly embrace "conservation of energy", but
> everything ever invented was impossible before
> it was invented. I'd like to keep an open mind
> (and keep my friends happy)
> that there might be some as-yet undiscovered synergistic effects
> that improve overall efficiency without violating
> the basic principles of thermodynamics we know today.
>
> Since most claims are bogus, a quick means to debunk
> them is in order.
>
> Adding a fuel flow meter is rather invasive, so
> I'm looking at ways to measure RELATIVE fuel flow
> non-invasively.
>
> I know nothing about the technology past what I learned
> in a few hours of googling.
>
> In steady state, the rate of fuel flow should be linearly
> proportional to the open-time of an injector times the number
> of injection events/unit time.
>
> But it's an electromechanical system with short time elements.
> It takes time for the magnetic field to build/collapse and more
> time for the mechanical parts to move.
>
> In a symmetrical system, this would make the fuel flow time
> approximately equal to the pulse width, shifted by the delay.
>
> I don't understand the terminology, but I'm reading about
> a 1ms time that needs to be added to the pulse width, on average.
> I'm leaving out all the complexity of voltage corrections and
> assuming the fuel pressure regulator is working.
>
> If I measure the pulse width and subtract 1ms, will I get a reasonable
> measure of relative fuel flow? I don't need ultimate precision.
> Any claim worth debunking claims BIG reductions in fuel consumption.
>
> There's also an issue of pulse-width modulation to reduce injector
> heating. Sounds like this just reduces average current, but the
> mechanical parts don't move during this interval. I can deal with
> sorting that out in software.
>
> What am I missing? Tips to improve accuracy without huge additional
> complexity appreciated.
>
> Remember, I'm not controlling anything or tuning an engine.
> All I want to do is say, "turn on your gizmo and show me the
> fuel flow drops to half," so I can get excited about your innovation.
>
> I don't even own a vehicle new enough to have fuel injection
> and the test car is not close to me. I'd like to start out
> pretty close to right.


Flow meter and injector signal will tell you nothing useful unless the
vehicle is in a closed environment like a dyno room and you can
duplicate the same drive cycles every time. Then you could actually
measure the devices impact.
Then you use an accurate measurement of the weight of fuel used over time.

However I also doubt the results your pals saw are real. Just not
possible for some add-on item to give that result on a modern computer
controlled vehicle. UNLESS they drove downhill with the engine off.

Take a look at the EPAs testing of some of these "gas savers" and you
will discover that none of them make a measurable increase in mileage on
a modern vehicle.

http://www.epa.gov/oms/consumer/reports.htm

additives:
http://www.epa.gov/otaq/consumer/420f09013.htm




--
Steve W.

jim wrote:
> mike wrote:
>> Scott Dorsey wrote:
>>> In article >, mike > wrote:
>>>> In steady state, the rate of fuel flow should be linearly
>>>> proportional to the open-time of an injector times the number
>>>> of injection events/unit time.
>>>>
>>>> But it's an electromechanical system with short time elements.
>>>> It takes time for the magnetic field to build/collapse and more
>>>> time for the mechanical parts to move.
>>>>
>>>> In a symmetrical system, this would make the fuel flow time
>>>> approximately equal to the pulse width, shifted by the delay.
>>>>
>>>> I don't understand the terminology, but I'm reading about
>>>> a 1ms time that needs to be added to the pulse width, on average.
>>>> I'm leaving out all the complexity of voltage corrections and
>>>> assuming the fuel pressure regulator is working.
>>> Assuming the fuel pressure regulator is working PERFECTLY. Which in the
>>> real world it doesn't; fuel pressure varies substantially between idle
>>> and highway driving.
>>>
>>>> If I measure the pulse width and subtract 1ms, will I get a reasonable
>>>> measure of relative fuel flow? I don't need ultimate precision.
>>>> Any claim worth debunking claims BIG reductions in fuel consumption.
>>> Under similar driving conditions, yes.
>>>
>>>> There's also an issue of pulse-width modulation to reduce injector
>>>> heating. Sounds like this just reduces average current, but the
>>>> mechanical parts don't move during this interval. I can deal with
>>>> sorting that out in software.
>>> Right, you can still tell where the thing opens and closes.
>>>
>>>> Remember, I'm not controlling anything or tuning an engine.
>>>> All I want to do is say, "turn on your gizmo and show me the
>>>> fuel flow drops to half," so I can get excited about your innovation.
>>>>
>>>> I don't even own a vehicle new enough to have fuel injection
>>>> and the test car is not close to me. I'd like to start out
>>>> pretty close to right.
>>> If you have a carb, you can just stick a flow sensor in the fuel line and
>>> be done with it. That's even easier... one sensor and a meter movement.
>>> --scott
>> I don't think we're communicating.
>> It's NOT my car.
>> The fuel fittings on that Honda were non-standard. Obvious way to install
>> a flow meter is to cut the hose. And it's not my car.
>> Looked like hooking a wire to the injector would solve the problem
>> I have...If I get the algorithm approximately right.
>>
>> Having said that, do you have a recommendation for a cheap
>> flow meter that works over the range of flows we have here...
>> and is gasoline and alcohol resistant?
>> Maybe I can talk the owner to installing one so he can calculate
>> actual MPG.
>
> What is a flow meter going to tell you?

