Flex Fuel Starter Tips

[BrodyO]

Hi everyone,

I've got a 2005 Chevy Colorado with an LY6, 7875, SEP 1000's and a 4L85e. I'm using an e67 ECU. I have the continental flex fuel sensor on a split return line. The sensor is pinned right to the ECU and seems to be working well based on the alcohol read out in the scanner.

I have my current fuel tank filled about half and half with 91E0 and pump e85 and I'm seeing a readout of about 40% alcohol which seems plausible. I have the flex fuel turned on in the calibration with the factory alcohol multipliers. I'm currently running closed loop speed density. I took it for the first drive tonight and have a few questions.

It seems the ECU might be slightly compensating for added alcohol but not enough IMO. The calibration I have in there right now was nice and rich (about 13.5 cruising, 12.3 WOT, 12.7 idle). With this calibration my idle is high 11's, my cruising and transients don't seem to have changed while watching my Innovate wide band gauge. I would expect everything to be richer than 12.4 AFR if I was fully adapted but my cruising and transients are telling me I'm quite a bit leaner than stoich.

Questions:

How long would you expect it to take for the ECU to fully adapt to a large change in alcohol content? Perhaps I'm just not giving it enough time but I had driven for at least 25 minutes with 40% alcohol before this log file was taken.

Is the best way to log EQ difference with flex fuel through a calculated channel? Since my current scanner is outputting AFR rather than lambda it's my normal EQ difference table still thinks it's way too rich. Basically I want to be able to do the standard copy, past 50% differences despite the alcohol content in the log file.

Does everyone stick with the factory alcohol multipliers in their flex fuel calibrations?

Do I need to be running closed loop in order to see proper/faster fuel adaptions?

If nothing else, I did completely eliminate the WOT knock retard I was seeing on 91E10! Just want to make sure my adaptions are correct before hammering this thing down the drag strip.

[JayRolla]

1st off without looking at anything you should be tuning in lambda instead of AFR. Also why shooting for such a rich idle and cruise? Shoot for 1.00 idle/cruise in lambda.

1. With your settings it should take a minute or so of e85 hitting the sensor for changes to happen.

2. I would run closed loop using o2's and STFT to get your target idle cruise.

3. I adjust the multiplier so I am getting full timing with 50% or more content.

4. You will probably never see knock again with 50% or more E so dont use that for tuning anymore. You want to use a dyno, track or at least draggy to get MBT now.

[BrodyO]

1st off without looking at anything you should be tuning in lambda instead of AFR. Also why shooting for such a rich idle and cruise? Shoot for 1.00 idle/cruise in lambda.

1. With your settings it should take a minute or so of e85 hitting the sensor for changes to happen.

2. I would run closed loop using o2's and STFT to get your target idle cruise.

3. I adjust the multiplier so I am getting full timing with 50% or more content.

4. You will probably never see knock again with 50% or more E so dont use that for tuning anymore. You want to use a dyno, track or at least draggy to get MBT now.

Thanks for the reply. I do tune in lambda and target lambda 1 for idle and cruise. I have been struggling to dial in my fueling with a hot engine/ambient temperature. My lambdas tend to lean out a fair bit when it's hot outside and the trucks been running a while so my rich idle/cruise helps ensure I don't go too lean. I know this is just a bandaid. As far as my AFR references, that's just based off of me reading the gauge on my dash on the fly, it gets logged into my scanner as lambda. I'm unaware if I'm able to change the output on the gauge from AFR to lambda, I'll look into that.

I will be turning on closed loop and STFT soon, Just need to drill and weld a couple 02 bungs for the narrow bands.

The multiplier I was referring to was regarding fuel only related to alcohol content. My worry is that I don't have enough multiplier in there even though my math says I do. With 40% alcohol it should be a stoich of 12.4:1 but I was able to run quite a bit leaner than that but I don't run leaner than 14.7 with this same calibration and 91E0 fuel.

