110 Octane Sunoco ?

[Royce Peterson]

I don't claim to be a chemist nor do I play one on TV. I am a semi - retired former A+P / IA with 40 years experience, nearly none of it with piston engined aircraft. The 11 years while working for the largest automaker in the world I mostly maintained their fleet of corporate jets but occasionally had to work on a experimental aircraft that belonged to a retired COO of the company. It was during this period of time that we had to defuel the aircraft several times, with me being the lucky recipient of lots of free fuel. My experience is that it's fabulous stuff for free. Better than anything you can buy at the pump.

Aircraft make the most power during take off, not at altitude. Hence the various power ratings for modern aircraft engines, max takeoff power, max cruise, etc. I don't know your guy and he's not here to defend himself. I only deal in facts.

   Royce my chemist friend said nothing about the "octane" characteristics at seal level. As you mentioned that can't change. He said the fuel was "formulated" for "altitude above sea level" with specific additives to perform better "up there" than at sea level. He also mentioned it was "good for a year in the ground" unlike "highway gas". With him having a PHD in chemistry , I took his advice.

[S7MS427]

   Royce my chemist friend said nothing about the "octane" characteristics at seal level. As you mentioned that can't change. He said the fuel was "formulated" for "altitude above sea level" with specific additives to perform better "up there" than at sea level. He also mentioned it was "good for a year in the ground" unlike "highway gas". With him having a PHD in chemistry , I took his advice.

On reason aircraft piston engines make such good power on takeoff is that they have an an extra control that you don't see in an auto engine, a mixture control. On takeoff, the pilot sets the mixture to full rich. This control also allows the mixture to be set for best power at altitude. Back before the introduction of 100LL, avgas had two octane numbers such as 80/87 or 100/130. The lower number was for the lean setting and the higher number for, you guessed it, the full rich setting. IIRC, avgas is also formulated to burn well at a somewhat lower RPM than mogas. Airplane engines operate at pretty much a steady state RPM once they get to cruise altitude. Full power is generally only need during climb, whereas in a car you are constantly changing RPM in traffic and only get to a steady state condition while in cruise on the open road. So two different formulations for two different usages.

[pbf777]

Avgas is great stuff too but you have to run a higher percentage in order to get the same results because it is only 100 octane while VP110 is 110 octane.

    He said the fuel was "formulated" for "altitude above sea level" with specific additives to perform better "up there" than at sea level.

    The formulation is not "ideal" for a racing engine , no question about that.
     Years ago I used to use the "green" AV gas . This was before the reformulation to "blue" Low  Lead 100. When it changed  I asked a friend who was a chemist for Conoco in the Santa Maria area regarding me still using it. He suggested that it should be mixed with pump gas to no more than 50% and not used above 11-1 static compression. "He" claimed that  the additive package WAS altered and not "happy" at sea level in undiluted form.   

      I'm also not an automotive fuel chemist, but I have tried to ask questions of supposedly knowledgeable persons who's response is often: it's to complicated to explain, and if they did, then they'd have to kill me, so I'm short on facts.  But I agree with the above observations and would like to add to them.

      First,  I have found that when running the AV gas, it requires more volume than say the race fuel, so although if running race fuel and substituting AV gas the performance may drop off, but not necessarily due to octane but rather a slight leaning effect (but then maybe your tune was to fat).  One generally will find that when tuned for AV gas say for driving around on the streets, but then for race day substitutes race fuel, the tune will be to fat, perhaps to the point of fouling the plugs, which is partly the formulation intent of AV gas to avoid, as many aviation engines intentionally run over-rich scenarios for the purpose of engine cooling requirements.  You can run a lot of AV gas thru the engine and still not foul a plug.

      And yes, 100LL is formulated with intent at altitude, and this may be witnessed as it demonstrates a faster flash rate than particularly the race fuels, perhaps one of the concerns when operating at street level particularly in hot environments, just make sure there's an electric pump at the rear to push the fuel forward.  This general is also realized as better cold starting of ones' performance engine, particularly those demonstrating poor cold start and low speed driveability, as the readily fuel flashes within the coldest and least turbulent of induction systems.  And again, the plugs last a lot longer in the street driving scenario.

      Also the 100LL is not an equivalent measurement number as compared to street or race fuels, it is of less resultant octane value as experienced in the engine, therefore a compounding factor in the mixing volumes even in excess of perhaps a lower numerical rating as presented in the example of the 100LL vs. Sonoco 110.  In my attempts to discern through experimentation, I'd guess it to be of something greater than typical street fuel to perhaps maybe say 96 octane.  One reason for some experiencing a greater value I believe is due to an effect of mixing fuels, this creating a new chemistry, every varying, depending on the mix, and all of this why the knowledgeable persons' statement of limiting this to engine of say 11:1 +/-.  And the particular quirks of one engine design versus others and its' relationship to the fuel also muddies the conclusions.  For example: in my Lycoming 260HP 540, with the MA6 helicopter carburetor (no altitude compensation function  & a tune for higher load, hence richer fueling), timing advanced from the factory specification of 25° to 28°, it performs significantly better but detonates on 100LL.  I have found in this application that a 60-30 mix of the 89 octane ethanol free ("RV" fuel) & 110 race fuel works best.  But that's only for this instance.         