Drive down the road at 55mph.
Read the fuel flow.
Switch on the magic device.
Read the fuel flow.
The MPG number is irrelevant. The question to
be answered is, "Did the magic device reduce fuel consumption?"
Sounds pretty simple to me. And a lot more reliable.
Instant debunker!!!
What am I missing???

There's some question whether the injector pulse width is a repeatable
measure of fuel rate over a wide range of operating conditions.
If it is, you can just add up the pulse widths to get the volume
and divide into the miles which can be determined from the pulse count
if you stay in the same gear, or the odometer if you don't.

Yes, calibration would be required if you cared. I don't.
It's quick debunking that I'm after.

If you take your foot off the
> gas the flow will decrease and if you step down on the gas the flow
> will increase. What conclusions are you going to draw from that
> information?
>
> Accurately measuring the amount of fuel consumed in 80 miles of typical
> driving would be a more meaningful way to determine mpg.

OK, how do you do that without modifying the vehicle?

People try to do that all the time by reading the pump
when they fill their tank. Averaged over several tanks
with the initial and final fills at the same pump may
be useful...just not quick. Doing it for two gallons on an
80 mile trip with fills at different stations is not useful.

And what do you consider typical? Changes in driving habits
can easily mask changes in efficiency. I've had some smart people tell
me how
some gizmo improved their gas mileage 10%.

I asked again six months later. The improvement disappeared when they
stopped
thinking about it and subconsciously driving less aggressively.

Whodathunkit? Putting a holographic sympathetic resonance enhancer
sticker on your gas tank doesn't improve gas mileage.

