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My understanding is that octane rating is about the fuel's ability to resist pinging or pre-ignition, the higher the octane the higher the cylinder pressure before pinging. Again IMU, ethanol is less energy dense than gasoline (petrol) and therefore an ethanol containing fuel will generate less power per combustion than 'normal' gas at the same octane rating. In general the octane rating of 'normal' gas does not relate to energy density. Higher compression engines require a higher octane fuel.

(I'm happy to corrected or enlightened further.)
 

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Fuel Economy and Performance
A gallon of ethanol contains less energy than a gallon of gasoline, resulting in lower fuel economy when operating your vehicle. The impact to fuel economy varies depending on the energy difference in the blend used. For example, E85 that contains 83% ethanol content has about 27% less energy per gallon than gasoline (the impact to fuel economy lessens as ethanol content decreases). Engines in gasoline vehicles, including flexible-fuel vehicles (FFVs), are optimized for gasoline. If they were optimized to run on higher ethanol blends, fuel economy would likely increase as a result of increased engine efficiency.

Ethanol also has a higher octane number than gasoline, which provides increased power and performance. For example, Indianapolis 500 drivers often fuel their race cars with E98 because of its high octane. Several projects currently under way, including the Co-Optimization of Fuels and Engines initiative, seek to understand the potential for improving engine efficiency through the use of ethanol blends and other high-octane biofuels.

From: Alternative Fuels Data Center: Ethanol Benefits and Considerations

So yes, for the same octane, ethanol produces less horsepower, but you can get a higher octane fuel with ethanol and if you can tune the engine to burn that fuel efficiently, you get more horsepower.

I am not sure you said something different...:)
 

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And to take this to 718, the fuel system cant handle E85 as is because it cant inject enough fuel.
Thats why there arent any tune for it.
E85 in Sweden hovers around 102RON, little less at winter.
 

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Sooo, I do understand ethanol has less BTU(energy) than gasoline per volume, therefore we in the US see less MPG from using E10 gasoline verses 100% gasoline (of the same octane rating). My experience is ~10% less mpg. But, my real question is regarding any or all of the tuning maps-whether it is Cobb, APR, Softtronic, etc: with which gasoline formulation are they intended, if any? Again, somewhere I read that one of the tuners recommended using E10 and if only pure gasoline was used that E10 be put in every 3rd fill-up. What type of gasoline are those who have a tune (and I assume this only applies to the US but I am really not sure if EUR uses any blended gasoline) using? As far as the energy output the calculus is a bit more convoluted with multiple variables (ethanol by its make up introduces more oxygen into the equation changing the stoichiometry). I don’t want to get too deep in the weeds, but just the answer: E0 or E10 or it doesn’t matter? (and on which formation are the power claims?)
 

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Some of you are not getting the difference with ethanol. It does contain less energy, but to get to the same equivalent air-fuel ratio you have to inject more, so the energy ends up about the same. I have a WRX that has a flex fuel sensor... it can run any blend of ethanol. I mostly run it on E85. On E85 it injects about 30% more fuel to get to the same equivalent mixture ratio (lambda). I had to put much larger injectors in to run E85. This is for two reasons. The first is that I need 30% more fuel at the same boost. The second is that because of the much higher octane rating I can run higher boost (which requires more fuel again)... so I end up needing about 50% more fuel. The end result is that the car runs about 270kW ATW on 93RON petrol. On E85 it runs abour 330kW ATW. For normal around town driving, the fuel economy is about 25% worse (use about 25% more E85 for the same trip).

One other thing to mention is that the engine will run cooler (lower combustion temp) with E85 and you actually get a higher density of air in. Because you stick 30% more fuel in the engine, and that fuel needs to be vapourised, and turning a liquid into a gas takes energy, that energy comes out of the air going in and cools the air (kind of like water injection). Therefore the same volume of air contains more mass (and you need to stick even more fuel in to compensate). The combustion temps at the same power are lower as there is more mass in the cylinder to absorb the energy.

Now if you are using a certain fuel that is rated at a certain octain rating. Regardless of the composition of ethanol it will have that octane rating and that will cause a similar effect on the level of ignition timing you can run. The difference is that with ethanol, you have to put more in to get the same air-fuel ratio. So in a less advanced ECU it might run a little lean with say 10% ethanol. But late model ECUs have wide band oxygen sensors so they can sense the air-fuel ratio and adapt the tune accordingly. Of course with too much ethanol, the fuel system may not be able to cope with the additional fuel requirements.

My thoughts are that the 718 fuel system will cope with low amounts of ethanol (10%) at the power levels the turbo can support. But E85 is probably a no go. So mostly you just need to match the octane of the fuel you are using to the tune. Otherwise if you run a 93 tune on 91, the ECU will be continually adjusting the tune to prevent knock and that would provide inconsistent performance.
 

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Ethanol aside, what is the maximum octane our cars can take without a tune? I noticed at the track the other day they had 98 RON (93AKI) and 104 RON (100AKI).
You can run high RON racing fuels in the 718 and the RON will be fine with the ECU and you should get the most power the tune is capable of (you should get no knock). But note that high RON racing fuels are typically bad for O2 sensors. So you may find you cause failure of the O2 sensor prematurely. They may also do bad things to cat converters?
 

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(y) Looking forward for it. And nah... i am not beta bricking my ECU ;)

Can´t find a APR "Service" center in germany that will recall me, answer my calls etc.have no nerve to drive 500km to be dissapointed again :(
So i have to wait.
 

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(y) Looking forward for it. And nah... i am not beta bricking my ECU ;)

Can´t find a APR "Service" center in germany that will recall me, answer my calls etc.have no nerve to drive 500km to be dissapointed again :(
So i have to wait.
It seems to be the case for all Europe APR dealers. Johan had to involve APR USA to get response from his nearest dealer. In my case I have been asking APR (USA) several times if there will be a tune for opf equipped 718’s and the answer was pretty vague. I am starting to concider FVD Brombacher, they have a flash tool and the knowledge to implement some features APR offer like left foot braking.
 

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Where are you based CupraLeon ?
I’m in contact with FVD for the exhaust Brombacher (sound Version) and I know they have ECU tuning tool...

Please let me know if you deal with them
Thanks


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Unfortunately it is not a given that APR will work on any 718. I attempted recently to have my MY17 718S flashed in Australia and was unsuccessful as it is not yet supported on my ECU "type". It will probably be supported when someone can get an ECU to APR, but not yet. I am not sure if my ECU type is unique to Australia. I know another member from Australia was recently able to get a MY17 718S flashed with Cobb. Not sure if my ECU type is the same as his.
 

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Where are you based CupraLeon ?
I’m in contact with FVD for the exhaust Brombacher (sound Version) and I know they have ECU tuning tool...

Please let me know if you deal with them
Thanks


Sent from my iPad using Tapatalk
I’m from Belgium, will keep you updated.
 

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I know another member from Australia was recently able to get a MY17 718S flashed with Cobb. Not sure if my ECU type is the same as his.
Yes. Yes I did.


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