wbgordon

What's the verdict out there on "up to 10%" ethanol content in the fuel we now are forced to put in our not-specifically-built-for-ethanol Porsche cars? I hear it's OK so long as it does not exceed 10%. But can we trust the oil companies making the "up to 10%" assertion?

Edgy01

Porsche has been working on producing an engine with reduced BTUs rather successfully. Years ago you wouldn't dare do what we're doing today.

As much as I feel we are being robbed by the oil companies by essentially stealing our octane, it's what it is.

1999Porsche911

What is a "not-specifically-built-for-ethanol" car?

There is absolutely no problem running E10 in your car. Other than slightly less power E10 has many benefits over pure pas.

Crazy Canuck

We've been forced to use "Up to 10% Ethanol Enhanced" gas at most stations here in Ontario for years. Octane is 94.

wbgordon

I wrote the above tongue in cheek but more pointedly to underscore the fact that Porsche cars were not built "specifically" to run on ethanol fuel, hence the question. From what I have heard (and for what it is worth), high-performance motors do not run as efficiently on the stuff.

Ray S

I have heard this "less power" claim made before, but i have never been able to confirm it via an authoritative source.

Obviously, E10 will reduce fuel efficiency but do you have any documents or web sites that you could direct me to that will verify E10 affects power output to the wheels?

purrybonker

I doubt your Porsche really cares very much about ethanol - there are apparently some issues (these have been discussed in many places) with high levels of ethanol, but very, very much less so with modern engine management systems.

Ethanol is an oxygenate (replacing MBTE in this role due to pollution/emissions concerns and is also targetted as a means to reduce reliance on fossil fuels - choke, cough, laugh, sneeze) and it actually has a high octane rating. Octane rating is not an issue in this context, all that octane rating really is is the speed at which the fuel mix releases energy as it is burned. That's why water injection is a way to compensate for less than desirable octane levels - it slows down the speed of burn (but contributes no energy, obviously)

Octane is not about power, BTUs are a measurement of power/energy. Ethanol has a high octane rating, but a lower BTU level per given volume than gasoline - so there are minor compromises in power and mileage in an ethanol fuel blend. BTUs or power is also not really a significant issue in this context.

Ethanol has a different stoichiometric level than gasoline - "stoich" is the optimum air-to-fuel ratio at which fuel may be burned to produce the maximum energy output, neither over-lean nor over-rich. If I recall correctly, gasoline is like 12.7 or something, ethanol around 11. Someone will correct me if I'm off target I'm sure.

In old engines (e.g. without O2 sensors) engines "tuned" for gasoline would run the risk of running over-lean with an ethanol blend. This could result in engine damage if not compensated for.

But all modern engines have engine management systems that modify air/fuel ratios to compensate for ethanol blended fuels.

So the clumsy answer to your question is that unless you're driving something prior to, say a 964 - your engine couldn't really care less about whether you put ethanol in the tank.

Also - the "oil companies" don't like ethanol - it is a PIA for them. Ethanol is a emissions and economic/political issue, that's all.

Crazy Canuck

There are fewer BTUs in Ethanol compared to regular gasoline. You have to burn more Ethanol by volume to equal the power contained in gasoline. THis equates to lower milage.

1999Porsche911

Actually, with me stating it, it must be so.

The BTU of E10 is 97% or so of the BTU of gasoline. Therefore, the ethanol produces less energy. This is such a small difference that a driver would never be able to notice.

E0 = 116,090 BTU's
E10 = 112,114 BTU's

Ray S

I understand that ethanol contains less energy. However, it is also my understanding that the ECU compensates for the small decrease in energy by using more fuel (thus producing lower gas mileage) to produce the same power level.

I have seen others also make the same "power reduction" claim that you are making. I'm not saying you are wrong (but that possibility does exist ), only that I'd like to read more about the testing involved to confirm the claim

I was just wondering if you (or anyone else) had any documentation to back up the info?

cviles

The biggest problem you'll have with ethanol at higher concentrations is it will start to eat components of the fuel system that aren't designed to handle it. Hoses and seals will be dissolved. Gasoline is used to cool your fuel pump, and ethanol is less efficient than gasoline for that. And ethanol burns differently than gasoline.

However, all current models handle 10% ethanol just fine -- My handy-dandy "Porsche and the Environment' guide that came with the latest Christophorus confirms this. Just don't put E85 in your car and you'll be fine.

V2Rocket

since when were us porsche guys ever concerned with MPG? lol...

Fahrer

As far as I am concerned, the energy content/octane is a relatively minor issue. The more imprtant issue is whether the materials in the Fuels system can handle the ethanol. Fuel systems are made of steel, SS, varying types of rubber, and different plastics including fluoropolymers, PA11, PA12, and for some tanks, PE. I know for a fact that one widely used plastic for fuel systems ( globally) is negatively affected by ethanol. I have first hand experience with fuel system problems with Saturn cars that used ethanol containing fuel for factory fill. Extraction of plasticizer from the fuel lines while the cars sat around resulted in severe driveability problems ( plugged fuel injectors).

I would definitely avoid any brand of gasoline that advertises that fact that it contains ethanol. I believe almost all cars are designed to operated satisfactorily on fuels containing alcohol but I am not convinced they have really fullytested the resistance of the fuel system materials to alcohols.

1999Porsche911

Sounds like you got your knowledge of E10 for some of the scare sites on the internet. ALL cars. That's ALL cars, are approved for E10, and NO manufacturer has reported any problems with E10 and corrosion.

BTW. energy content and octane are unrelated. Octane is not an energy producer.

There has been 30+ years of use of E10.

KBS911

"The BTU of E10 is 97% or so of the BTU of gasoline. Therefore, the ethanol produces less energy. This is such a small difference that a driver would never be able to notice."

So:

E0 = 116,090 BTU's x .90 = 104,481
E10 = 112,114 BTU's x .10 = 11,211
E-10 Total BTU = 115692

So that means net 398 BTU loss. Don't think it will make too much of a difference.

The real problem is if you have a boat with a fiberglass tank. Many boaters are experiencing problems with damaged fuel tanks.