>
> -jim
>
> -jim
>
>
>> Thanks, mike

mike wrote:
> jim wrote:
>> mike wrote:
>>> Scott Dorsey wrote:
>>>> In article >, mike >
>>>> wrote:
>>>>> In steady state, the rate of fuel flow should be linearly
>>>>> proportional to the open-time of an injector times the number
>>>>> of injection events/unit time.
>>>>>
>>>>> But it's an electromechanical system with short time elements.
>>>>> It takes time for the magnetic field to build/collapse and more
>>>>> time for the mechanical parts to move.
>>>>>
>>>>> In a symmetrical system, this would make the fuel flow time
>>>>> approximately equal to the pulse width, shifted by the delay.
>>>>>
>>>>> I don't understand the terminology, but I'm reading about
>>>>> a 1ms time that needs to be added to the pulse width, on average.
>>>>> I'm leaving out all the complexity of voltage corrections and
>>>>> assuming the fuel pressure regulator is working.
>>>> Assuming the fuel pressure regulator is working PERFECTLY. Which in
>>>> the
>>>> real world it doesn't; fuel pressure varies substantially between idle
>>>> and highway driving.
>>>>
>>>>> If I measure the pulse width and subtract 1ms, will I get a reasonable
>>>>> measure of relative fuel flow? I don't need ultimate precision.
>>>>> Any claim worth debunking claims BIG reductions in fuel consumption.
>>>> Under similar driving conditions, yes.
>>>>
>>>>> There's also an issue of pulse-width modulation to reduce injector
>>>>> heating. Sounds like this just reduces average current, but the
>>>>> mechanical parts don't move during this interval. I can deal with
>>>>> sorting that out in software.
>>>> Right, you can still tell where the thing opens and closes.
>>>>
>>>>> Remember, I'm not controlling anything or tuning an engine.
>>>>> All I want to do is say, "turn on your gizmo and show me the
>>>>> fuel flow drops to half," so I can get excited about your innovation.
>>>>>
>>>>> I don't even own a vehicle new enough to have fuel injection
>>>>> and the test car is not close to me. I'd like to start out
>>>>> pretty close to right.
>>>> If you have a carb, you can just stick a flow sensor in the fuel
>>>> line and
>>>> be done with it. That's even easier... one sensor and a meter
>>>> movement.
>>>> --scott
>>> I don't think we're communicating.
>>> It's NOT my car.
>>> The fuel fittings on that Honda were non-standard. Obvious way to
>>> install
>>> a flow meter is to cut the hose. And it's not my car.
>>> Looked like hooking a wire to the injector would solve the problem
>>> I have...If I get the algorithm approximately right.
>>>
>>> Having said that, do you have a recommendation for a cheap
>>> flow meter that works over the range of flows we have here...
>>> and is gasoline and alcohol resistant?
>>> Maybe I can talk the owner to installing one so he can calculate
>>> actual MPG.
>>
>> What is a flow meter going to tell you?
>
> Drive down the road at 55mph.
> Read the fuel flow.
> Switch on the magic device.
> Read the fuel flow.
> The MPG number is irrelevant. The question to
> be answered is, "Did the magic device reduce fuel consumption?"
> Sounds pretty simple to me. And a lot more reliable.
> Instant debunker!!!
> What am I missing???
>
> There's some question whether the injector pulse width is a repeatable
> measure of fuel rate over a wide range of operating conditions.
> If it is, you can just add up the pulse widths to get the volume
> and divide into the miles which can be determined from the pulse count
> if you stay in the same gear, or the odometer if you don't.
>
> Yes, calibration would be required if you cared. I don't.
> It's quick debunking that I'm after.
>
> If you take your foot off the
>> gas the flow will decrease and if you step down on the gas the flow
>> will increase. What conclusions are you going to draw from that
>> information?
>>
>> Accurately measuring the amount of fuel consumed in 80 miles of typical
>> driving would be a more meaningful way to determine mpg.
>
> OK, how do you do that without modifying the vehicle?

Well the easy way would be to hook a decent scan tool up and see what
percentage the fuel tank reads. Fill up the tank so the reading is say
90%. Zero the trip meter. Drive around till you hit 80-100 miles. Read
the percentage left and the mileage. Refill back to the original level.
Zero out and drive some more. See what the difference is.

The problem is that unless you drive the exact same way, under the same
conditions using the same gas you won't get accurate results.

Why?
Different additives and base stocks between supplies/stations/
If the air temps are different the readings will be different due to the
air density difference.
Unless you do the driving over the same route every time and using the
same throttle levels the results will be wrong.


>
> People try to do that all the time by reading the pump
> when they fill their tank. Averaged over several tanks
> with the initial and final fills at the same pump may
> be useful...just not quick. Doing it for two gallons on an
> 80 mile trip with fills at different stations is not useful.

Correct. But that is what you seem to think the flow meter will allow.
When it will not.
The first method is shown to work and be reliable.

>
> And what do you consider typical? Changes in driving habits
> can easily mask changes in efficiency. I've had some smart people tell
> me how
> some gizmo improved their gas mileage 10%.

Which is why you don't test with a human driver. You test using a dyno
and a computer controlling the vehicle.