[07GTS]

comp change thresh, is the percentage it will change before adjustment, factory has it set to 2% which i kept seems good prob dont need it lower then that, then u have the delay and transition volumes which is the fuel it will use in the fuel lines before the change in ethanol will affect the feed to cylinders, this is normally low just have to work it out based on where the sensor is located in the system, also proper and accurate injector data will make it all work alot better over the shift from petrol to e85

[BigTuner]

comp change thresh, is the percentage it will change before adjustment, factory has it set to 2% which i kept seems good prob dont need it lower then that, then u have the delay and transition volumes which is the fuel it will use in the fuel lines before the change in ethanol will affect the feed to cylinders, this is normally low just have to work it out based on where the sensor is located in the system, also proper and accurate injector data will make it all work alot better over the shift from petrol to e85

A wideband sensors only measure lambda, i.e. how close the air fuel ratio is to stoich, it does not know what fuel you are running. Almost all widebands that show AFR are showing it on the gas scale, they take the lambda reading, multiply it by 14.7 and give you your gas AFR. The moment you change fuel the numbers are not your actual AFR, if you are seeing an AFR of 14.7 on your wideband you are at 1 lambda which is what you are looking for. Forget AFR and get used to thinking in lambda and things will be much easier, with the advent of flex fuel and even the 10-15% alcohol in some pump gas AFR is outdated.

[BigTuner]

I can't believe there are any scanners out there that won't offer a lambda reading/output but I could be mistaken, I know on the AEMs that not only can you switch it to lambda with a press of the button the front face can be flipped around to show the graduations in lambda.

[sgod1100]

I can't believe there are any scanners out there that won't offer a lambda reading/output but I could be mistaken, I know on the AEMs that not only can you switch it to lambda with a press of the button the front face can be flipped around to show the graduations in lambda.

When I first got my FF sensor (running a E50-55% blend) all I needed to do was switch the scanner from afr to lambda and BAM..done.

[BigTuner]

When I first got my FF sensor (running a E50-55% blend) all I needed to do was switch the scanner from afr to lambda and BAM..done.

Yeah in the scanner its easy, but he was talking about watching his wideband gauge in the car while driving and I think that's where he's getting thrown off.

[sgod1100]

Yeah in the scanner its easy, but he was talking about watching his wideband gauge in the car while driving and I think that's where he's getting thrown off.

ohh gotcha..yeah, trying to still talk in terms of AFR once you go FF just gets confusing especially when running a blend. My WB gauge is actually hidden right by the right foot of the passenger...I didn't want any gauges shown in my car, but obviously needed it for tuning purposes

[JayRolla]

I can't believe there are any scanners out there that won't offer a lambda reading/output but I could be mistaken, I know on the AEMs that not only can you switch it to lambda with a press of the button the front face can be flipped around to show the graduations in lambda.

You blew my mind. Ive owned many AEM wbo2's for over 20 years and didnt know lambda was on the back of the faceplate. LOL.

[sgod1100]

You blew my mind. Ive owned many AEM wbo2's for over 20 years and didnt know lambda was on the back of the faceplate. LOL.

that makes two of us...lol

[BigTuner]

You blew my mind. Ive owned many AEM wbo2's for over 20 years and didnt know lambda was on the back of the faceplate. LOL.

Haha glad I could help, your results may vary, I can only confirm that the X-series gauges have the dual faced face plates, not sure about their other stuff.

[BrodyO]

A wideband sensors only measure lambda, i.e. how close the air fuel ratio is to stoich, it does not know what fuel you are running. Almost all widebands that show AFR are showing it on the gas scale, they take the lambda reading, multiply it by 14.7 and give you your gas AFR. The moment you change fuel the numbers are not your actual AFR, if you are seeing an AFR of 14.7 on your wideband you are at 1 lambda which is what you are looking for. Forget AFR and get used to thinking in lambda and things will be much easier, with the advent of flex fuel and even the 10-15% alcohol in some pump gas AFR is outdated.

Sorry total brain fart on my end. I work as an powertrain engineer for a large powersports manufacturer and all the data I look at is in Lambda so that's why this stuff had me confused a bit. So technically as I had it set up even with the 40% ethanol mixture I would've been targeting 14.7:1 for stoich via the gauge output despite the true stoich ratio of that fuel being 12.4:1. Before I saw your reply's I had looked up changing my gauge (Innovate LC-2) to a lambda output as you were all mentioning with your AEM's. It's not as easy on mine as it needs to be reprogrammed through an app but I ordered the proper cables and that's what I planned to do, that'll make much more sense to me going down the road and I'm due for a free air calibration anyways. I know what my engine sounds like when it's running too lean and I certainly never felt like that with this mixture so now it all makes sense.

Thanks to everyone for the help here. Much appreciated. Switching the gauge over to Lambda so all will be well. Wish they just came like that, I think everyone in the know agrees that lambda is the best way to do it.

For a deeper understanding of the gauge output, this video is great: https://www.youtube.com/watch?v=8IuYRVgMlDg