[clstan0113]

i have used 87 and 93, and seen absolutly no differnece at all... so for $$$$ sakes i am sticking with 87!

[TheKlic]

I have run all 3 and do feel that it likes the 93 better at night
during the day I can't feel a difference, but at night the cool dry air seems to work well with 93
but it runs fine with all of them
maybe I just think it feels better

[StblJmpr]

I used to work for testing lab that was responsible for testing all types of lubricants, fuels and other automotive fluids. You would really be surprised in the differences in the quality of gas in Canada.

Could you elaborate further?

Certainly. Additives is what makes gas different from one company to another. It's much like Pepsi vs Coke. It's the same thing, but the differences in recipe is the difference. They both use the same ingredients, but use different amounts of each. Gas is nearly the same way. Most gas companies use the same additives for their fuels. Again they use different amounts of those additives. Some companies use different additives altogether. And sometimes the mixtures vary depending on the time of year.

The worst fuel in Canada is made by a company that changes their fuel for winter or summer. They claim clean burning in the summer and gas line antifreeze in the winter. The additives they use for both cases do what they claim, but not everything is great. According to tests done at the lab, the summer gas causes a reduction in power, and the winter gas causes very poor combustion and leads to serious carbon buildups. This is only one example. There are others that I could explain, but I don't have the time.

I do not know about the US fuel companies. I have seen tests from EVERY Canadian company, and the differences between them is very surprising. Even the difference between grades is amazing. Even the difference in oil would boggle your mind. Companies like Canadian Tire do not make their own fuel or oil. Their oil is supplied by one of the big Canadian companies. Fuel on the other hand, is purchased based on who can supply them and what price they can supply at. You go to any non-brand name gas station, and you can get a different companies fuel each week.

Do some research. And then test those results by using fuel from each of the best companies on your list. Use what works best for your application. I know that my car, my wife's SUV and the bikes all run better on gas from different companies. Amazing but true.

[slayergsxf1]

Had the 87 in my hand today....couldnt do it and went with the 93....16 years with super cant switch now.

[Looneybonics]

I was the same way. I fed my bike the best for 2-3 years. But ya gotta look at like you're being selfish. Just because you think 93 tastes good to your bike doesn't mean it does. Your bikes favorite drink is 87. It's like havin a girl that loves to go to McDonalds more than going to an expensive steak house. You shouldn't pay more for something that doesn't make her/it as happy as the cheaper alternative. (If that makes any sense at all) More expensive isn't always better specially in the case of gas for the kat. 87 is better for the internal parts. I've made the switch and my bike works great still. Take the money you save and put it towards treats for your bike like fuel injector cleaner or mods or something.

Looney

[slayergsxf1]

Ive put 87 in my bike and it runs like shit.. I've tried it more than once,same result. I'll try 89 and see what happens,if it works I'll try the 87 and get back to you.But if it pings I will rant!!

[Looneybonics]

Higher octane gas is bad for the fuel injector. Try 87 with some injector cleaner. Also check out this post that I posted like a week ago. Loooots of useful information and a poll to give you some visuals on what kinda gas everyone is rockin.

What Kind of Gas do you put in your Kat?

[The CyberPoet]

Higher octane gas is bad for the fuel injector.

Ummm... we don't have fuel injectors... The kats are all carb'd...

I'm going to recover this issue because the original threads went astray in the KR crash that had the very nitty-gritty low down (for those who want to understand this fully). There are still some threads around that have a lot of good info, but none of them are complete...

Optimal "ideal" gasoline is comprised of two parts, n-heptane (seven carbon atoms on a 16-hydrogen-atom backbone) and iso-octane (eight carbon atoms on an 18-hydrogen-atom backbone). Heptane as a vapor is very explosive, so much so, that it tends to ignite spontaneously (predetonation/preignition) when subjected to a bit of over-pressurization or heated beyond a certain point. Octane on the other hand is much more stable, resisting the tendency to predetonate/preignite much better. But, because of the smaller molecule size of heptane, you can cram more of them into a gallon; and because of their inherent explosiveness, you can get more power out of that gallon than you can a gallon of pure octane.

Which leads us to modern engines. The inside of a modern engine compresses the fuel-air mixture quite a bit (about 11.2 times the ambient pressure on a Kat 600, 10.5 times the ambient air pressure on a Kat 750). This is enough to cause pure heptane to combust many times over. So instead of pure heptane, fuel producers mix in octane to help retard that reaction (to get the desired effect). And thus the percentage of octane is the octane rating (i.e. - an ideal fuel of 13% heptane and 87% octane would be labeled as having an octane rate of 87). Reduce the heptane and up the octane, and the fuel can handle more compression & heat without predetonating....

But nothing is ever quite that simple... And gasoline isn't usually made out of just heptane and octane, incorporating lots of other tanes and additives. So those figures are used as reference numbers. When a manufacturer says the fuel is 87 octane, what he is really saying is that his fuel, whatever it happens to be made out of, will behave, for all practical purposes, as if it was composed of 13% heptane and 87% octane.

