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High fuel consumption


gropula

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I agree with Grum on attacking the fuel system side of it.  I have a 2002 as well and this is in my list of things to do.  Would not hurt to replace the fuel filter while you're at it.

 

California gas has up to 10% ethanol and it does pull down your efficiency a lot.  Like ~10% or so in cars and trucks I've had.  Bike efficiency is a little less consistent to observe but should be equivalent.

 

So to give you a benchmark, my 2002 with full exhaust and a Rapidbike, but original fuel injectors and filter and no starter valve sync since 2008 or so is giving me 38-42 mpg consistently.  If I really wring it out for fun I will see 35 mpg or so.  Mostly commuting, with saddlebags which in the long ago dropped a few mpg on me.  
 

If you are using the upper half of the tachometer where VTEC activates, expect to be using a whole lot more fuel though!   You can drive it down low in the 30s if you are riding hard or at high RPM a lot.  Over the years I think most people on the forum have observed that VTEC can make your efficiency vary wildly, with some low RPM riders seeing nothing but 40+ and a lot of the racer chaser set or people who are just accustomed to riding a sport bike in the middle of the power band seeing numbers in the 30s.
 

 

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Does anyone know the inner diameter of fuel hoses connecting to the fuel filter or the inner diameter of the piping on the filter itself. I want to order a replacement one since OEM is stupid expensive.

 

Edit: the filter is 6 mm inlet/outlet. Bought one for a third of the OEM price. It's not hooked, but I'll put a longer hose and make the bend.

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17 hours ago, ShipFixer said:

I agree with Grum on attacking the fuel system side of it.  I have a 2002 as well and this is in my list of things to do.  Would not hurt to replace the fuel filter while you're at it.

 

California gas has up to 10% ethanol and it does pull down your efficiency a lot.  Like ~10% or so in cars and trucks I've had.  Bike efficiency is a little less consistent to observe but should be equivalent.

 

So to give you a benchmark, my 2002 with full exhaust and a Rapidbike, but original fuel injectors and filter and no starter valve sync since 2008 or so is giving me 38-42 mpg consistently.  If I really wring it out for fun I will see 35 mpg or so.  Mostly commuting, with saddlebags which in the long ago dropped a few mpg on me.  
 

If you are using the upper half of the tachometer where VTEC activates, expect to be using a whole lot more fuel though!   You can drive it down low in the 30s if you are riding hard or at high RPM a lot.  Over the years I think most people on the forum have observed that VTEC can make your efficiency vary wildly, with some low RPM riders seeing nothing but 40+ and a lot of the racer chaser set or people who are just accustomed to riding a sport bike in the middle of the power band seeing numbers in the 30s.
 

 

That has been my experience exactly. 

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  • 2 weeks later...

Alright, I got the injectors ultrasonically cleaned and renewed the KN filter with their kit. The fuel filter I cleaned out with a solvent since the aftermarket turned out to be 6mm outer diameter and I didn't want to inhibit fuel flow. Now I'm at 6.7L/100, which is fine and the bike runs great. I'll call this case closed.

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  • 3 weeks later...

I'm sorry to revive a thread that I've thought is closed. Sorry for you and my pocket. I've been testing O2 sensor readings, because the bike still doesn't run properly. Consumption is improved but still not good. The bigger problem I'm facing is that sometimes when I open the throttle the bike accelerates but then when I'm closing it the bike bogs down, loses power and then regains it abruptly and it surges forward with force. In the video I posted I'm reading the signal voltage from the no.1 O2 sensor. When I hold the throttle open, the revs should stay the same. But, the engine loses a couple of hundred revs every now and then. At that moment the sensor reads lean. It seems to me that there are missfires. If one of the cylinders doesn't fire a lot of air will go into the exhaust and then O2 will read lean. It could be that the spark is bad and it doesn't combust, or that the fueling is bad and it doesn't get the fuel in at all. There are no exhaust pops, which would indicate lack of fuel. On the other hand since fuel consumption is bad, that would indicate that fuel is wasted, but it doesn't combust in the exhaust. Here is a video: VFR 800 O2 sensor reading. I'd like to have some thoughts on this before I spend money on expensive plugs. 

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From my way of thinking if a cyl. is missing then the fuel isn't being burned and there should be a rich mixture. That would be if a spark induced miss. An injector issue would cause a miss and be lean if it wasn't injecting the proper amount of fuel. 

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I think it just can't get the right mixture at all throttle openings because of messed up throttle position sensor calibration. Tried adjusting the TPS sensor again. Of course if I adjust it so that it reads 0.5v on throttle closed it richens up when reving to 1.05v on the o2. If i adjust it around 0.4v it runs a bit leaner around 0.8v on the o2, but with occasinal drops to 0.4. I wonder if rapid bike evo or racing with their autotuning could sort out the fueling? They also have an option of throttle calibration in the software.

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