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Re: 991 Turbo S - Short Driving Report (owner)
apias:
RC:
I should mention that I use 100 octane fuel (in the US, this would be 103 octane fuel), Shell VPower.The other way around, perhaps?
Oops...of course 97 octane. 
I corrected it in the previous post, sorry about it.
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RC (Germany) - Rennteam Editor Porsche 991 Turbo S, Cayenne GTS (958), BMW X3 35d (2013)
Re: 991 Turbo S - Short Driving Report (owner)
A guy working in the engine electronic department once told me no difference between 98 and 100 Octane (he said “Perlen vor die Säue …” (sorry, can't translate this), “great marketing by the fuel suppliers”) even for turbo engines. The electronic part doesn’t differ between 98 (Super Plus) and 100 Octane (Shell V Power) and so the output can’t be different.
Re: 991 Turbo S - Short Driving Report (owner)
Itsme:
A guy working in the engine electronic department once told me no difference between 98 and 100 Octane (he said “Perlen vor die Säue …” (sorry, can't translate this), “great marketing by the fuel suppliers”) even for turbo engines. The electronic part doesn’t differ between 98 (Super Plus) and 100 Octane (Shell V Power) and so the output can’t be different.
The difference lies within the ECU software, if it can benefit from higher octane fuel or not. Sometimes there is a margin left where the extra 2 or 3 octane fit in quite nicely. Sometimes the benefit from higher octane fuel is only there under extreme temperature/air pressure conditions. If there is an engine type to profit from higher octane fuel, it is a turbo charged engine with a modern ECU system. The 991 Turbo S certainly qualifies. Don't expect wonders though, two to three octane more (assuming that VPower usually has 101 to 103 octane, as measured by a car magazine once) add maybe a maximum of 5% more power under certain circumstances. In the case of a 560 hp engine, this would mean aprox. 28 hp. Not much by any means but it was worth mentioning.
I think we discussed it before. The more power the engine has, the better the chances that the engine actually profits from higher octane fuel.
The reason I fuel up with VPower is simple: There is no 98 octane fuel at Shell stations, only 95 or VPower. If I would use 95 octane, power would decrease by at least 30 hp or so. Not worth it.
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RC (Germany) - Rennteam Editor Porsche 991 Turbo S, Cayenne GTS (958), BMW X3 35d (2013)
Re: 991 Turbo S - Short Driving Report (owner)
If a ECU is not tuned for the higher octane, the car won't make extra power.
Higher octane simply means it's harder to ignite. The 'extra' power simply comes from a higher compression afford by a harder to ignite gasoline. A factory car's ECU has been programmed to ignite at a certain compression pressure, and if that pressure can be reached with a lower octane rating, say 95, then 100 octane is not gonna make more power.
A higher octane gas can only help if the lower octane gas cannot maintain that pre-set pressure, say on a extremely hot day where the intake air is too hot causing the air/gas mixture to reach ignition point before max cylinder pressure.
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Re: 991 Turbo S - Short Driving Report (owner)
Whoopsy:
If a ECU is not tuned for the higher octane, the car won't make extra power.
Higher octane simply means it's harder to ignite. The 'extra' power simply comes from a higher compression afford by a harder to ignite gasoline. A factory car's ECU has been programmed to ignite at a certain compression pressure, and if that pressure can be reached with a lower octane rating, say 95, then 100 octane is not gonna make more power.
A higher octane gas can only help if the lower octane gas cannot maintain that pre-set pressure, say on a extremely hot day where the intake air is too hot causing the air/gas mixture to reach ignition point before max cylinder pressure.
Exactly what I was saying. Btw: The German Porsche ECU is set to 98 octane, 95 octane fuel would result in a power drop. Not sure about the US ECU mapping (as far as I remember, Porsche uses a different software mapping depending on regions, fuel quality, etc.). However, there is a tiny margin in the software mapping, so it would actually slightly profit from higher octane fuel and especially under the circumstances your mentioned (extreme temperatures, air pressure, etc.).