And that's not the end of the story yet either. Researchers at Diamler discovered about a century ago that fuel octane numbers behave differently under different load situations. For example, what happens in neutral at low RPM's is not the same as what happens in a hot engine under a heavy load while accelerating. And thus, two different standard methods for testing octane behavior were established - the Research Octane Number (RON) and the Motor Octane Number (MON). The RON represents an idle-type scenario. The MON better represents a hot engine under load, and is usually about 10 points lower than the RON for the same fuel. In Europe, the RON number is normally what is listed on the pump. In the USA, the RON and MON numbers are averaged together to come up with a Pump Octane Number (PON); normally on the pump you will see a sticker that says something like PON=(R+M)/2.
So, at least in the USA, we deal with PON numbers. 87 octane at the pump is actually an 87 PON. Now the problem with that is that we don't know what the actual RON and MON numbers are for that particular fuel formulation -- if the batch happened to have a higher-than-usual RON value and a lower-than-usual MON number, you might end up with the same 87 PON that suddenly behaves like crap under heavy acceleration...

Now to complicate matters a slight bit more:
Obviously, the higher the compression level of the engine, the more the fuel needs to resist predetonation. With modern small car engines and some motorcycle engines running as high as 13:1 compression ratios, these engines must generally use the highest octane fuels to avoid predetonation. The size of the cylinder and the RPMs of the engine play into the requirement heavily also. If you think about it rationally, the time for one cylinder of a 600 Kat (149cc cylinder) spinning at 10k RPM to be able to predetonate is pretty short (about 1/320th of a second). It also has a quite small surface area to produce heat concentrations at, with fresh fuel-air charge being crammed in (cooling down the cylinder) every 1/84th of a second at 10k RPM. By comparison, a chevy 350 V-8 running at 3k RPM has a 716.9cc cylinder, and is taking in a fresh charge every 1/25th of a second. That's a lot of difference in heat exposure times, both in terms of how long the detonation produce is left in the cylinder to heat it up, and in terms of how often fresh (cool) charges are sucked in. Thus, in situations where the compression ratio would dictate a nominal 93 octane, a much smaller cylinder that cycles at a much higher rate may be able to get away with a few points less, such as a 91 octane rating.

Now, remember, I said that compression ratios were a multiple of the ambient air pressure (at least on non-turbo/non-supercharged engines). As a result of the lower air pressure at higher altitudes, less air is sucked into the engine (and less fuel with it), reducing the actual pressure the fuel vapor is exposed to. This means that a lower octane rating can be used to get the same effect in high altitude locations. Thus, once you move away from sea level and up into serious altitudes, gas stations stop selling the standard 87/89/92 octane and the octane numbers start falling to figures as low as 84/87/90 instead. This fuel generally contains more heptane (or compounds which act like heptane) and thus is more explosive by definition, which helps make up for the power loss the engine suffers at altitude because of the smaller amount of fuel-air mix it takes in.

Special Exceptions:
1. If your engine has a large amount of carbon deposits in the cylinder (from poorly burned fuels), or sulfated ash deposits (from sulfate-ash rich motor oils), then these deposits can retain sufficient heat to pre-ignite the fresh fuel-air charge being sucked in, and/or produce sufficient of a change in the shape/size of the cylinder to raise compression to undesirable levels. In these cases, use of a higher octane fuel may stop the pre-ignition/pre-detonation from occuring because of the higher resistance values of octane. But that is a band-aide over a serious problem that should be rectified before it causes additional or subsequent damages (large carbon chunks falling off or building up too high can seize engines and break connecting rods & valves; small pieces will score the #$&% out of your cylinder walls and ruin your rings' integrity).
2. Katana engines which have been mechanically modified to alter the compression ratios through use of WiseCo bore-over kits, thinner gasket kits, turbo-chargers or super-chargers. All of these increase the compression ratio sufficiently to require higher octane fuels.

Which brings us full circle back to the beginning:
As long as the engine on your Katana has not had any mechanical changes that alter the compression levels AND is not a catankerous old carbon trap, then it requires nothing more than 87 PON (or 91 RON), and will not benefit from the extra predetonation/preignition resistance. Effectively, you are wasting your money on a non-benefit.
It would be much wiser for you to buy low-octane high-detergent-load fuel from a reliable dealer than to buy high-octane fuel from anyone. Specifically, I know the detergent loads in Chevron, Shell and Mobil are supposed to be superior in quality; in the case of Chevron and Shell, they are also generally superior in terms of quantity per gallon.

Cheers,
=-= The CyberPoet

[The CyberPoet]

Part 2.

RPM's verses cylinder loading and how it relates to octane requirements.

