Octane preference
#1
Burning Brakes
Thread Starter
Octane preference
Is anyone using less than 93 octane in a 997.2 S or 4S? What are you experiences with the performance and knocking using less?
#2
Rennlist Member
On a separate note, reduced octane is coming to all 50 states as the refiners will be required to reduce sulfur in the gasoline and a side effect is lower octane. Expect to see 91 and a wider gap in the price differentials as the refiners balance the supply & demand between the various grades.
#3
Burning Brakes
I'm in CA as well so use 91 as I don't have a choice; never had a problem. When I go to the track I juice it up with some 100 octane because I can, but don't really notice a difference except for some additional lightness in my wallet.
#7
Poseur
Rennlist Member
Rennlist Member
With the California max of 91 there is knocking but it is minimized by the rapid changes within the engine management system. There definitely is knocking.
Porsche recommends 93, and no higher. Any higher and it is simply wasted. If you have to mix your own (for racing, etc.) then take that into account.
Porsche recommends 93, and no higher. Any higher and it is simply wasted. If you have to mix your own (for racing, etc.) then take that into account.
Trending Topics
#8
Burning Brakes
Thread Starter
At the Jersey Shore we are getting 87 - 93.. I've put nothing but 93 in my 09 4S - no knocking. So dropping to 89 or 90 I think I'm hearing that I will get knocking, it's ok and it bothers me a little.
#9
Rennlist Member
" On a separate note, reduced octane is coming to all 50 states as the refiners will be required to reduce sulfur in the gasoline and a side effect is lower octane. Expect to see 91 and a wider gap in the price differentials as the refiners balance the supply & demand between the various grades. "
Are you sure about this? Where did you get your info? Link? I just had my car tuned from sharkwerks/EVOMSit and specified 93 octane as it is readily available here in KY. There are some ethanol 10% blends in TN and AL but they still claim 93. Another Obama mandate I presume?
__________________
Are you sure about this? Where did you get your info? Link? I just had my car tuned from sharkwerks/EVOMSit and specified 93 octane as it is readily available here in KY. There are some ethanol 10% blends in TN and AL but they still claim 93. Another Obama mandate I presume?
__________________
#11
I bought my car in Washington and drove it down to LA. Definitely did a little pinging when I was forced to switch over to 91. The engine learned quickly and it's extremely rare that get a ping now. But if you can get 93 use it.
#12
Race Director
We in CA get nothing higher than 91 (except at track and special gasoline stations) and both my cars run OK. But a trip that had me driving my Turbo up through Wyoming (among other states) and with opportunities to fill the Turbo's fuel tank with 93 octane (at low prices only dreamed of here in CA!) I wish I had 93 to run here. The engine was noticeably more responsive and just seemed more alive.
I never felt any gain in HP which makes sense. The energy content is nearly the same (and premium often has more energy per unit than low octane) between 91 and 93.
The real difference, the real benefit, in running the right grade of octane is the DME can trigger the spark a lot sooner so the fuel starts burning sooner and develops max pressure just the piston is best positioned to turn this in to rotational energy at the crankshaft. Because 93 is more resistant to forming pre-ignitable compounds ahead of the advancing flame front 93 octane doesn't lead to detonation.
Running too low an octane costs you fuel economy. The spark is delayed -- to avoid the higher pressure in the cylinder which leads to detonation -- so the pressure developed is less and peaks at the wrong time. Less energy is derived from the burning of the lower octane fuel. Additionally the retarded spark raises exhaust gas temperature which subjects everything it comes in contact with to higher operating temperature which is life shortening.
#13
Race Director
" On a separate note, reduced octane is coming to all 50 states as the refiners will be required to reduce sulfur in the gasoline and a side effect is lower octane. Expect to see 91 and a wider gap in the price differentials as the refiners balance the supply & demand between the various grades. "
Are you sure about this? Where did you get your info? Link? I just had my car tuned from sharkwerks/EVOMSit and specified 93 octane as it is readily available here in KY. There are some ethanol 10% blends in TN and AL but they still claim 93. Another Obama mandate I presume?
__________________
Are you sure about this? Where did you get your info? Link? I just had my car tuned from sharkwerks/EVOMSit and specified 93 octane as it is readily available here in KY. There are some ethanol 10% blends in TN and AL but they still claim 93. Another Obama mandate I presume?
__________________
Here's a link:
http://www.epa.gov/otaq/documents/tier3/420f13018a.pdf
The fine print:
http://www.gpo.gov/fdsys/pkg/FR-2013...2013-08500.pdf
Don't go blind reading this last document.
EPA estimates the cost at 1 penny per gallon. And if you like your health insurance you can keep it. Oh wait, wrong forum.
Oh, I don't know how removing sulphur affects octane. In diesel fuel removing the sulphur affected the cetane rating of the fuel, lowered it as the chemical process used to remove the sulphur was rather brutal, chemically speaking.
One possible way -- just a WAG -- is the refineries in order keep the cost of fuel down might cut back on octane as this adds cost to the fuel.
#14
Advanced
Join Date: May 2013
Location: Brisbane, QLD, Australia
Posts: 65
Likes: 0
Received 0 Likes
on
0 Posts
Brisbane, Australia - 98 Octane - Generally Shell V-Power...
Didn't realise petrol in the US had such a low Octane rating (although the US may use MON, not RON or similar). We have
- 91 (ULP)
- E10 (10% Ethanol)
- 95
- 98
Its worth noting that the Octane rating does not refer to the amount of Octane in the fuel -its a relative measure of the fuel's anti-knock properties (see wikipedia)
Didn't realise petrol in the US had such a low Octane rating (although the US may use MON, not RON or similar). We have
- 91 (ULP)
- E10 (10% Ethanol)
- 95
- 98
Its worth noting that the Octane rating does not refer to the amount of Octane in the fuel -its a relative measure of the fuel's anti-knock properties (see wikipedia)