>
> I asked again six months later. The improvement disappeared when they
> stopped
> thinking about it and subconsciously driving less aggressively.
>
> Whodathunkit? Putting a holographic sympathetic resonance enhancer
> sticker on your gas tank doesn't improve gas mileage.
>
>>
>> -jim
>>
>> -jim
>>
>>
>>> Thanks, mike


--
Steve W.

Steve W. wrote:
> mike wrote:
>> jim wrote:
>>> mike wrote:
>>>> Scott Dorsey wrote:
>>>>> In article >, mike >
>>>>> wrote:
>>>>>> In steady state, the rate of fuel flow should be linearly
>>>>>> proportional to the open-time of an injector times the number
>>>>>> of injection events/unit time.
>>>>>>
>>>>>> But it's an electromechanical system with short time elements.
>>>>>> It takes time for the magnetic field to build/collapse and more
>>>>>> time for the mechanical parts to move.
>>>>>>
>>>>>> In a symmetrical system, this would make the fuel flow time
>>>>>> approximately equal to the pulse width, shifted by the delay.
>>>>>>
>>>>>> I don't understand the terminology, but I'm reading about
>>>>>> a 1ms time that needs to be added to the pulse width, on average.
>>>>>> I'm leaving out all the complexity of voltage corrections and
>>>>>> assuming the fuel pressure regulator is working.
>>>>> Assuming the fuel pressure regulator is working PERFECTLY. Which
>>>>> in the
>>>>> real world it doesn't; fuel pressure varies substantially between idle
>>>>> and highway driving.
>>>>>
>>>>>> If I measure the pulse width and subtract 1ms, will I get a
>>>>>> reasonable
>>>>>> measure of relative fuel flow? I don't need ultimate precision.
>>>>>> Any claim worth debunking claims BIG reductions in fuel consumption.
>>>>> Under similar driving conditions, yes.
>>>>>
>>>>>> There's also an issue of pulse-width modulation to reduce injector
>>>>>> heating. Sounds like this just reduces average current, but the
>>>>>> mechanical parts don't move during this interval. I can deal with
>>>>>> sorting that out in software.
>>>>> Right, you can still tell where the thing opens and closes.
>>>>>
>>>>>> Remember, I'm not controlling anything or tuning an engine.
>>>>>> All I want to do is say, "turn on your gizmo and show me the
>>>>>> fuel flow drops to half," so I can get excited about your innovation.
>>>>>>
>>>>>> I don't even own a vehicle new enough to have fuel injection
>>>>>> and the test car is not close to me. I'd like to start out
>>>>>> pretty close to right.
>>>>> If you have a carb, you can just stick a flow sensor in the fuel
>>>>> line and
>>>>> be done with it. That's even easier... one sensor and a meter
>>>>> movement.
>>>>> --scott
>>>> I don't think we're communicating.
>>>> It's NOT my car.
>>>> The fuel fittings on that Honda were non-standard. Obvious way to
>>>> install
>>>> a flow meter is to cut the hose. And it's not my car.
>>>> Looked like hooking a wire to the injector would solve the problem
>>>> I have...If I get the algorithm approximately right.
>>>>
>>>> Having said that, do you have a recommendation for a cheap
>>>> flow meter that works over the range of flows we have here...
>>>> and is gasoline and alcohol resistant?
>>>> Maybe I can talk the owner to installing one so he can calculate
>>>> actual MPG.
>>>
>>> What is a flow meter going to tell you?
>>
>> Drive down the road at 55mph.
>> Read the fuel flow.
>> Switch on the magic device.
>> Read the fuel flow.
>> The MPG number is irrelevant. The question to
>> be answered is, "Did the magic device reduce fuel consumption?"
>> Sounds pretty simple to me. And a lot more reliable.
>> Instant debunker!!!
>> What am I missing???
>>
>> There's some question whether the injector pulse width is a repeatable
>> measure of fuel rate over a wide range of operating conditions.
>> If it is, you can just add up the pulse widths to get the volume
>> and divide into the miles which can be determined from the pulse count
>> if you stay in the same gear, or the odometer if you don't.
>>
>> Yes, calibration would be required if you cared. I don't.
>> It's quick debunking that I'm after.
>>
>> If you take your foot off the
>>> gas the flow will decrease and if you step down on the gas the flow
>>> will increase. What conclusions are you going to draw from that
>>> information?
>>>
>>> Accurately measuring the amount of fuel consumed in 80 miles of typical
>>> driving would be a more meaningful way to determine mpg.
>>
>> OK, how do you do that without modifying the vehicle?
>
> Well the easy way would be to hook a decent scan tool up and see what
> percentage the fuel tank reads.

