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Old 05-17-2010, 02:32 PM   #841
Warren
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Octane Ratings and The TW200 (or any other air/oil cooled engine for that matter)

I wasn't sure where to put this - But wanted to share my research with all my TW200 friends...

Read around the web and you'll find opinions as far as the eye can see - Right, wrong or indifferent - So I am going to add yet another...

One that has piqued my curiosity is octane requirements - How they are determined? What scenarios can require a change? And the ever looming question of that happens if you run a higher than recommended octane in your engine?

I've spent quite a bit of time pulling research, exchanging emails with fuel manufacturers, and doing some barely-scientific testing on my own TW200. So I present what I have gathered and put for yet another opinion for everyone to chew on, and welcome your respectful and thoughtful criticism!

First let's cover some basics:

What is an Octane rating? Octane, simply put is the anti-knock rating of the fuel. The actual chemicals used to raise the anti-knock properties has changed over the years, but lead was the first used in the WWI time frame.

Now we move here to a very key point in gasoline, and one argued to death for ages. Assuming the same gasoline manufacturer (let's use Chevron), whether you use 87, 89 or 91 (or any other Octane rating) the amount of available power, BTU's or whatever you want to label it is identical. This is regulated by the fuels Specific Gravity (SG): Octane, or anti-knock components do not affect it.

One more key point that must be stated is the burn rate of 87, versus 89, versus 91. I've heard everyone say that 91 burns slower than 87... Simply not true. Based on input from Rockett Fuels and Shell, once ignited the fuels burn at the same rate and provide the same energy.

A summary of the above paragraphs reveals this basic statement:

Octane is used to delay ignition of the fuel/air mixture (utilization of anti-knock compounds). Once ignited the fuel, regardless of octane rating, burns at the same rate and delivers the same amount of energy (power).

That's quite a mouthful, but after tons of research and communication - I believe it.

Now let's look at what octane is trying to accomplish: It's all about proper timing...

Our goal is to time the fuel air explosion so that it begins it's critical expansion right at about top dead center. That means that sometime just before top dead center, we need to have a balanced mixture of fuel/air (stoichiometric), it needs to be properly compressed, then it has to be ignited - Preferably by the spark plug!

Herein lies a combination of many factors - Compression ratio, engine timing (spark), engine temperature, and octane rating (resistance to ignition). So you can see that in timing octane plays a very large role.

I think that gets the basic fundamentals out of the way - And hopefully gets your brain engaged - Good or bad as I continue...

Let's focus on the TW200, an air/oil cooled fixed ignition engine.

We have relatively low/low-mid compression and Yamaha recommends a minimum Octane of 86 (R+M)/2 - RON of 91. RON is the European measure of anti-knock quality, but let's just focus on US measure for now.

So that means we just fill ti up with 87 and ride our booty's off right? Well, maybe... We need to look at other than standard requirements we may need to factor in.

The first that may become a factor for many is fuel storage. Octane can deprecate 1-2 points per month depending on what type of container it is is - Plastics are worse, metal is better. Do you fill up with 87, then it takes you a month or more to go through the tank? If so you are not meeting the recommended requirement.

Is that a bad thing? Maybe not - It depends on your riding style and conditions.

Another very key factor that raises octane requirements is engine temperature. This is the big-daddy exclamation point for the TW200, or any air/oil cooled engine. How many of you have been riding out in the desert, or pushing a tough headwind, or pulling steep grades/trails, and detected detonation (pinging)?

These all have one very important thing in common - Higher engine operating temperatures. As engine temperature increases, our fuel ignites sooner and that can be absolutely destructive in short order if we don't back off the power - The good news is we can use octane to help regulate and correct timing.

Yamaha hints at this on the side panel and in the Owner's Manual by stating:

"Your Yamaha engine has been designed to use regular unleaded gasoline with a pump octane number [(R+M)/2] of 86 or a research octane number of 91 or higher. If knocking (or pinging) occurs, use a gasoline of a different brand or premium unleaded fuel"

Okay that's a mouthful - But a hint... Two key points I want to pick at from this quote are highlighted. Or higher simply opens a door for you - Permission as it were to use a higher octane fuel, and premium unleaded fuel hints at a grade: 91 octane or greater is the definition of premium fuel.

