What ocatane
#11
02-15-2009 | 09:28 AM
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#13
02-15-2009 | 11:25 AM
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What ocatane
<div class="FTQUOTE"><begin quote>Originally posted by: rvessar
I am not tring to argue with you I knew they recommended 91 or 92 I just wanted to know what other people ran ,that is why I asked to see if I should switch.If I was tht ignorant I wouldnt have asked.</end quote></div>
Sorry to come off so strong, but little scolding may save you a lot of future grief!!! You can damage your engine running 87! 91 octane gas is a lot cheper than new valves.
And, asking what someone else runs doesn't make any sense, seeing that they may not be running the right thing either!
I am not tring to argue with you I knew they recommended 91 or 92 I just wanted to know what other people ran ,that is why I asked to see if I should switch.If I was tht ignorant I wouldnt have asked.</end quote></div>
Sorry to come off so strong, but little scolding may save you a lot of future grief!!! You can damage your engine running 87! 91 octane gas is a lot cheper than new valves.
And, asking what someone else runs doesn't make any sense, seeing that they may not be running the right thing either!
#16
02-15-2009 | 12:03 PM
Range Rover
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From: Millgrove Ontario
What ocatane
<div class="FTQUOTE"><begin quote>Originally posted by: Gimpster
Yes, like the fellers have touched off on... What quad ?
I have guidlines I follow when building an engine for what fuel it should be running per application. Cam and timing specs go hand in hand with head cc, swept deck volume, exhaust, carb, head flow etc... in order to figure the correct octane.
In a nut shell... Detonation occors after TDC into the power stroke (downward movement of the piston after compression) and pre detonation occors early during the compression stroke.
Example of pre-detonation would be an engine demanding 91 octane when 87 is used. The 87 will ignite quicker so with the engine timing set for 91 (slower burning fuel) which is advanced timing, it will cause harmfull pre-detonation.
Hence an engine demanding 87 octane, running with 91 octane the flash is late and causes detonation.
Both can cause engine component failure. both make a pinging sound under throttle up situations. Pre detonation is often noted through blown head gaskets, bent rods, burned intake valves. Detonation is more noted on broken ring lands burnt exhaust valves etc...
If you are really good tuner, looking at the piston you can identify fuel wash and see it's affects from both pre-detonation and detonation affects are having on the piston.
The detonation difference when running 91 in an engine designed to run 87 is mainly as described above, a waste of money, think it out. Some detonation relief is absorbed through the exhaust valve opening. carbon deposits are accelerated.
Pre detonation from running 87 octane fuel in a 91 octane engine will do harm as the timimg is advanced too far for one. The 87 in this situation flashes it's burn quicker and will build heat.
Why higher octane in some engines ? Number one is they will run cooler at higher RPMs. Normally these engines are designed to generate their power curve higher in the RPM range where heat is more a factor to be concidered than in a low RPM engine.
Confused yet ? LOL
Lower octane fuel, burn flash is quicker = hotter= less compression needed
Higher octane fuel, burn flash is slower = cooler= higher compression needed
----- Gimpster -----
edited for spelling</end quote></div>
Now that some serious info thanks for that i always ran high octane just cuz i thought it was better...hmmm maybe i will rethink that decision!
Yes, like the fellers have touched off on... What quad ?
I have guidlines I follow when building an engine for what fuel it should be running per application. Cam and timing specs go hand in hand with head cc, swept deck volume, exhaust, carb, head flow etc... in order to figure the correct octane.
In a nut shell... Detonation occors after TDC into the power stroke (downward movement of the piston after compression) and pre detonation occors early during the compression stroke.
Example of pre-detonation would be an engine demanding 91 octane when 87 is used. The 87 will ignite quicker so with the engine timing set for 91 (slower burning fuel) which is advanced timing, it will cause harmfull pre-detonation.
Hence an engine demanding 87 octane, running with 91 octane the flash is late and causes detonation.
Both can cause engine component failure. both make a pinging sound under throttle up situations. Pre detonation is often noted through blown head gaskets, bent rods, burned intake valves. Detonation is more noted on broken ring lands burnt exhaust valves etc...
If you are really good tuner, looking at the piston you can identify fuel wash and see it's affects from both pre-detonation and detonation affects are having on the piston.
The detonation difference when running 91 in an engine designed to run 87 is mainly as described above, a waste of money, think it out. Some detonation relief is absorbed through the exhaust valve opening. carbon deposits are accelerated.
Pre detonation from running 87 octane fuel in a 91 octane engine will do harm as the timimg is advanced too far for one. The 87 in this situation flashes it's burn quicker and will build heat.
Why higher octane in some engines ? Number one is they will run cooler at higher RPMs. Normally these engines are designed to generate their power curve higher in the RPM range where heat is more a factor to be concidered than in a low RPM engine.
Confused yet ? LOL
Lower octane fuel, burn flash is quicker = hotter= less compression needed
Higher octane fuel, burn flash is slower = cooler= higher compression needed
----- Gimpster -----
edited for spelling</end quote></div>
Now that some serious info thanks for that i always ran high octane just cuz i thought it was better...hmmm maybe i will rethink that decision!
#17
02-15-2009 | 02:29 PM
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What ocatane
<div class="FTQUOTE"><begin quote>Example of pre-detonation would be an engine demanding 91 octane when 87 is used. </end quote></div>
Maybe it''s a local linguist thing but I think you ment to type pre-ignition instead of pre-detonation. Never heard of pre-detonation?
Good read for those who like to learn about such things.
Maybe it''s a local linguist thing but I think you ment to type pre-ignition instead of pre-detonation. Never heard of pre-detonation?
Good read for those who like to learn about such things.
#18
02-15-2009 | 07:32 PM
Range Rover
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What ocatane
<div class="FTQUOTE"><begin quote>Originally posted by: gambler_m_99
The higher octane burns slower and produces less heat, but not enough that you will ever notice.</end quote></div>
Wrong, this is a common misconception of octane numbers.
A higher octane fuel simply means it can wait longer for the spark to ignite the fuel. This means less chance of a hot spot in the engine igniting the fuel before the spark and flame front get a chance to. That is all it is.
The higher octane burns slower and produces less heat, but not enough that you will ever notice.</end quote></div>
Wrong, this is a common misconception of octane numbers.
A higher octane fuel simply means it can wait longer for the spark to ignite the fuel. This means less chance of a hot spot in the engine igniting the fuel before the spark and flame front get a chance to. That is all it is.
