antman89iroc

With today's gasoline supply being mostly blended up to 10% ethanol, should the target fuel ration be altered in our programs? I tried to search for the stoichiometric ratio for 90/10 but did not find anything definative. Seems it would be >14.7 since ethanol is somewhere in the 9.5 range. Any thoughts?

fasteddi

iTrader: (2)

I don't know but this is a interesting topic and im eager to hear some ideas on this.

RBob

iTrader: (1)

Not trying to blow you off, a search will bring up some interesting discussions. IIRC, 10% ETOH and 90% gasoline has a stoich of about 14.2:1

If the engine was tuned with 100% gasoline, then changed to 10% ETOH, the BLMs will increase a bit to make up for the difference. You could change the stoich AFR, along with the others in the calibration. This will keep the BLMs more stable.

The TPI ECM code (maybe not the '85 ECM?) uses percentages from stoich for the other AFR values, so only need to change the one (stoich). Other ECMs have AFR tables, in which all should be changed.

The key is to understand that an O2 sensor, NB or WB, read and report in lambda. The reported AFR from a WB is dependent upon the stoich value used for the conversion from lambda to AFR.

We could get a lot deeper into the use of WB sensors. The reported lambda will also change dependent upon the ratio of hydrogen to carbon content of the fuel. This is why when spraying a lot of methanol the target AFR is richer then what would be expected.

When spraying a 50/50 mix of methanol and water, which doesn't burn, the reported AFR gets richer. This is because it adds hydrocarbons to the exhaust, which the sensor detects.

RBob.

Orr89RocZ

iTrader: (20)

Yep above is well put. Lambda is the best way to tune. Lambda of 1 is stoich regardless of fuel. Its just air fuel gauges are programmed to read based on fuel type. Gas is 14.7 to 1. So using different fuels may have same lambda but read different air fuels based on readout programming. The difference between gas and 10% ethanol blend is small so it may not be worth changing out in the bin. Its not hard to do tho so its up to you. Just leave it a but richer if you dont

antman89iroc

Thanks guys, keep the info coming.

A search here on 3gen RBob? I admit I haven't tried that yet but my searches on the net have yielded a lot of info but applying it to my tune is another story. I didn't really want a Phd just whether it is recommended and to what value.

The availablity of fuels in my area are 99+% blended. UP TO 10% but not necessarly 10%. So I am reluctant. The only local 100% gasoline sources are 87 & 110! And the 110 octane is leaded. Not really an issue for me (no cat) but the $7.99/gal price is prohibitive unless it was just for tuning and/or racing.

Anyway, I would like to learn more for the purpose of this tune and the use of a WB which is coming soon. In fact some of my other posts are in regard to infusing the WB data in my logging sessions w/o a dedicated input.

And Orr, I understand the concept of lambda being Stoich but in regard to the type of fuel wouldn't you have to "tell" the WB/program what stoich should be?

Ronny

iTrader: (1)

Stoich is Stoich 1.0 Lambda. 100% consumed. Could be corn liquor(my personal favortite) or E85. If you use A/F and do not inform controller of fuel I believe it will show 14.7/1 on gauge as stoich for E10. If you tell controller it is E10 then 14.2/1 would be stoich on gauge. I have never changed controller so I run E10 and it shows in CL 14.7 or so.

Is this right guys?

RBob

iTrader: (1)

Yes, can also use google or other search sites to search TGO.

After the keywords add this:

site:https://www.thirdgen.org/forums

That will cause the search engine to confine it's search to TGO.

RBob.

LastC3

There have folks doing some testing of E85 .... information that would probably lend to the E10 issue ... though I would agree E10 would probably not need much, if any, changes to what we're doing today ...... (except as noted by RBob ... thx for that as we're seeing mostly E10 these days)
What I've picked up that I thought important is ..... 1) E85 stoich value of this mixture is around 9.65 2) requires 25-20% more fuel. (negates the lower cost) but also may require larger injectors and fuel pump/lines etc. 3) E85 does contain a higher Octane Rating however this just means it is further resistant to knock, which could be dangerous especially if using any boost. Running cooler is certainly an advantage, but still questionable at to additional power (there are more opinions on that too)
see more on this discussion .......

http://www.arizonacorvetteenthusiast...howtopic=19256

Interesting topic though .... thus the only reason for my looking about for info ......

xch3no2

No Phd necessary, just read.

antman89iroc

So, for the purpose of my tune, the current availability of ~90/10 fuel may "require" a slight adjustment of the A/F ration in the calabration.

To better understand the topic and apply it to any re-calibration, the basic understanding I have is...

The Air to Fuel ratio is just that, the amount of air in pounds (or grams or tons) devided by the about of fuel.

Stoichiometric expresses the ratio where all the fuel present can be (or has been) burnt for "x" volume of air. It is 14.7/1 (14.7# of air to 1# of fuel) for a "standard gasoline" (affected very slightly by the chemical make up of that "gasoline") but is a different "ratio" for different fuels. For example: Stoich for Ethanol would be 9.0/1.

Lambda is the expression of the Actual A/F ratio devided by Stoich. Sooo at Stoich, Lambda is 1.0 and at "richer" levels Lambda will be <1 and "leaner" levels Lmbda will be >1. For example running 10% rich would be expressed as 0.9 Lmbda. Since the Stoich is higher/lower for different fuels, since Lambda = Actual AF/Stoich, it will still be 1.0. for that "different" fuel.