Let me try to sum things up a bit:

* If you are using 86 and you're not pinging - Celebrate and be happy
* If you are pinging for your riding style, or if you even THINK that you may on a proposed outing due to load, temperature or terrain - Pony up for the premium, or try 89 etc.

As summer approaches keep this in mind and listen to your engine. We only have 196cc's, and we can really work the little bugger hard (I know I ask a lot of her).

Let's see if we've got the myths covered then I'll present my testing.

1. Premium burns slower: No - It only ignites later because it is more heat and ignition resistance. Once ignited it burns just as quick as the low octane fuel
2. Premium has more power: No - Power is based on the fuels specific gravity (SG), not octane rating. SG is consistent throughout a manufacturers specific product line
3. Premium won't completely burn and leave bad deposits - See number one, while ignition is delayed (slight) there is more than enough time for the fuel charge to completely burn in almost all cases - If there were some residual unburnt fuel it would not leave deposits, since deposits are created by the burning if fuel. It may in fact provide a cooling affect
4. You're wrong Warren because I can tell my engine has more power with premium: This can be the case in an engine that has carbon buildup which has artificially increased the compression ration, thereby requiring premium fuel. Before the use of premium fuel you were likely pre-igniting and reaching full combustion before top dead center
5. Your engine will run hotter if you use premium where not called for: No - The anti-knock (octane rating) does nothing to change the actual energy of the fuel - The actual burn itself and energy released is the same irregardless.

I know I am getting tired of writing, and you are probably tired of reading, so here is a summary of my testing and I'll be finished. I wanted to focus on the temperature debate: i.e running premium makes the engine run hotter.

I decided to fuel with 87 (lowest available here) and pull Interstate 8 East up to Descanso from Alpine. On this roughly 10 mile uphill stretch, the last 2ish miles or so is a wide-open throttle stretch where I hold around 55 mph, so I thought this would be a perfect place to check speed and engine temperature (a good hefty load). I planned on running 60 mph fixed until the point it required me to hold full-throttle - Then take the temp/speed measurement at the Hwy 79 exit sign.

I used a small IR thermometer set to record max temperature. I practiced throughout my Saturday ride holding it on a specific spot on me left leg so I could consistently point it at the same spot at the base of the cylinder head. During this I did notice that moving it around was insignificant as the temperature in the head/cylinder area was very consistent.

I completely de-fueled the TW (including laying it on the side to empty the secret reserve), pumped 5 gallons of 87 into my Jeep, then put 1/2 gallon in the TW.

Outside air temp before both runs was 72.1

Engine temp before initiating each run was between 190-197 degrees

Two runs on 87 revealed the following:

Speed (GPS): 54 and 55
Temp (peak): 256 and 262

I completely de-fueled the TW, pumped 5 gallons of 91 into my Jeep, then put 1/2 gallon in the TW.

Two runs on 91 revealed the following:

Speed (GPS): 53 and 55
Temp (peak): 257 and 261

What do I make of these numbers? Insignificant... The only conclusion that can be drawn is that octane had no affect on the runs regarding temperature, power or speed.

So in conclusion - Do not be afraid to use 89, 91, 93 or whatever if you feel you may be in a scenario that increases engine temperature.

For me, I was quite often pinging on 87 through the hills and deserts of San Diego, and so far 89 has been good... As summer fully blooms I expect I'll put in 91... Just in case...
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Old 05-17-2010, 09:11 PM   #842
villageidiot
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Thanks for puttin it all out there for us to absorb. very well written, i enjoyed readin it.
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Old 05-18-2010, 12:49 AM   #843
LostAussie
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Kick Starter

Will the kick-start from an older (late 80's - Early 90's) TW200 fit on a 2007 model?
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Old 05-18-2010, 02:59 AM   #844
Turborob
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LostAussie; yep it'll fit.

