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  • Fuel Injected bike questions....

    My 2008 FI bike 10k miles runs fantastic. But only getting 35-37 mpg last 2 tankfulls riding reasonable mix of city/highway.

    I noticed it idels sometimes high even after warmed...about 1100-1200 rpms...other times it settles into a 900 rpm lope perfectly after 2 minutes. I'm assuming the idle being higher could contribute to poor fuel economy. Driveability is great and pulls hard to 115 mph. Smooth as butter. Only thing I have noticed is that at 85 mph while steady cruising it flutters just a bit at that certain mph/rpm but not like a flat spot or dead spit...just an odd little flutter. Tank clean fresh 87 and seafoam.

    Doesn't appear to have any intake/vacuum leaks I can pinpoint. PCV is connected but has zero tune which allows factory computer to control the show and no "input" from any competing tune from PCV. 02 sensor harness have simulators and exhaust has plugs in exhaust ports. K&N RA067 air intake sucks a ton of air (very noisy) and brand new battery and plugs.

    Since the idle is commanded by the computer and from what I've read/been told the 02 sensors do NOT give the computer information that would lead to any actual "adjustment" to the running of the bike....kinda confused as to why the idle isn't consistent and always 900 rpm?
    LET'S RIDE

  • #2
    I can't recall every having a fast idle like that. I don't often hit 85 unless on the throttle during a pass but it's always been smooth pulling until I roll off the throttle. That 35-37 seems pretty consistent to what I get (still stock down to the AIS). I have gotten low 40's a few times but not a lot.

    Comment


    • #3
      I have not had my R* a year and have not ridden in the last 6 months because of my knee but 35-37 was what I was getting when I was riding. I am also stock with the AIS still hooked up. I typically ride 80-85 MPH

      Comment


      • #4
        I just assumed the fuel injected bikes would get better mileage than the carb bikes?
        LET'S RIDE

        Comment


        • #5
          Generally that seems to be the case (FI vs. carb) but not here. It's too bad Ivan never did a reflash for the Road*. I'd be curious to see if that would have helped the MPG.

          Comment


          • #6
            Regarding Ivan remaking the stock ecu, the stock ECU is not reprogrammable. I get in the low 40s. Go to the thread that talks about facts and tips for fuel injected road stars and look for the part that talks about a small vacuum tube under the tank. I would also totally disconnected the aftermarket processor you have, reinstall the O2 sensors and see what results you get.

            Comment


            • Brad_G
              Brad_G commented
              Editing a comment
              Ok so that answers the part about modifying the stock ECU. I'm not sure what you are referring to about the vacuum tube. I scanned the thread you mention (very quickly) and didn't see anything that jumped out regarding vacuum tube. Thanks.

          • #7


            * Quote from Gadgetman728 - Look at both ends of the small rubber vacuum hose under the tank that goes to the injectors. Is the end that came off the intake end soft, swollen, spongy, split? If so, the rest of the FI guys need to know this. I recommended this easy mod, but no one wants to do it. It made a new bike out of mine. That sensor, to me anyway, seems VERY important, and a perfect vacuum signal seems needed. Good luck, it's easy.

            The FI bikes seem to run really well under all conditions. I've posted several times to check that particular hose because of it's importance and it's proximity to fuel and the way the vacuum lines can swell, split and leak without much visual damage. This damage causes air leaks which the FI bikes HATE, trust me, I chased the problem for the first 6000 miles I owned my bike, with ZERO help from the dealer I bought it from, they were clueless.

            Late 2014 my 08 started having an intermittent error. After riding down the road for awhile at highway speeds, when I would need to slow down for a stop sign, as I decelerated, my bike would drop below idle and die. It doesn't do it every time, so it doesn't really effect too much. I rode all day Sunday 1-18-15, and it never happened once.

            The springtime tune up - new plugs, new gear and engine oil, filters and a vacuum line check is going to be done in a couple of weeks. If I find anything in there amiss, I'll post it.
            I wish we could adjust more things, but overall the Stock FI bike needs very little maint. or fuel adjustments compared to the carbbed bikes.
            It's interesting that Flyman1971 would state that all stock Road Stars run really lean then point to the black in the tailpipe as the tip. They run close to stoichiometric during closed loop cruise but richer at idle and at throttle settings above cruise. The rich idle is for smoothness and is the reason for the 20 minute idle cutoff. Keeps from overheating the converters and bluing the mufflers. The richer settings above cruise are for cooling especially during hot temperatures but are still in the max power range.

