Another Word About Octane

[El Toro]

Good assessment. That's why it was so easy to sort to NEPRT.

Everyone buys gas and drives nearly every day. So everyone knows all they think they need to know about this.

My take on it is "Who cares? It's a free market. Let the marketing guys catch their lawful prey."

 

[HotRodZilla]

Good assessment. That's why it was so easy to sort to NEPRT. Everyone buys gas and drives nearly every day. So everyone knows all they think they need to know about this.

My take on it is "Who cares? It's a free market. Let the marketing guys catch their lawful prey."

Exactly. It's not my money, and I'm sure none if you are planning on leaving me any when you die. SO, spend it on whatever you want. If we look at it logically, do 99% if us really NEED our motorcycles? Nope, which proves, we're already slightly irresponsible with our money. Shit, hookers and blow would probably be just as fun, and maybe less expensive. I blow money on shit I'm sure some of you would frown on. BUT it's mine, so I get to choose.

Haha...Have fun! We only get 1 turn, so might as well get our way every now and then.

 

[wetwolf]

Actually, hookers and blow can get pretty spend, pretty quickly.. DAMHIK

 

[garyahouse]

Bought myself a treat recently: 2015 SRT392 Challenger. It's my 4 wheeled FJR. So of course, I've been doing some posting on one of the forums. They got into the discussion about octane recently. Interesting to note that there is a VERY big difference of opinion there. The octane gurus there... are so sure that their experience outweighs any facts presented.

One of the things I've always appreciated about this forum is that for the most part, information provided here rarely misses the mark. We typically manage to come up with the right conclusions as we discuss things back and forth. And that goes for our beloved NEPERT-land.

Funny how human nature is so emotionally attached to the myth -- that truth must be rejected. Just pick the subject: race, politics, and religion or oil, car tires and octane: truth can't be proven to a man with his fingers in his ears.

Bottom line: it's always refreshing to me to read the words of someone sharp enough to shut up when they're unsure, speak up when it matters, and post up when they KNOW that what they're contributing is fact.

No place like this place.

 

[08FJR4ME]

After reading the prior post to yours Gary you are correct. There is no place like this. LOL You even get facts you don't necessarily need to know.

Good morning all,

Dave

 

[mcatrophy]

...Funny how human nature is so emotionally attached to the myth -- that truth must be rejected. Just pick the subject: race, politics, and religion or oil, car tires and octane: truth can't be proven to a man with his fingers in his ears.

...

"There's none so deaf as those who will not hear."

 

[pista]

The knocking is caused by the fuel charge igniting before the piston reaches TDC because the fuel volatility is too high for the temperature and compression of the charge. That's why they call it preignition.

Mostly correct.

To clarify, if you wait until the piston reaches TDC to ignite the fuel charge, you"re already too late.

Carry on...

 

[garyahouse]

I did a great deal of technical reading on the subject of the flame front. I got curious because of this particular thread and had some spare time. Flame front is affected by so many things; for example piston speed, squish area and combustion chamber shape, plug location, compression ratio, swirl, mixture ratio, temperature, RPM, throttle opening, engine load, cylinder deposits, the timing, and last but not least, octane. Keeping a performance engine on the cutting edge is an engineer's nightmare.

Even an engine designed to run on say for example, 91 octane... may well need 92 octane soon enough because of deposits in the combustion chamber and on the backside of the intake valve. It's amazing how quickly these deposits begin to form and how even little things like that can and do change the octane requirements of an engine. That's one of the reasons guys have become so fond of putting a catch can on engines like my 392 HEMI. They reason that oil mist being pumped back into the intake through the PCV valve surely contributes to these deposits.

One of the big issues we have as back yard "tuners" is that it's so hard to determine just how much octane is actually enough. Even if we escape the "more has got to be better" myth, how much is just right? We typically don't have any gauges to help us determine just when the ECU begins to retard timing to negate detonation. We get to guess at this much of the time. And that's where all the disagreement comes from. We find ourselves at the mercy of the manufacturer's recommendations, and the oft-times uninformed opinions of others. But I wonder:

Wouldn't it stand to reason that when manufacturers set their "recommended fuel grade" for a given engine, that they might just add in a little bit of cushion to their recommendation? If engine "A" only needed 90 octane to run properly, what's to stop the manufacturer from recommending 91 octane to cover their behind? Maybe, maybe not. Just musing a little here...

Gary

 

[Mr_Canoehead]

That's why they have knock sensors on most cars these days - it gives the engineers the comfort to tune to the ragged edge both for power and economy. And yes, you will never know that the ECU is dialing it back. The modern combustion chamber is modeled very carefully to not ping.

On the other hand, our FJR's don't have knock sensors and I have never heard a ping under any conditions burning regular. My BMW will ping on anything less than 89 Octane and it is LOUD on a motorcycle - if it pings, you'll know.

 

[El Toro]

If you can't feel it, or hear it, you should forget about it.

 

[garyahouse]

Hmmm

My hearing is going and I forget about practically everything. How's 2 outa 3 Toro?

Gary

 

[El Toro]

67%

But how do you really feeeel about it?

 

[MajBach]

All my vehicles get 87 octane, ethanol laced, regular gas.Some only get run 2 or 3 times a year.

Most sit all winter without any treatment.