Like I said before though, 28 hp or less may not matter much on a 560 hp car.
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RC (Germany) - Rennteam Editor Porsche 991 Turbo S, Cayenne GTS (958), BMW X3 35d (2013)
Re: 991 Turbo S - Short Driving Report (owner)
Whoopsy:
Cause we wrote the posts at the same time but you posted a tad earlier than me haha
Porsche spec-ed 93 octane here in North American using the measuring method here. that that works out to be around 95? Using the European rating?
I think 96 but I'm not so sure. I learned something about 3 points difference between the US and European octane rating but still not sure about it.
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RC (Germany) - Rennteam Editor Porsche 991 Turbo S, Cayenne GTS (958), BMW X3 35d (2013)
Re: 991 Turbo S - Short Driving Report (owner)
Nevermind, found the conversion.
Europe uses RON, Research Octane Number, which is about 8-10pts higher than MON, Motor Octane Number. And North America uses AKI, Anti-KNock Index, which equals to (R+M)/2, so Europe gasoline will have a 4-5 pt higher rating than North American rating.
Our best common retail gasoline is 94 from Chevron, which is almost like 100 stuff in Europe. Normal Premium is 91, so it's like 96 European gas. Porsche spec-ed 93 AKI here so only Chevron 94 can be used without lowering HP.
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Re: 991 Turbo S - Short Driving Report (owner)
Yes, 100 is better than 95 Octane. With 95 Octane your engine delivers less power but needs more fuel. So you can’t even save money. (Don’t laugh, I have a friend who tried to save money and always used “Super” instead of “Super Plus”. “My car has more than enough power for driving in the city”)
But I think Whoopsy is right: If a ECU is not tuned for the higher octane, the car won't make extra power.
Re: 991 Turbo S - Short Driving Report (owner)
RC:
Whoopsy:
Cause we wrote the posts at the same time but you posted a tad earlier than me haha
Porsche spec-ed 93 octane here in North American using the measuring method here. that that works out to be around 95? Using the European rating?
I think 96 but I'm not so sure. I learned something about 3 points difference between the US and European octane rating but still not sure about it.
AKI (US) to RON (EU) conversions can't be done as a straight conversion, like °F to °C because you really need to know MON to calculate AKI as the average of the 2 values -- (RON+MON)/2.
But, you can get rough values as
- AKI = RON * .955
- RON = AKI * 1.048
So, for example, 100 RON ~ 95.5 AKI and 93 AKI ~ 97.5 RON
Re: 991 Turbo S - Short Driving Report (owner)
Lars997:
check this: http://en.wikipedia.org/wiki/Octane_rating
That has a good example of why you can only roughly convert from RON to AKI. Above, I posted a rough conversion of RON 100 ~ AKI 95.5, but from the table on that page:
| Shell V-Power in Italy and Germany | 100 | 88 |
That's the RON and MON, respectively, for the indicated fuel (I believe that's the fuel RC is using), which gives an AKI of 94, rather than the rough, generic calculation without knowing MON of 95.5
Re: 991 Turbo S - Short Driving Report (owner)
apias:
Lars997:
When American are talking about "premium"... do they talk about 89 or 92?
- ~87 = "regular"
- ~89 = "plus"
- ~92 = "premium"
In Colorado, the highest octane is 91, although I use E85 (85% Ethanol, 15% gasoline) in my Evo which is 107 octane and only costs $2.75/gallon, or only about $0.75 per Liter (race fuel of similar octane costs over $9/gallon at the track).
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73 Carrera RS 2.7 Carbon Fiber replica (1,890 lbs), 06 EVO9 with track mods. Former: 73 911S, Two 951S's, 996 C2, 993 C2, 98 Ferrari 550
Re: 991 Turbo S - Short Driving Report (owner)
Grant:
apias:
Lars997:
When American are talking about "premium"... do they talk about 89 or 92?