Look on the TW200 forum where a few people have done it.
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Old 05-18-2010, 06:57 AM   #845
villageidiot
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Laugh

first tw200 ride,

took the twout the truck and fired it up. before i could get my helmet and gloves on, the bike dies. nearly killed the battery before just bump startin it. fires up and off to work i go, about 5 miles. after work i tore the carb down and cleaned the pilot jet, and drilled the main jet up 3 sizes...making it equivilant to a 132. put back together, its no longer cold blooded and no longer back pops after hard decelleration

rode it at about 50mph indicated the 11 miles home with a grin on my face, even though it decided to rain on me the whole way home

so pleased with this bike as of yet.
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Old 05-18-2010, 08:08 AM   #846
Streamin' E
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Nice write-up Warren. One thing that people might consider though is that detonation starts before you can hear it...
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Old 05-18-2010, 08:10 AM   #847
Warren
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Quote:
Originally Posted by Streamin' E
Nice write-up Warren. One thing that people might consider though is that detonation starts before you can hear it...
Very true, very true...
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Old 05-18-2010, 10:46 AM   #848
roguesteelheader
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Well I am back

After I sold my Husky 610 TE I thought my riding days were over. Well my wife has been wanting to look at scooters and I just do not think they are that safe. Remember I have been riding for over 50 years and think you need to throw your leg over something not step in to it. Well she has bad arthritus in her hips thats why we sold her 650 V Strom. Anyway I have been wanting one of these little guys for awhile and so I showed her a photo of a TW and she loved it. With to low seat height she can get on one fine. Well I sarted looking and found 2 one is a 06 and one 07 both with under 600 miles. So we are headed over to central Oregon Thursday to pick them up. Then the fun begins. I am sure mine will get some goodys to make it run a little better. Sure glad I kept my riding gear. Anyway thats my story. I will be hangin around on here again.
Pete
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Old 05-19-2010, 07:30 AM   #849
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Octane

Enjoyed your write-up as well, Thanks Warren.
Gerry
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Old 05-19-2010, 08:09 AM   #850
Warren
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Quote:
Originally Posted by roguesteelheader
After I sold my Husky 610 TE I thought my riding days were over. Well my wife has been wanting to look at scooters and I just do not think they are that safe. Remember I have been riding for over 50 years and think you need to throw your leg over something not step in to it. Well she has bad arthritus in her hips thats why we sold her 650 V Strom. Anyway I have been wanting one of these little guys for awhile and so I showed her a photo of a TW and she loved it. With to low seat height she can get on one fine. Well I sarted looking and found 2 one is a 06 and one 07 both with under 600 miles. So we are headed over to central Oregon Thursday to pick them up. Then the fun begins. I am sure mine will get some goodys to make it run a little better. Sure glad I kept my riding gear. Anyway thats my story. I will be hangin around on here again.
Pete
Awesome Pete!
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Old 05-19-2010, 11:45 AM   #851
roguesteelheader
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Thanks. We can't wait to get them home and serviced and checked over.
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Old 05-19-2010, 01:45 PM   #852
City Man
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Some good information there Warren – thank you for your write-up and taking the time to post it.
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Old 05-19-2010, 04:24 PM   #853
Wheelie Nelson
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I figured I would add my pics to this thread.

2009 with a TurboCity rear rack, a Cortech Sport Tailbag, TTR225 stainless header, FMF pipe (the new one made for the TW200), a Jimbo shield, a white front fender, Fiamm HK9 horn, D2moto foot pegs, 14/45 gearing and an o-ring chain. I plan on getting a Clarke tank when it's out, and adding some new bars.





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Old 05-19-2010, 06:29 PM   #854
villageidiot
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spent the better part of tuesday night on the bike. rode side streets from newport beach where i work, home to midway city, then up to LA to meet up with my moped club. traffic was horrible on the way up, but on the way back the ride was nice and smooth. its like mc donalds says. "i'm lovin it"
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Old 05-19-2010, 08:11 PM   #855
D1EHARD
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Raised front fender mod...

Hey guys, just wanted to post up pics of my brother's TW. We put on a new front fender tonight and it turned out great. He went with an Acerbis supermoto front fender, blue/white, looks factory! We drilled in under the headlight and braced with some homemade brackets. Changes the whole look of the bike.

Here are pics:





These are badass little bikes.
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