justin

On another note, my 80 will only run well with 93 octane, if I run 87 it clatters at higher rpm's. Never tried 91 octane.

bigs

Yes, I know. Hence the question about toluene. Actually, I just found a very interesting and informative previous thread from the 951 forum (Mixing fuels, rocket science?). Think I'll give it a try.

fst951

Hi Steve.

Tetraethyl Lead work rather nicely!!! It just makes things tough on a catalytic convertor. Toluene works nicely as well, but you won't be able to take advantage of it at this altitude. The Porsche spec is for sea level, Steve.

Good luck.

david928

Couple of questions:

I used 87 octane in my old Toyota and it would knock like crazy when going up hills. I switched to 89 octane and it ran a lot better. Is "knock" the same thing as "detonation"?

The Allies in WWII used 100 octane aviation gasoline in their airplanes. I read that it was a big advantage over the German planes. Was it because they could operate the engines at higher compression ratios, thus more power?

Ron_H

Correct me if I have this wrong, but as I understand it increasing the octane rating creates more carbon deposits which in turn slightly raise the actual compression ratio creating a demand for higher octane which increase the carbon deposits....ad infinitum. Thus, using the lowest possible octane will prevent this endless cycle and allow your engine to live longer.

I use 87 octane in my '86.5 and have always used it in my 911s including my two 911 E engines. Not ever a problem with detonation. My 928 runs to redline from rest without a problem. I know I am denying Ahnald and company some revenue but they really don't need it that badly; just need to trim the fat of gubmint a little more.

bigs

Dang it Garrity! Somebody with knowledge is always spoiling my fun!

Let me see if I can reason out why -

Fuel apparently must be metered, I presume, according to simple air volume. As altitude increases, air becomes less dense per the same amount of volume. Therefore, simply by virtue of the increased altitude, the mixture automatically moves toward the more rich end of the scale, resulting in less danger of knocking.

So, if that were the case, am I correct in presuming that the engine management system would not sense any need to "detune" the engine to prevent knocking with 91 octane fuel? And therefore there really isn't any improved engine performance to be realized by increasing octane at this altitude...?

Ketchmi

You may be in the wrong profession Bigs, wanna' trade for a week or two?

bigs

Fair warning, Dave - to be a gynecologist you gotta be able to do an engine rebuild through the tailpipe!

The other problem is, I fear you wouldn't wanna trade back after the two weeks!

goliver

Bigs,

Are you running an X pipe? Do you still have your cats? Don't answer out loud. If no, do you have any friends at the local air strip? If yes, 100LL will get you way on your way to trying Dave (Sharkskins) method out. Otherwise, The closest 93 I found on my way out west from Boston last summer was way back in Iowa.


Regards,

bigs

Geoff -

I'm not currently running an X pipe - but I very well might be a month from now. And even then I think I'll keep the cats. I'll have new 30lb injectors and a new RRFPR. I'll also likely have a piggyback computer (don't ask me any details about that - I'm just putting my trust in Ketchmi!) He thinks these mods will get me somewhere around + or - 30 extra rear wheel ponies.

These things are what got me to wondering about finding a way to increase my octane in the first place. But I'm guessing Dave Lomas will dyno tune the fuel mixture to run OK on 91 octane. Cuz I certainly can't find anything else around these parts.

I'm also guessing if I ever drive the car down to sea level, I'd be wise to look for 93 octane.

At some point in time, I'm probably also gonna give in to the incessant badgering from Dave and Garrity at Motorsport to SC my car. I mean, a guy can resist temptation only so long!

ErnestSw

Dave,
You also have to learn the two finger hand shake!

goliver

Bigs,

I'm sure if Dave is doing the tuning you will be fine. Stop resisting the temptation and get the GTS blown. Yeehaw!

Regards,

Tony

The stuff does work, but unless your running boost under marginal conditions ie..hot..high boost..high duration loads, it isnt worth it. The stuff KILLS as well. It will mess you up if not carful. Just go out to the track and pony up for some 100 race gas to experiment if you need to. The stuff in the bottle at the store is worthless from what ive heard.

NickT

I asked a chemist here about it, he said he has tried it before and damn near melted the cats. Burned the carpet inside the vehicle.. His short answer to me was "noooooooooo"

Dubai 94GTS

1) Octane is measured using 2 methods; RON & MON. So when comparing ratings you need to make sure you are using the correct "unit". From memory, in the US, pump octane rating is valued @ (RON+MON)/2. RON is usually 7~10 octanes more than MON.
2) Toluene (Methylbenzene) is used in blending gasoline; similar to MTBE its an oxygenating additive. I would not touch pure toluene or even get near it. It can be absorbed through the skin and it attacks the nervous system (at appropriate dosages); brain and associated wiring.
3) I would not use it in my car either. For starter it is an organic solvent; God knows what it will do in our 10+ yr old cars. There are better ways to boot the octane (Chevron, STP additives)
4) You need to go with the minimum octane that eliminates knock (early detonation), unless the car has ignition retard. I use 93 RON in my car and it works like a charm.
BTW, since it is an organic solvent, the cheapest toluene you can get is from a hardware store (home depot, ace..)