What gas octane should I use in a 2007 FJR

[conwest]

Quote: So...conwest was right....but he didn't know it....or why......

:clapping: ...ahhem...and after all those posts no less. But seriously folks, it takes a big man to admit it. :yahoo:

 

[v65]

Maybe, just maybe, we ought to just fill the tank and go for a ride.

Probably a better idea than what I did, I just borrowed two books on gas dynamics. 1300 pages from now maybe I will really understand the effects of supersonic flame fronts :blink: Peter is a bastard on so many levels :lol:

 

[jestal]

Would indexing the plugs have any beneficial effect to adding power or reducing potential to detonation? You often hear the engine tuners mention indexing the plugs to present the incoming fuel charge the most direct exposure to the spark. Also would the position of the electrode be better served by indexing to maximize the cooling off during the end of the power stroke and during the exhaust stroke?

In some very highly tuned engines indexing the plugs might provide a tiny bit of power....but I think the effect is un-measureable in most cases. It wouldn't have any noticeable effect on detonation. The indexing is usually most effective in situations where there is extreme in-cylinder mixture motion such that the motion trys to quench or blow out the spark. Indexing can "protect" the initiating flame kernal and help with more stable combustion.

I have seen studies on indexing plugs on a variety of different combustion chambers from production engines and it showed absolutely no gain in those cases. By the same token, there have been dyno comparisons with spark plugs with multiple ground electrodes (the infamous Bosch Plus 4 plugs) and they were shown to reduce power a bit. Not a lot but measureable and repeatable. The thought is that the redundant ground electrodes tend to shield or impede the initiating flame front and/or quench it to some extent due to the multiple heat sinks to soak up the heat. Not the sort of result you would expect from the marketing for those plugs!!

In many pure competition engines, especially drag race engines with very high compression ratios, the spark plug ground electrode can come pretty close to the piston dome at TDC. Some engines like this need to have the plugs "indexed" to keep the ground electrode to the one side or the other so that it does not hit the piston. This problem may be confused with indexing for more power.

The eletrode that needs "cooling" is the center electrode, not the ground electrode that would be indexed. Unless the ground electrode were somehow shielding or acting as a wind break to prevent the center electrode from the mixture it really will not affect the heat range of the center electrode or how hot it runs. The center electrode cools by rejecting heat to the shell of the spark plug so the projection of the center electrode and the length of the porcelean is what governs heat range, not the position of the ground electrode.

There can be an issue with cooling of the ground electrode itself, especially with very high compression, highly turbocharged engines and engines running nitrous oxide. Most tuners in those situations know to clip the ground electrode to shorten it considerably to improve the cooling and reduce the extension of the ground electrode away from the shell.

In any case, concerns about indexing and the center and ground electrode cooling would affect pre-ignition, not detonation.

 

[jestal]

Quote: So...conwest was right....but he didn't know it....or why......


:clapping: ...ahhem...and after all those posts no less. But seriously folks, it takes a big man to admit it. :yahoo:

Don't break your arm patting yourself on the back.... :lol: :lol: :lol: You were only right in about 1 % of the cases of pre-ignition.... :lol: :lol: :lol: Running higher octane fuel will still not prevent preignition in most all the other cases.

The OEM's actually allow for the detonation induced pre-ignition phenomenon. Part of the spark plug heat range testing when a new engine is developed is to confirm that the recommended plug is cold enough to run at full throttle with some degree of detonation present. Scary testing to have an engine at full output, max RPM continuous on a dyno and then dial the spark up until light, audible detonation is present and then leave the engine to run like that for 20 minutes. If the heat range is correct then no preignition will result as the plug will be cold enough withstand the detonation at full throttle.

Not to belabor this, but this is one area that one is always at risk when switching brands of spark plugs. The OEM plugs are tested extensively for heat range, cooling capability, detonation resistance, etc. Other brands of replacement aftermarket plugs are rarely if ever actually tested in the engine in question. The aftermarket supplier just makes sure that they screw into the holes and the heat range is usually based on "engineering judgement" to be sure it will not cause pre-ignition. Most of the time this is pretty low risk as the different plug makers know how their plugs cool and what the heat ranges are relative to other brands but there are exceptions. I know of one case where an engine failed due to preignition when an Autolite aftermarket plug was installed. It was the "correct" Autolite plug called out for that engine but the heat range was several heat ranges too hot and it destroyed the engine. Increased octane would not have helped....

 

[warsw]

Not to belabor this, but this is one area that one is always at risk when switching brands of spark plugs. The OEM plugs are tested extensively for heat range, cooling capability, detonation resistance, etc. Other brands of replacement aftermarket plugs are rarely if ever actually tested in the engine in question. The aftermarket supplier just makes sure that they screw into the holes and the heat range is usually based on "engineering judgement" to be sure it will not cause pre-ignition. Most of the time this is pretty low risk as the different plug makers know how their plugs cool and what the heat ranges are relative to other brands but there are exceptions. I know of one case where an engine failed due to preignition when an Autolite aftermarket plug was installed. It was the "correct" Autolite plug called out for that engine but the heat range was several heat ranges too hot and it destroyed the engine. Increased octane would not have helped....

