using 14.047 for desired AFR and not 14.63?
Before reading or responding please note the ? at the end. When we buy gas today it is very difficult to stay away from 10% ethanol. When setting up our tune we use an AFR as 14.63 approx for the most part and 1 for lambda and EQ. But what is the correct Base AFR to use with the fuel in the market today.
AFR is based on 14.63 part of air to 1 part of fuel. But when you do the math with 10% ethanol it seems way off to me. So I did just a little math for an open discussion and input. 10% ethanol has a correct AFR of 8.8 to 1, I think.
so since the fuel in general has 10% ethanol and the AFR for that is 8.8 approx I used the following formula. (14.63x90%) = 13.167+(8.8x10%)=14.077 or (14.63x9=131.67)+(8.8x1=8.8)=140.47/10=14.047AFR. Is 14.047 AFR or 14.077AFR the correct base to use for AFR with todays gas? If so what does this do to EQ and Lambda?. This seems correct to me so does anyone know what the adjustment should be?
Thanks in advance,
98 tigershark :throw::crash::nixweiss::blahblah:
That is what my understanding is too but it seems wrong.
That is my understanding also. But if the trims are trying to adjust (learn) to 14.63, it would seem that the PCM is learning to make the car run lean. Enough to make the LTFT off by quit a bit it would seem. The reason I brought this up is there is another members post on the forum who is having LTFT trims off by as much as 20%. If it is not a bad fuel filter or intake/exhaust leak it seems to me it could be the fuel he gets has changed to cause this.
Thanx,
98 tigershark
What happens if we use 14.07 for stoich?
In {B3601} can we use 14.07 and be Ok with the trims or is it the EQ that is the deal here? There is not one Gas station I am aware of in close range of were I live that sells Gas without 10% ethanol.
98 tigershark
Anyone else interested to confirm the results? A volunteer?
Before I do this it would be nice to know for sure that you guys dont already know what is going to happen. I think also that I am more than willing to do this but it would be best if we could get 3 or 4 of us as to compare for accuracy and then we could compare logs and see for sure. Are you guys sure you dont already know?
98 tigershark
Does that mean we can use E85
hello vetteboy,
I want to make it perfectly clear that I do not know the answer to this but it would seem that we could then use E85 and the PCM would automatically adjust to stoich regardless of fuel as the sensors would show a very lean condition and then adjust the trims to a 1 EQ accordingly?
That still does not sound right. I am certainly not saying anyone is wrong as I do not know, It just sounds wrong to me with the 97-2004 PCMs.
So are you interested in trying a little experiment 5.7ute suggested?
Using 14.07 for afr and comparing logs?
Looking for help,
98 tigershark
Quote:
Originally Posted by
vetteboy2k
I believe the narrow bands will adjust to stoich of whatever the AFR is of the fuel your running. So if pure gasoline they will adjust to stoich which is 14.68 and if E10 14.07 being stoich is stoich and the sensors don't know the type of fuel your running.
That would be really great!
Thanks 5.7ute,
That is a very nice offer if you have the time and it does not have to be today as you are probably very tired late in the day. But when you can find the time that sounds great as I think this will become more and more of an issue with fuel in the future. I would sure appreciate getting my brain around this and knowing for sure (It took me getting a serious brain disease to prove to my wife I had a brain, really). I may be wrong but I think when you put 14.07 into B3601 that becomes the EQ of 1. I guess we shall see soon enough. Thank you so much and I am still willing to try it, but I think we need a few volunteers to compare logs and notes as I am not a pro at this ind of thing.
98 tigershark
Quote:
Originally Posted by
5.7ute
I can have a look after work with the Roadrunner hooked up.(In about 9 hours) You would see an instant change in commanded AFR that way.
That was kind of my next question?
When we are setting up our WBO2 sensors Like an "whatever brand" and
it has you use 7.35 for half or .5 EQ or Lambda (look at the PID definitions and formulas in the scan,pid selection)). If the PCM kind of does the flex fuel thing as GM308 says (that seemed logical and also matches the flex fuel tables too in the later PCMs) Does that mean we cannot really use the given of 7.35 for AFR for one half of the WBO2 equation and then add what ever the WBO2 sensor says for the other half which is the actual reading? If so that suddenly does become a factor to take care of I think? I am not sure I said that right but it would seem we would have to use EQ or Lambda as Greg and Jeff say but! how does this affect the WBO2 configuration, how the 97-04 PCMs think and EFILive WBO2 PID?
98 tigershark
Quote:
Originally Posted by
mr.prick
Couldn't you use {B3601}/{EXT.WO2AFR1} = External Wideband EQ
What if the WBO2 setting for Lambda1 (14.7AFR) does not match EQ1 {B3601} exactly?
That is kind of what I have been trying to say, Thanx mr.prick
I think GM uses the 7.35 for half of the PID calculation or close to it as an adjustment and has something to do with the EQ to Lambda thing, I dont really know but it seems that way. (you know the 7.36 or .5/ ADV1 or 2 thing were it says that bank one is 2.20 or approx before you change it to the WBO2). I still dont think I said that right. Anyway awhile back I read that the PCM simulates one of the banks and one is the actual as to Bank 1 sensor 1, bank 2 sensor 1. I will try to find the GM or EFILive article I read.
98 tigershark
Quote:
Originally Posted by
mr.prick
I can't match Lambda1 to EQ1 exactly between the WBO2 settings and {B3601}.
Off topic
I just looked at an old log and found
GM.AFR differed ever so slightly than what is set in the tune.
Example:
----------{B3601} = 14.628573 AFR
Actual commanded = 14.627930 AFR
Difference-------- = 00.000643
When PE kicked in GM.AFR was slightly lean too.
Is there a multiplier somewhere?
does that take into account BSFC and VE%?
I thought the PCM knows to or uses (BSFC) the brake specific fuel consumptions change to adjust for nat asp or forced induction for the COS's and also the uses VE% too. Maybe just for WOT?
98 tigerhark
Quote:
Originally Posted by
5.7ute
Just to clarify {B3601} Our pulsewidth calculation by the PCM would be this.
IBPW=( Airmass/({B3601}/commanded EQ)/IFR) + offsets
Correct?????
Going by this an error in B3601 would still cause an error in our airflow model if we are commanding away from stoich like in a custom OS.
Thanks for doing the math
Thanks for doing the math 5.7ute. You should look at SSpdDmon link regarding E85. its pretty scary and means were I live we get the crap fuel year round. That really sucks!! But since we get the crap fuel all the time I guess it at least will be consistent for tuning so thats a positive. By the way since the AFR is set for 10% ethanol it would take a bigger pulse width as the fuel milage does also go down, Right! as it seems your math is right to me and it should be a longer IBPW.
Thanks again as I think this will be very important to learn as I sure am.
98 tigershark