Fuel economy off a bit...

Help Support FJRForum:

Fred W

1 Wheel Drive
Joined
Nov 9, 2006
Messages
17,535
Reaction score
3,645
Location
Eastern VT
At the risk of ending up in the NEPRTs, I have a fuel economy question, but with an added twist (I think).

So, as long as I've been riding my '05 I've been getting 200-210 miles before the flashing fuel reserve on the gauge, and then I've run 50 or more miles into reserve and still only put ~ 6 gallons in. Right at 40-42 mpg like clockwork.

After bashing the lil' bambi this past fall, I had the shop do the TPS recall / replacement thing (finally) while the bike was in getting re-beautified. Since that time my fuel economy has dropped noticeably.

For example, on Saturday we took a very leisurely ride-about with the ionbeam's and FJReady doing some real touristing through the Massachusetts north shore (Gloucester, Rockport, etc.), where I expected to get phenomenal mileage, but I only netted ~36 mpg. Hell, that's what I got last year sporting around in West Virginia, by god! I've noticed this to be the case for the past several tanks, and not many have been explainable by heavy use of the right hand. Something seems fishy.

I am hesitant to declare that the observed difference is as a direct result of the TPS replacement. After all, it might just be a coincidental combination of the seasonal change in fuel mixture at the pump added to the bigger, cold weather windshield, etc. (hence the NEPRT risk) But the TPS replacement does seem to be correlated with the change, time wise.

Note that I do have a PCIII USB installed (O2 sensor disconnected) with a fairly aggressive fuel map to cure the "lean surging at steady cruise" problems that I had. I'm considering reconnecting the O2 sensor and running a zero map for a while as a test just to see if the old surging issue has been effected at all by the new TPS. Wouldn't that be a kick in the ass? If my original surging complaints were partly due to the TPS that I hesitated to get recalled? I would love if I could go back to closed loop mode and ditch the PCIII, but I'm betting the best I'll be able to do is to maybe switch to a less aggressive fuel map.

I'm just wondering:

1) if anyone else happened to notice any change in fueling / fuel economy when they had their TPS recall done. I know, for most it was a long time ago...

and

2) if it even makes sense that changing the TPS would/could cause the bike to run richer.

Clearly this would only be possible with the fuel injection in open loop mode. I know it goes in and out of closed loop mode (if/when the O2 is connected) depending on certain conditions, but my understanding of which exact conditions is not entirely clear. If anyone has a reference or cite that shows this in some detail it would be most appreciated. FWIW - I can not find this info in either the FSM or FJR Orientation guide.

 
Last edited by a moderator:

FJRBluesman

Some call me... The STIG!
Joined
May 23, 2007
Messages
6,004
Reaction score
127
Location
Orange County, CA
Fred;

I have not had the TPS done on my bike, to my knowledge, it's used.

I sometimes get different readings from my fuel gauge at certain mile points, but my mileage is still about 40mpg commuting. I do notice a difference, and you didn’t mention this, when I change my stock windscreen in the winter, to the huge barn door V-Stream, my mileage drops by about 3mpg. Did you change up on windscreens or put on the trunk? The PCIII I would suspect is not your gas mileage friend either.

 
Last edited by a moderator:

BwanaDik

Members++
Joined
Jan 21, 2008
Messages
1,691
Reaction score
18
Location
Santa Fe , NM
Are you calculating your mileage by hand or just using the MPG readout? I get about 36-37 actual mileage when I calculate it from my fuel logs but the readout is always at least 5 MPG higher (PCIII also with Wally map)

 

03HiYoSilver

Members++
Joined
Aug 20, 2006
Messages
1,848
Reaction score
17
Location
Atlanta, GA
Fred,

I had my TPS done a few years ago and my gas mileage did go down as well, much to my surprise. It was about 2-4 mpg.

Unfortunately, they would not give me the old TPS since it had to go back to Yamaha due to warranty...it was still good.

So I have no idea why this would cause this change.

 

ahchiu

FJR Commander
Joined
Sep 9, 2008
Messages
2,955
Reaction score
170
Location
Sammamish, WA
You might want to check the position of the TPS, it my have been installed a little off, get into the Diag screen to check the readings they should read from 16-99

16 @ idle and 99 and full throttle.

 

Fred W

1 Wheel Drive
Joined
Nov 9, 2006
Messages
17,535
Reaction score
3,645
Location
Eastern VT
All mileage calculations are the old fashioned, hand calculated type based on elapsed miles (I reset one trip meter each fillup) and gallons pumped. The faster 1st gens ain't got no fancy shmancy mpg readout in the display. ;)

While I have put my Rifle barn door windshield on recently, I initially noted the loss of mpg with the same shield that it went in the shop with on, the Rifle sport (midsize), so I am inclined to discount that. The winter blend gas is a possibility.

