Stoichiometric with E40 PCM

[Mez]

My stock 2005 C6 Stoichiometric table is 14.7 no matter what % of ethanol. I normal run Shell or Exxon 93 octane but who knows what the % of ethanol is in the gas today.

Should I change this?

[eficalibrator]

Since your car is not a flex fuel vehicle, it doesn't matter if any cell other than the 0% ethanol stoich point is populated. It will only use that cell unless it has either a real or virtual flex fuel sensor enabled.

Pure iso-octane is 14.68:1, e10 is more like 14.13:1 so you'd be wise to at least split the difference in most regions today. It WILL change from tank to tank anyway, so it's a good idea to allow for closed loop correction after you've completed the tuning.

[LSX378]

Originally Posted by eficalibrator

Since your car is not a flex fuel vehicle, it doesn't matter if any cell other than the 0% ethanol stoich point is populated. It will only use that cell unless it has either a real or virtual flex fuel sensor enabled.

Pure iso-octane is 14.68:1, e10 is more like 14.13:1 so you'd be wise to at least split the difference in most regions today. It WILL change from tank to tank anyway, so it's a good idea to allow for closed loop correction after you've completed the tuning.

Greg, have you had any luck with enabling Flex Fuel on non flex fuel GM vehicles?

Thanks!

[eficalibrator]

There's a bunch of roadblocks to changing over to flex fuel that make it a bad idea:

1) Fuel system hardware, the in-tank hardware (level sender, wiring contacts, etc...) are all stainless on ethanol capable vehicles to avoid corrosion and dissolution.
2) There's A LOT more to changing the calibration than just flipping the flex fuel enable switch. There's a bunch of background tables that you don't see in HPT for FFV's that need to be calibrated specific to that engine/vehicle for the detection to work correctly.

In short, it's more trouble than it's worth. It's a far better idea to start with a flex fuel vehicle in the first place and just use the factory tuned calibration/hardware.

[Mez]

Thanks. Since the 2005 C6 does not have a flex fuel sensor as you indicated, I'll stay with the factory setting.

In any case, I try to avoid any ethanol blended fuels which are typically 10% or less. In Texas, its not as common as other parts of the country.

[Big Loser2]

I really do not want to convert to E85 but since the PCM already has all the info set up to adjust to the ethanol percentage how difficult would it be to add the sensor so it could at least adjust for the 10% or less. It seems that all of the fuel stations in south Florida have gone to that. Also what would be some good indicators to scan for to verify ethanonl is in the system. If none of the above would work would it be a good idea to to set the Stoichiometric to somewhere around 14.4?

[RWTD]

Big Loser2, please read eficalibrator's posts above.

In short:

You're not going to be able to just add the sensor, and if you could, tuning for such would be a nightmare, especially being that the current softwares do not have all the necessary parameters to make it function properly.

So, in other words, as Greg said, split the difference between the stoich values, and roll with it.

[LSX378]

Originally Posted by eficalibrator

There's a bunch of roadblocks to changing over to flex fuel that make it a bad idea:

1) Fuel system hardware, the in-tank hardware (level sender, wiring contacts, etc...) are all stainless on ethanol capable vehicles to avoid corrosion and dissolution.
2) There's A LOT more to changing the calibration than just flipping the flex fuel enable switch. There's a bunch of background tables that you don't see in HPT for FFV's that need to be calibrated specific to that engine/vehicle for the detection to work correctly.

In short, it's more trouble than it's worth. It's a far better idea to start with a flex fuel vehicle in the first place and just use the factory tuned calibration/hardware.

Thanks Greg. Thought as much. Will stick with changing the stoichiometric & PE table for the mix that is in the tank. Already have a stainless tank, getting stainless fuel line, and need to check the sender etc very soon. Apparently ethanol is 1 million times more conductive than gasoline, so like you say, stainless (etc) is essential.

