Seriously bad gas mileage.

[Fred W]

No, the octane rating of gasoline is based solely on at what pressure (temperature) it will auto ignite. It is not a direct measurement of density.

The octane rating of gasoline is measured in a test engine and is defined by comparison with the mixture of 2,2,4-trimethylpentane (iso-octane) and heptane that would have the same anti-knocking capacity as the fuel under test: the percentage, by volume, of 2,2,4-trimethylpentane in that mixture is the octane number of the fuel.

That doesn't mean that fuel is composed that way, that is just how the scale was composed. (IOW 93 octane rated gasoline is not 93% iso-octane and 7% heptane) The actual additives to the base gasoline that produce the higher octane rating will insignificantly lessen the fuel density, not by very much. The caloric value of the fuel will be slightly less due to that same factor. Warmer fuel will also have a lower density and will have a similar (negligible) effect.

As mentioned previously, using higher octane fuels is useful in engines designed with higher compression ratios or those with forced induction that pre-compress the intake charge resulting in a higher effective compression, to prevent the detonation or pre-ignition (knocking) which can be mechanically detrimental to the engine's longevity. When used with these higher compression ratios that modified engine will produce more power, not because the high octane fuel contains more power, but because the engine will extract more of the available power content from the fuel via the higher compression (not to mention that you can cram more fuel air mixture in per stroke).

The burn rate of various octane rated fuels is the same once ignited (via spark). No (additional) raw fuel will be ejected in the exhaust stream by using too high an octane (a common fallacy). THe fuel will burn to the same degree and no added carbon deposits will be produced. The caloric values and densities of these fuels is the same for all intents. The fuels will perform nearly identically with the main difference being that the higher octane rated fuel will not spontaneously combust as early in high compression situations. So, on a relatively low compression engine using a higher octane fuel (with all other things remaining equal) will not affect your gas mileage significantly for the better or worse.

In the past, premium gasolines would often have more detergents added in order to help justify the increased prices. In modern times, most fuel companies will now admit that they use the exact same detergent packages in all grades of fuel and only alter the formulas between grades to produce the higher octane rating.

 

[NMRoadRunner]

You could move to a higher elevation. It's above 5500 feet here and I get 49 to 52mpg if I'm not riding with the likes of HRZ, he tends to burn a little more fuel than I do.

 

[ionbeam]

...In the past, premium gasolines would often have more detergents added in order to help justify the increased prices. In modern times, most fuel companies will now admit that they use the exact same detergent packages in all grades of fuel and only alter the formulas between grades to produce the higher octane rating.

The demands on fuel over the last ~20 years have changed as engines have gone from lazy carburetor, imprecisely controlled open loop systems to fuel injected, highly tuned closed loop power plants with sensors never before imagined on street engines. Along the way combustion deposits on valves and fuel injectors became significant problems in addition to the usual combustion chamber and ring deposits. This resulted in Top Tier Gasoline being formulated with detergents in all grades of gas. As time progressed some of the bigger gas companies started adding even more detergents in the higher grades.

 

[puppychow]

Update:

Plugs were fine. I noticed the bike seemed to be idling a bit high. At ~1200rpm. I dialed it back down to what I eyeballed as ~1100. Manual calls for 1000-1100. Still OK to keep it at ~1100 perhaps?

While the tank was up, I also decided to do a TBS. #3 cylinder as reference, #4 was reading high, #1 and #2 were reading low, definitely off by enough to warrant an adjustment, but not terrible. Got them all as close to #3 as I possibly could get. Not sure if that is going to help. Maybe.

I didn't see any pinched wires or hoses or anything of such nature which showed any evidence of having gotten pinched under the tank.

Will be buttoning it up later tonight if not tomorrow, unless there is anything else I might want to check, while the tank is up? Is there?

This weekend I will take a nice long ride, see what the mileage does. Will report back afterwards. Thanks!

 

[SoCalFJR1300]

Hmm, premium Top Tier Gasoline typically comes with extra detergent additives.

All the grades of Top Tier fuel have detergent additives, I guess the question would be how much do you need?

In all my almost 40 years of driving I've never had a fuel related issue, but I almost always use name brand or "Top Tier" fuel.

I never spend the extra money on 91/93 unless the engine calls for it, I don't want to give the obscenely rich oil companies any more of my hard earned money!

 

[Fred W]

+1

Only a few vehicles I have ever owned benefited from greater than 87 octane fuel. The HO turbo SAABs being one exception. They did (do) run perfectly fine with lower octane as the knock sensors will back off the boost pressure and ignition advance, but at the detriment of reducing the fun factor somewhat.

Burying the boost gauge to the right is something that produces acceleration that makes you smile almost as much as riding an FJR.

 

[puppychow]

Just out of plain curiosity. For a TBS, why is #3 cylinder the baseline cylinder? I mean what is so special about #3 cylinder or is it just arbitrary on the part of Mama Yamma since you have to pick something as a baseline, so why not #3?

Curious minds want to know!

 

[mcatrophy]

Just out of plain curiosity. For a TBS, why is #3 cylinder the baseline cylinder? I mean what is so special about #3 cylinder or is it just arbitrary on the part of Mama Yamma since you have to pick something as a baseline, so why not #3?
Curious minds want to know!