But I am very interested to hear that at least one other has experienced this. And I will most definitely go into diags and check the readings. I probably ought to do the same to the PCIII (It has a similar internal function). Thanks very much for that suggestion, ahchiu. I'll report back what I find. (sure wish I had done a "before" check).

 
Last edited by a moderator:

ionbeam

2 FUN
Joined
Jun 24, 2005
Messages
8,817
Reaction score
1,768
Location
Sandown, NH
The TPS is simply a linear resistor with a wiper that is mechanically locked to the throttle shaft. At idle the wiper will have between 650-750mV on it. As the throttle is turned the throttle shaft rotates, which moves the resistor wiper in lock step. All the TPS does is tell the ECU how far the throttle is open. Read here. You can check your TPS via the diAG screen at 01, simply twist the throttle and read back the throttle position as a percentage. Idle = 15-17% open and WOT = 97-100% open. The span of the resistor is fixed, all you can set is the offset at idle. The resistor itself is linear.

The only ways the TPS can be 'bad' is if the TPS wasn't calibrated during install or if the rubber seal on the TPS wasn't seated correctly and is leaking vacuum. Because of one hard to reach screw on the TPS some shops will pull the entire fuel rail off to access the TPS. This opens up a large number of opportunities for things to go wrong.

One or two tanks where mileage is very different can simply be an anomaly. The southern part of NH is required to serve oxygenated fuel but it is only elective in other parts of the state. I find that when I buy gas up no'th I get better mileage.

FWIW -- when I ride alone I average 35-38 mpg, when I ride with my wife I average 40-42 mpg, when I follow Fred W I average 42-45 mpg, when I follow Cota95 I average 45-48 mpg :blink: Very consistently. Fred follows me and he gets bad gas mileage -- coincidence? ;)

Fred, give me a call, I learned a heck of a lot about the FJR's fuel use by running my FJR with a vacuum gauge on the throttle body and a volt meter on the TPS. What I have to say is simple, but it would take a lot of writing to spell it out (so to speak).

Edit: I see I type slowly and most of what I said has already been covered!

 
Last edited by a moderator:
Joined
Jul 18, 2005
Messages
2,525
Reaction score
-2
Location
Southwest
If you ride here:

4128705716_8140813e3d_o.jpg


And, because you'll (probably) be holding the throttle in somewhat the same place (very little to no throttle movement) -- the ECM will look to the O2 sensor for input and go into closed-loop stoichiometry mode.

Where all similar FJRs (stock Gen Is or stock Gen IIs) get the same gas mileage (they're all the same...). :eek: :)

Anything else -- and 'you become the engineer'... :blink: :huh:

 
Last edited by a moderator:

Fred W

1 Wheel Drive
Joined
Nov 9, 2006
Messages
17,535
Reaction score
3,645
Location
Eastern VT
OK, well my Diag 1 showed 16% at idle position and 99% at WOT.

and the PCIII shows 0% and 100% at the appropriate spots.

So I guess the TPS is installed and all aligned correctly.

I did get to reset the two errors that were stored: 15 and 30. The 30 I am all too aware of (see 2nd icon in my sig). but the 15? :unsure: Hmmm...

(TPS shorted or open circuit) Either that was somehow generated when they replaced my TPS or maybe my TPS really was on the way out before it was replaced. I know that I never saw any errors pop-up on me.

Oh, well... this is all so anti-climactic. After a brief discussion with the Professor, I'm now betting that it's just the winter mix fuel that they coincidentally happened to change over to in the time that the bambi basher was laid up in October. So I guess I'll just have to wait 'till the spring and expect that my mileage will go back on up to my normal 40-42mpg once we get the good gas back.

We now return you to your regularly scheduled forum content, where this week we find the fng trolling, instructing us all on how to post only when sober and with proper dignity, and Howie sending him back comical photoshopped pictures... ;)

 
Last edited by a moderator:

ahchiu

FJR Commander
Joined
Sep 9, 2008
Messages
2,955
Reaction score
170
Location
Sammamish, WA
OK, well my Diag 1 showed 16% at idle position and 99% at WOT. and the PCIII shows 0% and 100% at the appropriate spots.

So I guess the TPS is installed and all aligned correctly.

I did get to reset the two errors that were stored: 15 and 30. The 30 I am all too aware of (see 2nd icon in my sig). but the 15? :unsure: Hmmm...

(TPS shorted or open circuit) Either that was somehow generated when they replaced my TPS or maybe my TPS really was on the way out before it was replaced. I know that I never saw any errors pop-up on me.

Oh, well... this is all so anti-climactic. After a brief discussion with the Professor, I'm now betting that it's just the winter mix fuel that they coincidentally happened to change over to in the time that the bambi basher was laid up in October. So I guess I'll just have to wait 'till the spring and expect that my mileage will go back on up to my normal 40-42mpg once we get the good gas back.