The engine on the Katana, like many high-rev'ving motorcycle engines, utilizes an overlap in exhaust and intake timing, and closes the intake valves after the piston has already started rising up in it's stroke. Effectively, it goes like this:
Detonation pushes the piston down.
End of the stroke, piston starts rising again.
Exhaust valves open, exhaust gases start getting pushed out.
Piston keeps rising, pushing the spent products out the exhaust valves.
Intake valves open (piston still has a little bit of rise to it); the flow of the exhaust out the exhaust valves has now set-up an air current which starts drawing fresh fuel-air in through the intake.
Piston tops out and starts back down, exhaust valves start to close (any fresh charge that made it into the exhaust gets sucked backwards).
Intake valve maximize their opening size, piston continues to drop, more charge is sucked in.
Piston hits bottom and starts back upwards - Intake valves still open.
From here on out, is where stuff changes depending on RPM.
Low RPM: the rising piston shoves some of the fresh charge backwards through the carbs, then the intake valves close all the way, piston continues it's compression stroke, spark happens 4 degrees before the piston gets to the top of it's stroke (9 degrees for those with advancer kits).
High RPM: the rising piston pushes upwards, but the speed of the fresh air coming in through the intake valves is so high that it continues to load the cylinder inspite of the piston moving upwards, resulting in maximum loading. Then the intake valves close all the way, piston continues it's compression stroke, spark happens 4 degrees before the piston gets to the top of it's stroke (9 degrees for those with advancer kits).

This difference means that maximum compression ratios only occur at the RPM levels where this type of positive loading can happen inspite of the piston rising (instead of being pushed backwards through the carbs). Thus, this is also the primary time that octane numbers are really critical on a healthy engine (because this is the only time the maximum rated compression will actually occur).

This particular bit of engineering is why the torque curve of the Kat falls where it does -- 6800 RPM upwards on a typical Kat motor -- because that is the zone in which positive cylinder loading occurs inspite of the rising piston. Real easy to see on a dyno's output if you look at the torque curve.

Below that 6800 RPM limit, the compression ratio on the engine is lower than the factory-listed compression ratio, because air (& fuel) is being pushed back out of the cylinder... which means for those who baby their Kats and stay out of the primary torque power-peak, the octane requirements would be even lower than the ones recommended by Suzuki...

Cheers,
=-= The CyberPoet

[Looneybonics]

*Pulls CP aside and whispers*

What have I told you about undermining me infront of people? Hmm? If I say we have fuel injectors dammit we have fuel injectors. You just play along and look pretty.

*Talks normal so everyone else can hear/read cuz you can't read what I said above because it's emoted in a whisper*

I was thinking about how it created deposits and instantly thought of fuel injector. I happen to have 3 fuel injectors on my bike. It's a special mod yoooou wouldn't know about.

[Looneybonics]

*Thinks to self* I think they bought it.

[Tomcat92187]

Great explanation cyberpoet.... Just to reinforce what you said about cylinder wall surface area contributing to predetination:
I drive a firebird formula with a 350 LT1 10.5 compression ratio. I am uncomfortable even using 91 octane in it. I put 87 in it 2 summers ago and I never will again--It is always full of 93. I have noticed that there is widespread confusion about octane ratings. Even at the track (1/4mi) some guys are mixing in race fuels with unmodified engines, probably in hopes that it will uncover a few extra hp (but it wont). Great explanation though, I think you just about covered it...

[The CyberPoet]

Even at the track (1/4mi) some guys are mixing in race fuels with unmodified engines, probably in hopes that it will uncover a few extra hp (but it wont). Great explanation though, I think you just about covered it...

Well, that brings us to fuels that are rated above 100 octane (how can anything contain more than 100% of something else?). Fuels rated abover 100 octane contain compounds which behave as if they had more than 100% octane -- because there are other compounds that are even more resistant to predetonation and preignition. These fuels also usually contain some form of oxygenator (TANE, MTBE, etc) which frees extra oxygen from the fuel to mix into the reaction at time of detonation. This effectively does increase the combustion pressure levels, which should result in *slight* increases in total power output -- not because of the extra predetonation or preignition protection, but specifically because of the extra oxygen coming into the equation.
This is basically a weak version of the same thing that happens when you spray nitrous oxide (NOx) into your engine; the nitrogen is neutral and the extra oxygen adds to the power output rate.
If you could design a filter to filter out only pure oxygen (O2) and ran that through your engine instead of ambient air, you would net yourself about a 8 times (800%) increase in power out of the engine. It would also burn almost perfectly clean, with virtually no by-products that commonly result from current combustion techniques. Creating such a filter system using modern twin-layer ceramic filtration methods wouldn't be all that hard (although you'd have to use some form of serious over-pressure system like a supercharger to force the gases to flow & separate through the filters, and you'd need a very large surface area to feed even a small cylinder). The problem with this is that no modern engine can take the pressure and heat that would result (pressures that would split even pure titanium, heat levels that would melt even the strongest metals); adding just a little extra oxygen in the form of NOx already strains modern engines heavily.

Cheers,
=-= The CyberPoet

[Junior]

I used to work for testing lab that was responsible for testing all types of lubricants, fuels and other automotive fluids. You would really be surprised in the differences in the quality of gas in Canada.

Who gives a shiate about fuel. There are more important questions Jmpr can answer.

What LUBE tested better? KY or Astroglide?





You fools and your gasoline debate.

[The CyberPoet]

What LUBE tested better? KY or Astroglide?

You fools and your gasoline debate.

Wet brand personal lube :P
or silk...

Cheers,
=-= The CyberPoet