Am I crazy or what????????

[lancruza]

OK, here's a description of my bike. I've got an 09 XB9SX, 7K miles with a Jardine exhaust. The PO put on the Jardine and I doubt that he put a different map on the ECM. I don't know that 100%, but I doubt it. So here's the scenario... I always run premium gas, 93 octane in the bike. Well a couple of days ago I accidentally put in 87 octane. I realized it after it was too late. I was expecting the bike to spit and sputter along as it burned the el-cheapo octane. But guess what? I think this is the best the bike has ever run. HUH??? What's up with that? It feels smoother. Less popping on decel. And I swear it feels like the bike is running cooler. So go ahead and fire away. Am I imagining all these things? Is this an indication of a tuning problem? I think I'm gonna run another tank of 87 through her just to see if this is a fluke. Wasn't expecting this to happen

[Zolten]

I'm not completely educated on this but I will say that the fuel map that you have now probably is the original. I had the same thing with my '06 XB12ss; equipped with a K&N, a Jardine and a PO who didn't play with the ECM. I've always put 93 fuel into the tank because the [my 2006] manual calls for 91 octane and it may contain up to 10% ethanol. My bike had plenty of backfire on decel before I burned a specific map from Buelltooth and now fixed that issue, plus I can engine brake much more successfully. Night and day difference. So, I recommend doing the same, of course.
Anyway, back to the question. I don't think you're crazy because I believe the compression ratio has a direct impact on what fuel is required (Again, I might be wrong.) Perhaps with the original fuel map and the aftermarket components of your bike, that map supplied a different amount of fuel into the cylinder and make is work that way. Perhaps the first gas you bought was just bad quality to begin with. I do know for sure that you should follow the manual with the fuel recommendation. I've read studies on this that basically stated putting high octane fuel in an engine that does not require it is just a waste of money. There was no measureable difference with performance or deposits inside. Lower octane, however, did create a measurable difference. More importantly, it was the overall quality of the fuel being used.

[lancruza]

I'm not completely educated on this but I will say that the fuel map that you have now probably is the original. I had the same thing with my '06 XB12ss; equipped with a K&N, a Jardine and a PO who didn't play with the ECM. I've always put 93 fuel into the tank because the [my 2006] manual calls for 91 octane and it may contain up to 10% ethanol. My bike had plenty of backfire on decel before I burned a specific map from Buelltooth and now fixed that issue, plus I can engine brake much more successfully. Night and day difference. So, I recommend doing the same, of course.
Anyway, back to the question. I don't think you're crazy because I believe the compression ratio has a direct impact on what fuel is required (Again, I might be wrong.) Perhaps with the original fuel map and the aftermarket components of your bike, that map supplied a different amount of fuel into the cylinder and make is work that way. Perhaps the first gas you bought was just bad quality to begin with. I do know for sure that you should follow the manual with the fuel recommendation. I've read studies on this that basically stated putting high octane fuel in an engine that does not require it is just a waste of money. There was no measureable difference with performance or deposits inside. Lower octane, however, did create a measurable difference. More importantly, it was the overall quality of the fuel being used.

First off, Welcome Zolten. Thanks for the reply. As far as having bad quality gas, that's definitely not the issue. I've had this CityX for almost 1 year. I've put premium in the bike from various different stations. It's not been running bad, at least I didn't think it was running bad. But now, the bike is running noticeably better. A similar thing happened years ago with one of my Land Cruisers. I had been running premium in it. A friend pointed out to me that Toyota spec'd 87 octane. I switched over to 87 and it ran better. I've been using 87 in it ever since. I just wasn't expecting this result.

[Zolten]

Thanks for the welcome, lancruza. I think you have inspired me to test this out for myself, too.

[Subarubrat]

Octane is perhaps the most misunderstood aspect of fuel. What a higher octane does is retard the combustion event until conditions are right, running too low of an octane allows the combustion event to occur too early. An engine running higher compression ratios or a higher effective ratio (forced induction) will generally need a higher octane fuel. If you have an engine tuned for a given compression ratio or amount of boost that works with 93 octane and you go to a lower octane that will cause all kinds of problems. Running a higher octane than your engine needs provides no benefit and there is less energy in a gallon of high octane fuel than a gallon of lower octane fuel. Strictly speaking 89 octane has more "go" than 93, but this difference is very slight compared to the gains from a higher CR on higher octane. The marketing methods of the gas retailers has created a deliberately deceptive impression that higher octane "premium" fuels will create more power. Using too high of an octane can cause the ignition to delay too long and cost you power. There are allot more factors that come into it play and combustion chamber shape/squish band, etc. can create a greater deviation than octane in one motor while octane could be the deciding factor in another motor. Over the web it can't be said that this IS what your seeing, but it could be.

[njloco]

Interesting read, ^^^^^^^^^^^^^^^^^.

[lancruza]

I did a little research and reading last night about octane, especially about running lower octane. None of the descriptions that I read described the way that my bike is running on this lower octane. Most of the descriptions indicated that with lower octane there would be pinging or knocking(pre-detonation). There's not been any of that at all, so far. It was also stated that an engine would run hotter on lower octane. Like I said in my first post, it feels to me like the bike is running cooler and smoother. So is running the lower octane going to damage the engine IF I don't have pinging and IF the engine is running cooler and smoother? Obviously I don't want to damage my engine. It's mighty tempting to try and keep the bike running like she currently is running.

[njloco]

I have a vw Corrado, It calls for 91 ? as I recall, I use regular and have never had a problem. Back in the days of leaded gasoline, we would mix premium and regular and end up with a better burning fuel, you had to experiment a little to see what each car liked but they always seem to ran better. So I don't think your crazy, certifiable maybe but not crazy.

[user_deleted]

levan: this thread might take on a life of its own along the historical lines of spark plug gapping/oil/tires/brake pads on this and many other forums. having said that my amateurish thoughts are as follows: i suspect that during XB engine development and testing, one of the parameters taken into serious consideration would have been what octane fuel would provide best performance and longevity. for whatever the reasons were and whatever the outcomes were from exhaustive testing and R&D the decision was made that 91 octane and higher worked best. personally i'd stick with the factory recommendation. just the fact that these motors do NOT have any sort of "knock sensor" as part of the electronics package or any other component to alter ignition timing based on performance and fuel being used scares me away from lower octane rated fuel. just my opinion.

[Subarubrat]

I did a little research and reading last night about octane, especially about running lower octane. None of the descriptions that I read described the way that my bike is running on this lower octane. Most of the descriptions indicated that with lower octane there would be pinging or knocking(pre-detonation). There's not been any of that at all, so far. It was also stated that an engine would run hotter on lower octane. Like I said in my first post, it feels to me like the bike is running cooler and smoother. So is running the lower octane going to damage the engine IF I don't have pinging and IF the engine is running cooler and smoother? Obviously I don't want to damage my engine. It's mighty tempting to try and keep the bike running like she currently is running.

Running timing too far advanced can cause unnecessary engine heat without resulting in more power, and it has been theorized that running a higher octane can delay combustion resulting in the same effect in some engines, I tend to agree that this could be the case and why you are seeing lower temperatures with an earlier combustion event as if you advanced your timing to delay it. This is really lab stuff and I am not saying it "is" without question the cause but a possible one that could explain your results, yes.