For tuners, a Holy Grail of Injector voltage Offset

[XfireZ51]

Originally Posted by Hib Halverson

Being that this is a tuning thread, let me hijack it a bit.

What do you guys do for engines forced to run on E10?

Do you work with E10's different stoich or do you just tune for a certain lambda value from your wideband?

Lambda is lambda regardless of the stoich which is why tuning for E85 can be simpler than it looks. Lambda is the measure of O2, not AFR. We have 10% ethanol here in the Midwest and I reset my calibration to use 14.3 as stoich.

[XfireZ51]

Originally Posted by VetteVet

For anyone wondering what this thread was all about, I just stumbled upon this, which explains it very nicely.


http://www.injectordynamics.com/GMDATA.html

Jep

Basically you can think of the injector offset as an analog to spark advance.
Injector opening time will vary based on pulse width and voltage. The calibration has modifier tables for both. Different injectors will have differing characteristics for both.

[Hib Halverson]

Originally Posted by XfireZ51

Lambda is lambda regardless of the stoich which is why tuning for E85 can be simpler than it looks. Lambda is the measure of O2, not AFR. We have 10% ethanol here in the Midwest and I reset my calibration to use 14.3 as stoich.

I understand "lambda is lambda".

What I was asking is how many here on the net who are doing their own cals are bothering with figuring what's stoich, or are tuning for lambda regardless of the fuel.

Also, my understanding is E10 is seldom actually 10% ethanol and that E10 out of pumps varies widely in how much ethanol is actually in the gas. I'm looking for any evidence of that. Do you test your blended gasoline or have you just assumed it's 10%?

[WARP TEN]

Originally Posted by Hib Halverson

I understand "lambda is lambda".

What I was asking is how many here on the net who are doing their own cals are bothering with figuring what's stoich, or are tuning for lambda regardless of the fuel.

Also, my understanding is E10 is seldom actually 10% ethanol and that E10 out of pumps varies widely in how much ethanol is actually in the gas. I'm looking for any evidence of that. Do you test your blended gasoline or have you just assumed it's 10%?

In Illinois we supposedly have 10% ethanol in gas. I work at a BMW dealership and the techs told me that one time a local car came in running very poorly and they tested the gasoline. It was 28% ethanol. Variations in ethanol are not uncommon for us to see. -- Bob

[Hib Halverson]

I had a Corvette tech at a Chevrolet dealer who has Kent-Moore's gasoline tester that he's tested pump gasolines said to be E10 at anywhere from 5% to 32% ethanol.

I got to thinking. If you calibrated for E10 and got stuck with some 5%, no big deal, but if you calibrated for E10 and unbeknownst to you, got a tank of "E32" then ran the car hard? You'd be getting poop-loads of KR and probably burning pistons.

That piqued my curiosity enough that I wanted to get the Kent-Moore tool. I found it's just been discontinued, however, I've found some other "ethanol test kits" on the market that might work well.

Still researching.

[VetteVet]

Originally Posted by Hib Halverson

I had a Corvette tech at a Chevrolet dealer who has Kent-Moore's gasoline tester that he's tested pump gasolines said to be E10 at anywhere from 5% to 32% ethanol.

I got to thinking. If you calibrated for E10 and got stuck with some 5%, no big deal, but if you calibrated for E10 and unbeknownst to you, got a tank of "E32" then ran the car hard? You'd be getting poop-loads of KR and probably burning pistons.

That piqued my curiosity enough that I wanted to get the Kent-Moore tool. I found it's just been discontinued, however, I've found some other "ethanol test kits" on the market that might work well.

Still researching.

In the recreational marine industry, ethanol is a bigger problem than in the automotive world. Mercury Marine sells ethanol test kits. They cost about $9.00 and since they don't use any type of consumables, the kit can be used indefinitely. You can drive over to your local Mercury Outboard or Mercruiser dealer and pick one up(FYI, I'm not receiving anything from Mercury Marine for the plug).

Jep

[XfireZ51]

Flex Fuel Sensor

http://www.zeitronix.com/Products/ECA/ECA.shtml

[Hog]

Even if you figured out the E% of the fuel your putting in the tank, that will change a bit depending on whats already in your tank before filling. The emptier the tank before filling the better.

12570260 Lists at $639 and can be had for $378.

The more modern ECM's run a virtual ethanol meter, using inputs from the O2 sensors to tell the ECM what E% is being fed to the engine.

This is the "Stoich. AFR vs. %Alcohol in Fuel" Table from a 2011 GM truck

Stoich Ethanol
Ratio Percentage
14.670 0%
14.314 6.25%
13.958 12.5%
13.602 18.75%
13.245 25%
12.890 31.25"
12.534 37%
12.177 43.75%
11.821 50%
11.466 56.25%
11.109 62.5%
10.753 68.75%
10.397 75%
10.041 81.25%
9.684 87.5%
9.329 93.75%
8.973 100% ethanol

There is even a table that compensates for the way different alcohol percentages effects the speed at which the fuel evaporates off the cylinder wall.

Can you just keep adjusting the stoich point until O2 trims fall into line? Obviously a pain if burning chips, more for a tuner running an emulator.

peace
Hog

[XfireZ51]

Hog,

You'd want to set the Stoich for the known fuel then tune. That's what I have done. It'd be nice to have a sensor for real time fuel analysis then dynamically adjusting Stoich. Has anyone ever done a FlexFuel using Speed Density rather than MAF?

[Hog]

Originally Posted by XfireZ51

Hog,

You'd want to set the Stoich for the known fuel then tune. That's what I have done. It'd be nice to have a sensor for real time fuel analysis then dynamically adjusting Stoich. Has anyone ever done a FlexFuel using Speed Density rather than MAF?

Yes you are correct if you know the Ethanol percentage, I was was wondering if you could adjust the stoich point until the trims were close if you DIDNT know the exact Ethanol percentage. thats how the virtual flexfuel ECM's do it as they dont use an actual ethanol sensor anymore.

peace
Hog