High Octane Gas

Is there any real advantage to using very high octane gas in US spec Ferraris? There are several gas stations around Phoenix that sell "racing fuel" with octane ratings above 100 and I've often wondered if there would be any noticeable performance advantage to be gained, or does the engine management system cope best with normal premium fuel (91 octane in AZ).

 

The car is built for premium fuel so there is no real advantage to using a higher octane.
Interestingly enough the higher the octane rating the less the fuel wants to burn - extraordinary, but true, and easy enough to see if you think about it for a second. Fuel additives were first put into gas in the late 1930s in an effort to get more performance out of aircraft engines. The problem was that when the engine’s compression ratio was increased the fuel would detonate under pressure. It would ignite before the spark plug fired and it would also start to burn unevenly in different parts of the combustion chamber, all of which was bad for the engine and, worse still, made it produce less power than before. You could (and can) actually hear the small explosions that knock bits out of the piston - it is the knocking sound produced when you floor an older car in a high gear at a low speed. The 1930s solution was to introduce a lead formula that made the gasoline harder to burn - compression alone would not ignite it, the gasoline needed the flame front of a spark plug.

Interestingly enough Germany, which produced its avgas from coal, never copied the formula during the war. With no more horsepower available from piston engines they moved to jets while the allies, with octane rated gas, kept on building larger and larger piston motors.

Sorry - most of that was a bit off point. I think 91 octane is OK. The car’s computer and compression ratio will keep it from detonating.

 

Alex -- You posted this in "vintage" section, and F models in this section do not have adaptive/smart engine control systems so there is no advantage to using a fuel with a higher octane rating than the minimum specified. If you mean on a newer model F, try reposting (and maybe give exact model) in that F model's section.

 

I thought I was in General. I will repost.

 

Thanks Wayne - please delete the dupe thread

 

This was moved to GF? Can we get some kind of ruling on this?

 

Octane rating for my Ferraris 360 Modena is confusing and most everyone has a theory. I have read numerous articles and white papers and I am still confused as what the correct octane rating is for my car. Also, based on my research higher-octane fuels do not mean slower burn. Higher-octane fuel is simply more resistance to knock (detonation and pre-ignition). It seems the burn rate has to do with volatility, and vapor pressure and those are controlled based on seasons and geographical locations here in the States.

Here’s where the confusion starts: the owner’s manual specifies 95 RON that is a Euro Research Octane Number and the newer owner’s manual specifies 95 - 98 RON (page 6.12). Here in the States the pump's octane rating is (RON+MON)/2 or the average of Research and Motor. I have not been able to find any mathematical equation that correlates RON to MON, hence the confusion. The latter method however corresponds to a higher RON. I have experimented and determined 93 (RON+MON)/2 gives me the best acceleration time in 3rd gear going from 30 – 60 MPH. This test may be flawed, I don’t know. But this moment there isn’t any other method that I know.

In my opinion it is impossible to determine the correct octane rating solely based on the owner’s manual minimum recommendation of 95 RON, since there is no equivalent fuel here in the States to correspond to 95 RON. It is also difficult to determine the correct octane rating through mixing fuels and experimenting on the dyno due to its repeatability and margin of error. Also, in my opinion it is difficult to determine if 91 (R+M)/2 at the pump is sufficient for my car since the engine management could retard the timing to eliminate knock if 91 is not sufficient.

I would definitely like to hear more expert opinion with data.

 

Interesting point...here in the NW, most premium is 91, and occaisionally 92 octane. Higher is not readily available...I had a Dinan software upgrade done to my BMW 540, yet they set it all up for 93 octane gas...so I am most likely not getting much performance advantage...

 

4i2fly -- I can't recall the source, but 3~4 years ago when we were hashing this around I came across a website that indicated that the "sensitivity" (= RON-MON) of modern fuels is about 10 (which would put 98 RON = 93 AKI). An internet search on "RON, MON, sensitivity" might give you more.

 

I found a couple of documents that specify sensitivity as RON - MON ~ 10 while not exact one can derive the equivalent RON for the pump octane (M+R)/2 method here in the States. And so a 91 (M+R)/2 has ~96 RON and 93 (M+R)/2 has ~98 RON. This may explain why I recorded better acceleration times from 30 -60 in 3rd gear with ~93 pump octane. I also noticed as octane increased above ~93 the elapsed acceleration time did not change.

I think it is too complicated to figure out if a brand of high-octane fuel would give your engine more power or not, since there are components like boiling point, fuel octane distribution and volatility to mention a few that would affect the running efficiency of engines at different ambient conditions.

 

The short is , no.

The best thing you want to do is run the rating that comes closest to the suggested rating and to mind your compression ratio; your manual suggests 95-98 RON that translates to something close to / between 98 and 91 octane here in the US. Running 91, 93 or even 100 will have a nominal difference; if you were running higher than stock compression, edging on 12:1 or higher, then 91 octane, on a hot day, would probably trigger your knock sensor & your ECU / FI mgmnt. would retard your ignition timing to keep your piston crowns in one piece.

The long of it is, too long.

Regards.

 

93 octane is a must for the 7 (Mazda RX7 ported 13B engine). 93 octane is a must for my Al V8 in the 240Z. 93 octane is a must for my supercharged 96 Miata. I have no choice.

http://members.cardomain.com/snapshot1.

 

In a NA car I would say just run the higher stuff when you plan on driving the car hard and outside heat is up. This probably won't give you more power but it could keep you from losing power due to retarding and save on damages from any knock.
But in a turbo or supercharged car I would say yes. You could very likely see some performance gains from running race gas. My experience is that a lot of turbo cars have computers set from the factory kinda in the middle (simply put) of it's timing range and a notice of higher octane can also see more advance in timing getting a little more power. Or even some are retarded a lot in the base form seeing 93 octane. A Twin Supra is a good example or a Skyline too. I remember reading a the "Power Pages" of Super Street (I think) and see them get about 15 RWHP (with AWD disabled) from their base run just from adding an Off Road Octane buster.
So hot day, hot track, hot car, couldn't hurt.