Does the ecu have enough timing advance to use 92 octane fuel

[HotRodZilla]

The FJR's motor has a compression ratio of 10.8:1. I could have sworn I read somewhere that premium fuel isn't even a consideration until ratios start hitting the 12:1 and above areas. Again, if Yamaha put 87 in their owners manual, why would anyone believe running 93 has to be better?

While looking, I found a good article from Road&Track. Says pretty much what any other article says: "Premium fuel isn't needed unless specified, but if you insist, it won't hurt anything." I did note that it also says many ECUs have "preset ceilings" and can't take advantage of higher octane fuel anyway. As simple as the FJR's ECU seems to be, and with no mention of it from Yamaha, I'm betting this ECU will NOT compensate for higher octane fuel.

Can't some of you guys just ride the dammed things?

https://www.roadandtrack.com/new-cars/car-technology/news/a18008/premium-fuel-futures/

 

[Redfish Hunter]

Isn't there another thread for you guys to tell us how stupid we are?

MY owners manual says, "Your Yamaha engine has been designed to use regular unleaded gasoline with a pump octane number [(R+M)/2] of 86 or higher, 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."

I interpret that as a MINIMUM requirement and that the ECU will adjust itself according to what is put in the bike. I do not know what the ECU does and does not do with regard to higher octane fuels and apparently neither does anyone else on this forum. If we cannot answer the OP's serious question, why must we continue to insult him?

And yeah, you guys can remind me I said that at some point in the future. I know that was a hypocritical statement on my part and it will come back to haunt me.

 

[Powerman]

Ran bikes on the dyno (not FJR's) that made less HP on higher octane than needed.

Probably not noticeable by the butt dyno.

I've seen sportbikes run racing gas with stock compression that made noticeably more HP on premium.

Doesn't hurt a thing to run it if you want. I do love the smell of race gas.

 

[ionbeam]

I'll go out on a limb and say that the FJR does not adjust spark timing for fuel octane. The FSM states that the ECU uses the Crank Position Sensor to determine ignition timing. It does not say 'also uses input from the O2 sensor' and the FJR does not have knock sensors.

To check the engine timing, the FSM says to use a timing light and look at the timing marks (shown in the manual) and they should be within 'this range' and again, it is shown in the manual. I take that to mean that no matter what fuel is used the ignition timing will always fall within this narrow range.

You can certainly (waste your money and) run higher octane fuel for zero benefit and near zero advantage. Top Tier premium fuel may have enough additive package in the fuel to offset the deposits encouraged by insufficient temperature/pressure to fully burn the higher octane fuel.

Yamaha sez this about spark timing:

The voltage of [the Crank Position Sensor] is then input into the ECU, which calculates the position of the crankshaft
and the speed of the engine. The ignition timing is then determined in accordance with the calculated
data, in order to determine the corresponding injection timing. Based on the changes in the
time intervals of the signals generated by the pickup coil, the ECU calculates the ignition timing
advance to suit the operating conditions.

There is no mention of octane compensation.

All Gens FSMs states that at idle the timing is -5° BTDC. With a 1,050 rpm idle speed this is a very conservative number, I would have expected -12° to -15°. This is probably in part due to the relatively low compression ratio of the FJR's engine.

The speed that the gas burns is fixed, the cylinder compression is fixed, the speed of the piston varies. There is a very stable map that determines when to ignite the fuel/air for maximum power and to ensure that fuel/air burn is complete within ~15% of the piston travel on the power stroke to achieve maximum power. Heck, once upon a time ignition was adequately managed by intake vacuum and spring controlled centrifugal weights.

The Gen III (ES) also has a diagnostic port on the ECU which can be used to read all the engine sensors, record and map sensor output and a whole lot more. It is possible to change some settings, but the FSM does say:

The diagnostic tool cannot be used to freely change the basic vehicle functions, such as adjusting the ignition timing.

So Yamaha still continues to protect their ignition spark timing.

 

[wfooshee]

MY owners manual says, "Your Yamaha engine has been designed to use regular unleaded gasoline with a pump octane number [(R+M)/2] of 86 or higher, 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."
I interpret that as a MINIMUM requirement and that the ECU will adjust itself according to what is put in the bike.

If it adjusted anything, there wouldn't be knocking or pinging with the lower octane.

Octane is resistance to pre-detonation. if the fuel ignites before the spark, then it's igniting before the engine is ready for it. it tries to shove the compressing piston backwards, creating the knock.

The OP is under the assumption that earlier spark equates to power, which I don't think is the case, or he may be thinking that higher octane equates to more power, which I know is not the case. high-compression engines, i.e. those built to produce more power, require higher octane fuels to keep the motor from going ker-blammo. The power is in the engine design, not the fuel.

In some '80s-era GM turbocharger applications, like the V-6 turbo Trans-Am and the 4-cylinder Sunbird turbo, the knock sensors trigger spark retardation. That was the only protection against low octane in those engines. Personally, I'm not sure what good that does. If the engine's knocking, the spark hasn't happened yet, so what good does retarding it do? probably my understanding is incomplete. Better systems actually limit boost on input from the spark sensor, thus reducing cylinder pressure, by opening a wastegate on the turbo. I had such a system in my '90 Ford Probe turbo, and it was sensitive to octane. It would give 9psi boost with premium, but only 6 with regular. Timing had nothing to do with it.

As stated before, if the motor knocks with regular, put higher octane in it. you might wanna investigate what's wrong with the motor, too, 'cause it ain't s'posed ta need higher than regular.

And if the price difference between regular and premium isn't an issue for you, then use regular and send the money you save to this Paypal address: walter at inacompnet dot com.

 

[N4HHE]

The FJR's motor has a compression ratio of 10.8:1. I could have sworn I read somewhere that premium fuel isn't even a consideration until ratios start hitting the 12:1 and above areas. Again, if Yamaha put 87 in their owners manual, why would anyone believe running 93 has to be better?

It's not a simple issue of compression ratio. Valve timing and ram intake effect matter as to final combustion pressure. And shape of combustion chamber has effect. Toyota Prius has a 13:1 mechanical compression ratio but specifies 87 octane. Makes it work with variable valve timing, throttle by wire, and that electric motor can provide instant power when program delays throttle.

 

[N4HHE]

Ran bikes on the dyno (not FJR's) that made less HP on higher octane than needed.Probably not noticeable by the butt dyno.

Octane rating is not a measure of energy content. Makers of race gas know their customers are paying for any advantage they can get so they formulate with as much energy as they can. It's listed on the VP data sheet.

 

[Ignacio]

If we cannot answer the OP's serious question, why must we continue to insult him?

Great point!

And a variety of folks (not you) have totally lost what the OP is and not getting a clue they should be hanging out in NEPRT threads.

If somebody actually does have an answer...they should PM me and I'll eagerly and easily open the thread back up for them to respond.