Milan

That's the problem though, the sensor is measuring gasoline, not ethanol. It's assuming that anything in the tank that's not gasoline is ethanol.

So in that situation, it would think something like E55 was in the tank...not accurate.

Final question, what happens to ethanol when you store it for long period of time? It attracts water.

Go run straight water through your FF sensor..it will say E100

Podium

You obviously don't like flex fuel or e85 so I don't get why you're in this thread. It works and it works well. Hoepfully we can get this thread back on track.

wilson34

I have had much success running flex fuel in my CTS-V, obviously I ran a wideband so I was always able to verify the sensor to make sure there was no "lack of reliability" according to Milan. Every does need to understand the storage issues with E85, but other than that I don't see the problem with taking advantage of the additional octane from E85.

TTBlueZ06

Milan was running a stock bottom end ls6 on E85 with a YSI making 1000hp years ago... Do not make assumptions because you disagree with their logic.

slow ride

I would rather have flex fuel than not if using pump e85 imho. In our area they don't require strict ethanol content at the e85 pumps so now it can very e55-e83. Most of ours test at e70-75 which is fine, but it wouldn't hurt to have a bit more information from the sensor even if it can read false due to water content.

LTstewy8

It adjusts fuel trims (assuming fuel trims are not turned off/ open loop) the same way it always does on a non-wideband capable pcm. The narrowband targets stoich regardless of ethanol content or fuel type.

As for water detection, the sensor will output a specific frequency outside of normal operating range (50-150Hz) if water is detected (180hz maybe?). There is an associated trouble code (P0178) for this condition on vehicles equipped with flex fuel from the factory

Pekka_Perkeles

Maybe P0177 instead?

"FFS circuit range/performance" sounds good.

Very good to know anyyway. I was not aware of this.

Supercharged111

I have a problem with this. People who read the big secret on here and don't do it armed with that info never were going to anyway. The people that do would have still figured it out some other way. Seems pointless to keep the secret as most people are too scared to touch wires much less start PCM/OS/segment swapping things around.

LTstewy8

Not exactly sure which dtc it would report, but just to clarify- you would need an ecm capable of taking advantage of that particular flex fuel sensor functionality.

Sorry to derail the thread, I'm looking forward to some good results for those who are trying to make it happen.

Podium

And what does it matter what he had? Doesnt justify being a ********. I know plenty of guys who make high power and dont know what they are talking about.

Drewstein

You're expecting someone who invested time and money in something to give it to you for free; that's the issue. Maybe if you PM the guy and compensate him for the info then they would share it.

Podium

His point it that why comment if youre not going to share anything. I agree with that.

Milan

It doesn't matter because the stock flex fuel was not intended for performance applications. Unless you have a wideband off of each bank that is constantly adjusting fuel trims there is no point in knowing what percentage of non-gasoline you have in your tank.

If you want proper flex fuel you will need standalone. Just because some shops got it to work with the stock ECU doesn't help much. The stock setup was inadequate from the factory. Now if you have a Cobalt SS or something that has a factory wideband, that's a different story.

Supercharged111

Thank you.

Please expand on this, I don't see the need for widebands here since all a factory O2 does is trim. Narrowbands only read in lambda* so it doesn't matter what the AFR is especially with a fuel sensor telling the PCM where to start.

Milan

All o2 sensors read in lambda.

The stock narrowbands only function in closed loop, when you go WOT you are in open loop. Most modern performance cars will use the widebands to correct to what AFR/lambda/etc. you are commanding. Without this, there is no way to properly do flex fuel IMO. Sure the factory PCM has similar functionality, but it was only designed for a stock vehicle

Supercharged111

If your VE and MAF is set up correctly then commanded fueling matches delivered. I fail to see how flex fuel would affect this. Correcting WOT AFRs real time seems like a bass ackwards way to do it. Am I missing something here? Aside from the water thing.

Milan

MAF? Who is that applicable to in this forum?

So your approach is to tune on 100% gasoline, then do another tune on E98 and have the ECU be able to interpolate the values in between with 100% accuracy?

Supercharged111

I can't say, i've never dealt with E85 before. But I know the stock stuff can interpolate or else it wouldn't be flex fuel. Again, what am i missing here? Should I go pull up a stock flex fuel tune and report back?

5 Liter Eater

The purpose of this thread is to discuss retrofitting a C5 with another compatible PCM with the flex fuel tables and setting up the tables to do just that; determine the ethanol content and alter stoich to in-tern alter fueling based on the content. Also to add or remove timing based on ethanol content.

Sure an aftermarket system with closed loop WOT is better but there are plenty of gen4 PCM guys making tons of power on varying levels of corn and the PCM adjusts fuel and timing based on the ethanol content in closed loop or open loop. Granted it's not correcting fueling at WOT in open loop but it knows the ethanol content and it knows how to adjust the fuel so if you're commanding .8 lambda you get it on pump or corn or anywhere in between. I haven't seen mine differ much. EG if I dial my tune in on 93 and then run the same boost on corn I don't have to alter my VE.

BLOWNBLUEZ06@RKT Performance

This discussion reminds me of the virtual flex fuel option which can be quite nice in that if the flex fuel sensor mis-interpreted the ethanol content due to water contamination, virtual flex fuel would be able to see past this and act accordingly.

To answer another part of the discussion, technically it is possible to tune a car on 93 and then E98 and interpolate in between and achieve reasonable accuracy. Of course nobody would want to do that and then push their setup to the ragged edge with respect to commanded lambda, but you can certainly keep it safe and hold a significant margin for error by fattening it up a bit and softening up the tune.
As a Haltech dealer, I own a Haltech Elite2500 and have installed and tuned a handful. While it's certainly nice to have all the features that it offers, I consider it to be more of a luxury than a necessity. If a customer came to me and said " I want my car to be able to run ***** out with max performance and Flex fuel capability", I would insist on a good stand-alone ECU.