Interesting.
What's the accuracy of the fuel readout?
Do I need to obtain a different scan tool for every vehicle I want to
check?

Fill up the tank so the reading is say
> 90%. Zero the trip meter. Drive around till you hit 80-100 miles. Read
> the percentage left and the mileage. Refill back to the original level.
> Zero out and drive some more. See what the difference is.
>
> The problem is that unless you drive the exact same way, under the same
> conditions using the same gas you won't get accurate results.
>
> Why?
> Different additives and base stocks between supplies/stations/
> If the air temps are different the readings will be different due to the
> air density difference.
> Unless you do the driving over the same route every time and using the
> same throttle levels the results will be wrong.
>
>
>>
>> People try to do that all the time by reading the pump
>> when they fill their tank. Averaged over several tanks
>> with the initial and final fills at the same pump may
>> be useful...just not quick. Doing it for two gallons on an
>> 80 mile trip with fills at different stations is not useful.
>
> Correct. But that is what you seem to think the flow meter will allow.
> When it will not.

Please elaborate on why the flow meter won't measure FLOW.
While I'm waiting for that answer, I'll jump ahead...

Assuming I really do want to measure flow, I'm asking
if measuring the injector pulse width and frequency and
applying some math won't give me RELATIVE data that's almost as
good as an inline mechanical flow meter. All I gotta do is
clamp a current transformer on an injector wire.

IFF the injector injects some number of microliters per
microsquirt-millisecond,
(And IFF is the question)
why can't we just add up all those microsquirt-milliseconds
and learn the total microliters in real time, big time, 4-4 time
or any other time we want???
For my purposes, what I want to know is the rate of fuel
consumption right now, in real-time.

When I did the math, most of the terms canceled out.
For a fixed gear ratio, with the clutch out,
Gallons/Mile is directly proportional to the width of the
injector squirt. If you drive twice as fast, you get
twice as many squirts, but travel twice as far.
Only variable remaining is the width of the injector
pulse (assuming the squirt volume is directly related to pulse width).
Yes? NO?
Sounds WAY too simple, but that's what my math sez.

> The first method is shown to work and be reliable.
>
>>
>> And what do you consider typical? Changes in driving habits
>> can easily mask changes in efficiency. I've had some smart people
>> tell me how
>> some gizmo improved their gas mileage 10%.
>
> Which is why you don't test with a human driver. You test using a dyno
> and a computer controlling the vehicle.

We're getting way off track. All I wanted was a reasonably
repeatable method to measure fuel flow in real time without
spending any money or modifying the vehicle or buying any specialized
equipment.

Turn on your gizmo, maintain same speed, does the fuel consumption go
down? Simple! Doesn't cover all driving conditions, but with a few
tests under different repeatable conditions, it should be relatively
easy to convince an enthusiast that his gizmo ain't workin'.
>
>>
>> I asked again six months later. The improvement disappeared when they
>> stopped
>> thinking about it and subconsciously driving less aggressively.
>>
>> Whodathunkit? Putting a holographic sympathetic resonance enhancer
>> sticker on your gas tank doesn't improve gas mileage.
>>
>>>
>>> -jim
>>>
>>> -jim
>>>
>>>
>>>> Thanks, mike
>
>

mike wrote:
> Steve W. wrote:
>> mike wrote:
>>> jim wrote:
>>>> mike wrote:
>>>>> Scott Dorsey wrote:
>>>>>> In article >, mike >
>>>>>> wrote:
>>>>>>> In steady state, the rate of fuel flow should be linearly
>>>>>>> proportional to the open-time of an injector times the number
>>>>>>> of injection events/unit time.
>>>>>>>
>>>>>>> But it's an electromechanical system with short time elements.
>>>>>>> It takes time for the magnetic field to build/collapse and more
>>>>>>> time for the mechanical parts to move.
>>>>>>>
>>>>>>> In a symmetrical system, this would make the fuel flow time
>>>>>>> approximately equal to the pulse width, shifted by the delay.
>>>>>>>
>>>>>>> I don't understand the terminology, but I'm reading about
>>>>>>> a 1ms time that needs to be added to the pulse width, on average.
>>>>>>> I'm leaving out all the complexity of voltage corrections and
>>>>>>> assuming the fuel pressure regulator is working.
>>>>>> Assuming the fuel pressure regulator is working PERFECTLY. Which
>>>>>> in the
>>>>>> real world it doesn't; fuel pressure varies substantially between
>>>>>> idle
>>>>>> and highway driving.
>>>>>>
>>>>>>> If I measure the pulse width and subtract 1ms, will I get a
>>>>>>> reasonable
>>>>>>> measure of relative fuel flow? I don't need ultimate precision.
>>>>>>> Any claim worth debunking claims BIG reductions in fuel consumption.
>>>>>> Under similar driving conditions, yes.
>>>>>>
>>>>>>> There's also an issue of pulse-width modulation to reduce injector
>>>>>>> heating. Sounds like this just reduces average current, but the
>>>>>>> mechanical parts don't move during this interval. I can deal with
>>>>>>> sorting that out in software.
>>>>>> Right, you can still tell where the thing opens and closes.
>>>>>>
>>>>>>> Remember, I'm not controlling anything or tuning an engine.
>>>>>>> All I want to do is say, "turn on your gizmo and show me the
>>>>>>> fuel flow drops to half," so I can get excited about your
>>>>>>> innovation.
>>>>>>>
>>>>>>> I don't even own a vehicle new enough to have fuel injection
>>>>>>> and the test car is not close to me. I'd like to start out
>>>>>>> pretty close to right.
>>>>>> If you have a carb, you can just stick a flow sensor in the fuel
>>>>>> line and
>>>>>> be done with it. That's even easier... one sensor and a meter
>>>>>> movement.
>>>>>> --scott
>>>>> I don't think we're communicating.
>>>>> It's NOT my car.
>>>>> The fuel fittings on that Honda were non-standard. Obvious way to
>>>>> install
>>>>> a flow meter is to cut the hose. And it's not my car.
>>>>> Looked like hooking a wire to the injector would solve the problem
>>>>> I have...If I get the algorithm approximately right.
>>>>>
>>>>> Having said that, do you have a recommendation for a cheap
>>>>> flow meter that works over the range of flows we have here...
>>>>> and is gasoline and alcohol resistant?
>>>>> Maybe I can talk the owner to installing one so he can calculate
>>>>> actual MPG.
>>>>
>>>> What is a flow meter going to tell you?
>>>
>>> Drive down the road at 55mph.
>>> Read the fuel flow.
>>> Switch on the magic device.
>>> Read the fuel flow.
>>> The MPG number is irrelevant. The question to
>>> be answered is, "Did the magic device reduce fuel consumption?"
>>> Sounds pretty simple to me. And a lot more reliable.
>>> Instant debunker!!!
>>> What am I missing???
>>>
>>> There's some question whether the injector pulse width is a repeatable
>>> measure of fuel rate over a wide range of operating conditions.
>>> If it is, you can just add up the pulse widths to get the volume
>>> and divide into the miles which can be determined from the pulse count
>>> if you stay in the same gear, or the odometer if you don't.
>>>
>>> Yes, calibration would be required if you cared. I don't.
>>> It's quick debunking that I'm after.
>>>
>>> If you take your foot off the
>>>> gas the flow will decrease and if you step down on the gas the flow
>>>> will increase. What conclusions are you going to draw from that
>>>> information?
>>>>
>>>> Accurately measuring the amount of fuel consumed in 80 miles of typical
>>>> driving would be a more meaningful way to determine mpg.
>>>
>>> OK, how do you do that without modifying the vehicle?
>>
>> Well the easy way would be to hook a decent scan tool up and see what
>> percentage the fuel tank reads.
>
> Interesting.
> What's the accuracy of the fuel readout?
> Do I need to obtain a different scan tool for every vehicle I want to
> check?

