Edgy01

I happen to still have a can of ST104--will see if if is lead-free first,--to try.

romeroe

I noticed a knock this weekend at an AX school for the first time - I usually don't have the windows open though. It might have been a low-idle issue as I was coming into the staging area. I use Chevron Techron 93.

cobra06

Commercial octane boosters are really only going to raise the octane rating by decimal points. Most are toluene based. You can safely use toluene, octane rating ~114 to gas. F1 cars ran it at %85 toluene + fillers .
I've used it when tracking the turbo at %35 toluene/the remainder 93 octane.
Paint stores sell it at about $35.00/5 gallons.
It doesn't melt rubber fuel hoses but careful when pouring into tank, it's not clear-coat friendly. I mixed in VP-Racing fuel jugs with a pour-hose.

Formula to obtain new octane with toluene added:

( Gallons_of_gas * Octane_of_gas ) + ( Gallons_of_toluene * 114 )
___________________________________________________
Total Gallons

FWIW

bdmason

91 octane? California doesn't allow 93 octane? I'm just curious

Edgy01

I think that it's just really rare in Calif.

jhbrennan

One of the benefits of the RUF supercharger conversion is the lowered compression - Denver premium is 91 octane too.

1999Porsche911

You will never experience octane knock running 91 octane fuel in Denver. That is like running 94+ at sea level.

jhbrennan

That's what I've been told but I do get detonation in my motorcycle here when I didn't in Texas and the only change was the octane and the altitude.

1999Porsche911

If you are sure your bike is getting detonation and not pre-ignition, then I would suspect either your timing is screwed up or your plugs are too hot for the altitude. If the gas you are using is a true 91 octane, the gas is unlikely the cause in a properly tuned engine.

jhbrennan

Actually after I moved up here and AvGas (101LL) didn't fix the problem, I found out I had the wrong cam for the heads I was using. Cam change fixed it all. My only reason for the comment on the lower compression I'm running on the 997 is that it's one thing less I have to be concered about up here, especially with the oxigenated gas we have most of the year.

Ron Adair

Try adding race fuel concentrate to the 91 octane gasoline. Not an octane booster... 16 ounces added to 10 gallons of 91 octane gets you to 93 octane. I use it in my 993 and probably should start using it in my 997.

Check out their website: www.torcoracefuels.com. No affiliation, I just use their stuff.

bdmason

I guess that's one up for the east coast . Just about any service station I go to has 93 octane. There isn't much more we can brag about compared to CA. oh yeah no earthquakes here either.

Benjamin Choi

Is this normal operation? I'm getting this same knocking noise on cruising type speeds (click or click click) when applying throttle after I shift into 2nd... sometimes off the line in 1st, but not nearly as frequently as in shift, 2nd, then throttle click click.

500

My car does it too and we have 93 here in FL.

JW911

I've got no knock ever. Usually use 93 as that is the standard for premium gas in New England. Occasionally use 91 which is available at Sunoco. Never a problem with that either.