Mr_RPM
07-23-2010, 11:48 PM
well as most of us know octane is basically an additive to reduce pre-ignition on high compression engines. it raises the ignition temp to gas and also makes for a slower burn.
some say running to high of an octane will result in an incomplete burn because the compression was not high enough to ignite the fuel. also because it burns slower it wont burn completely in time and continue to burn on the exhaust cycle on a 4 stroke, being energy lost and making your machine slower. This could probably be diagnosed by a black plug im guessing.
A new gas station in my area was just built and they have a 100 octane gas pump. before all we had was the normal 93 octane and then 110 octane.
I'm going to be running 10.5:1 comp piston in my 110 and i wonder if i should run full 100 octane or mix it with some 93 octane. Im sure it wouldn't be high enough to effect the engine negatively and would only be a waste of money if anything.
Im just worried about getting the engine real hot, lets say climbing test hill at silverlake sand dunes. being at full throttle constantly with little airflow over the engine will get the engine pretty hot i would imagine. the dunes are hard on your stuff esp on a 90 degree day.
im going to try running 100 octane first then maybe dilute it if needed, its really not that much more expensive.
another thought though is with a bigger cam the longer duration will lesson compression a little because the intake valve may not close perfectly on time for the comp stroke. so maybe it wont be close to 10.5:1 comp after all. i have also been told you need to run high comp pistons with stage 2 type cams (full race, high end types) to make up for this symptom
anyway what octanes have you guys ran in your engines and with what compression. my dad had to mix 110 and 93 to a 3:2 ratio for the yz490 (had like 13:1 with OEM piston...) to keep it from knocking.
I dont know much about high octane on 2 strokes as far as running to much, anyone?
just a rant on octane since i haven't seen one here before, and a chance for us all to share what we know and maybe gain a basic understanding on what octanes to run with diff machines at diff compressions.
My only experience is i have gotten away with a octane ranging from 87-93 on a 400ex with 11:1 with a stage 2 hotcam camshaft.
some say running to high of an octane will result in an incomplete burn because the compression was not high enough to ignite the fuel. also because it burns slower it wont burn completely in time and continue to burn on the exhaust cycle on a 4 stroke, being energy lost and making your machine slower. This could probably be diagnosed by a black plug im guessing.
A new gas station in my area was just built and they have a 100 octane gas pump. before all we had was the normal 93 octane and then 110 octane.
I'm going to be running 10.5:1 comp piston in my 110 and i wonder if i should run full 100 octane or mix it with some 93 octane. Im sure it wouldn't be high enough to effect the engine negatively and would only be a waste of money if anything.
Im just worried about getting the engine real hot, lets say climbing test hill at silverlake sand dunes. being at full throttle constantly with little airflow over the engine will get the engine pretty hot i would imagine. the dunes are hard on your stuff esp on a 90 degree day.
im going to try running 100 octane first then maybe dilute it if needed, its really not that much more expensive.
another thought though is with a bigger cam the longer duration will lesson compression a little because the intake valve may not close perfectly on time for the comp stroke. so maybe it wont be close to 10.5:1 comp after all. i have also been told you need to run high comp pistons with stage 2 type cams (full race, high end types) to make up for this symptom
anyway what octanes have you guys ran in your engines and with what compression. my dad had to mix 110 and 93 to a 3:2 ratio for the yz490 (had like 13:1 with OEM piston...) to keep it from knocking.
I dont know much about high octane on 2 strokes as far as running to much, anyone?
just a rant on octane since i haven't seen one here before, and a chance for us all to share what we know and maybe gain a basic understanding on what octanes to run with diff machines at diff compressions.
My only experience is i have gotten away with a octane ranging from 87-93 on a 400ex with 11:1 with a stage 2 hotcam camshaft.