Not if the vehicle is OBD II or CAN or newer. Fuel level is as accurate
as the sender unit in the tank. As long as the vehicle orientation is
the same it will read the same.

>
> Fill up the tank so the reading is say
>> 90%. Zero the trip meter. Drive around till you hit 80-100 miles. Read
>> the percentage left and the mileage. Refill back to the original
>> level. Zero out and drive some more. See what the difference is.
>>
>> The problem is that unless you drive the exact same way, under the
>> same conditions using the same gas you won't get accurate results.
>>
>> Why?
>> Different additives and base stocks between supplies/stations/
>> If the air temps are different the readings will be different due to
>> the air density difference.
>> Unless you do the driving over the same route every time and using the
>> same throttle levels the results will be wrong.
>>
>>
>>>
>>> People try to do that all the time by reading the pump
>>> when they fill their tank. Averaged over several tanks
>>> with the initial and final fills at the same pump may
>>> be useful...just not quick. Doing it for two gallons on an
>>> 80 mile trip with fills at different stations is not useful.
>>
>> Correct. But that is what you seem to think the flow meter will allow.
>> When it will not.
>
> Please elaborate on why the flow meter won't measure FLOW.
> While I'm waiting for that answer, I'll jump ahead...

The flow reading is WORTHLESS, Very few systems run dead headed, They
run with an open loop through the system.

Fuel comes from the pump up the line, into the fuel rail and out through
the fuel pressure regulator and back to the tank through the return
line. The injectors use a portion of the fuel coming through the system.

>
> Assuming I really do want to measure flow, I'm asking
> if measuring the injector pulse width and frequency and
> applying some math won't give me RELATIVE data that's almost as
> good as an inline mechanical flow meter. All I gotta do is
> clamp a current transformer on an injector wire.

That is the same basic idea that most of the instant mileage readouts
use. However the ECM that does the calculations uses all the sensors on
the vehicle as data inputs to compare against the map programming and
load of the vehicle. The problem is that those maps are not going to be
easy to find, and you cannot just guess at them.

>
> IFF the injector injects some number of microliters per
> microsquirt-millisecond,
> (And IFF is the question)
> why can't we just add up all those microsquirt-milliseconds
> and learn the total microliters in real time, big time, 4-4 time
> or any other time we want???
> For my purposes, what I want to know is the rate of fuel
> consumption right now, in real-time.

Then grab a vehicle that has that built in and test using it. Adding it
to a vehicle that doesn't have it can be done IF the ECM supports it.
BUT even then the instant readouts are a joke. The only true number is
an average over time. That is the only real way to tell if there is a
difference.

Take a look at the testing that was done on the electronic gimmick on
the EPA site. Note how they were told that they didn't test it correctly
and that they didn't follow the directions because they used it on a
newer vehicle. So they went out, found older vehicles and followed
everything that the maker said they needed to do. The thing still didn't
work.

>
> When I did the math, most of the terms canceled out.
> For a fixed gear ratio, with the clutch out,
> Gallons/Mile is directly proportional to the width of the
> injector squirt. If you drive twice as fast, you get
> twice as many squirts, but travel twice as far.
> Only variable remaining is the width of the injector
> pulse (assuming the squirt volume is directly related to pulse width).
> Yes? NO?
> Sounds WAY too simple, but that's what my math sez.

