Recommended octane for 82 SC...

len911 · 12-19-2005, 05:00 PM

I'm purschasing a set of P/C from an 82SC for a rebuild and was wondering whad did the factory recommended for octane rating. Do they take premium? I believe CR is 9.3:1... Thanks! Lou

dd74 · 12-19-2005, 05:21 PM

Use the highest you can get, which in NJ is what? 92?

In CA. the highest is 91, and even that isn't high enough - at least that is what I've found in the spring and summer.

Incidentally, that's also what Steve Weiner once told me, at least about CA - that 91 is possibly pushing the envelope with high comp. 3.0s and factory curve settings.

walt · walt's Garage

Yes, use the highest octane possible. It is difficult to detect any pinging in these cars due to the noise level, so don't risk it.

Charlie V · Charlie V's Garage

I normally run 92 octane for day to day driving (Spring thru Fall). And, 94 octane for auto-x and DE events.

In Canada you can get 94 octane at Chevron stations. Don't feel a performance difference, but it feels good to give it the best available. Only $3.75 USD for a US gal. As I refer to the price - liquid gold.

Kraftwerk · 12-19-2005, 08:18 PM

What was the highest octane available in 1983? I often wonder this when I fill up, I also wonder what the 100 octane "race-gas" would be like that they sell in Brooklyn (miles from any race track by the way) Gonna try it one day but it is like 6.70 per gallon...

sammyg2 · 12-20-2005, 05:54 AM

If the timing is set to factory specs and everything is tuned correctly, IMO regular unleaded will be just fine.
Premium will make you go faster by removing weight from your wallet.
If you don't feel comfortable with regular fr whatever reason, you can use mid grade instead.

RickM · RickM's Garage

I'd also take into account that NJ gas is currently oxegenated. IMO, it doesn't perform as well as the warm weather formula.

twobone · twobone's Garage

I have an 81' SC and I had been told that we can run on regular gas (87).

Given the high compression of the 3.0ltr engine (9.3?), I'm going to switch back to a higher octane next spring. sadly, I've got a tank-ful of crap gas, so I'm going to add some octane boost

sammyg2 · 12-20-2005, 08:22 AM

Octane boost that can be purchased at retail stores is a total joke. A bottle of that stuff in a half a tank of gas might raise the octane by .4 if you are lucky.
That means if you have 87 octane in there now, you might be able to raise it to 87.4 at the most.
Save some money and top it off with premium or 100 octane unleaded av gas if you really want to raise the octane.

I ran my 1980 SC (9.3 to 1 compression) on regular unleaded 87 octane and it ran just fine but I switched to premium unleaded 91 octane when I added the turbocharger.
I took the engine apart about a year later to replace the dilavar head studs and found absolutely no evidence of pinging, pre-detonation, pre-ignition or whatever. Baded on that I would suggest that paying for premium is wasteful for an SC unless the timing is advanced or other things are modified beyond stock.
YMMV

dd74 · 12-20-2005, 09:35 AM

Your best bet for raising octane is race gas or a race gas blend.

Since my compression is now 10.8:1, I sometimes have to use 105 octane race gas that I buy from a local San Fernando Valley provider. I mix in 5 gallons of this with the rest 91, and come out with about 96 octane.

Though it seems to do the trick, I will regardless retard my timing a bit to be on the safe side.

The 105 octane is the nastiness smelling stuff ever. It's like rotted skunk parts. But damn is it pretty pouring in - it's light lavender colored.

larry@oma · 12-20-2005, 09:57 AM

i agree with sammyg2, 87 octane works great in my stock 1978sc. if i recall correctly, 87 octane is the recomended fuel in my owners manual.i have tried 91 octane ,could tell no difference. except as previously posted here "makes it go faster by making your wallet weigh less" 1978 911SC

stlrj · 12-20-2005, 11:22 AM

If I'm not mistaken, all 911's from 1972 until 1986 were designed by the factory to run on regular.

However, depending on how obsessive compulsive, paranoid or hearing impaired you happen to be, premium would be an acceptable placebo.

oliver88 · 12-20-2005, 11:25 AM

i have had no issues run mid grade in my 3.2 with euro pistons (10.3 to 1 CR)...no pings on the track or street.

SC-targa · 12-20-2005, 11:59 AM

When the timing and mixture are stock, regular 87 octane gas works just fine.

Regards,

Jerry Kroeger

Bill Verburg · Bill Verburg's Garage

Factory spec for '82 and '83 9.3 SC engines was 91RON

remember that (RON+MON)/2 is what is posted on US pumps

So figure US pump 93 as what you want.

sammyg2 · 01:08 PM

91RON is always higher than MON (usually by around 10 points)so 91 RON s equivalent to approximately 87 PON = (R+N)/2

http://www.btinternet.com/~madmole/Reference/RONMONPON.html

Bill Verburg · Bill Verburg's Garage

Yes , and my C3 ran perfectly on 87 leaded but needed 93pump unleaded, that was w/ 8.5 cr

sammyg2 · 12-20-2005, 02:06 PM

Wow, 93 PON is roughly equivalent to 97 RON. Pretty high for that low of a CR. I'd have to say that wasn't normal.

Bill Verburg · Bill Verburg's Garage

Quote:

Originally posted by sammyg2
Wow, 93 PON is roughly equivalent to 97 RON. Pretty high for that low of a CR. I'd have to say that wasn't normal.

No, the just the way it was.

Rick V · 12-20-2005, 04:48 PM

The owners manual for my 82SC calls for 91. I only have 89 or 93 to chose from in Va. so I opt for the 93.

When I bought my car it had a tank of el-cheepo stuff in it and it pinged like an old Volvo. IMO anything above 91 will do you well with a stock car.