- ~87 = "regular"
- ~89 = "plus"
- ~92 = "premium"
In Colorado, the highest octane is 91, although I use E85 (85% Ethanol, 15% gasoline) in my Evo which is 107 octane and only costs $2.75/gallon, or only about $0.75 per Liter (race fuel of similar octane costs over $9/gallon at the track).
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73 Carrera RS 2.7 Carbon Fiber replica (1,890 lbs), 06 EVO9 with track mods. Former: 73 911S, Two 951S's, 996 C2, 993 C2, 98 Ferrari 550
E85 is 107 octane? 
Are you sure?
Read this: There is no requirement to post octane on an E85 dispenser. If a retailer chooses to post octane, they should be aware that the often cited 105 octane is incorrect. This number was derived by using ethanol’s blending octane value in gasoline. This is not the proper way to calculate the octane of E85. Ethanol’s true octane value should be used to calculate E85’s octane value. This results in an octane range of 94-96 (R+M)/2. These calculations have been confirmed by actual-octane engine tests."
Examples of this mis-citation can be found at the Iowa Renewable Fuels Association titled "E85 Facts" which cites a range of 100-105, and a document at the Texas State Energy Conservation Office titled "Ethanol", which cites a 113 rating.
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RC (Germany) - Rennteam Editor Porsche 991 Turbo S, Cayenne GTS (958), BMW X3 35d (2013)
Re: 991 Turbo S - Short Driving Report (owner)
Thanks for the forum and excellent thread. Have a question. I saw somewhere on the thread that having an option for Plus steering was considered a bad idea. Can not find anywhere really explanation why.
The reason for question is that my dealer has a few 991TS cars on stock with full options including Plus steering. I am considering trading in my previous generation turbo for a new turboS. Getting one straight away rather then waiting is certainly a nice thought. So wanted to check.
Thanks in advance.
Re: 991 Turbo S - Short Driving Report (owner)
NSXER:
I have power steering plus in my 2013 2CS. Supposedly lower effort for parking and slow speed maneuvering. Was a $270 option. Driven cars without & I can't tell any difference. Some say it deadens the steering feel.
Save your jingles.....
Of course it does but only at lower speeds (which can be annoying, especially if it is slippery in rain/snow).
If you couldn't tell any difference, it wouldn't make much sense in the sense that it wouldn't assist you at low speeds, would it? 
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RC (Germany) - Rennteam Editor Porsche 991 Turbo S, Cayenne GTS (958), BMW X3 35d (2013)
Re: 991 Turbo S - Short Driving Report (owner)
RC:
NSXER:
I have power steering plus in my 2013 2CS. Supposedly lower effort for parking and slow speed maneuvering. Was a $270 option. Driven cars without & I can't tell any difference. Some say it deadens the steering feel.
Save your jingles.....
Of course it does but only at lower speeds (which can be annoying, especially if it is slippery in rain/snow).
If you couldn't tell any difference, it wouldn't make much sense in the sense that it wouldn't assist you at low speeds, would it?
Thanks for the answers. What is the definition of lower speeds? Does it mean parking or like 60 kph?
Re: 991 Turbo S - Short Driving Report (owner)
The amazing engineering side of the 991 Turbo S (standard driving mode, speed control set at 105 kph).
Not that it matters but it IS possible and I didn't try hard.
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RC (Germany) - Rennteam Editor Porsche 991 Turbo S, Cayenne GTS (958), BMW X3 35d (2013)
Re: 991 Turbo S - Short Driving Report (owner)
fritz:
RC, I think your post may need a little interpretation: The fuel consumption corresponds to over 29 miles / US gallon at an average speed of just over 60 mph.
Thanks, well done. Amazing, isn't it? My wife's X3 35d consumed 7.9 liters under the same conditions, practically the same (her average fuel consumption is 10.1 l though, mine is around 17 l when using Sport mode most of the time).
17 l / 100 km is aprox. 13.8 mpg.
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RC (Germany) - Rennteam Editor Porsche 991 Turbo S, Cayenne GTS (958), BMW X3 35d (2013)
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