      Well, that's my effort of adding fuel to this fire!         

      Scott.   

     
       

[TOBKOB]

On reason aircraft piston engines make such good power on takeoff is that they have an an extra control that you don't see in an auto engine, a mixture control.

Unless you go back to the Model A Ford...It's called the GAV valve...

TOB

[pbf777]

On reason aircraft piston engines make such good power on takeoff is that they have an an extra control that you don't see in an auto engine, a mixture control. On takeoff, the pilot sets the mixture to full rich. This control also allows the mixture to be set for best power at altitude.

      Just a note: as I mentioned previously, the air-cooled aircraft engine designs often utilize an over-rich fueling condition for the purpose of an additional engine cooling function, and this being beyond best jetting for performance is generally the result of the "Full-Rich" mixture control setting; but this is required for some of these air-cooled engines as otherwise they may suffer a cylinder over heat and detonation scenario under their maximum usable power routine of takeoff and maximum climb particularly if of tropic air temperatures and at higher air pressures of sea level thru low altitude are included.           

      This is not so unlike the current tuning exploits of over-rich values being executed today, particularly on the street vehicles with forced induction sums beyond that which the intended to run 93 octane pump gas will support.  This is often with the misunderstanding that even so, when the engine still experiences a detonation failure, the statement often made is that it apparently must have gone "lean", when in fact, it may have actually only been leaner to the point of better, or shall we say closer to "ideal" for best power, to bad the fuel wasn't more capable!           

      Scott.

[gt350hr]

   Royce my chemist friend said nothing about the "octane" characteristics at seal level. As you mentioned that can't change. He said the fuel was "formulated" for "altitude above sea level" with specific additives to perform better "up there" than at sea level. He also mentioned it was "good for a year in the ground" unlike "highway gas". With him having a PHD in chemistry , I took his advice.

On reason aircraft piston engines make such good power on takeoff is that they have an an extra control that you don't see in an auto engine, a mixture control. On takeoff, the pilot sets the mixture to full rich. This control also allows the mixture to be set for best power at altitude. Back before the introduction of 100LL, avgas had two octane numbers such as 80/87 or 100/130. The lower number was for the lean setting and the higher number for, you guessed it, the full rich setting. IIRC, avgas is also formulated to burn well at a somewhat lower RPM than mogas. Airplane engines operate at pretty much a steady state RPM once they get to cruise altitude. Full power is generally only need during climb, whereas in a car you are constantly changing RPM in traffic and only get to a steady state condition while in cruise on the open road. So two different formulations for two different usages.

      Thanks for presenting "the facts" Roy. I'm not a pilot but I did know about going full rich for take off. I started using AV gas 50 years ago and never found an issue "specific" to it's use except "some" lead spotting on the plug with pre 100LL formulation ( green colored gas). I ran that stuff straight with 11.5 CR.
     Randy

[Royce Peterson]

Many puddle jumper sized civilian aircraft still have mixture and carburetor heat controls because the aircraft are 40 or more years old. There is a basic physics reason for a richer mixture at sea level than you would use at say Denver Stapleton. There is less air in the atmosphere as altitude increases. Aircraft engines are tuned for best power at takeoff, full rich. As the aircraft climbs there is less oxygen in the air, so the fuel mixture must be decreased to maintain a stoichiometric ratio that is acceptable for that altitude. Modern aircraft piston engines use electronic fuel injection to maintain the most efficient mixture. Many aircraft have turbosuperchargers to offset the effects of altitude.

All of this leads to confusion of folks who work on cars, or who like to comment on the subject even though they themselves don't.

   Royce my chemist friend said nothing about the "octane" characteristics at seal level. As you mentioned that can't change. He said the fuel was "formulated" for "altitude above sea level" with specific additives to perform better "up there" than at sea level. He also mentioned it was "good for a year in the ground" unlike "highway gas". With him having a PHD in chemistry , I took his advice.

On reason aircraft piston engines make such good power on takeoff is that they have an an extra control that you don't see in an auto engine, a mixture control. On takeoff, the pilot sets the mixture to full rich. This control also allows the mixture to be set for best power at altitude. Back before the introduction of 100LL, avgas had two octane numbers such as 80/87 or 100/130. The lower number was for the lean setting and the higher number for, you guessed it, the full rich setting. IIRC, avgas is also formulated to burn well at a somewhat lower RPM than mogas. Airplane engines operate at pretty much a steady state RPM once they get to cruise altitude. Full power is generally only need during climb, whereas in a car you are constantly changing RPM in traffic and only get to a steady state condition while in cruise on the open road. So two different formulations for two different usages.

      Thanks for presenting "the facts" Roy. I'm not a pilot but I did know about going full rich for take off. I started using AV gas 50 years ago and never found an issue "specific" to it's use except "some" lead spotting on the plug with pre 100LL formulation ( green colored gas). I ran that stuff straight with 11.5 CR.
     Randy

[gt350hr]

   My apologies to all when I added fuel to the fire regarding AV gas.
    Sunoco 110 is very high quality racing gas. I use it in my Drag Race only '66 GT350 . Running my GT350 at the Mid America meet is on my bucket list.
    Randy