Am I getting warm here?

Since Ethanol burns at a richer ratio (9/1) than gasoline (14.7/1) blending the two will end up with a Stoich somewhere in between. It has been expressed here that a 90/10 may be about 14.2/1 Stoich.

Now, since the fuel available is blended, it has a different Stoich and therefor requires a slight adjustment in the tune.

Delima: If Stoich represents the point (A/F ratio) where "all the fuel that "x" of air can burn, why is a higher A/F ratio needed for max power? How can more fuel be burned if all the O2 is used?

Orr89RocZ

iTrader: (20)

For my LC1, what I mean is the voltage readings are programmed to read 7.35 to 22.39 air fuel for the digital gauges based on its default programming. My analog gauge only has 10 to 18 air fuel displayed and the formula is 2*volts + 10 = air fuel. So 0 volts is air fuel of 10. 5 volts is 20 even tho gauge range is to 18. 2.45 volts is considered stoich I believe for gas and I believe you want this to be the same volts for lambda 1 for stoich for any fuel.
If you need a different range of air fuels for different fuel types, stuff that may read ULTRA rich like stoich of E85 being 9.65 to 1 your WOT may be below 7.35, so you may need to program the gauge or controller to output correct range for the gauge to read stuff. LM1/LC1 innovate stuff has a program to select fuel type so it knows stoich and can multiply lambda's by stoich to obtain air fuel readouts, but it doesnt have E85 i dont think. I think it has pure methanol alcohol but not ethanol. Different curves for the readouts are displayed in there.

http://www.innovatemotorsports.com/s...C-1_Manual.pdf

Orr89RocZ

iTrader: (20)

Yes, less than 1 lambda is rich. Greater than is lean.

Most motors will run best around .8-.9 lambda on gas. Maybe slightly richer on E85 but close to .8 is good. For gas thats between 11.76 and 13.2 to 1 air fuel. For E85, if stoich is 9.65, then .9 lambda is 8.68 to 1 air fuel If the gauge is programmed to read the same way.

Theoretical max fuel consumed with max o2 is stoich but max power is always more fuel. I guess one reason is combustion temps are higher with leaner mixtures and you need richer cylinders to keep things cool. Parts wouldnt last long in a engine running that lean

xch3no2

As Orr said, extra fuel has a cooling effect. Some fuel may fallout ect.

It is an engine, not a lab experiment. Engines have design shortcomings and variable operating conditions. Inconsistent variables need to be covered.

antman89iroc

Lol, Ok I got it. The 14.7/1 is theroetical, but in real life it takes a little more fuel under power to keep it all together. Thanks!

Saar

lean is mean, but rich is safe.

something to keep in mind.

fasteddi

iTrader: (2)

In agreement there.



Great info guys

antman89iroc

I ran across an interesting article on this subject on the Innovative Motorsports web site.

http://www.innovatemotorsports.com/resources/news6.php

In fact, there is a wealth of knowledge on their site. Recommended!

Ok ok yeah I searched and I found. But I appreciate all your input as it helps me apply the information to my application.

RBob

iTrader: (1)

It is also a good idea to measure the ETOH content. Easy to do, and you may be surprised at the results.

RBob.

fasteddi

iTrader: (2)

How would one do that Rbob? Thanks.

lakeffect2

It's not a question of burning "more" fuel. It's making sure that all the available O2 has been used by injecting more fuel. The goal is to use every bit of the oxygen available. Adding fuel increases that chance. Therefore it's richer, as you are leaving some fuel unburned.

" Highway mode" is just the opposite logic, which is why it's considered a measure of economy in the sense of making sure all the fuel is burned by providing "more" relative O2 to fuel to insure it happens. Since we can't actually provide more O2, the ratio is changed towards >14.7/1 by reducing injected fuel for the given air supply available. Therefore it's leaner, as you are leaving some O2 unused.

antman89iroc

Ditto

The other idea I have is to purchase fuel at the same station/chain as much as possible in an attempt to reduce vairations. But actually measuring the content would be the holy grail of standardization.

The statement at the pump which says "up to 10%" is what concernes me. I may be getting the cart in front of the horse so to speak because the amount of affect the "mix" has is relitively small here and my tune is in process. However, it does appear to be worth addressing.

antman89iroc

ok I found it.

To determine the amount of alcohol in fuel

Get a small graduated container, like a test tube that will hold 100ml.
Pour 25ml of water in it.
Pour 75ml of the fuel you want to sample
Put a lid on it and shake, then allow to settle.
If Alcohol is present the "sample" at the bottom will increase
The original volume of the bottom section (W) was 25 ml. Once the solution has settled, there will be an increase in the volume of W by an amount (D). To determine the value of D, subtract 25 from the new level reading of W.
To determine the percentage of ethanol in the fuel sample, divide D (volume difference in W) by F (amount of original fuel sample) and multiply by 100 (the total amount of solution in the cylinder).

paraphrased from the below link

Read more: How to Measure Ethanol in Gasoline | eHow.com http://www.ehow.com/how_7781321_meas...#ixzz1zHGB3Sqp