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If you add a FCR carb, exhaust, and all other basic mods to the 400sm, does it need premium gas?
Premium Gas
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527 Posts
No...unless you're throwing in a higher compression piston, premium gas will do nothing for you.
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sweet, that's another advantage to buying the wr250x as well. The stupid gas station next to my house charges almost 75 cents more for premium sometimes. assholes. right now it's like 4.06, 4.36, 4.66 :rant:
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316 Posts
The octane rating on gas, simply put, is a measurement of the ammount of compression it can take before it detonates (explodes, basically) from the sheer compression (read: NOT a spark). This is bad, and you don't want it, it can cause knock and/or detonation in some motors to put the wrong type of gas in the engine.
So, if you have an engine that makes a lot of compression it will require a higher octane gas to prevent detonation (also engines that are turbo/supercharged). However, despite the myth, putting premium gas in a car that needs regular gas is a bad idea as well, it's made to be compressed more and may not burn enough.
The point I'm getting at is: Unless you're changing the compression on a motor, you keep using the same gas. And always use the gas the manufacturer tells you to. No offense, but they know better than you what gas to use in the engine they made.
So, if you have an engine that makes a lot of compression it will require a higher octane gas to prevent detonation (also engines that are turbo/supercharged). However, despite the myth, putting premium gas in a car that needs regular gas is a bad idea as well, it's made to be compressed more and may not burn enough.
The point I'm getting at is: Unless you're changing the compression on a motor, you keep using the same gas. And always use the gas the manufacturer tells you to. No offense, but they know better than you what gas to use in the engine they made.
no
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3,270 Posts
only in instances that REQUIRE premium gas. high compression, high boost, retardedly lean fuel/air mixture, etc. Putting 110 octane racing fuel into a 5 hp briggs and stratton isn't going to magically make it an 8 hp motor.
That's not entirely true... It's not "BAD", you just may not notice a significant difference. Higher octane ratings basically equate to a higher percentage of iso-octane by volume. In simple terms, it's a rating of how stable the fuel is (i.e. resistant to auto-ignition).
From basic thermodynamics, it's known that as you compress a given quantity of gas it heats up. In an engine, the mixtures in the cylinders is compressed until just before the "combustion point". Your spark plug then kicks in and you get your controlled burn.
With lower octane fuels, the lower level of stability means that the mixture can possibly ignite before the spark (before you want it to) due to the rapid increase of temperature from compression. This causes "knock", which I'm sure you guys have all heard of.
Anyway, my point is just that higher octain means it's more stable, not that it needs to be compressed more to burn. I just wanted to clarify that. In the end, though, the result is the same. You probably won't notice a big difference in a low compression engine.
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78 Posts
iv noticed if i put in anything under 94 (sunoco) it makes my bike pop non stop when i down shift but the 94 makes it run smooth like my buddys moms box after a bezilian!!!!
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its all in your head...if it really does run better, then you have something wrong with your engine ie. for some reason, your mixture is pre-igniting. It could be a large amount of carbon buildup is causing hot spots in your cylinder. Maybe your bike is running really hot causing the pinging. If your engine in your DRZ S is stock, there is NO WAY that your bike will run better on 93 with stock compression and ignition timing. It's basic science...
I will put money on the fact that if you were to dyno your bike back to back with the two different fuels, you would see more hp with 87 octane.
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527 Posts
Why would I pay 30 more cents for fuel that will make less power, make my bike feel more sluggish and burn less clean???
I don't know how many times people have to hear that higher octane does not mean higher power!
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310 Posts
This reminds me of my friends. They would run their cars out of gas, then put in 20 liters of premium in, and then a WHOLE bottle of octane booster into the tank before heading to the drag strip for street legal night. They thought their cars would run so much better. Stock motors too. When I protested they looked and laughed at me like I was a moron.
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An added point (having worked at a fuel station for a bit);
With todays fuel prices, many people are not choosing premium as it is expensive.
Fuel "shelf" life is no where near what it used to be.
You could be buying some not so fresh fuel which is 100% the opposite of what you are TRYING to accomplish by spending the extra coin.
Best bang for the buck, set the bike to run on say 104 or something similar, tune the bike for it, mix it yourself so its perfect every time. Call it a day.
Or if your engine is under 13:1 ish (and/or not boosted like crazy) just run regular and "save your money".
With todays fuel prices, many people are not choosing premium as it is expensive.
Fuel "shelf" life is no where near what it used to be.
You could be buying some not so fresh fuel which is 100% the opposite of what you are TRYING to accomplish by spending the extra coin.
Best bang for the buck, set the bike to run on say 104 or something similar, tune the bike for it, mix it yourself so its perfect every time. Call it a day.
Or if your engine is under 13:1 ish (and/or not boosted like crazy) just run regular and "save your money".
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527 Posts
:lol: yup, I used to see the same thing all the time!
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:lol: yup, I used to see the same thing all the time!
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3,270 Posts
I used to do that, as well. Though I was running a road course for 40 minutes at a time in the desert. My thought was that, since the car was running on the verge of overheating (or running on the edge of the red...I HATE idiot gagues) for about 30 of the 40 minutes, it was a bit of piece of mind. I wouldn't even think about doing that at the drag strip. 9-20 seconds of "hard driving, followed by 60+ minuted of cool down....:headshake
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462 Posts
I just checker in my SM owners manual and Suzuki recommends using 91 octane "or higher" unless in Canada then it says use a minimum of 87 octane.
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