We now return you to your regularly scheduled forum content, where this week we find the fng trolling, instructing us all on how to post only when sober and with proper dignity, and Howie sending him back comical photoshopped pictures... ;)
Try running some Seafoam through your system.

 

Fred W

1 Wheel Drive
Joined
Nov 9, 2006
Messages
17,535
Reaction score
3,645
Location
Eastern VT
Try running some Seafoam through your system.
Thanks. I may very well do that, just as a course of my winterizing layup procedure. I generally don't stabilize the fuel in fuel injected vehicles since they do such a good job of sealing up the fuel tanks and pressurized rails. But carby vehicles get a shot of Stabil. I'll get a can of seafoam and use that this year instead so I can run a shot through the FJR.

One other thing that I could try, though it's probably too late now; ionbeam reminded me that I have a tendency that most of us probably do, and that is of using the same fuel stations habitually. I tend to go for Mobil or Irving stations most often since they are the closest to home. Or maybe it's that I'm attracted to their colorful signs or sumpthing? :blink:

A particular brand of fuel will fill all the stations in a given area from the same bulk tanker loads, so they would all change over their fuel mix simultaneously (within a few days). Choosing a different brand, or filling up in a radically different geography, might result in different mileage, thereby proving that the fuel mix is the culprit. Unfortunately, it is now so deep into the fall season, most of the other brands have probably followed suit by now, so I'll have to be patient and just wait for spring to get my mileage back.

 

08FJR4ME

-WYNPRO-
Joined
Apr 10, 2008
Messages
3,919
Reaction score
668
Location
Acushnet, MA
Try running some Seafoam through your system.
Thanks. I may very well do that, just as a course of my winterizing layup procedure. I generally don't stabilize the fuel in fuel injected vehicles since they do such a good job of sealing up the fuel tanks and pressurized rails. But carby vehicles get a shot of Stabil. I'll get a can of seafoam and use that this year instead so I can run a shot through the FJR.

One other thing that I could try, though it's probably too late now; ionbeam reminded me that I have a tendency that most of us probably do, and that is of using the same fuel stations habitually. I tend to go for Mobil or Irving stations most often since they are the closest to home. Or maybe it's that I'm attracted to their colorful signs or sumpthing? :blink:

A particular brand of fuel will fill all the stations in a given area from the same bulk tanker loads, so they would all change over their fuel mix simultaneously (within a few days). Choosing a different brand, or filling up in a radically different geography, might result in different mileage, thereby proving that the fuel mix is the culprit. Unfortunately, it is now so deep into the fall season, most of the other brands have probably followed suit by now, so I'll have to be patient and just wait for spring to get my mileage back.
Fred,

You should be buying your gas from these retailers.

> Here are some large companies that do not import Middle Eastern oil:

> Sunoco.............................. 0 barrels

>

> Conoco........................... . 0 barrels

>

> Sinclair.......................... 0 barrels

>

> BP / Phillips..................... 0 barrels

>

> Hess. ............................. 0 barrels

>

> ARC0............................ .. 0 barrels

>

> Maverick.......................... 0 barrels

>

> Flying J. ........................ 0 barrels

>

> Valero............................. 0 barrels

>

> Murphy Oil USA * .................. 0 Sold at Wal-Mart

Just a thought????

You might want to try running with the larger windscreen in the down position and see what the results are. Guaranteed your mileage will improve. Works for me.

 

Fred W

1 Wheel Drive
Joined
Nov 9, 2006
Messages
17,535
Reaction score
3,645
Location
Eastern VT
As mentioned earlier, the observation of mpg loss was over a several weeks period immediately following my deer strike and subsequent TPS replacement. That happened on September 28th, so yes the temperature has been dropping, but some days have been quite balmy and I still experienced lower mpg.

And Dave, I have the rifle tuning block and keep my windshield pretty well tipped back all of the time, except when it's really cold. Mostly because I don't like having to see too much of the road through the shield.

 

Harald

"Superior Gen 4" Rider
Joined
Aug 21, 2007
Messages
2,018
Reaction score
183
Location
Port Angeles, WA
Fred, I vote for winter fuel. My mileage recently dropped a few mpg with no other changes to my bike. Seems to happen each winter around this time.

 
Joined
Jul 18, 2005
Messages
2,525
Reaction score
-2
Location
Southwest
As mentioned earlier, the observation of mpg loss was over a several weeks period immediately following my deer strike and subsequent TPS replacement. That happened on September 28th, so yes the temperature has been dropping, but some days have been quite balmy and I still experienced lower mpg.
Taking the deer strike (and subsequent repair) and TPS replacement out of the equation, a couple notable gas mileage reducers are: poor flowing air filter element and dragging disc brake caliper. Of course, the timing must be coincidence... :blink:

Both pretty easy to check and remedy, if nec.

 

Latest posts

Top