:agree:.............And everyone here knows it ....BRP's line of whooey not with-standing ............My mechanic ( & best friend ) and I ACTUALLY tested it and found in the 2014 RT anything but 87 is a waste of money ......................let the flaming begin....ha ha ha ..........Mike.........................................................................................And for those of you who truly believe and espouse that the 2014 RT MUST use at least 91 Octane ................What do you think is going to happen to the engine if you DON'T...............................I really want your opinions on this question..........I bet I don't get one single answer
I'm brave or stupid, but I'll take that bet...Like Charlie Daniels,...
So, 87 is the one you prefer. Dare I ask, do you run pump fuel with no additional additives or are you adding other products (not octane booster) to your pump gas? May I ask if you have a preferred brand?
I shall believe you are willing to go with an 87 octane with nothing added.
Without crazy details, there is a difference between detonation and preignition. Often they are posted about on the internet with wrong meanings or applications.
Preignition is the ignition of the compressed air / fuel mixture by typically the spark plug if advanced to much or also, something hot enough in the combustion area to ignite the fuel. This could be overheated carbon deposits, a sharp machined edge from production, a super heated edge of an exhaust valve that is floating or has poor tip clearance and more. Regardless the fuel is ignited and burns at the wrong time. Burning fuel is a controlled burn or flame front. The key is controlled flame, but at the wrong time.
Detonation is an uncontrolled combustion event. Rather than igniting the fuel / air, the compression pressure, too low of an octane, or a manifold pressure that is too high for the relative load can cause the fuel to detonate. Detonating is like TNT or explosives. It is an instantaneous event with no control of the burn to speak of.
So, good inside the combustion chamber is controlled burn, bad is explosions inside the combustion chamber. Detonation is a very high cylinder pressure. The short duration and high pressure can destroy heads, pistons, bend rods, snap cranks, and destroy bearings.
87 vs 91, 93 or even unleaded race gas.
87 octane will burn in the engine. Will it detonate or cause issues. If an engine is monitored by a Knock Sensor, this device has the ability to allow the engine mapping to be taken to the limits of programing, and then if along the way of the ECM adjusting mixture and timing vs temps, Mass Airflow, Manifold pressures and load, it senses a knock. Far more sensitive than what we would hear since the Knock Sensor is feeling the engine, not listening, the ECM will make adjustments to control parameters to remove the knock.
It is true and sometimes discussed that the best octane to run is the lowest possible that will not knock. Typically because the flame will travel faster and utilize all the fuel. Less discussed is that with more octane, and an appropriate engine map, the timing can be increased slightly to allow more time to burn the higher octane fuel.
So why is lower better sometimes. It can be a timeframe situation, in milliseconds, the combustion event takes place. At say 4000 rpm your one cylinder is completing 66.66 firing events per second. Each event requires a precise time, in degrees before top dead center to optimize the engine. If the rpm is doubled to 8000 that is 133.33 events per second, we turn race bikes close to 15000, this is 250 engine events per cylinder, per second.
Why does the octane matter, the often least amount required octane, will reduce the burn time. If the octane is higher and optimized, the timing must be advanced to allow enough time to burn all the fuel. If the timing is advanced, this is beginning the burn more degrees before top dead center. Simply, a few degrees will create more initial pressure to get the engine to turn past top dead center and begin the downward stroke that makes the power.
So why recommend a higher octane. If the fuel burn can begin sooner, and burn longer, there may be more net power from the power stroke. It can also be a short stroke engine or radical port or valve timing that dumps unburned fuel into the exhaust. There are no doubt many variables.
For many years I have tuned 2 strokes. From simple carb tuning of all circuits to port work, case work and even modifying cranks and reed blocks, plus pipes. The high performance 2 stroke is more critical than a 4 stroke in regards to the engine getting less rpm from higher compression, higher case or secondary compression, or less than ideal gasoline and octane. My current 2 stroke everything including lawn equipment runs 100ll avgas with Klotz r50 premix oil. The fuel is stable, does not destroy seals or rubber carb parts. Is the octane too high, maybe for the lawn equipment, but my yard smells like a track when I whippersnipper the grass. My KTM 250, came with a pretty conservative head design. It was capable of running pump gas. The low crank pressure and a squish band dimension and clearance created many problems in power output and the bike would never jet clean. Simply modding the head saw huge gains and easy jetting. The 100ll fuel may seem excessive, but there is benefits to the lead added into the fuel. Overall, simply a good compromise.
I have tested 100ll in my old and now sold YZ426f race bike. One would expect the 100ll to give good results. Did not happen. The tolulene that is in the fuel slows the burn time. Not really a big concern, and was not except to make the engine accelerate. Basically the off corner performance was bogging and had no snap. Pump gas ran better but jet suffered. Running unleaded Sunoco 105 was very good performance wise, but the fuel contained MTBE as an oxygenator, the fumes of the fuel and exhaust were brutal, plus MTBE is not good for you.
In our Spyder we typically run Chevron 93. Not so much for octane, but rather better feel through the mid range power and most importantly the cleaning additives including Techron. I also use a Yamaha product to lessen corrosion and preserve the fuel.
Can lower octane run good and give good numbers, yes. Why does BRP say 91 minimum, they designed the ECM parameters for that octane. Is 93 too high, maybe, we could likely run 91 and see better numbers and save a few dollars.
The best advice is a quality fuel. Consistency counts. In regards to Alaska and other areas where the fuel all comes from the same refinery, yes it does happen. The thing that makes it different is the additive packs are done as it leaves the holding tank and this makes the Chevron / Teaxco different than Exxon / Mobil and those of the corner store.
The chips were pushed into the center of the table...there's more but I need to get bicycle stuff done.
PK
:2thumbs:
