bigs

I've read a bunch of threads and some other articles on using toluene to boost octane. I've not seen anything over 91 (R+M/2) available here in Utah.

Anybody here actually tried it in a shark? Any personal experience? Any performance enhancement?

G Man

I may be wrong, but from what I have seen on the subject of octane is that it is advisable to use the lowest you can without detonation. I have read that the higher octane fuel actually has less energy than lower numbers. I run regular in my cars with no problems.

bigs

Hmm... interesting.

All the threads I've read claim improved performance with 93 octane gas - although above that, there seems to be no extra advantage.

And the owner's manual, as well as the sticker on the inside of the gas tank door, recommend 93 octane for the 928.

(Great avatar BTW!)

ErnestSw

There's NO octane booster out there worth the powder to blow it to hell, including toluene.

1981 Shark

Previous posts have indicated the only thing increased by octane booster is the seller's wallet. Don't know personally, but would like to see someone with experience chime in.

MBMB

Another toluene thread.
And another. (Andy has experience with it.)
The Rennlist search engine interface.

Someone with more experience than me will chime in, but essentially higher octane makes gasoline harder to burn (less likely to detonate). Engines with higher effective compression ratios require higher octane to prevent detonation (assuming that the car doesn't cleverly retard the timing). Use the lowest-octane fuel you can get away with without detonation. More octane than is necessary means less power than is possible.

Garth S

All of the heterocyclic and aromatic based compounds, such as toluene and xylene will reduce volatility, slow flame front propagation - and are used as octane enhancers; however, unless the engine has been modified adequately to require an octane increase - go with Ernests sage advice.

bigs

I guess what I'm asking is...

If Porsche recommends 93 octane and I can only get 91, am I missing anything of value?

Apoc

That is interesting. I don't have the owners manual for my 79 Jap Import but the recommendation on the gas cap says 100 Octane. I am currently running it on 98 Octane (I think, I will have to recheck the Octane rating of Premium next time I am there). Did early models require a higher Octane than later models? Or is this just a peciliarity of the Japanese models?

Steve

bigs

Or, another way of stating my question:

I know that lower octane fuel is actually more volatile than higher octane fuel. But also more susceptible to knock.

So, if I'm using a lower octane fuel than the manufacturer recommends, won't I lose power - not because the lower octane gas is less volatile or less "powerful" - but because the engine management system will "de-tune" the engine to compensate for the lower octane fuel so as to prevent knock?

That's why I'm wondering if there's a way to increase octane to the 93 that Porsche recommends. I know the little bottles of snake oil at yer neighborhood Pep Boys won't do anything of value. But I have read that toluene might.

SharkSkin

Bigs, it will take some doing to figure out. Best way might be with a G-Tech and some high-octane. Do some runs with 91, then empty the tank out and try again with the same amount of higher-octane in the tank. You'll only get more power if the engine is currently running with less than full spark advance with 91. If timing is being retarded due to knock sensor activation, then you're leaving horsepower on the table.

BrianG

First acquaint yourself with the 2 different "Octane Rating" systems. Then make sure that what your manual spec's is given in the same rating system as your local gas-station pump is indicating.

bigs

Actually I have, and it is.

Pump octane, at least here in Utah, is the average of MON + RON/2. That's the same formula that's listed on the inside of my fuel tank door.

bigs

Great thought! I'd like to - if I could only find 93 octane fuel or a way to "make" it!

justin

Ok, the low down on octane booster, say you are running 91 octane gas, and you walk into a autoparts store and see a bottle of booster that reads 4 point gain in octane, so most people think ewww, I would have like 95 octane if I buy this 5 dollar bottle, well the answer to that is, WRONG, the 4 point gain is .4, see the decimal, in other words you would then have 91.4 octane, not 95 octane, BIG rip off.