OCTANE RATING QUESTION FOR CHEMISTRY WIZARDS

In the U.S. we use (RON + MON)/2, usually listed on the pump as (R+M)/2
Other countries only use RON.
RON = Research Octane Number
MON = Motor Octane Number
RON vs. MON = different testing procedures, RON gives a higher number.

Our 93 is comparable to their 97. There is no point in adding additional octane if the engine doesn't need it.

 

Which 91? California 91, winter 91 or regular 91?

 

The typical method for converting Europe's "RON" octane rating to the North American "AKI" octane rating is to multiply the RON rating by .95 to get the AKI. So 97 RON would be 92.15 AKI. The other quick and dirty method is to subtract four units from the RON rating....

So 91 AKI divided by .95 equals 95.8 RON.

There are various octane booster additives available at auto supply stores. You can try them to see if it makes a difference...I believe the Ferrari manual states 91 AKI is the fuel requirement. Higher shouldn't make much difference. Less octane than 91 could mean less performance, as the knock sensor will retard the ignition if it sense pinging from the lower octane fuel.

There are chip programming companies out there, and they often times will optimize their chip to your car, taking in to account the fuel available to you. I have seen one company that makes chips for Ferraris optimized at 91 AKI and also for 93 AKI.

 

The 91 octane is to punish all the flakey libs that live in Cali. No, not really....

Unocal had the patent on California Reformulated Gasoline (RFG). All the other companies decided they would just sell lower octane gasoline instead of paying Unocal the 5 cents a gallon royalty. Now that Chevron bought Unocal and the patent effectively died as a condition imposed by the FTC to approve the merger, you might think the octane rating would creep back up. But since octane costs money, and Californians are conditioned to use 91, it will probably stay the same unless one of the refiners decides for marketing reasons to offer 93 forcing the other to follow. See why your gasoline is different below.

http://www.exxon.com/USA-English/Files/US%20Gasoline%20Map%20100102.pdf

 

Works for me but here's another. http://www.npra.org/issues/fuels/state_bb/us_fuels_map.pdf

 

The little octane booster bottles you find at auto parts stores are a complete waste of time. Most of them are comprised almost entirely of an aromatic hydrocarbon like Toluene or Xylene, which have r+m/2 octane ratings of 114 and around 117, respectively.

So, the average can of octane booster is around a pint. If your fuel tank holds, say, 15 gallons of 93 octane pump, and you dump a pint of 117ish octane booster into it, you'll have a net result of around 93.16 octane. Woo, raised it one and a half points, and basically accomplished nothing save made SuckerCo a bit richer as you just dropped $5-10 bucks on 1/8th a gallon of high octane go juice (by comparison, 100 octane race fuel is around $5/gallon).

So, if you fill your tank with 10 gallons of 93 pump, and then dump in 5 gallons of Sunoco GT100, for example, you've got ~95.4 octane. A significant increase.

For a naturally aspirated engine running less than 12:1 compression, 93 octane pump should be plenty to keep you out of detonation, even while flogging it on a track.

If you're unfortunate enough to live in California, and are forced to use the swill they call gas over there, I'd definitely mix race fuel with it if you're playing with timing maps.

If you're feeling an increase in power after using higher octane fuel than you normally do, it's because the computer has been pulling timing to prevent detonation/pre-ignition. Better gas, more timing advance, more Horsey Music.

There is a limit, however, when adding octane will no longer provide any benefit, and simply increase cost.

 

Not sure what it is in Cali. Around here it goes for ~$5/gallon.

 

And here in WA we have high gas tax (actually, the highest in the country)
high sales tax
medium property tax
no income tax

Race gas will probably be about the same cost across the country. What usually makes the fuel cost increase for standard regular/89/premium is the special blends required for each market. Since race fuel is exempt from emissions law, because it is supposed to be for track use only, it generally stays pretty flat. ($5/gallon as previously mentioned.)

 

Quit your complaining! We in the People's Republic of Taxachusetts have high sales tax, high income tax, high property tax, expensive fuel, AND Ted Kennedy.

Birdman

 

Maybe do the calcs to create a tank of 95 and see how it runs. It may end up being well worthwhile for those fun occasions.... Then again, it might be a waste of $ and at least you can tell us this before we waste our hard earned

Do we really have cheap property tax in CA? I'm paying 8K a year to have Antonio do anything BUT be the mayor.....

 

whenever i'm in newport i'll use 100 octane only. usually costs me just over $110 per tank. but man the difference! esp now since i've added boost. runs smoother and the exhaust smells alot cleaner. too bad it'll only last me a day of "cruising" around

 

Not intending to hijack this thread anymore than it has already been, but while on the subject of gas, I have just done a search on lead substitutes and so forth. The Lusso has had ongoing issues for years with crap in the gas and we are finally going all out to purge everything and get the gunk out. Once completed, the question is.... do we add "stuff" to the gas or not?

I have read here that since the 250 has Alumin(i)um heads, they have valve seat inserts so are not susceptible to lack of lead problems. I have also read of one 330 owner who has used regular unleaded without additives for 100,000+ miles with no issues. Then of course there are the other statements - "only run without additive if you want to spend 25K having the heads redone".

So. What's the consensus? If an additive, which one? Most lead substitute additives claim to boost octane also. I suspect that with the low CR that Ferraris have had (until 348s) that regular unleaded will suffice in terms of octane.

Thanks...

 

The ECU doesn't know what you have in the tank. What it knows is when you run into detonation, and as a result, when to pull timing so it is reduced/eliminated. If you're noticing significant performance gains when you crank up the octane, the fuel you were running before you did is not adequate.

As a general rule of thumb, baring any odd circumstances (endurance racing, extremely hot climates, oddly shaped combustion chambers prone to hot spotting, etc), you won't see any benefit to running greater than 94-95 octane in a naturally aspirated engine with a compression ratio below 12:1, assuming a stock EFI computer with un-messed-with timing and fuel maps.

When it comes to forced induction applications, or NA engines running huge timing, the sky's the limit. I've seen engines run into pre-ignition on C16.

 

correct, i also have another oddity - i'm still running the CIS so i have no feedback or ignition interplay. the electromotive also has no way of knowing if i'm detonating either so it takes a good ear and big balls to get pushy with the timing at 10~12psi and 9:1 compression the higher the octane the more HP and less chance of 'BOOM' so $100 tanks are cheap insurance when i want to run hard.

mmmmmmm C16 is very tempting! when i update the electromotive i'll run a tank. BTW i have no cats or O2 on the early CIS so lead isn't an issue.

 

The irony of higher octane gasoline is that it has less energy than lower octane. That's right - there is theoretically more performance using a lower octane, PROVIDED you are not suffering detonation.

GCalo, I understand what you are saying about a "noticeable performance improvement" when you used 92, but unless you were suffering severe detonation, it really should not be possible to feel a difference. If you were detonating badly on 91, something else would be wrong with the car.

Having said that, what I would do is get something like a g-tech or some other performance computer and do side-by-side tests with the various gas and test your results. I suspect they may be much closer than you imagine.

on a turbocharged/supercharged car, higher octane is a godsend, because it lets you bump the boost (or lets the ECU bump the boost, sometimes). On a NA car, higher octane should have no effect - actually a net negative effect, as long as you weren't detonating on the lower octane.

You may have had a tank of bad 91 gas if you noticed a big improvement with 92 over 91.