[Pete@SpecialistTuning]

How does Diablosport advertize this programer as just install and fill up and enjoy?

https://www.diablosport.com/index.ph...isplay&pid=112

Pete

[LSX378]

Originally Posted by Pete@SpecialistTuning

How does Diablosport advertize this programer as just install and fill up and enjoy?

https://www.diablosport.com/index.ph...isplay&pid=112

Pete

If this is plug once, and play many, for any fuel mix without further adjustments, then it is what the factory ECM (at least a late model GM ECM) will do anyway. I can switch back and forth on a late model GM without touching it, though it does raise lean/rich DTC's once PE is used (at least from empty gas, to full E85 and vice versa), so for peace of mind, I do re-cal the ECM for the relevant stoich. Of course, revising DTC's is a "head in the sand" way of avoiding the situation......

I would guess, if a single calibration serves all situations, then they are relying on closed loop operation and trims to keep things running in tune, and have made some calibration changes to ensure starting, PE, and other open loop situations are mostly covered too.

Not optimum, but it is a solution, with unknown long term effects. Especially around stainless steel lines and fittings as Greg/EFI Calibrator points out. People will buy it and merrily motor along.

[Blades]

Originally Posted by eficalibrator

Since your car is not a flex fuel vehicle, it doesn't matter if any cell other than the 0% ethanol stoich point is populated. It will only use that cell unless it has either a real or virtual flex fuel sensor enabled.

Pure iso-octane is 14.68:1, e10 is more like 14.13:1 so you'd be wise to at least split the difference in most regions today. It WILL change from tank to tank anyway, so it's a good idea to allow for closed loop correction after you've completed the tuning.

Is E10 technically different from "Contains up to 10% Ethanol" labels seen @ seen at gas stations? Do you think this is going to raise the incident of detonation from "bad gas" from older gas stations? As in, water accumulation is going to separate the gas from ethanol and we're not going to be seeing all that much 'high-test'.

For this 10% blend, would the sensor even be all that accurate? Are there any cheap ways to identify the quality of the blend? I am running open loop, even so.. running cl would only set target afr to 14.7 when, as you say, it should be lower. Why haven't non-flex cars changed with the introduction of 10% eth? Makes me want to carry around a bottle of toluene, if it weren't so toxic.

[eficalibrator]

Originally Posted by Blades

Is E10 technically different from "Contains up to 10% Ethanol" labels seen @ seen at gas stations? Do you think this is going to raise the incident of detonation from "bad gas" from older gas stations?

The "gasoline" we buy at stations is a cocktail of various base stocks, octane improvers, detergents and other crap that varies from day to day. You never REALLY know exactly what you have, but it's still a good idea to try and be closer from the start.

For this 10% blend, would the sensor even be all that accurate? Are there any cheap ways to identify the quality of the blend? I am running open loop, even so.. running cl would only set target afr to 14.7 when, as you say, it should be lower. Why haven't non-flex cars changed with the introduction of 10% eth?

Going from a stoich of 14.68 to 14.13 is only a 4% shift, well within the limits of most vehicles. Factory fuel injectors have a tolerance of +/-6% anyway. Couple this with the above statement that "pump gas" blends vary from batch to batch gives us the reason why closed loop exists in the first place. All actual calibration/certification work at the OEM level is done with pure Indolene (stoich = 14.56:1) anyway. We allow closed loop to pull in the differences as customers drive the car in real world situations with real world fuels.

I just like having the trims as close to 0% as I can get them before I throw in any fuel spec changes. If I know that we have an average of about 5% EtOH content, it makes sense to bake that 2% shift of the stoich point into my PCM calibration from the start. That way I'm looking at trims of -1% to +1% instead of 0% to 4% as the blend changes.

[Blades]

Thanks for the reply. One more quick question, does the added ethanol impact flow rate? I suppose all these small variances could add up to a dangerous afr error in some cases.. ie people running OL. Would it be wise to set the stoich value somewhere in the middle of a presumed 10% eth? 14.4 maybe? I'm sure my estimated inj offset table is more of a threat.

[eficalibrator]

Originally Posted by Blades

Thanks for the reply. One more quick question, does the added ethanol impact flow rate?

The fluid densities of ethanol and gasoline are close enough to be negligible as far as injector flow rates are concerned.

Would it be wise to set the stoich value somewhere in the middle of a presumed 10% eth? 14.4 maybe?

Originally Posted by Me at the start of this thread

Pure iso-octane is 14.68:1, e10 is more like 14.13:1 so you'd be wise to at least split the difference in most regions today.