            The ECU is programmed by an engineer for a given volumetric efficiency. Change that and with the possible exception of closed loop the ECU won't adapt. Change it enough like the member with the 45mm throttle body and closed loop won't even adapt. That throttle body was intended to be used with the higher capacity injectors being sold back then.

            The FI bikes can be altered with exhaust, etc. but that won't necessarily make them faster. The stock ones are pretty darned fast.


            The 2 Tech Tips I want to submit here are:
            1) Even if your hoses are attached, they may have deteriorated and loosened over time. Don't just look at it and assume it's tight enough, take it off both ends and visually inspect it, mine was still tight at the sensor end, but swollen, over sized & spongy on the intake end. Spongy probably because of close proximity to fuel. - Change them and feel the difference.u
            2) I highly recommend Silicone Hi Temp Vacuum Tubing as a replacement alternative.

            If I posted some other time that the vacuum tubing was hooked to the fuel injectors, my error. I've always known, but may have explained it wrong once. The Vacuum tubing definitely goes from the nipple on top of the intake and runs straight to the sensor.

            And... as I keep preaching, this little hose is as important to FI bikes as Jetting & float adjustment on the carbbed bikes.

            They generate they're own voltage based not the amount of heat. The hotter they are, the more voltage... and the cooler the less. That's how they read the state of the exhaust gases, based not the amount of voltage the O2 sensor sends to the ECU; then the ECU adjusts the amount of fuel injected accordingly. If the O2 sensor is failing, they don't generate enough voltage. Think of it this way, if they bike is running lean, the exhaust temp will be hotter and the O2 sensor, via the ECU, will adjust the fuel mixture accordingly, there by making it more rich and cooling the exhaust gases. If the exhaust temp is too cold, the voltage level is too low and the ECU thinks it's running too rich and leans out the fuel mixture in the injectors. Get it?

            They're called O2 sensors for the purpose of monitoring oxygen present in the spent gasses.

            The zirconia sensors, once they reach operating temperature, do just that.

            I with a richer than normal mixture, not enough oxygen on the O2 sensor will drop the voltage telling the ECU to lean it out, and vice versa.

            Comment


            • Brad_G
              Brad_G commented
              Editing a comment
              Thank you for posting that. I saw that vacuum hose when I was tapping into it for my cruise control. I'll make a note to check it periodically.

          • #8
            What are the plugs look like, how is the smell,? I think if you disconnect the O2 sensors it runs on a default program?. Any error codes? Mileage by RS odo or gps?

            Comment


            • #9
              Originally posted by brianmac View Post
              What are the plugs look like, how is the smell,? I think if you disconnect the O2 sensors it runs on a default program?. Any error codes? Mileage by RS odo or gps?
              Mileage by odometer No error codes
              Smells fine not lean or rich
              02 have simulators so "act" like connected
              LET'S RIDE

              Comment


              • #10
                Well looks like my mileage is on point.....
                Attached Files
                LET'S RIDE

                Comment


                • #11
                  My 2008 got 50 miles per gallon last year at starfest on a calculation based on 23 gallons of fuel. I typically get 40 to 44.

                  Comment


                  • #12
                    I expected this fuelie bike to de better than carb...but not the case for me. I'll spray some starting fluid around but don't anticipate to find anything. My vacuum hose was fine/soft/pliable when I removed tank. Talked to tech support at PCV and they said Yamaha does have a speed limiter on the fuelie bikes and that it can't get removed by the PCV. It really runs fine and I'll take my EZ Tach along with me to verify the idle rpm next ride.
                    LET'S RIDE

                    Comment


                    • #13
                      A properly tuned Carb or fuel injection version doesnt really change the mpg in typical experiences…. O2 sensor simulators cause the ECU to default to preprogrammed tuning…. Doesnt perform closed loop corrections to adjust the stochiometric burn efficiency of varying manifold pressures, air temps, fuel mixture ratios, and engine timing…. Think about what a fuel injected closed loop system is designed to accomplish… this has been effectively defeated by O2 simulators….

                      your experienced gas mileage is more a result of your right hand aggressiveness and changing barametric pressures…

                      temperature of the motor will have a pronounced effect on idle speed due to ‘predetonation” effects of high cylinder temps, air filter flow characteristics can slightly choke an engine, fuel quality can also vary from different name blends and gas station storage methods… many factors affect fuel quality…. And last but not least…. Head winds, tailwinds, traffic airflow turbulence can all effect your day to day mileage expectations….

