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stioc (guest) View all posts in this topic  
Fri May 11, 2012 1:56 pm
Higher octane will help in certain situations - FAQ is not gospel        

BrianM wrote:
DKspokane wrote:
At 12.4 compression, the Ninja has a high performance engine.


You just made an assumption that isn't true. Motorcycle engnines != Car engines, there's a world of difference.

But, use whatever the hell you want... it's your bike and your money. But don't, for fucks sake, try to convince anyone that knows Anything about motorcycles/fuels of what you think (unless you want to get into an argument and be thought a fool).

And the reason your engine feels smoother/quieter on higher octane fuel is because the fuel is less volitile (after all, octane is a rating to measure the resistance of detonation/preignition), so there's less "combustion" process going on (which is where the "less performance" comes into play). It's measureable on a dyno, so go see for yourself.

But the EX250 motor is definatally NOT a high performance engine. Why would it be? The bike is no where near a high perofmrnace bike (and never has been), it's a sporty looking standard.

Brian


I disagree that the bike vs. car engines are different - how?? A liquid cooled 4 stroke internal combustion engine is what it is. I also disagree that the EX250 motor is NOT a high performance engine - what do you consider high performance? Is a CBR600RR or an R6 high performance enough? Have you compared the compression ratios and rev limits to those? The EX250 engine IS a high performance engine, higher performance than say a Honda ST1300 V4 which redlines at 6500rpm.

I do agree that higher octane generally won't help without fuel injection and a knock sensor because there's nothing retarding or advancing the ignition timing to take advantage of the octane. However, if it were FI the higher octane would definitely help. For e.g. many car manuals state that you must use higher octane when towing, why? I would guess it's because they tested and found that while under normal circumstances the engine performs adequately under a high load condition the higher octane will keeping the engine running cooler, prevent pre-ignition, detonation and provide slight power advantage. I would say if you're doing two up riding on your EX250 in the 100deg summer heat the higher octane will help.

The FAQ is not Gospel guys.

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