Amber Gramps

sweet dreams



not here....keep looking, it's in here somewhere...

special tool

84_Carrera

You guys know that higher octane doesn't provide more power by itself, right?

The higher the octane, the lower the energy potential but the more resitant to pre-detonation.

In order to take advantage of that 100 octane, you need to modify igntion timing (a chip) or other technique like increased compression ratio that specifically takes advantage of the ability to not detonate.

The higher octane fuels also burn "cooler", typically requiring more detergents to prevent buildups, because on their own, they do tend to carbon up.

87 = hotter (and therefore cleaner), and more energy potential. If you're not detonating with it, that's your best course of action. 93 = cooler (and therefore not as clean), lower energy, but less prone to detonating, so you can take advantage of ignition timing changes. Rule of thumb, use the lowest octane fuel you can without detonation. In the pre-knock sensor 911's I would tend to play it safe, personally, & go with Super, but that's just my opinion.

In my SHO, with the knock sensor & the PCM adjusting timing automatically, I run 87 for around town. If I know I have a dyno or other event, I'll run a tank of 93 & reset the PCM prior.

Amber Gramps

remember that it is mixed down to 95 octane tops. after 20 years at over 30,000 miles a year and at that, 600,000 miles driven just for work let alone my personal miles, my butt dyno has proof that a 4 point jump in octane is a real gain. going from 87 to 91 is often the difference in being alive with $4.00 less in my pocket and being dead with $4.00 more. yes it is that big a differance. life is too short to use regular unleaded.

it's kinda funny that a tank of 95 octane costs only $70.00 more than 91 and can provide such better performance and fuel economy that in the end it is almost a break even deal. lets face it guys, when I gotta drag my wife around with me in the car, it could use the help.

Mike Murphy

Well, Fred, what about additives? Doesn't the Premium fuel have better additives than the regular stuff? That's one good reason to go with the good stuff.

sjanes

If you butt dyno is telling you that 100 in a stock 3.2L makes the car faster, you need a butt tuneup

Going from 87 to 91 will make a difference in a car that requires 91, not in a car that requires 87.

http://www.state.mn.us/mn/externalDo...ctaneFacts.pdf

Graufuchs

Thats great thanks doug....I wish I had that around here...

old man neri

A bit of a tangent. The manual for my '88 recommends 92 octane. I can find 93 octane at a few stations. However, I can find 91 almost everywhere. Is putting 91 in a bad idea?

Amber Gramps

sjanes, how are you...

OUCH! from a local none the less. come on back me up on this. I'm on the right side of the argument. I really had no intention of this going any further than filling a private request from fty. I do love the hard time.

go back and do a search on "100 octane" and see who has my back on this...

sjanes

Actually, "Ontario CA" is the province of Ontario in Canada. I assume this is the thread you were referring to: https://rennlist.com/forums/showthre...ght=100+octane.

DARISC

Hey Doug! You do realize that relying on your butt dyno is equivalent to relying on your cranial calculator without first removing it from its rectal storage place, don't you?

Cheers

(couldn't call you when you were in C'bad - illness in family)

Steve Weiner-Rennsport Systems

For MANY reasons, Doug's "butt dyno" is on solid "footing" here,..............

Amber Gramps

I would let steve have the last word here guys...

have a good weekend

DARISC

Pure unleaded gasoline has a "specific energy" of about 131 megajoules/gallon, which varies +/- 4% from batch to batch & season to season.

Pure unleaded gasoline is the starting point for all gasoline formulations (referring to formulations to change the octane # of the gas).

Pure unleaded gasoline which contains additive/s to raise its octane # has exactly the same "specific energy", ergo, it CANNOT produce more power than before it had the additives put in, UNLESS the additives used to raise the octane # are combustible and have a higner specific energy than the gasoline to which they are added, which they don't.

That is basic chemistry / physics, not my opinion or what I personally have found to be true.

Raising the octane # is done SOLELY to control detonation, NOT to raise the specific energy (power)of the mixture.

Until the above scientific facts (not MY science) are shown to be scientifically wrong, hearing someone say that high octane gas, in and of itself, produces more power, leaves me with the same impression as being told that, contrary to 99.999% of what scientists say, the earth is flat.

Any Bonafide chemists/physicists out there to verify what I'm saying.....or set me straight?

DARISC

I sure wouldn't suggest who should have the last word here, but if I did, I'd say that 84_Carrera pretty well sums up the generally accepted understanding of this matter.

Cheers