GPM usage if ICE during idle?

[SPL Tech]

When the car is in the ready position, but in park, and the ICE comes on to charge the battery, anyone know how many GPM of fuel the vehicle uses? Sometimes I sleep in my car and it can be 100 degrees out. I have always wondered how much it would cost to just keep the A/C on all night. I can do the math on ICE on/ off time, but I need to how how much fuel the ICE uses while charging the HVB at ide.

[HannahWCU]

If I remember right when I had my scangauge hooked up, it burns about 0.65GPM.  The CMax doesn't actually idle when it cuts on to charge the battery, I think it runs at around 1900 RPM while charging (if the ICE is warm).  Someone might correct me on this.  I am doing this from memory and my memory isn't what it use to be.

[wab]

I hope you dropped a decimal point.

6 tenths a minute seems high, very high.

[Adrian_L]

.06 G/m sounds more likely.   You'd go through a tank of gas in 3.5 hours of the ICE running.

We've got an environmental 3-minute idle limit in British Columbia.  I know Colorado has strict laws.   I suspect California as well. 

 

Even if you have no ethical concerns about leaving a car on all night you could easily get busted by the cops if there is a bylaw. 

 

[plus 3 golfer]

When I've looked before when ICE was up to operating temperature, idle fuel burn flips between 0.5 and 0.6 gallons/hour.  RPM is about 1050ish and SOC increasing starting from high 30%.   It's virtually impossible to get accurate measurements since ICE shuts off after several seconds when starting with accelerator pushed to floor (I assume since SOC is "fine" and ICE doesn't need to run).  I don't recall what the HP or torque values of ICE were.

 

The question is at what SOC would trigger ICE to come on and shut down when the car is in ready to drive mode.  From what I recall as I stated above ICE will not stay running with SOC in the high 30s. So, I doubt one will see much of a SOC increase say 3-4% or about 50 Wh and based on my observation likely no more than 100 Wh.   If AC, fan an other system loads are 500 W continuous with ambient at 100*F, that's about 6 -12 minutes to deplete the 50 - 100 Wh.  I would also guess that ICE/MG1 should quickly replace those Wh.  I think worst case might be a few tenths of a gallon an hour.  Then, one gallon of gas might give you 5+ hours of AC use.

 

Another way to look at this is 1 gallon of gas has about 33.7 kWh of energy.  Assume ICE at idle is very inefficient and that only 10% of the energy in the fuel is used to charge the HVB at idle.  So, that's 3.37 kWh per gallon.  Divide the 3.37 kWh by the load of 0.5 kW and one gets 6.7 hours of AC per gallon of gas.   

[fotomoto]

Prius campers have reported 3/4 gallon per hr using a/c.  So at todays gas prices, that's about $12 per night!  YMMV with the CMax.

[HannahWCU]

I hope you dropped a decimal point.

6 tenths a minute seems high, very high.

 

Sorry, that should have read GPH  :doh:

Edited February 19, 2015 by HannahWCU

[markd]

I spend some time in the car with it idling and my mpg has dropped from 38.2 down to 36.4 in the last two months. I have to be warm but still.

[SPL Tech]

Prius campers have reported 3/4 gallon per hr using a/c.  So at todays gas prices, that's about $12 per night!  YMMV with the CMax.

That seems incredibly inefficient. Most standard 4-cyl cars only burn 0.2 gph or so. Not sure what they burn with the AC, probably not 3x as much.

Edited February 21, 2015 by SPL Tech

[fbov]

Where do you get 0.2 gph? I get more like 1.5 gph!

 

Engine intake displacement per revolution - 900cc, 0.9L, so 900L/miinute @ 1000 RPM

 

Air has a mass density of 1.2 kg/m^3 @ 20C (68F), and 1 m^3 = 1000L, so @ 1000 RPM, the car pumps 1.08 kg of air per minute.

 

Emissions controls require that fuel is added based on the stochiometric ratio for an air-gasoline mixture, 14.7:1, so that's 0.073kg of fuel per miinute.

 

From there, it's a simple matter of units conversion:

-  based on fuel density of 0.775 kg/L , it's 0.095 L/minute, and

- based on 0.264 L/gallon, it's 0.025 gallons/minute and so 1.5 gallons/hour @ 1000 RPM

 

What am I missing that we differ by a factor of 10?

 

Have fun,

Frank

[Adrian_L]

Sounds about right (better than my .06/min estimate).  Golfer reported that his was about .01 gallons/minute when tested.   Pretty efficient, either way.

Edited February 24, 2015 by Adrian_L

[SPL Tech]

Where do you get 0.2 gph? I get more like 1.5 gph!

 

The first few Google websites I checked.

 

http://www.quora.com/How-much-gas-does-a-car-burn-per-hour-while-idling

 

http://www.candlepowerforums.com/vb/showthread.php?158002-Gas-consumption-while-idling%28parked%29

 

http://cinemacarsound.com/how-much-gas-do-i-burn-while-idling-at-the-drive-in/

 

I recall reports saying my old 2009 VW Jetta TDI used less than 0.3 gph of diesel.

Edited February 26, 2015 by SPL Tech

[Adrian_L]

Can we agree that it's probably in the ballpark of  0.3-0.6 gallons/hour.

[fbov]

...What am I missing that we differ by a factor of 10?

 

The first few Google websites I checked.

 

http://www.quora.com/How-much-gas-does-a-car-burn-per-hour-while-idling...

