All the gas in my area "may contain up to 10% ethanol" so I've set my Stoich AFR at the "0" cell to 14.13. I'm wondering if/how the computer can detect what value on the table it needs to calculate from. I understand how the values tie into PE, but can the ECM detect what % or alcohol is in the fuel?
some cars/trucks have a sensor that determines what %ethanol you have. so if you have the sensor then yes it can tell what % it is, if you dont then no.
06 GTO M6: flowmaster 40 mufflers, x pipe, resonator removed, K&N cold air kit - sold
08 G8 GT: flowmaster 50SUV mufflers, x pipe, resonators removed, ever changing tune, CAI sometime soon.
I've got a C6 corvette. I'm not sure if it has a sensor????
No sensor in the vette that I am aware of (never seen a vette with a flex fuel sticker on it)
Yes, it will help, it will reduce your positive trims and it will give you a richer final AFR which will make the car faster IF you have not tuned it for VE/MAF already. If you have, you will need to completely start over again after setting the stoich value to the new value.
Also, you might want to split the difference. Since it "may" contain up to 10%. I have 14.4 in mine. As well as lots of others on here. Can't rememer who, but a couple guys have test kits to check how much ethonol they are really running. I'm not that picky yet.
98 TA
06 1500hd cc 4x
I have a test kit and here in NCalifornia every station I have checked has 10% in it. The new law effective Jan 1st is all gasoline will have 10% min ethanol in it here in California or at least major populated areas anyway.
I cant see why gas companies wouldnt put 10% in it anyway any area or any state for that matter cause its cheaper for them to male and more profits the more ethanol there is in it.
Dont just split the difference not knowing exactly how much is in it spend $30 for a test kit that will last forever and tell you whats in it and set table correctly.
Last edited by Z06SUPERCHARGED; 01-24-2010 at 10:24 PM.
16 psi on E85
You dont really need to buy a test kit, a 100 ml (or whatever the imperial equivilant ist) graduated cylinder is all that is required. Add 10ml of fuel, then top remaining 90ml with water. Put a stoper in the top and give a thorough shakeing. Because the alcohol is hydroscopic, it bonds with the water seperating from the fuel. Allow it to settle and seperate, you will now appear to have more water and less fuel. The amount of fuel missing divided by 10 is you ethanol percentage. My "kit" was less then $5.
Unless the flex fuel functionality was operating, either by hard sensor as used ~2005 & earlier, or "virtual fuel sensing" as offered in current GM FF vehicles, it will operate only in the "0" cell in the table.Originally Posted by turboffr
You'll know when you have the right number as the trims will be around zero as BBA notes. That is if the MAF is still operating with factory intake etc.
If you know your baseline with pure gas, then you can use your trims to get an indication of degree of ethanol in the fuel. Roughly.
The 2005 Corvettes definitely don't adjust Stoch for ethanol.
In the past, Central Texas would normal sell 93 octane with no ethanol. I really worked at getting my LTFT % between 0 and -3%.
But than about 2 months ago, I got a my first tank of 10% ethanol and saw my LTFT% go 3-5% positive so I changed Stoch to 14.2 and my LTFT were back to normal.
But when I filled up over weekend at a Shell station a little south of Austin, I noticed my LTFT % went way negative, so I changed it back to 14.68 and my LTFT % were back to 0-3% again.
2014 Corvette, Z51, 3LT, 7-Speed, NPP, 2 tops, Exposed Carbon Fiber roof, FAY, Laguna Blue, Kalahari, Museum Delivery.
I found this in another forum....
gpsman1
Re: How to test for gasohol percentage
You can use this separation method to test for any percentage.
Here's the math to be more precise, but of course, the precision will be limited by the quality of your measureing device.
Cheers,
-John
My own tests and results:
http://www.greenhybrid.com/discuss/f...centage-20909/
Per BBA's recommendation in another thread, I'm considering trying this to reduce the LTFT's on a stock engine. Around 10% currently. Would it be a good idea to adjust any of the tables (PE comes to mind, I'm sure there are others) that reference this Stoich AFR setting? Or would that just be undoing the corrective nature of making the Stoich AFR more realistic?
2009 G8 GT
Yes the water beaker method works well for figuring %.
Last edited by hobbesnmina2001; 02-01-2010 at 01:26 PM.
1999 Corvette Coupe LS1 A&A Vortech V3SI A4
2012 Ford F150 Ext Cab Ecoboost
2002 Corvette Z06
Tried the method in SweetS10V8's post. Some sloppy technique on my part probably skewed the results. But they still agreed pretty well with the sticker on the gas pump. ~10% alcohol.
