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Mileage increase after running out of gas


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  • Member Contributer

Hi,

 

I noticed a considerable increase in my bike's mileage after I ran out of fuel. I used to get around 200-230 kms (125 to 142 miles) before I saw the fuel light, now I see 170-180 kms (105 to 111 miles). I can also smell unburnt fuel indicating rich mixture.

 

My bike has a derestricted ECU by Guhl racing (higher redline, derestricted 1st and 2nd gear, removed top-speed limiter), de-catted with a Akropovic slip-on and K&N air filter. The bike was dynoed after the de-cat process, the derestriction of the ECU was done after the dyno session though. 

 

I can tell with certainty that I did not have this problem before I ran out of fuel. Is it possible that running out of fuel somehow initiated an emergency procedure where the ECU is providing too much fuel?

 

Your feedback would be much appreciated.

 

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  • Member Contributer

No idea....

But a good excuse to say "merhaba!!!" to you :goofy:

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  • Forum CEO

There is a limp home mode on the ECU when a sensor is out of tolerance, MAP sensor, or temp, whatever. It is programmed to just plug in a safe fuel map for most situations and it is often very poor on fuel economy. Perhaps running out of gas reset a sensor that was not reading in tolerance.

 

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You didn't mention the FI Light on the bike's instrument panel.  If there's no FI Light illuminated the bike's ECU (and the various sensors that it monitors) are not compromised in any way.

 

Just a thought (pure speculation on my part):

 

fuel flowing through the injectors cools them as it goes through, remember that injectors are actually just as much a part of your bike's electrical system as they are part of the bike's fuel system.   In a running-out-of-gas scenario one of your injectors may have overheated as electricity flowed through it without any fuel flowing an is now damaged (the injector's electrically controlled solenoid coil part).  Your drop in mileage and the smell of unburned fuel could be caused by one (out of your four total injectors) sticking open.

 

You can hand test the solenoids of injectors individually using a 9-volt battery and a couple bits of wire.  Just making contact with the 9-volt battery will cause the solenoid of a healthy injector to move, and you will hear it make a little "ping!" noise.

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29 minutes ago, GreginDenver said:

You didn't mention the FI Light on the bike's instrument panel.  If there's no FI Light illuminated the bike's ECU (and the various sensors that it monitors) are not compromised in any way.

 

There is no FI light, everything seems to be in order from the cockpit. So I guess that rules out the limp-mode, is that correct?

 

I rode my bike for a little while longer and while I noticed the somewhat drop in the fuel range, I chalked this up to my more agressive riding during that period. Since it started fine and showed no ill-effects I didn't give it too much thought to be honest.

 

I now sold my bike to a very nice gentleman and he reported a 20% increase in fuel economy compared to his previous two VFR1200Fs, I got worried. Would it throw a fault code if the injector/s are stuck open?

 

 

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24 minutes ago, Dutchy said:

No idea....

But a good excuse to say "merhaba!!!" to you :goofy:

 

Hi Leon, it's been a long time ...:beer:

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1 hour ago, arrow said:

 

I now sold my bike to a very nice gentleman and he reported a 20% increase in fuel economy compared to his previous two VFR1200Fs, I got worried. Would it throw a fault code if the injector/s are stuck open?

 

 

No, there would be no FI light indication for a malfunctioning injector.  The ECU doesn't get any "feedback" from the injectors, all it does is provide a path-to-ground (negative) for the 12 volt power that is continuously supplied to the injectors for the period of time (in milliseconds) that it (the ECU) has determined for correct fueling of an individual cylinder at any given moment in time.

 

Actually there are FI light "blink codes" for if the ECU completely loses contact with one of the fuel injectors (a failed injector situation due to a loose plug or broken wiring for example), but there's nothing beyond that.  If the ECU loses contact with a fuel injector (a failed injector) the FI light will blink a code and the engine will "fail safe" and will not start.

 

But the ECU will continue to allow the engine to run with a malfunctioning injector.

 

This is what makes diagnosing a failed injector or clogged injector so difficult.  Because the ECU thinks it's doing the job properly.  Same goes for a failed (or failing) fuel pressure regulator.  In both of these cases there is no internal ECU fault indication.  Your only indication is external, like your sudden drop in fuel economy and the smell of unburned fuel that shows the engine (or an individual cylinder) is running over-rich.

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