Any special consideration for e-10?

[radkon]

So should you tune e-10 stoich for the same as "gas" to 14.68 AFR? I am tuning my Tahoe and since its flexfuel capable it has a ethanol sensor in the tank. No matter what I did I couldn't get the AFR to read 14.7 on my wideband, all I got was 13.8.

I remembered our gas is e-10 (90% gas 10% ethanol) and after some fooling around I found the stoich table in HP tuners has a linear scale from 100% gas to 100% ethanol and low and behold e-10 was right around 13.8 AFR I set e-10 for ~ 14.6 AFR and voila! worked perfectly. After cruising for about 60 miles I noticed a 2 MPG gain on the tahoe.

Searching around I've found that E-10 stoich is between 14.03 and 13.9 AFR does that mean I should set the AFR on my other cars to 14.03 as well since they don't have ethanol sensors or should I leave it at 14.68 and call it a day?

[EC_Tune]

Without the ethanol sensor (or virtual sensor like the NBS E85 trucks and such) the car/truck can not determine ethanol quantity.

[radkon]

Without the ethanol sensor (or virtual sensor like the NBS E85 trucks and such) the car/truck can not determine ethanol quantity.

I understand that but should I change the stoich ratio (in the car without the senor) from 14.68 to 14.03 if I know my gas contains E-10?

[eficalibrator]

Yes, if the gas has significant ethanol content and the vehicle does not have a fuel composition sensor, you should change the stoich point in the ECU calibration.

Stock vehicles get away with it because the shift between E0 and E10 is inside of the allowable fuel trim limits for closed loop. If you plan to spend more time operating at the outer edges of the engine's performance envelope, you want the ECU to know the proper stoich ratio. Otherwise, "10% enrichment" may no longer really be 10% enrichment.

[radkon]

Yes, if the gas has significant ethanol content and the vehicle does not have a fuel composition sensor, you should change the stoich point in the ECU calibration.

Stock vehicles get away with it because the shift between E0 and E10 is inside of the allowable fuel trim limits for closed loop. If you plan to spend more time operating at the outer edges of the engine's performance envelope, you want the ECU to know the proper stoich ratio. Otherwise, "10% enrichment" may no longer really be 10% enrichment.

Thanks Greg, I just pulled out my copy of your book this morning to review and see if this was addressed. Do you have any other tips on tuning flexfuel vehicles? Perhaps an addendum to your book?

Also can you define significant ethanol content? Should I be concerned about tuning an LS1 based engine (GTO) to 14.68 and running e-10 in it? What I may do is pick a median AFR say 14.2 or so and leave it be

[eficalibrator]

Do you have any other tips on tuning flexfuel vehicles? Perhaps an addendum to your book?

Also can you define significant ethanol content?

The next book will focus on standalone speed-density systems. I'm sure a LOT of it will apply to those of you interested in S-D tuning on these cars as well though.

10% is "significant" in my book. If you know that you always have this blend (some areas only get it seasonally), I would change the stoich point accordingly.

Keep in mind that ethanol is ~112 octane, so as you mix it in greater %'s, the knock threshold goes up as well. I recommend you take advantage of this with a bit more ignition lead at WOT once you've got the proper AFR.

[radkon]

The next book will focus on standalone speed-density systems. I'm sure a LOT of it will apply to those of you interested in S-D tuning on these cars as well though.

10% is "significant" in my book. If you know that you always have this blend (some areas only get it seasonally), I would change the stoich point accordingly.

Keep in mind that ethanol is ~112 octane, so as you mix it in greater %'s, the knock threshold goes up as well. I recommend you take advantage of this with a bit more ignition lead at WOT once you've got the proper AFR.

Thanks Greg! Any "word on the street" when the next book is due?

[Rhino]

Without the ethanol sensor (or virtual sensor like the NBS E85 trucks and such) the car/truck can not determine ethanol quantity.

Can you explain the virtual sensor? Is this something we could emulate on another PCM? Specifically I'm working on an '02 LS1 swap. I would love to convert it to a true flex fuel operation, rather than running only e85.

EDIT: Finally found the answer with a search. I guess I'll have to look to an E40 PCM swap if I want it to work.

