E15 gas coming

[adias]

E15 gas is coming with the promise that E91 will always be available. I doubt the latter.

Our cars on E10 have some issues that I, personally, mitigate dropping 4oz of StaBil 360 on every tank. What is the situation with E15?

[gamin]

Somebody please chime in here. I am sure that I am not the only one interested in this subject.

[tirwin]

This has been coming for a long time. Is there something new?

It began with the push for E10. The rationale was to reduce US dependence on foreign oil. Other people believe it was to line people’s pockets who had an investment in ethanol. There is money involved and therefore there are “scientific” claims to back up every agenda.

Some people are saying that E15 is ok for cars post-2001. I’ve never seen any rationale on how they arrived at 2001 and not 2000 or 2002 or 1935. Other groups claim that ethanol gas causes premature engine wear.

I have lawn equipment that explicitly says E10 or non-ethanol gas only with a big no E15 sticker.

It will be a long time before E15 is the only thing available.

I have 91 non-ethanol available locally so that’s what I try to use in the 911. 93 E10 is the normal premium. I’ve noticed in California that I rarely see 93. Mostly premium gas is 91 as I recall.

[RedCoupe]

I've learned not to trust the ethanol percentages stated on the pumps. My son has an off road racer that runs on E85. We have a test kit that we check every batch of fuel we buy. E85 has ranged from 60 percent alcohol to well over 90. So, with E10 on the pump we may already be occasionally seeing E15 (or more).

[David Inc.]

I don't know if it's still happening but there were investigations done into gas stations years ago that found many increasing the ethanol percentage in regular gasoline to raise the octane to premium levels, resulting in damage to vehicles. E10 was found to range from 15-20% ethanol at some of these stations.

[tirwin]

As I understand it, ethanol increases the octane level which reduces the possibility of detonation. I don't understand why that would damage an engine. Lower octane = greater risk of detonation. Modern engine management has knock sensors which can dynamically adjust timing in the event that detonation occurs. So some of the rationale for why certain year cars are "ok" is probably has to do with some data that says some percentage of cars manufactured after date X have some kind of minimum engine management functionality to avoid these problems. Just guessing though.

The purported problems with ethanol is that is traps moisture and can damage components like seals.

[gomezoneill]

The purported problems with ethanol is that is traps moisture and can damage components like seals.
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^ THIS ^

[GH85Carrera]

Originally Posted by gomezoneill

The purported problems with ethanol is that is traps moisture and can damage components like seals.
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^ THIS ^

The ethanol traps water and is really really bad for CIS systems. Even a little water in the FI system will cause real issues if the car sits long.

And be sure ALL the rubber fuel hoses have been replaced. Ethanol will eat fuel hoses and even fuel injectors if they just site for a while.

[WolfeMacleod]

Originally Posted by tirwin

This has been coming for a long time. Is there something new?

.

I don't want to PARF this up, but..

https://www.epa.gov/newsreleases/epa-delivers-president-trumps-promise-allow-year-round-sale-e15-gasoline-and-improve-1



https://www.reuters.com/article/us-usa-biofuels-ethanol/trump-lifts-curbs-on-e15-gasoline-to-help-farmers-angering-big-oil-idUSKCN1T11BN

My understanding is that E15 in the summer will cause increased smog.

[GH85Carrera]

Yep, but the corn farmers and corn states will make millions. It is a big powerful lobby.

[spuggy]

Originally Posted by tirwin

As I understand it, ethanol increases the octane level which reduces the possibility of detonation. I don't understand why that would damage an engine. Lower octane = greater risk of detonation. Modern engine management has knock sensors which can dynamically adjust timing in the event that detonation occurs. So some of the rationale for why certain year cars are "ok" is probably has to do with some data that says some percentage of cars manufactured after date X have some kind of minimum engine management functionality to avoid these problems. Just guessing though.

Increasing the proportion of ethanol in the fuel requires a richer mixture to achieve stoich. Too lazy to do the math, so found this AFR Gasoline - E10 Wide Band 02 sensor tuning using Lambda, which contains this quote

Stoich for gas is 14.7 AFR. Stoich for Ethanol is ~9.00AFR. That means that Stoich for E10 would be (14.7 x 0.90) + (9.00 x 0.10) = 14.13AFR.

So if the marked as "up to 10% ethanol" E10 at the pump is actually 15-20% ethanol, it'll need even more fuel to hit lambda.

The issue is that older cars may be limited to how much extra fuel they can deliver, can't easily be tuned to deliver extra fuel in some part of the range and not others - or simply don't know that they need to/can't react to different fuel on different days.

This extra fuel requirement is just dandy in a flex-fuel system that dynamically senses the composition of the fuel arriving at the sensor and adjusts fuel/ignition to suit. With a stand-alone ECU, wire in a $50 GM fuel sensor, set up trims and good to go.

Good luck doing that with carbs or CIS - especially if whatever you're getting at the pump is varying wildly from day to day...

Even a Motronic won't work well - they run closed-loop on the O2 sensor so can compensate (at least up to the limits of fuel injector capacity) - but IIRC they go to a fixed map for WOT. Which, of course, was designed for E0 gas. So, if left standard, that map will logically result in leaner and leaner mixtures as the proportion of ethanol increases....

Originally Posted by tirwin

The purported problems with ethanol is that is traps moisture and can damage components like seals.