 

I recall reports saying my old 2009 VW Jetta TDI used less than 0.3 gph of diesel.

And the answer is:

Volumetric efficiency - how efficiently the engine exchanges air

Manifold air pressure - how much is the engine being throttled? 

plus a little for RPM.

 

This calculation doesn't work for diesels, as they aren't throttled and have no need to maintain the stochiometric ratio, but rather run so lean the engine can't go any faster.

 

thanks,

Frank

[plus 3 golfer]

Where do you get 0.2 gph? I get more like 1.5 gph!

 

Engine intake displacement per revolution - 900cc, 0.9L, so 900L/miinute @ 1000 RPM

 

Air has a mass density of 1.2 kg/m^3 @ 20C (68F), and 1 m^3 = 1000L, so @ 1000 RPM, the car pumps 1.08 kg of air per minute.

 

Emissions controls require that fuel is added based on the stochiometric ratio for an air-gasoline mixture, 14.7:1, so that's 0.073kg of fuel per miinute.

 

From there, it's a simple matter of units conversion:

-  based on fuel density of 0.775 kg/L , it's 0.095 L/minute, and

- based on 0.264 L/gallon, it's 0.025 gallons/minute and so 1.5 gallons/hour @ 1000 RPM

 

What am I missing that we differ by a factor of 10?

 

Have fun,

Frank

Where did you get the 900 cc for the intake?   With variable valve timing it seems that the intake air could be cut quite a bit by holding the intake valve open longer into the compression stroke especially at idle.  If this is the case, the fuel consumption based on 900 cc at idle may be overstated.  

 

I'll search the manual for range of valve timing.

Edited February 27, 2015 by Plus 3 Golfer

[fbov]

I made no assumptions regarding valve timing, beyond the standard Atkinson reduction, 10% less intake displacement than exhaust, and 50% of the total for a 4-stroke. It'd be interesting if they had modes other than Atkinson, max pumping loss (for donwhill assist), and closed (no pumping loss).

Frank

[plus 3 golfer]

Below is what the service manual says on VCT.  When I have time, I may record this operation and see what happens with the timing.

 

Variable Camshaft Timing (VCT) System

Overview

The intake phase shifting (IPS) VCT system enables rotation of the intake camshaft relative to the crankshaft rotation as a function of engine operating conditions.

The VCT system has several operational modes: idle, part throttle, wide open throttle (WOT), and default mode. At idle and low engine speeds with closed throttle, the PCM determines the phase angle based on airflow, engine oil temperature and engine coolant. At part and wide open throttle the PCM determines the phase angle based on engine RPM, load, and throttle position. VCT systems provide reduced emissions and enhanced engine power, fuel economy and idle quality. The VCT system also has the added benefit of improved torque.

The VCT system knocking and noise concerns are diagnosed in the Workshop Manual. For additional information, refer to the Workshop Manual Section 303-00, Engine System — General Information. Verification of incorrect VCT phasing on a warm engine operating below 1500 RPM can be isolated using a stethoscope and by monitoring the PIDs using a scan tool. If the VCT phaser does not maintain correct valve timing, low oil pressure or oil flow restrictions are primary possible causes. Verify correct oil pressure and flow, refer to the Workshop Manual Section 303-00, Engine System — General Information.

Variable Camshaft Timing (VCT) System

The VCT system consists of an electric hydraulic positioning control solenoid, camshaft position 11 (CMP11) sensor and a trigger wheel. The CMP trigger wheel indicates the camshaft position signal. A crankshaft position (CKP) sensor provides the PCM with crankshaft positioning information in 10 degree increments.

1. The PCM receives input signals from the intake air temperature (IAT), cylinder head temperature (CHT), CMP11, throttle position (TP), mass airflow (MAF), and CKP sensors to determine the operating conditions of the engine. At idle and low engine speeds with closed throttle, the PCM controls the camshaft position based on engine coolant temperature, engine oil temperature, intake air temperature, and mass airflow. During part and wide open throttle, the camshaft position is determined by engine RPM, load and throttle position. The VCT system does not operate until the engine is at normal operating temperature.

2. The VCT system is enabled by the PCM when the correct conditions are met.

3. The CKP signal is used as a reference for camshaft positioning.

4. The VCT11 solenoid valve is an integral part of the VCT system. The solenoid valve controls the flow of engine oil in the VCT actuator assembly. As the PCM controls the duty cycle of the solenoid valve, oil pressure and flow advances or retards the camshaft timing. Duty cycles near 0% or 100% represent rapid movement of the camshaft. Retaining a fixed camshaft position is accomplished by dithering (oscillating) the solenoid valve duty cycle.
   
   The PCM calculates and determines the desired camshaft position. The PCM updates the VCT11 solenoid duty cycle until the desired position is achieved. A difference between the desired and actual camshaft position represents a position error in the PCM VCT control loop. The PCM disables the VCT and places the camshaft in a default position if a concern is detected. A related DTC is also set when the concern is detected.

5. When the VCT11 solenoid is energized, engine oil is allowed to flow to the VCT actuator assembly which advances or retards the camshaft timing. One half of the VCT actuator is coupled to the camshaft and the other half is connected to the timing chain. Oil chambers between the 2 halves couple the camshaft to the timing chain. When the flow of oil is shifted from one side of the chamber to the other, the differential change in oil pressure forces the camshaft to rotate in either an advance or retard position depending on the oil flow. 

Edited February 28, 2015 by Plus 3 Golfer