bone crusher
Alignment Specialist
There was a thread several months ago where I posted a lot of data regarding the octane issue...if someone does a search, they'll find it...
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- Thread starter JKSPYDER13
- Start date
In simple terms The higher the octane the slower it ignites,it's needed in a high compression engine to control pre ignition. Somebody with better typing skills can explain it much better.
Note RT= 87 minimum RTS= 91 minimum, That's minimum you can go higher.
Firefly
Active member
:agree:
B
BillGargan
Guest
scudrunner
RT-S PE# 536
So breaking it down, lower compression, faster burn during the power stroke so the fuel burns completely prior to the "blow" stroke. If your fuel is burning slower, unused fuel will be pushed out the valves causing fouling on the plugs and valves.
The corollary, if your compression is high (and 12.2 is high), you want slower burning fuel. The LOWER octane will burn too fast for the power stroke causing pinging or knocking and loss of power, not to mention lower mpg's.
Since the engine is engineered for 91 or higher octane, that's what I'm putting in it. It might run ok with the 87 or 89, but eventually it will catch up.
The corollary, if your compression is high (and 12.2 is high), you want slower burning fuel. The LOWER octane will burn too fast for the power stroke causing pinging or knocking and loss of power, not to mention lower mpg's.
Since the engine is engineered for 91 or higher octane, that's what I'm putting in it. It might run ok with the 87 or 89, but eventually it will catch up.
Firefly
Active member
And those specs are incorrect.
The 990 in the RS has been tested by a few out here and it's actually around 9:1 .
Firefly
Active member
'high' compression is a relative term.... Many engines that are considered 'high' compression spec 87 octane....
Run the minimum that the manual says. If you have knocking or pinging--- you need to raise the octane.
scudrunner
RT-S PE# 536
The RS specs call for min 87 octane, the RT specs call for min 91 octane.
That sounds about right for the compression specs.
That sounds about right for the compression specs.
NancysToy
Motorbike Professor
Eggshells work, too! :roflblack:I use banana peels in my Mr. Fusion every since I installed the Flux Capacitor.
Sarge707
Active member
Firefly
Active member
Nope--- just passing on what others have stated. Dunno why there is a difference between what they list and what some have measured.... but I'm sure you can come up with another nutty conspiracy theory.
Add that one to your list......:roflblack:
Not neccessarily 9.0:1 but into the 9's ....could be 9.9:1. :f_spider::
http://www.spydertalk.com/forums/topic/9277-compresion-ratio/page__view__findpost__p__79615
Firefly
Active member
Yup--- in addition to Ken posting this (and telling me directly), the Aerocharger people have stated the same (their findings are what prompted me asking Ken).
I'll take the word of these two professionals on their findings, but I certainly wouldn't say that BRP is 'fibbing'.
If he CC'd them I'd think those would be static numbers.
Hard to say, but then again those engines are made by Rotax.....maybe the air is thicker in Austria.
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