[chakoman]

I did some experimenting with the stioch afr in my 07 silverado. I have e-10 where i live so I changed the stoich afr to 14.1 because i do not have a fuel comp sensor. I figured my fuel trims would go positive to shoot for the richer mixture but I was wrong. The pc was actually pulling fuel. mind you this is in closed loop. I then changed the stoich to 15 to try lean cruise. The pcm started adding fuel thus positive trims. Just a little food for thought.

[EC_Tune]

There are flex fuel truck cals that you could run in a car application. You'll lose VATS though. Then you can wire in the flex fuel sensor from the trucks. 04 Vette/GTO/Truck used the same PCM and the truck had flex fuel capability.

[Rhino]

There are flex fuel truck cals that you could run in a car application. You'll lose VATS though. Then you can wire in the flex fuel sensor from the trucks. 04 Vette/GTO/Truck used the same PCM and the truck had flex fuel capability.

Thank you for the reply. I do appreciate your time and effort. I'm excited to get this going. As this swap is destined for a '68 Camaro, I'm not too interested in VATS. I'll have my own kills built into the system.

Do you happen to know if the '04 GTO used the same PCM as the '05+ years? A better way to word the question would be; Can a more modern PCM could be used with a 24 tooth reluctor and cable throttle body? If I can find one, it would save some time and money by not having to do a significant amount of parts swap on my engine as well. (reluctor wheel, front cover, cam sensors, etc...)

EDIT: It looks like the GTO retained the 24 tooth reluctor through it's run. It was the Crate and Vette motors that swapped to the 58x reluctor. The '04 GTO utilized a cable actuated throttle. As long as the same PCM was used on the '04 as the '05+ GTO's I think it would work. Unfortunately the wiring harness is completely different between my '02 LS1 PCM and the E40. Looks like I'm needing to do a little searching.

[EC_Tune]

None of the LS2 or later engines (05+ GTO/SSR/Trailblazer SS) run cable throttle so I would go with the 04 PCM.

[GVBHunt]

So am I correct to assume that no vehicle (trying to determine if my '07 NBS Sierra has this sensor) that is not E-85 compatable has this Fuel Composition Sensor and that the Stoich AFR table that goes from 0-100% alcohol content is only reading the 0% field to come up with the AFR?

[GVBHunt]

Anybody?

[EC_Tune]

The NBS trucks use the "virtual" sensor" as in no actual sensor.

[Gh0st]

Here's some questions:

1. How do you KNOW how much exact ethanol is in your fuel? Don't the pumps say "MAY contain UP TO 10%"?

2. I'm assuming after you change the stoich, you'll have to go redo all of your VE/MAF tables all over agian.

[EC_Tune]

^^ A VERY good point! Up to does not mean =.

[radkon]

Here's some questions:

1. How do you KNOW how much exact ethanol is in your fuel? Don't the pumps say "MAY contain UP TO 10%"?

2. I'm assuming after you change the stoich, you'll have to go redo all of your VE/MAF tables all over agian.

Well my 03 Tahoe has a sensor in the tank and I picked up the commanded AFR which is what brought up this whole discussion (1st thread).

The sticker on the pump and a test kit (which I'm sure aren't cheap, if even available) are probably the only ways to tell.

[Joe_G]

Great thread, we now get E10 year round so this of interest to me.

What kind of adjustments would be needed for WOT fueling? Would the same parameter apply as described above, that is, E10 stoic is 14.03 vs 14.69 for gas, or 95.5%...so if I want to run 12.6 WOT AFR, should I run 12.04 AFR at WOT?

I should add that I've got a wideband installed and access to a dyno and try to tune my car for highest horsepower yet remain safe as I drag race it quite a lot. So since I'm stuck with the lower BTU content of E10 I'm interested in knowing if I can get more power out of it. I know at my last 2 dynos (with E10, though I didn't think about that at the time) I'm getting best power at about 12.6 (never tried richer and leaner has no more power) and 24 degrees of timing (more timing doesn't add power, and it doesn't knock at 24).

Also - for those that adjusted stoic to 14.03, did you notice any change to MPG or the way the car runs and drives?

[MikeGyver]

...What kind of adjustments would be needed for WOT fueling? Would the same parameter apply as described above, that is, E10 stoic is 14.03 vs 14.69 for gas, or 95.5%...so if I want to run 12.6 WOT AFR, should I run 12.04 AFR at WOT?...

I'd like to know that, too. You have me wondering if that's why my truck has always been so knock prone. Even though it is 93 octane, maybe I still need more fuel in boost. It's been a lot of years since we haven't had E10 here.