Shockingly , they all start up and run. Every time.

Must be the Slick 50.

 

[MajBach]

Our price for E10 is about two bucks a gallon these days. And that's even with our new increased gas tax that went into force on July 1st.
I use real gasoline in the bikes. No Ethanol. E0.

Today before my ride I filled up. Usually the difference from grade to grade is more than it was today. Today it was a dime.

I don't buy motorcycle gasoline on price. I buy E0, and pay the premium to get it. I buy E0 because sometimes any given bike can sit for several weeks in the garage while I'm choosing to ride others.

So today the three grades of E0 were priced at $2.59, $2.69, and $2.79.

I sprung for the 93 octane. Did it matter? Probably not. But my gas mileage on today's trip (fill up at start and full fill up again at end to same level) was 20% higher than normal. I was quite surprised. I was not particularly well behaved, with the speedo sitting at 80 mph and above for most of the trip, and with bursts for passing as high as 100 mph. I was expecting to have lower than usual gas mileage.

Took the words right out of my fingertips. I always buy the cheapest fuel with no ethanol. In Canada that's often only premium and only at certain stations. Having ridden mainly State-side all season, it seems to vary significantly from State-to-State; as do octane ratings (really, 83 octane??!!) My last trip was in Wyoming and Utah was almost entirely 6000' altitude and higher. If the OAT is warn as well, my bike frequently pings if I don't shift down. Higher octane seems rectify this.

 

[thewrenchbender]

Bearing in mind this is NEPRT. Been legally driving since '78, riding since '80, tearing shite apart and putting it back together as long as I can remember.

Was around in the bad good ol' days of manufacturers struggling with emissions standards with primitive technology by today's standards (electronically controlled carbs, etc) when a rattle at part-throttle application was the norm.

Recently had an in-depth discussion with a guy that rebuilt/tuned the one-barrel Holley on the former Air Force munitions trailer tug that we use to drag the 25,000+lb bizjet I maintain around.

His take on the local gasoline available WRT to octane is that the basic "87 octane" gasoline is totally unsuited to carbureted engines-primarily in his opinion because he has noted that there is very little consistency in specific gravity. But the 89 octane tends to be very consistent-according to him.

My only personal experience with it in the motorcycle realm was in a big-bore high-compression single-cam (RC Engineering 327-back when they were the Honda drag engine gurus) CB750. I can't say that it ran any "stronger" on aviation 100LL, but it definitely allowed me to roll on the throttle without "the rattles" in 5th gear. On the premium pump gas that was available at the time, I had to drop 2 gears on the highway to accel without preignition.

BTW also have previous experience with true detonation on turbo-supercharged big-bore relatively low-rpm aircraft engines. Trust me-if you experienced detonation on yer bike-you would notice.

I don't truly gather empirical data on my FJRs, just pound the crap out of them. I have never had the ECM computed MPG vary more than 1.5 mpg +- from 39.5 on any of the fuel I've purchased (tanks that get burned two-up or for about a month after a "performance award" is another story-wow 45+ mpg) I do periodically treat a tank with Berryman B12 or Chevron Techron as penance for the cheap 87 that I run 95% of the time. Would like to tell you I've never put premium fuel in it or that I only run E0, but....

One of my other daily-drivers is a Whipple supercharged F150. It was tuned for "93 octane", and on occasionally pings a little at WOT. Saw a SRT392 Charger with a catch can on it at a car show this weekend. The blower guys that I trust say that at higher boost levels inhaled (pressure-fed?) crankcase oil blow-by can lead to serious issues, from the oil itself, not from deposits caused by it.

Have never had the opportunity to run an FJR much over 1,000 feet msl, and have to date not noticed any rattling at any time/gear/speed/throttle setting running generic 87 unleaded. YMMV

 

[dravnx]

Anecdotal evidence to say the least but on my last trip, I was often riding between 6000' and 10,000', I always use the cheapest fuel at the station I happen to stop at and not once did I detect or notice pre-ignition.

 

[Mr_Canoehead]

Bearing in mind this is NEPRT. Been legally driving since '78, riding since '80, tearing shite apart and putting it back together as long as I can remember.
Was around in the bad good ol' days of manufacturers struggling with emissions standards with primitive technology by today's standards (electronically controlled carbs, etc) when a rattle at part-throttle application was the norm.

Recently had an in-depth discussion with a guy that rebuilt/tuned the one-barrel Holley on the former Air Force munitions trailer tug that we use to drag the 25,000+lb bizjet I maintain around.

His take on the local gasoline available WRT to octane is that the basic "87 octane" gasoline is totally unsuited to carbureted engines-primarily in his opinion because he has noted that there is very little consistency in specific gravity. But the 89 octane tends to be very consistent-according to him.

89 is usually mixed at the pump - 50% 87 and 50% 91. So, if the 87 has no consistency in SG, the 91 must have very good consistency....My feeling is that anything with Ethanol is bad for carbureted engines.

 

[art miller]

My 2014ES has 28460 miles on the clock. I have ridden over the Cascades, Sierras, Rockies, and Smoky Mts. The only gas I have used has been regular 87octane. On occasion starting out in 2nd gear (not intended) I will hear a little valve noise but with acceleration it quickly disappears. The overall MPG on the bike is 48.0. FJR forever for me!!!