I was amazed at how quickly gas evaporates. I left the graduated cylinder sitting out for an hour or two and about 5mL disappeared. Now I see why cars have all that EVAP equipment. And why California uses those elephant trunk looking gas pump nozzles.
2009 G8 GT
Is it lame to answer your own question?
I've pretty much convinced myself that any EQ numbers in the tune should not be changed just because the stoich setting is changed. Some related rambles here if anyone cares to shoot some holes in the logic. Around post #14.
http://www.hptuners.com/forum/showthread.php?t=27792
2009 G8 GT
That is absolutely correct! Whatever numbers were plugged in for commanded AFR at WOT (power enrichment) should be left the same. This is where looking at things in terms of Lambda instead of AFR make life a heck of alot easier when dealing with these ethanol blended fuels.
2017 Silverado LTZ
This is why Im trying so hard to learn Lambda and EQ, instead of AFR.
AFR will confuse you when you got to, say, E85. I dont know what the eqivalent of 12.5:1 is for E85 off the top of my head. If Im using EQ or lambda I dont have to, all I have to know is the stoich of my fuel. Your numbers should fall inline since they are simple % based off of stoich.
In conventional AFR thinking EQ Ratio = stoich/AFR
so if i wanted to use Lambda rather than AFR, then EQ Ratio = 1/ Lambda
and to convert Lambda to AFR, then AFR = Lambda/stoich
IF Gas Stoich = 14.68, 1 lambda, and E10 Stoich = 14.20, 0.96 Lambda
We have to change the stoich table in the 0.00 cell from 14.68 to 14.2 to run E10 correct ? so from lambda 1 to 0.96
Wouldn't that change your lambda from 0.85 to 0.88 if you wanted to run 12.5afr with gas and e10 while in PE ?
Wouldn't you have to change EQ either way to reflect the change in Lambda?
I've never tuned with E10, so i haven't thinker a lot about this, maybe is because i don't think in Labmda yet
Gas AFR Stoich 14.68
E85 AFR Stoich 9.765
change the afr value to reflect e85 stoich in the tune,0.00 cell, no need to change anything with the WB, should i shoot for a 14.7 afr as always and adjust the trims as always ?
EQ for E85, change it to be 0.7812 to shoot for a 12.5 AFR , EQ=(stoich/desired afr) or (9.765/12.5), should i look at WB to read 12.5 still ?
My OLFA would be all 1's, and maybe i'll need to adjust EQ min for cold starts if i was operating in SD OL only, so instead of 14.7, i'd assume 9.765 as the new stoich for E85, and adjust EQ min as necessary to achive desired AFR at idle (14.7 per WB), same for part throttle VE, use PE for WOT with 0.7812 if i wanted to achieve 12.5 at WOT ?
Last edited by bluegoat06; 02-11-2010 at 03:03 PM.
I think there is some confusion here. A stoich mixture of any fuel is always lambda = 1. It makes things simple.
I don't think so. Just like stoich for any fuel is 1. Max power is always something like lambda = 0.85 - 0.90. Those are the magic numbers. Not 12.5 AFR. Multiply 0.85 x [stoich for whatever fuel you're dealing with] to get the target AFR for that fuel. Or better yet, don't bother calculating the AFR at all. The AFR values change per fuel. Lambda's don't.
I used to think in Lambda. Why, oh why, did I let the hot rodding world corrupt my thinking?!
This is tricky. Even though 12.5 really isn't the magic number for all fuels, a lot of meters will probably show this whenever lambda = 0.85. Because a lot of meters are set up to show us what we're used to. They measure in lambda but translate that to gasoline AFR for us. 14.7 x 0.85 = 12.5. I guess as far as meters are concerned, 12.5 is sort of a magic number. Just don't think that way within your tune.
I recently stumbled onto this thread. Similar to this one. With comments from some reliable sources.
http://www.hptuners.com/forum/showthread.php?t=26662
2009 G8 GT
I've been working on this lately and it kind of hit me one day and I literaly said, "oh, well, duh of course".
I kept thinking my wideband was wrong because it always showed around 14.5 in closed loop. Then I thought my o2s were wrong because I have longtube headers, but then I realized, they are both right!.
The o2s switch around lambda = 1, stoich, the same thing. I have ethanol blended fuel in my area. Lambda=1 for ethnol is lower than gasoline, so therefor the stoich for gas/eth blend is lower than the 14.68 I kept looking for.
For the 10% blend I have in my area, the real stoich is about 14.47. How do I know this? I changed the stoich values in the table then logged. When my wideband shows an AFR error of 0 in closed loop then I know the trims are correctly putting me at the true stoich.
Also, you need to change your PE values to reflect whatever values you put in the stoich afr table since your final AFR in PE is determined by "stoich/pe table value".
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