Gas consumption idea??

[JojoJaro]

On Diesels, the fuel pump (AKA Lift Pump) delivers the maximum fuel rate the engine could possibly need all the time. The IP (sometimes AKA High Pressure Pump) regulates the fuel flow to the injectors and returns the excess. The injectors themselves also return the extra fuel it does not need. (I suspect this is true for fuel-injected gas engines also. For carb engines, I don't know.)

To accurately measure fuel consumption in all conditions, you need to measure the feed flow and subtract the return flow. If your flow meters are accurate, you should get a steady-state fuel rate consumption. Instantaneous fuel rate consumption might still be a little tricky since it takes a little lag for the return flow to keep up with fuel consumption.

On the other hand, vehicles with OBDII already has many of this information. You can retrieve this info and calculate you instataneous MPG. This is how a ScanGauge works.

[Phantom240]

On Diesels, the fuel pump (AKA Lift Pump) delivers the maximum fuel rate the engine could possibly need all the time. The IP (sometimes AKA High Pressure Pump) regulates the fuel flow to the injectors and returns the excess. The injectors themselves also return the extra fuel it does not need. (I suspect this is true for fuel-injected gas engines also. For carb engines, I don't know.)

To accurately measure fuel consumption in all conditions, you need to measure the feed flow and subtract the return flow. If your flow meters are accurate, you should get a steady-state fuel rate consumption. Instantaneous fuel rate consumption might still be a little tricky since it takes a little lag for the return flow to keep up with fuel consumption.

On the other hand, vehicles with OBDII already has many of this information. You can retrieve this info and calculate you instataneous MPG. This is how a ScanGauge works.

Well in a carburetor, you have a bowl where fuel is kept as it is siphoned into the motor, and though the fuel pump constantly feeds it, it doesn't overflow because it has a float like a toilet. When the float is up, the fuel bypasses the bowl. As the engine consumes the fuel in the bowl, the float goes down, and lets fuel back into the bowl.

[scribs212]

I just bought one of these, its a scanguage II, they're amazing for watching your fuel consumption and monitering all other engine paramiters. You can use it to read fuel mileage, as a trip odometer, cleanmpg.com is a great websight for all kinds of gas saving techniques that is user implimented(meaning controlling your foot). Hypermiling is amazing.

http://www.scangauge.com/

[jimbo40]

You just like to hear yourself talk or what?
Thanks again BoyntonStu

[BoyntonStu]

On Diesels, the fuel pump (AKA Lift Pump) delivers the maximum fuel rate the engine could possibly need all the time. The IP (sometimes AKA High Pressure Pump) regulates the fuel flow to the injectors and returns the excess. The injectors themselves also return the extra fuel it does not need. (I suspect this is true for fuel-injected gas engines also. For carb engines, I don't know.)

To accurately measure fuel consumption in all conditions, you need to measure the feed flow and subtract the return flow. If your flow meters are accurate, you should get a steady-state fuel rate consumption. Instantaneous fuel rate consumption might still be a little tricky since it takes a little lag for the return flow to keep up with fuel consumption.

On the other hand, vehicles with OBDII already has many of this information. You can retrieve this info and calculate you instataneous MPG. This is how a ScanGauge works.

Excellent information, thanks.

I was thinking out loud hoping for your response and explanation.

I never knew about the return gas.

Do you believe that the instant MPG gauge built into a car is accurate enough for the 10 mile test?

Is the ScanGauge any more accurate that the built in MPG gauge?

BoyntonStu

[timetowinarace]

In my opinion, if you want accurate fuel consumption rates, you have to use weight rather than volume. You have to bypass the stock fuel tank and use one you can remove and weigh. Not practical for most testers.

Electronics like the scangauge will give decent guesses on a short run. But anything other than the method above on a short run will be inaccurate. Even for the electronics, short run results are useless. Use a monthly average.

[BoyntonStu]

In my opinion, if you want accurate fuel consumption rates, you have to use weight rather than volume. You have to bypass the stock fuel tank and use one you can remove and weigh. Not practical for most testers.

Electronics like the scangauge will give decent guesses on a short run. But anything other than the method above on a short run will be inaccurate. Even for the electronics, short run results are useless. Use a monthly average.

Darn!

Wouldn't it be nice to be able to drive down the road diddling the controls for max MPG?

In my car there is an instant MPG gauge.

When I am driving with cruise control set at 65 and getting 29 MPG, when I begin to go uphill, the MPG instantaneously drops to about 22 MPG or so.

If I turn the cruise control off and coast uphill, the MPG will go even higher than 29 as the car slows down.

Wouldn't this information be useful for testing the Hydroxy effect?

BoyntonStu

[scirockett]

In my opinion, if you want accurate fuel consumption rates, you have to use weight rather than volume. You have to bypass the stock fuel tank and use one you can remove and weigh. Not practical for most testers.

Electronics like the scangauge will give decent guesses on a short run. But anything other than the method above on a short run will be inaccurate. Even for the electronics, short run results are useless. Use a monthly average.

Bingo. I'll second all of the above.

A carb'd motor is the only gas setup where an inline flow meter will be anything close to "accurate".. plus, watching friends burn thru 150 gal of fuel in their boat and find their fuel flow meter 10-15 gallons of is not assuring at all.. Since fuel injected motors will return fuel to the tank, the only other thing I thought about was rigging a seperate measurable tank, fuel pump, and accumulator in the cabin to monitor fuel consumption. otherwise weight is the only option.

code readers link scangauge are not close to accurate and cannot be used for this kind of testing. on the otherhand, stand alone setups can more accurately measure fuel.. the problem for BOTH is that is what the computer THINKS is being delivered. MANY little things can effect this: condition of the injectors, exact pressure maintained by the FPR, vac/boost or lack there of on rising rate regulators, etc.. So ECU assumtions may be helpful, but surely can't be used for consumption calculations..

[Smith03Jetta]

Darn!
BoyntonStu

See my thread for additional comments!

[wrxdrvr]

In my opinion, if you want accurate fuel consumption rates, you have to use weight rather than volume. You have to bypass the stock fuel tank and use one you can remove and weigh. Not practical for most testers.

Electronics like the scangauge will give decent guesses on a short run. But anything other than the method above on a short run will be inaccurate. Even for the electronics, short run results are useless. Use a monthly average.

I have had my ScanGauge for 3 1/2 years now and can say without a doubt that it is accurate and precise. Once you set it up with the info that conforms with your vehicle and + - % of how much actual gas you put into tank. Yes monthly numbers are more accurate as for average MPG but for the highest MPG testing for highway driving, or average MPG on that tank, the ScanGauge is as accurate as it gets. Once I have set up the ScanGauge By filling the tank up to the top, where I can see the gas and can't put in any more, I ran it to empty and filled it up again... It was 56.1L out of 56.0L that the ScanGauge said it should take.