E85/Flex Fuel
09-08-2008, 08:25 AM
#3
Senior Member
Join Date: 04-11-2008
Location: Eastpointe,MI.
Posts: 663
Surprise,surprise.The fuel feed pipe and canister purge pipe are the same parts as the older cars.The fuel tank meter with pump MAY be the same-there's a double listing in the catalog.That means that GM may supercede the old part with the later part or that someone just goofed up the listing.
09-08-2008, 09:10 AM
#4
Founding Member
Join Date: 11-23-2007
Location: Texas
Posts: 8,210
E85 compatible vehicles no longer use an alcohol sensor to determine and adjust for alcohol content of the fuel in the tank. Instead, the vehicle calculates the alcohol content of the fuel through measured adjustments. The ethanol calculation occurs with the engine running after a refueling event has been detected via a measured change in the fuel level sensor output. The virtual flex fuel sensor, V-FFS, algorithm temporarily closes the canister purge valve for a few seconds and monitors information from the Closed Loop fuel trim system to calculate the ethanol content. This logic executes several times until the ethanol calculation is deemed to be stable. This may take several minutes under low fuel flow conditions such as idle, or a shorter time during higher fuel flow, off-idle conditions.
Air-fuel ratios and the corresponding ethanol percentage are updated following each purge-off sequence. The fuel alcohol content percentage value can be read on a scan tool.
When an E85 compatible vehicle is built, an ECM replaced, or if the learned alcohol content has been reset with a scan tool, the fuel system will need to contain ASTM gasoline with 10 percent or less ethanol content. A minimum of 11 liters (3 gallons) must be put in the tank in order for the vehicle to recognize a refueling event. It is not necessary to turn the ignition OFF in order to have the refueling event recognized; however, local safety regulations should be followed.
After the refueling event, the system registers the amount of fuel that was added, relative to the amount that was in the tank. Reading fuel trim and O2 sensor activity, the system determines if the fuel added was either ASTM gasoline or ASTM E85. Based on that determination, the system adjusts to the expected alcohol mix in the fuel tank, and then the fuel trim and O2 sensor activity fine-tunes the adjustments. The system must remain in Closed Loop in order for this adjustment to occur. Numerous short trips after switching from gasoline to E85, or E85 to gasoline, can result in driveability symptoms due to the inability of the system to adjust for fuel composition by not attaining Closed Loop operation.
Air-fuel ratios and the corresponding ethanol percentage are updated following each purge-off sequence. The fuel alcohol content percentage value can be read on a scan tool.
When an E85 compatible vehicle is built, an ECM replaced, or if the learned alcohol content has been reset with a scan tool, the fuel system will need to contain ASTM gasoline with 10 percent or less ethanol content. A minimum of 11 liters (3 gallons) must be put in the tank in order for the vehicle to recognize a refueling event. It is not necessary to turn the ignition OFF in order to have the refueling event recognized; however, local safety regulations should be followed.
After the refueling event, the system registers the amount of fuel that was added, relative to the amount that was in the tank. Reading fuel trim and O2 sensor activity, the system determines if the fuel added was either ASTM gasoline or ASTM E85. Based on that determination, the system adjusts to the expected alcohol mix in the fuel tank, and then the fuel trim and O2 sensor activity fine-tunes the adjustments. The system must remain in Closed Loop in order for this adjustment to occur. Numerous short trips after switching from gasoline to E85, or E85 to gasoline, can result in driveability symptoms due to the inability of the system to adjust for fuel composition by not attaining Closed Loop operation.
09-08-2008, 11:20 AM
#5
New Member
Join Date: 08-17-2006
Location: midwest
Posts: 16
driveability symptoms
The system must remain in Closed Loop in order for this adjustment to occur. Numerous short trips after switching from gasoline to E85, or E85 to gasoline, can result in driveability symptoms due to the inability of the system to adjust for fuel composition by not attaining Closed Loop operation.
does this mean the fuel cap must be sealed or a problem will occur?
if the computer decides that there is gas and there is actually e85 would there be a problem and what kind?
Have you heard what kind of "driveability symptoms" result?
09-08-2008, 11:48 AM
#6
Founding Member
Join Date: 11-23-2007
Location: Texas
Posts: 8,210
I would like to understand this better.
does this mean the fuel cap must be sealed or a problem will occur?
if the computer decides that there is gas and there is actually e85 would there be a problem and what kind?
Have you heard what kind of "driveability symptoms" result?
does this mean the fuel cap must be sealed or a problem will occur?
if the computer decides that there is gas and there is actually e85 would there be a problem and what kind?
Have you heard what kind of "driveability symptoms" result?
The only time we have seen problems with adding E85, is when the customer adds fuel while the engine is running (which is only surpassed in stupidity by someone smoking when fueling). As long as the engine is off the ECM will recognize that fuel has been added.
09-08-2008, 12:07 PM
#7
Senior Member
Join Date: 09-09-2006
Location: Fresno, California (formerly of Modesto, Ca. -- hometown of George Lucas, formerly of Winnipeg, Mb.)
Posts: 930
Why would anyone want an E85 HHR in the first place? The fuel costs more than regular gas, and you have to fill the tank twice as often. And how many gas stations outside of Beverly Hills supplies E85?
Now, when GM produces a Hybrid HHR... then I'll be impressed.
Now, when GM produces a Hybrid HHR... then I'll be impressed.
Last edited by Nor-Cal HHR Club; 09-08-2008 at 12:08 PM. Reason: added more text.
09-08-2008, 12:13 PM
#8
Senior Member
Join Date: 01-31-2007
Location: New Hampsha
Posts: 2,479
It is more expensive in Cali???
Goose
09-08-2008, 05:14 PM
#9
Banned
Join Date: 10-24-2006
Location: The Show-Me State
Posts: 1,761
My Car is Drunk, Occifer!!
So, if the fuzz pulls you over and they state that they can smell a moderate or strong odor of alcohol, just tell 'em it's the car! They can put their little breath tester in the tailpipe and get a reading...
Now that's old school. I haven't heard that in a long time.
