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Post by Deleted on Jun 8, 2013 18:32:43 GMT -5
I understand it changes the timing curve.
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Post by jerseyboy on Jun 8, 2013 18:54:45 GMT -5
The tank is so small on my 150 I run premo in it all the time,,it cost me like $4.25 to fill up here at the Hess.I may try lower octane,,do you think it will improve performance?
As for the octane changing the timing curve well extra octane allows you to add more timing thus=more power,,not sure if it will be so noticeable on a little gy6 single.
Tom
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Post by millsc on Jun 8, 2013 18:57:25 GMT -5
i use 91 octane, have used 89 before didn't notice any difference, but like you said doesn't take much to fill up so i stick with 91
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Post by DaveC on Jun 8, 2013 19:26:53 GMT -5
With a compression ratio of 10:1, it needs premium don't it?
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Post by Deleted on Jun 8, 2013 19:35:15 GMT -5
Ive tried all. Stock,  is slower. 87 better  runs best. |
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Post by millsc on Jun 8, 2013 19:45:20 GMT -5
ive only put 91 in my new scoot with the airsal and stock head
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Post by prodigit on Jun 9, 2013 0:26:53 GMT -5
In short: NO! In long: It depends on 2 factors, IMHO: 1- If your engine is running too lean, premium fuel can prevent pre-detonation, due to overheating, and, 2- Premium fuel can have added premium ingredients (esp BP's fuel), that has more stored energy per cc than regular fuel, causing better performance with less fuel. There is a 14.7:1 air/fuel ratio that must be kept for best performance of the scooter. If you're running lean (eg: 16.7:1), the bike's performance goes down. However, if you fill your tank with more energetic fuel, the ratio may go upto eg: 16.7:1.1 using more energetic fuel, which basically is the same as 14.7:1; as the AFR is different for different type of fuels or flammable liquids. That being said, if a CDI pre-detonates, there's nothing that premium can or will be able to improve on this. If it pre-detonates too early causing the engine to overheat, premium fuel could help even earlier predetonation, caused by the overheating of the cylinder on the compression stroke, but at that point you're destroying your scooter by allowing the CDI to detonate too early in the combustion stroke. There is a sweet spot where the spark should spark, any earlier, and most of the energy released will be lost to heat (as it's energy is released too early to press the piston down, thus it goes sideways towards the cylinder walls). If it is too late, too much of the energy is wasted as hot exhaust, as at the moment of combustion, the cylinder is already on it's way down, and whatever energy is still remnant in the hot gasses will be exited through the exhaust valves. Just some remarkable inspiration of the moment guys  |
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Post by rockynv on Jun 9, 2013 10:36:46 GMT -5
Better answer is maybe.
Depends on the compression ratio and cam already installed in your engine. Many don't realise they needed to run a higher octain fuel until after the damage is already done. Low compression engines usually can get by with regular while 9 to 1 and 10 to 1 compression ratios should probably use mid grade and anything 11 to 1 or higher should be using premium. It is a combination of camshaft grind, compression ratio, air/fuel ratio and timing along with any tendency the engine has to build up deposits in the combustion chamber. You may have to go up a grade to help minimize the deposits that can cause early engine failure.
One sign that you may need to go up a grade is frequent valve adjustments. On my previous bike I was doing montly valve adjustments if I ran regular grade gasoline however jumping to mid grade would stretch that out to 2 or 3 months as it helped prevent wear on the valve seats, especially on the exhaust valve which would get tight and need to be loosened up monthly when running regular.
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Post by hank on Jun 9, 2013 15:09:01 GMT -5
Hi
DX
I use higher octane with higher compression engines My April has a 12.5:1 and my BBK scoot had about 11:1 so i used the highest octane i could find
In my case 94 any thing lower and my scoots predetonate and run poorly it all depends on the scoot in questions engine performance
Take care and ride safely
Yours Hank
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Post by indymoped on Jun 9, 2013 15:26:03 GMT -5
Some scoots say they only need 87 some say 91 or higher. I always run because air cooled engines can get very hot. Even most lawnmowers specify 91 or higher. Anyways timing has nothing to do with what octane you should be running. But I would strongly recommend running 91 or higher. Octane also DOES NOT give you anymore power. It is strictly to prevent pre-ignition/detonation. |
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Post by Deleted on Jun 9, 2013 18:49:27 GMT -5
Why does mine seem to run better on midgrade than premium? I thought higher octane retards the combustion somewhat leading to inefficient combustion if its not needed. My 10:1 ratio says I dont need it and if i use it it seems slower.
As for the advanced timing im thinking back to the muscle car tuning days when we advanced the timing for more power it would knock. Premium would solve that problem so I thought it would work the same way on these scoots.
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Post by prodigit on Jun 9, 2013 19:12:57 GMT -5
There are not that many chinese scoots that come stock with high compression engines.
It's rare to even find Korean models, unless they have fuel injection, but even then...
High octane is not helping early detonation due to an advanced timing on the CDI, but predetonation (or detonation of the fuel before the spark plug fires), which could both be caused by high heat, or high compression (as under high heat fuel ignites faster, and air is under a higher pressure).
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Post by indymoped on Jun 9, 2013 20:00:22 GMT -5
Just run whatever fuel runs the best for you. As long as its not knocking or pinging you'll be fine. If you hear a sound that sounds like marbles rattling in a can then you need to up your octane.
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Post by jerseyboy on Jun 9, 2013 21:37:48 GMT -5
Just run whatever fuel runs the best for you. As long as its not knocking or pinging you'll be fine. If you hear a sound that sounds like marbles rattling in a can then you need to up your octane. The only other sound that I hate more is my wife asking me to do the dishes..  |
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Post by rockynv on Jun 10, 2013 3:23:50 GMT -5
You may or may not hear anything with all the ratteling and wind noise so you have to be carefull not to go on sound alone. Damaged sparkplug electrodes and frequent valve adjustments are the other tells that need to be considered.
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is slower. 87 better 
runs best.
