Flex fuel on the C5
Safety Car
Joined: Jan 2008
Posts: 4,797
Likes: 52
From: Boise
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
Burning Brakes
Joined: Sep 2016
Posts: 979
Likes: 102
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
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
Burning Brakes
Joined: Nov 2006
Posts: 892
Likes: 1
From: Pittsburgh PA
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.
Pro
Joined: Jul 2016
Posts: 520
Likes: 52
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.
Drifting
Joined: Feb 2006
Posts: 1,585
Likes: 15
From: New Hartford IA
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.
Racer
Joined: Apr 2007
Posts: 262
Likes: 3
From: Austin TX
It just takes care of it huh? How is it properly adjusting the fuel trims without a wideband?
In my experience flex fuel sensors are not accurate at all. Here is a scenario for you:
If you have 1 gallon of pump gas, E10, and you pour 1 gallon of water in there. So now you have 50% water, 50% E10. What is the ethanol content sensor going to read?
In my experience flex fuel sensors are not accurate at all. Here is a scenario for you:
If you have 1 gallon of pump gas, E10, and you pour 1 gallon of water in there. So now you have 50% water, 50% E10. What is the ethanol content sensor going to read?
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
Burning Brakes
Joined: Oct 2005
Posts: 1,089
Likes: 82
From: Kauhava, Finland
"FFS circuit range/performance" sounds good.
Very good to know anyyway. I was not aware of this.
Safety Car
Joined: Jan 2012
Posts: 3,956
Likes: 520
From: Da U.P.
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.
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Racer
Joined: Apr 2007
Posts: 262
Likes: 3
From: Austin TX
Sorry to derail the thread, I'm looking forward to some good results for those who are trying to make it happen.
Burning Brakes
Joined: Sep 2016
Posts: 979
Likes: 102
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.
Last edited by Podium; Jul 9, 2017 at 09:50 PM.
Melting Slicks
Joined: Feb 2006
Posts: 3,191
Likes: 43
From: Scottsdale Az
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.
Burning Brakes
Joined: Sep 2016
Posts: 979
Likes: 102
His point it that why comment if youre not going to share anything. I agree with that.
Safety Car
Joined: Jan 2008
Posts: 4,797
Likes: 52
From: Boise
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.
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.
Safety Car
Joined: Jan 2012
Posts: 3,956
Likes: 520
From: Da U.P.
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.
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.
Last edited by Supercharged111; Jul 10, 2017 at 07:17 PM. Reason: Meant to say lambda, not stoich
Safety Car
Joined: Jan 2008
Posts: 4,797
Likes: 52
From: Boise
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
Safety Car
Joined: Jan 2012
Posts: 3,956
Likes: 520
From: Da U.P.
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.
Last edited by Supercharged111; Jul 10, 2017 at 10:10 PM.
Safety Car
Joined: Jan 2008
Posts: 4,797
Likes: 52
From: Boise
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?
Safety Car
Joined: Jan 2012
Posts: 3,956
Likes: 520
From: Da U.P.
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?
Le Mans Master
Joined: Aug 2002
Posts: 8,472
Likes: 38
From: Houston TX
St. Jude Donor '11
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.
Last edited by 5 Liter Eater; Jul 11, 2017 at 04:23 PM.
Supporting Vendor
Joined: Apr 2012
Posts: 2,673
Likes: 370
From: Forney TX
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.
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.
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.
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