And hoses. And turns to varnish in the fuel system if allowed to sit too long. And is hydroscopic, so the water it retains can rust components in the fuel system.

[tirwin]

Good stuff, spuggy!

[tirwin]

By the way, many of the auto makers are pushing back on E15 because of the lack of long-term evidence of the implications.

Just do some basic math. They are concerned about potential liabilities of premature component failures. At a minimum they have warranties they have to stand behind. And let's face it, the general public isn't going to care who's at fault if E15 starts causing problems. Customers will just blame the car manufacturers. In our litigious society, you can see class-action lawsuits coming.

And I get their position. From an engineering perspective, you always have a certain set of assumptions. Violate those assumptions and all bets are off. Were they really planning for E15 to be used en masse across their entire fleet a decade ago? I doubt it.

My soapbox on this is that all of these changes to fuel and environmental requirements are forcing the auto industry to make disposable vehicles. What is the environmental impact of that in the long run? It can't be good either. Just look at all of the precious metals required to make batteries in hybrids. Raise your hand if you think that is sustainable either.

[pmax]

Originally Posted by spuggy

Good luck doing that with carbs or CIS - especially if whatever you're getting at the pump is varying wildly from day to day...

Even a Motronic won't work well - they run closed-loop on the O2 sensor so can compensate (at least up to the limits of fuel injector capacity) - but IIRC they go to a fixed map for WOT. Which, of course, was designed for E0 gas. So, if left standard, that map will logically result in leaner and leaner mixtures as the proportion of ethanol increases....

Later CIS systems has a lambda sensor which can compensate as well.

[tirwin]

I think spuggy’s point is that our older lambda CIS systems are calibrated for 100% non-ethanol stoich, which is different than E10 and E15 stoich.

[pmax]

Originally Posted by tirwin

I think spuggy’s point is that our older lambda CIS systems are calibrated for 100% non-ethanol stoich, which is different than E10 and E15 stoich.

Good point about the non ethanol stoich which both CIS/lambda and Motronic adjust to using a similar O2 feedback (which is what I was trying to say in my previous post). But yeah, the ratio is wrong for Exx. Perhaps a new chip for the ECU in the latter adjusted to the lower stoich ? The system already has a gas selection switch if I recall. No programmability in the CIS "ECU".

[spuggy]

Originally Posted by pmax

Later CIS systems has a lambda sensor which can compensate as well.

Yes; both the CIS and Motronic systems have a narrow-band. Not useful for anything other than part-throttle, as neither use the lambda sensor for WOT.

Being off due to %-age of ethanol seems like it could be kind of a big deal to me - for example, instead of wanting 14.7 AFR for stoich, on E20 you'd need AFRs of 13.56.

At cruise, you'd be fine, if the system can add enough fuel to compensate - stoich is stoich.

But when you drop out of closed-loop, you use the cells in the map. Or the control pressure. And those were set based on gas with 0% ethanol.

With E0 "real" gas, an AFR of 12.0 is often considered best for acceleration, with 12.5 AFR being "good" for WOT (on "old" combustion chamber designs).

Which is 0.8 and 0.85 lambda, respectively.

With E10 or E20, AFRs required for those lambda numbers vary; my back-of-envelope sums (which could easily be wrong but don't look insanely off) say E10 AFRs of 11.52 and E20 AFRs of 11.04 are 0.8 lambda.

So a factory system only ever intended to use non-ethanol gas - with AFR values to suit - don't look optimal on E10 - and only get worse as the percentage of ethanol goes higher.

At best, higher percentages of ethanol for normally-aspirated cars mean you are leaving power on the table. To say nothing of burning more gas.

For EFI turbos, the obvious thing do is to say "hey-ho" and start buying E85, cranking up boost control to take advantage of the anti-detonation properties...

[spuggy]

Originally Posted by pmax

Good point about the non ethanol stoich which both CIS/lambda and Motronic adjust to using a similar O2 feedback (which is what I was trying to say in my previous post). But yeah, the ratio is wrong for Exx. Perhaps a new chip for the ECU in the latter adjusted to the lower stoich ? The system already has a gas selection switch if I recall. No programmability in the CIS "ECU".

No, actually, stoichiometric ratio is stoichiometric ratio. Period.

That's what both narrow-band and wide-band O2 sensors report.

The AFR necessary to achieve stoichiometric ratio varies depending on what fuel you're running.

And this is why most these days tune in terms of lambda...

[tirwin]

My understanding of Stabil 360 is that it addresses some of the issues of ethanol fuel like the water absorption and prevents varnishing. No idea how it would work on E15. I suspect it doesn’t change the stoich value, but it would be nice to know for sure.

In theory you could adjust CIS to be a little richer at idle and WOT by setting fuel pressures. I guess it would be ok for non-lambda CIS. But for lambda you’re stuck with the O2 sensor that is calibrated for E0 gas.

[tirwin]

Originally Posted by spuggy

No, actually, stoichiometric ratio is stoichiometric ratio. Period.

That's what both narrow-band and wide-band O2 sensors report.

The AFR necessary to achieve stoichiometric ratio varies depending on what fuel you're running.

And this is why most these days tune in terms of lambda...

But stoichiometric is different for gasoline and diesel, no? 14.7 for gasoline and 14.5 for diesel. I thought that’s what you were getting at.