How MPG Computer Works ???? - Toyota Nation Forum : Toyota Car and Truck Forums

wiseowl · 02-02-2008, 10:53 AM

Does anyone know how the gas gallons burned is acquired by the miles per gallon computer? I understand the miles is received from odometer data but the gas used puzzles me.

The gas is looped back to the tank so there can't be a flowmeter in the fuel circuit. The only thing I can think of is the gas burned is calculated by the amount of time the injectors are open. However I woulf think this method would be inaccurate because of the variation in fuel pressue, wearing of the injectors over time, deposit build-up on the injectors, etc.

Any ideas or comments????

geoff5093 · 02-02-2008, 10:57 AM

From my understanding it's determined the same way that the ScanGauge calculates it. I know when using the ScanGauge, it determines the MPG by the fuel consumption and speed (possibly also by the engine RPM's and load).

And yes the ECU knows how much fuel is being consumed, which is determined by gallons per hour.

Tobeit · 02-02-2008, 11:13 AM

Are you series about that question, i.e. how the on board computer calculates MPG? ...it's not as difficult as you might think.

njerald · 02-02-2008, 11:15 AM

It is described in the Service Manual.

It gets a fuel consumption volume from the Number 1 fuel injector and distance traveled since last refueling and calculates an average economy.

My meter reads 1.6 mpg (average over 23,000 miles) higher than actual average fuel mileage.

So about 6% too optimistic.

njerald · 02-02-2008, 11:17 AM

Quote:

Originally Posted by Tobeit

Are you series about that question, i.e. how the on board computer calculates MPG? ...it's not as difficult as you might think.

Yes, he's really series (sp)!!!!!!!!!!!!!

robob2 · 02-02-2008, 11:20 AM

Quote:

Originally Posted by njerald

Yes, he's really series (sp)!!!!!!!!!!!!!

Well, spelling was correct, it was the wrong word......

njerald · 02-02-2008, 11:23 AM

Quote:

Originally Posted by robob2

Well, spelling was correct, it was the wrong word......

He was just lucky in that respect.

AYC_SportsFan · 02-02-2008, 12:43 PM

Do all Camry's have this feature????

geoff5093 · 02-02-2008, 01:19 PM

Quote:

Originally Posted by AYC_SportsFan

Do all Camry's have this feature????

Nope, I know the Hybrid does and I believe the XLE does as well.

Tobeit · 02-02-2008, 01:38 PM

Quote:

Originally Posted by njerald

He was just lucky in that respect.

Funny guy, he

. Shall I track your typo's

. Btw, got your problem solved with your car dealer (aka your meaningless SUCKER posts)?

wiseowl · 02-03-2008, 01:13 PM

Thanks everyone

I guess the fuel volume data comes from the amount of time the #1 injector is open. Toyota must know the average fuel volume the the injector can squirt for a given ampunt of time and a given pressure.