From memory, that's the one the throttle cable is attached to, might have something to do with it.

 

[Fred W]

Yep. Throttle cables goes directly on #3 and the (adjustable) linkages to each of the others goes out from that one.

But the TBS prescribed by Yamaha in the FSM is only adjusting the throttle bypass air screws at idle, for which it doesn't really matter which cylinder is used as a reference. Using #3 as a reference doesn't make any particular sense, except that by never touching the air screw on one of the 4 cylinders, it makes it less likely that the adjuster will drive the idle too high or too low for the idle adjuster to bring it back to spec. In other words, you won't get them all too far out or in because #3 is remains untouched and they all need to balance with him.

I generally pay no attention to that part of the procedure and just turn all 4 air screws out 3/4 of a turn and then knock the high ones down and the low ones up from there. The goal is to have the same vacuum on all 4 cylinders and the idle at 1100 rpm. What the absolute vacuum will be in that condition is not adjustable. It will be whatever it will be.

 

[gumba]

I have 4-5 dirty air filters for sale. They all have 20k mi. on them. I will guarantee a 3-5% increase in mpg. I want $40 ea.. My mpg always tanks with a clean air filters.

 

[gixxerjasen]

Only a few vehicles I have ever owned benefited from greater than 87 octane fuel. The HO turbo SAABs being one exception. They did (do) run perfectly fine with lower octane as the knock sensors will back off the boost pressure and ignition advance, but at the detriment of reducing the fun factor somewhat.
Burying the boost gauge to the right is something that produces acceleration that makes you smile almost as much as riding an FJR.

My MINI is the same way. Hello, my name is Jasen and I'm a boost addict.

 

[Fred W]

Hey, if you have to be on 4 wheels, at least make it a turbo!

 

[Chiefblueman]

Only a few vehicles I have ever owned benefited from greater than 87 octane fuel. The HO turbo SAABs being one exception. They did (do) run perfectly fine with lower octane as the knock sensors will back off the boost pressure and ignition advance, but at the detriment of reducing the fun factor somewhat.

Burying the boost gauge to the right is something that produces acceleration that makes you smile almost as much as riding an FJR.

My MINI is the same way. Hello, my name is Jasen and I'm a boost addict.

+1 My 335i twin turbo with tuner set to map 2, premium in the tank and a shot of octane boost = yeeeehawww. I loves me some boost!! She'll run on regular, but not much fun.

 

[DennisJ]

Another useful Fuel Logbook applicaton can be found at https://www.gasbuddy.com/ Enter your ZipCode in the location box at the top of the page and the Fuel Log Book link will show up in the middle of the tool bar.

 

[ANZAC]

Did the first mileage check on my 2003 and I got 32 mpg. This is commuting in the Portland area so lots of stop and go.

I am also checking into the lack of performance below 2000 revs such as vacuum leaks etc.. Replacing the TPS this weekend and checking hoses and connectors again. Had another rider ride my bike and he said it ran great so maybe normal bit I dont think so.

 

[ANZAC]

Did the first mileage check on my 2003 and I got 32 mpg. This is commuting in the Portland area so lots of stop and go.
I am also checking into the lack of performance below 2000 revs such as vacuum leaks etc.. Replacing the TPS this weekend and checking hoses and connectors again. Had another rider ride my bike and he said it ran great so maybe normal bit I dont think so.

Checked plugs - looked fine

Checked for vacuum leaks - none found

Cleaned electrical connections again

Replaced TPS and set to 15-99

Bike seems to be running richly and hesitating right at around 2000revs. Swipe of exhaust shows dark carbon rich like soot.

 

[puppychow]

Test the fuel pressure regulator. My mileage readings were all over the map this weekend, but I was at very high elevation most of the weekend. Ranging from about 4000 feet to over 7700 feet. Mileage for different fill ups ranged from 36 mpg to 50mpg.

 

[ANZAC]

Thanks Puppychow

Man I really hope it's the regulator. I am slowly but surely learning the FJR but should be getting better than 32mpg even if I have the big CB screen and trunk aboard.

 

[Harald]

I'm one of those people that never gets those super fuel mileage numbers that others report, no matter what vehicle I drive.

For what it's worth, my 07 FJR used to get around 40 with my normal mixed city/hwy riding. I installed a pcIII with a modified smoothness map and mileage dropped 2-3mpg. Winter drops my mileage another couple mpg further with the Vstream windshield installed and raised up constantly. My last couple fillups have been just under 35 mpg.

I don't mind the "low" FJR mileage because I just compare it to what I'd be getting in my crew cab dually 4x4 pickup that's powered by a V10 through 4.30 gears. Never get over 10 mpg in that pig, with 8 mpg being more common around town.

 

[ANZAC]

So I guess 32mpg is not too bad considering,10% ethanol winter fuel, large Cee Bailey screen, Givi trunk and crappy performance below 2000revs due to possible fueling problem.

Oh, and wonderful Portland traffic but that is one of the reasons I ride to make commuting fun and use the HOV lane on I-5 which shaves off at least 30 minutes of time riding home.