                      perform your tests in laboratory conditions and the data would be a bit more meaningful…

                      Comment


                      • brianmac
                        brianmac commented
                        Editing a comment
                        yeah, what Tcontrol said, ok , yeah. deafault thingies

                    • #14
                      Originally posted by Tcontrol View Post
                      A properly tuned Carb or fuel injection version doesnt really change the mpg in typical experiences…. O2 sensor simulators cause the ECU to default to preprogrammed tuning…. Doesnt perform closed loop corrections to adjust the stochiometric burn efficiency of varying manifold pressures, air temps, fuel mixture ratios, and engine timing…. Think about what a fuel injected closed loop system is designed to accomplish… this has been effectively defeated by O2 simulators….

                      your experienced gas mileage is more a result of your right hand aggressiveness and changing barametric pressures…

                      temperature of the motor will have a pronounced effect on idle speed due to ‘predetonation” effects of high cylinder temps, air filter flow characteristics can slightly choke an engine, fuel quality can also vary from different name blends and gas station storage methods… many factors affect fuel quality…. And last but not least…. Head winds, tailwinds, traffic airflow turbulence can all effect your day to day mileage expectations….

                      perform your tests in laboratory conditions and the data would be a bit more meaningful…
                      I was told that the O2 sensors do not give information to the computer that is used to make these actual adjustments. It was more to set trouble codes than anything else.? However what you saying makes more sense that the 02 sensors would provide info for tuning afjustments. However I don't know if those slight changes would affect mileage much at all. Bike runs great and is getting what it is "supposed to" from what I can see in terms of mpg.
                      LET'S RIDE

                      Comment


                      • #15
                        Actually…. At idle rpm, the ecu is in open loop configuration and the motor uses a preprogrammed tuning map… O2 sensor inputs are ignored….

                        once engine comes off of idle rpm (no i do not know the trigger point)…. The ecu will begin a closed loop tuning map and utilize all available inputs to provide the best stochiometric burn efficiency as determined by the ECU programmer…. As i understand it, the stock ECU does not allow aftermarket tuning modifications to the firmware…

                        i believe there are aftermarket ECU’s available that will allow end-user modifications…. But since i am an old carb man…. I have not researched or have definitive ‘Roadstar’ experiences to relay to my fellow gearheads…. I would bet there are still some tweakers on this site that have had mixed success using aftermarket ECU’s…. But i think the general concensus is the OEM ECU pretty much accounts for most engine performance modifications attempted by these clinic members without custom mapping….

                        Comment


                        • #16
                          Mine seems to run really well the way it is so I'm not going to mess with it Only thing I would do is that I would take it to a local race bike specialist with Chassis Dyno and he has lots of experience with PC5 tuning. Let him put a sniffer pipe in the exhaust and have at it.
                          LET'S RIDE

                          Comment


                          • #17
                            Sounds like when checking the vacuum tubing one end is connected to the throttle body and the other end is connected to a sensor, what sensor is it? I'm just trying to find out what hose to check, I've not checked any sensor hoses on my FI bike.
                            2012 Road Star Silverado S

                            Comment


                            • Brad_G
                              Brad_G commented
                              Editing a comment
                              The only vacuum hose I saw on mine was attached to the intake runner near the rear cylinder. I believe it's basically the same location as the carb'd bikes.

                          • #18
                            Originally posted by Brad_G View Post
                            The only vacuum hose I saw on mine was attached to the intake runner near the rear cylinder. I believe it's basically the same location as the carb'd bikes.
                            It's a small quarter inch hose underneath the back bone of the frame. I don't know where it runs to or from. It's hard to see.

                            Comment


                            • #19
                              Originally posted by Shores View Post

                              It's a small quarter inch hose underneath the back bone of the frame. I don't know where it runs to or from. It's hard to see.
                              Yeah it's a standard vacuum size. It leaves the intake up through a mess of stuff for the throttle body and it's connectors and exits along the left of the frame rail to a sensor that's just down the frame from the key switch area. You can see it in this pic (upper left) where I put in a "T" and valve to go to my cruise control/vacuum reservoir.

                              Comment


                              • #20
                                Thanks Brad!
                                2012 Road Star Silverado S

                                Comment

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