And it is way to simple. When you test an injector for flow you use a
pulsed current to open the injector, then you use the known pressure on
the rail, viscosity index of the test fluid (usually something like
stoddard solvent) and a very accurate timer.
In your case you will only know the pulse width (which changes EVERY
time the injector fires) You won't know the fuel pressure unless you
install a gauge.

>
>> The first method is shown to work and be reliable.
>>
>>>
>>> And what do you consider typical? Changes in driving habits
>>> can easily mask changes in efficiency. I've had some smart people
>>> tell me how
>>> some gizmo improved their gas mileage 10%.
>>
>> Which is why you don't test with a human driver. You test using a dyno
>> and a computer controlling the vehicle.
>
> We're getting way off track. All I wanted was a reasonably
> repeatable method to measure fuel flow in real time without
> spending any money or modifying the vehicle or buying any specialized
> equipment.

Then you go with the scan tool. Fill up to a set amount, drive around
and back to the start, record the fuel used, repeat a few times so you
know whet the vehicle gets for an average. Then repeat the process with
the gadget in place.
There is NO quick and repeatable method that is also free or devoid of
modifications.

You are asking for the same thing that you derided your pals of
"something for nothing"

>
> Turn on your gizmo, maintain same speed, does the fuel consumption go
> down? Simple! Doesn't cover all driving conditions, but with a few
> tests under different repeatable conditions, it should be relatively
> easy to convince an enthusiast that his gizmo ain't workin'.

Not really. Most of these people will come at you and tell you that
YOU'RE just not testing it correctly.
Or that it takes more than one tank to work, Or that you are not using
it correctly.

Why? Because they KNOW that it works for them...

>>
>>>
>>> I asked again six months later. The improvement disappeared when
>>> they stopped
>>> thinking about it and subconsciously driving less aggressively.
>>>
>>> Whodathunkit? Putting a holographic sympathetic resonance enhancer
>>> sticker on your gas tank doesn't improve gas mileage.
>>>
>>>>
>>>> -jim
>>>>
>>>> -jim
>>>>
>>>>
>>>>> Thanks, mike
>>
>>


--
Steve W.

mike wrote:

> > What is a flow meter going to tell you?
>
> Drive down the road at 55mph.
> Read the fuel flow.
> Switch on the magic device.
> Read the fuel flow.
> The MPG number is irrelevant. The question to
> be answered is, "Did the magic device reduce fuel consumption?"
> Sounds pretty simple to me. And a lot more reliable.
> Instant debunker!!!
> What am I missing???

That would work great if getting better fuel economy was something
that can be "switched on"

It's not like you can flip a switch and your BMW becomes a Prius

-jim

>
> There's some question whether the injector pulse width is a repeatable
> measure of fuel rate over a wide range of operating conditions.
> If it is, you can just add up the pulse widths to get the volume
> and divide into the miles which can be determined from the pulse count
> if you stay in the same gear, or the odometer if you don't.
>
> Yes, calibration would be required if you cared. I don't.
> It's quick debunking that I'm after.
>
> If you take your foot off the
> > gas the flow will decrease and if you step down on the gas the flow
> > will increase. What conclusions are you going to draw from that
> > information?
> >
> > Accurately measuring the amount of fuel consumed in 80 miles of typical
> > driving would be a more meaningful way to determine mpg.
>
> OK, how do you do that without modifying the vehicle?
>
> People try to do that all the time by reading the pump
> when they fill their tank. Averaged over several tanks
> with the initial and final fills at the same pump may
> be useful...just not quick. Doing it for two gallons on an
> 80 mile trip with fills at different stations is not useful.
>
> And what do you consider typical? Changes in driving habits
> can easily mask changes in efficiency. I've had some smart people tell
> me how
> some gizmo improved their gas mileage 10%.
>
> I asked again six months later. The improvement disappeared when they
> stopped
> thinking about it and subconsciously driving less aggressively.
>
> Whodathunkit? Putting a holographic sympathetic resonance enhancer
> sticker on your gas tank doesn't improve gas mileage.
>
> >
> > -jim
> >
> > -jim
> >
> >
> >> Thanks, mike