so just a small recap for my small brain to catch up here.
the narrow band o2s drive to a lamda of 1.00 at all times (afr 14.7 that most of us know and love) regardless of fuel? so if e10 has a stoic afr of 14.1 and i swap to e70 the nb will still drive to a stoic (best burn) for the e70 but display it as 14.7 afr?
As long as they are calibrated correctly.
Different fuels require different AFRs to reach stoich, but the end result is still a mix that the nb/wb interpret as Lambda 1.00 which the gauge displays as 14.7 from my understanding.
Last edited by HeavyChevy305; 01-16-2016 at 08:17 AM.
2023 Ford Maverick 2.0T AWD
narrowbands or widebands don't really "drive to" but "switch around" lambda 1.0, yes. Switch Around meaning they normalize their readings at stoich with some margin or error/adjustment/flexibility. Messing with the switching voltages just pushes the error more towards lean or rich, depending on how you adjust it.Originally Posted by runsfromdacops
if the stoich value in the tune is 14.68 and you run E10 then the trims will be larger positive trims to obtain stoich for E10. If you switch to E70 the trims will be very large positive trims to hit stoich for E70. this is why you want to adjust the stoich value as close as possible to your fuel in the tank, to keep the trims small so you don't run out of trim room, plus large trims mean large swings in fueling at different load/rpm/throttle combinations and the car will not run smooth and might not be safe either. basically you have less control.
this is why newer calibrations in newer cars have 14.11 or 14.08 in the stoich table because these cars were built and calibrated after pumps had switched to E10 from E0....Gen 3 stuff was built when E0 was common. if you are running pump 93 today I would have 14.1 in the stoich table.
I was going to answer but Higgs already got it, so yeah, that's pretty much the answer
It will drive towards just over/under lambda=1 no matter what fuel is in there. The stoich AFR value is used as the basis of calculating how much fuel to inject, but it's constantly move around according to feedback from the O2 sensor (i.e. "closed loop").
And yes.. widebands read lambda, multiply it x whatever fuel it's setup for (usually 14.7) and spit out the number. You can literally put a wideband on a car running ethanol and it will show 14.7 at stoich even though obviously that isn't true. Lambda=1 is, however, still very true.
That's why just switching to lambda and saying to hell with AFR is easier for most. Takes some getting used to in the beginning obviously..
i understand that NBs dont "drive" towards anything but switch up/down around 14.7 to make sure the tune is right.
what i dont get is are you guys saying that the NBs with deal with a fuel switch to say e85 and push the tune towards stoic for e85 or towards E0 ?
They will always "switch" around LAMBDA = 1.
but lambda =1 will change based on fuel type right?
so they will always adjust to the best burn (stoic)for what ever fuel type it is running on?
Lambda=1 is stoich, doesn't matter what fuel is being used
You have to remember that the O2 sensors are reading OXYGEN. They don't really care (or even know) what fuel is being used..
Stoich AFR will change based on fuel type but no matter what Stoich AFR is, Stoich Lambda is always 1.0
This is why you want to think in terms of lambda because it is not a variable, it is a constant. lambda is not a moving target. AFR is a moving target. Always easier to hit a stationary target, right?
Let the O2 sensors do the work rather than you trying to calculate on the move. The O2 sensors knows where Lambda 1.0 is at all times no matter what. AFR is derived in our brains and then in our computers.
Lambda is the real world, neo....AFR is the matrix.
gasoline gets an EVEN BURN with 14.7 parts of air and 1 part of fuel.
E85 gets an EVEN BURN with 9.85 parts of air and 1 part of fuel.
Lambda 1.0 is an EVEN BURN.
Hi everyone thanks for all the input on this subject. To clear it up all the readings I got were via my wideband reading lambda not AFR. Maf/ve spot on 0.99-1.02 locked in open loop. Changing the stoich back to stock definitely brought things back in line.I still haven't decided if I am even going back in to closed loop as the car is running so good right now. I guess as with most things in the tuning world sometimes what works for some wont work for others. This(after much hair pulling)worked for me. I know if I do go back to closed loop there will be some o2 tweaking because of all the cam reversion and I may not feel like dealing with it.
Last edited by 2002bird; 01-20-2016 at 06:42 PM.
I think it is a good Idea to tune to E10 on cars. My reasoning, is that if you actually DO get true E10 in your tank, then your tune should be spot on, however if you happen to get E0 in the tank, then the car will be in error rich. Which in my opinion is the better way to be in error. From every single car I have ever tuned that is a stock tune to start out with, they will have positive (Rich) fuel trims at every cell. It only makes sense. The car started out at a specific efficiency, and things only go down over time, never up. So my point it, that eventually your tune is going to error where the car starts to populate positive fuel trims. So in the case that you are on an E10 tune, and you get E0 in your tank, there is a much better chance that your lean error is just going to mix in with your positive fuel trims, and the car will actually combine the two to where either is not so dramatic. Just my 2 cents. Obviously if you run a car in Open loop, this need not apply.
Positive fuel trims means it's ADDING fuel, meaning it would be lean without that additional fuel.
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