I switched from the stock plugs (NGK CR8E) to the NGK Iridium (CR8EIX) plugs. I really don't see any difference in the way they preform and the stock plugs still looked great after 8K miles. My thoughts are to go 16k before I even look at them again. Would I be better off staying with the stock plugs or do you think Iridum's will be OK?

 

[jestal]

Based on the testing I have done/seen the iridium NGK plugs are an excellent product. They are not worth so much in terms of immediate power or driveability compared to fresh production (non-iridium) plugs but they are worth a lot in terms of longevity and maintaining that "fresh" level of driveablity and performance almost indefinitely. NGK is a reputable and very knowlegeable spark plug manufacturer from my experience so I do tend to trust them a bit more than some others.....based purely on the "inside" information I have seen regarding their production process and process control/quality. They are an OEM supplier of many different spark plugs despite what the plug might be labeled as. Mileage perceptions with spark plugs vary all over the map but I have seen case after case where iridiums performed "like new" in automotive engines with well over 100K miles on them. Well over..... Engine development on the dyno used to eat plugs years ago but the iridiums hold up almost indefinitely. I have seen very slight power gains attributed to irridium plugs compared to equivalent/new other plugs but that is insignificant compared to the way the iridiums live. I personally use the iridium plugs simply because it eliminates one more maintenance chore. I wouldn't have any concerns myself with running 16K or much longer with irridiums without looking at them....I plan to ride much longer than that on them unless some unexplained driveability issue crops up.

My Honda CBX was always notorious for eating plugs. Tried a variety of brands. The last set I put in several years ago was the NGK iridiums and I haven't even looked at them since. In that application they are working well.

 

[onlyblue]

Mmmm... absolute statements: "....the ONLY reason to...." "....fine in any vehicle...". Some engines have knock sensors and take advantage of higher octane fuels to use more ignition advance for more power and economy. These engines may have combustion chambers of a certain design; a high compression ratio; or, forced induction (supercharging or turbocharging). That's why there are other octane rated fuels available and the reason/s for same.An engine so configured and equipped (w/a knock sensor) may be forced to run at less than optimum timing settings by the use of low octane fuel.

Hence the problem with these threads, it takes a lot of work to flesh out the truth - which has been done before. For example, you failed to mention that a vehicle designed to burn low octane fuel may not properly burn high octane fuel, and so in this case more can actually be worse.

Correct me if I am wrong, but the FJR is designed for 87 octane, I don't recall anyone claiming more performance from higher octane fuels on this platform.

I could be mistaken, but the manual lists a requirement of at least 87 octane. I am not a fan of needlessly throwing my money away on anything. I expect more when I pay more. Without addressing the many different manufacturer gizmos for compensating for knock, pinging, pre-ignition, etc, the basics are that as a gas is compressed the temperature at which it will ignite decreases. So, we can create pinging, knocking etc, by increasing compression or by increasing the engine temperature, or both. That's one reason why higher altitude environments (lower ambient atmospheric pressures) offer lower octane fuels at the pump. The FJR1300 is probably in the mid range for compression in a streetable motorcycle. I've run various tankfulls of different octane gas over the last 3-4 months and never experienced pinging or knocking. Depending on the conditions, if the engine temperature remains low enough, a mid grade (87-89 octane) may not ever knock or ping. I did notice something that I had also noticed in a couple vehicles I've owned and tested in a similar way: there are measureable and repeatable small mileage gains when I've used the higher octane fuel. Since this isn't a case of eliminating "ping" or knock, I'm not familiar with the science that would explain the MPG gain. Generally when I check the increased mileage against the price difference for the higher octane, it's a wash. In my most recent check on the FJR, a complete run through a tank full of 87 octane yielded 46.4 mpg. No hardbags, to and from work (37 miles round trip) average speeds around 33 mph, and driving in a fashion to try to get the best mileage I could. The current tank of 93 octane that I'm checking is clocking 49.2 mpg doing the same commute at the same speeds. I think it's interesting that the 6% gain that I'm presently seeing with the FJR is about the same kind of difference I saw on ocassion with a vehicle check that I'd done. My notes tell me it was a gain from 18.1 mpg to 19.7, 8.8% difference. If there's less than a 6% difference in the higher octane fuel, it is more economical for my FJR.

Burn what you want, but just don't throw your money away without seeing a tangible benefit.

 

[ibsunburnt]

When I bought my 05 I filled her up with 87 for two or three tanks and noticed a slight tap, tap, tap. I changed to 89 and the tapping was gone overnight. I have thought about trying the 87 again but for the few cents difference it's not worth the tap dance so I'll stick with the 89.