Poor fuel economy

Hi

i own a VFR800X 2013. 
it’s had a few owners, and has covered 12,000 miles, 2,000 miles in my hands. 

modifications done:

1: pair valves disabled and blocked, air box bunged. 

2: flapper valve disabled / disconnected 

3: arrow end can ( all done by first owner )

4: O2 eliminator fitted, exhaust plugged. ( by me )

5: Previously fitted K&N air filter (clean) and new spark plugs ( by me )

6: Hyperpro shock and fork springs ( by me )

7: Handlebar conversion to Renthal bars ( I just hated the plastic shrouds )
 

previous owner also balanced starter valves, no idea how well, but other work seems competently done. Bike sounds fine, nice even beat when warm and the fuelling seems fine. Smooth even power delivery, no hesitancy or snatchiness. 

I was getting 6.1 miles per litre commuting in London ( heavy traffic )

The exhaust also smelt very rich at start up. Lots of white steamy clouds in winter temperatures. 
 

I recently fitted the O2 eliminator as the O2 sensor looked very sooty in the hope it would address the rich mixture. 
I then got 8.1 miles per litre. Happy days. 
It has since started heading back towards the previous figure. Now at 6.8 miles per litre. The weather has improved, so some of this might be happy throttle related. 

I’ve run seafoam in the tank twice also, in case it cleans up the injectors. 
 

My questions are

1: What is a normal fuel consumption figure for this engine when city commuting?

2: If its uncharacteristically low, what might be causing it? I don’t drive like a madman. 
3: Where is the fuel pressure regulator on this bike? It’s not on the fuel rail, like on previous models. 
4: could it be the MAP sensor or thermostat?

5: could it be a dripping injector issue and they need ultrasonic cleaning?

6: am I chasing ghosts and these engines are just very thirsty 😉

thank you for any help or information 

While not addressing your concers directly, I can provide some comparison to my fifth gen experience (200,000+ miles since Aug. 2006). I routinely get 45 to 55 mpg and have achieved as high as 60+ mph on a 100 mile ride on The Black Canyon of the Gunnison River at a SumSum meet-up of VFRD members. I am no knee-dragger but I do know how to wring the neck of the righthand twist grip on occasion.

All my fifth gen engines have been have been completely stock.

For me, Honda engineers have created the perfect combination of everyday commuting, long-distance traveling, and occasional track days.

(I deliberately do not calculate fuel mileage for track riding - that would spoil the fun.) :wheel:

Are you using Ethanol blended fuel? Your VFR can't advance the timing to optimize fuel burn with the higher octane, and as Ethanol fuel has a lower calorific value compared to straight gasoline your fuel economy therefore is not as good?

By adding O2 sensor eliminators, how do you know you are getting the optimal A/F ratio?

Cold start "white steamy clouds" would suspect as normal condensation, provided it disappears when the engine is warm, might also be worse with Ethanol blended fuel.

Make sure that with the "Flapper Valve mod" the main vacuum hose has been properly blocked off.

If your 2013 VFR800X is similar to the 2014 VFR800F there is no Fuel Pressure Regulator as per previous gens.

A MAP sensor issue should flag a Diagnostic Trouble Code if it is faulty. And any issue with your Thermostat should indicate a change to its normal running temperature. Or be much slower to warm up if in the open state.

For a bike only having done 12,000 miles I'd be surprised if it had a leaky injector.

Also the 800X is more upright so probably has greater wind drag, than the 800F.

Recent fuel economy check on my 2014 8gen.

4.02ltr per 100k's =

4.02ltr per 62.137miles =

15.46 miles per Litre.

Yes, you should be getting at least 10-miles/ltr, even 12 is common. Ethanol-blended petrol lowers mileage by -10%, certainly not completely responsible for the -50% you're getting. Some possible issues:

1. sticky injectors? Possibly, but they don't result in +100% more petrol going into engine though. Typically dirty injectors will spray less-than-desired volume, never more. So dirty injectors should actually improve your mileage, not decrease it.

2. FPR is integrated into pump. Don't need to mess with it, just measure pressure in fuel-rail and compare to numbers given in manual to determine if pump & FPR are working properly.

3. as mentioned, disconnecting O2-sensor makes mixtures richer. Default fuel base-map is richer-than-optimal for safety in case you ride on super-hot day or encountre sub-standard petrol. Then O2-sensor feedback is used to lean-out mixtures to stoich 14.7:1 ratios. Sooty O2-sensor (and probably sparks too), shows you've got rich-mixture. Failed O2-sensor may also cause richness as it sends "lean" signal to ECU, thus tricking ECU into injecting more than normal amounts of petrol. Replacing failed O2-sensor rather than removing it, is proper repair for this issue.

4 . removing PAIR system can introduce vacuum-leaks. Measure intake-manifold vacuum at idle with warmed-up engine. This is only way to determine if you do or do not have vacuum-leak. Post your measured vacuum values here.

5. related to vacuum-leaks is MAP-sensor. Unless it's outright broken, as in generates signal outside of normal 0.25-4.79v operating-range, ECU won't throw code. However, that does not mean it's sending proper signals within that range. With vacuum-leak, it will send higher-load-than-actual signal to ECU. Again, tricking ECU into injecting more than normal amounts of petrol. Measure output-voltage of MAP-sensor at idle with warmed-up engine.

6. ECT sensor sends status of engine: cold or warmed-up. Failed ECT will always indicate "cold" to ECU. Thus ECU will always use fuel-enriched cold-start cycle full-time. This injects +20-25% more petrol than normal to help start cold engine. However, if ECU never detects that engine's warmed-up, it will keep on injecting too much petrol. Go through standard test in manual for determining if ECT is good or bad.

7. IAT sensor sends temperature of outside air to ECU. Colder air has more oxygen per volume than hot. IAT signal allows ECU to compensate for differences in air-density with changes in temperature. Failed IAT sensor will tell ECU that air is always "cold" and ECU will inject more than proper amounts of petrol. Go through standard test in manual for determining if IAT is good or bad.

You see... ECU is blind-man sitting in dark room and it's trying to inject petrol and send spark properly. In order for it to work properly, it needs to know exact environmental conditions outside: engine/coolant-temp, engine-speed & position, amount of air going into engine, amount of throttle-opening, etc. It gets this data via sensors and if a sensor is misadjusted or reporting improper data, ECU will therefore inject incorrect amounts of petrol or set off sparks at wrong time.

Avoid desperate shotgun approach of throwing random parts at bike. Replacing perfectly-working parts with brand-new perfectly-working parts won't change anything. Need to measure and test to arrive at numbers. Then compare those numbers you've measured with standards listed in manual to determine if part is good or bad. Only when confirmed part is bad, then replacing it would make difference. Most of time, it's an adjustment issue that's problem and not any particular part itself.

Interesting development on autos. Modern Toyota and Hondas use wideband O2-sensors rather than previous flip-flop sensors that can only detect 14.7:1 stoich mixtures. With higher-resolution of these air-fuel sensors, ECU is able to run in lean-burn mode of leaner 16:1-17:1 mixtures under low-load steady-state cruise conditions.

They also don't go into open-loop mode that ignores O2-sensor under WOT to use super-rich mixtures like previous engines. Some of them can actually maintain stoich 14.7:1 at WOT all way to redline. This is actually better since combustion is hottest at this ratio and generates more power than rich mixtures. Overall, these fine-tuning tweaks gets +10-20% more mileage than previous engines. 

a stuck-open thermostat or anything that keeps engine temperature below optimum will waste fuel.

Before anything see if you have problem but  we have to remove variables. Clean O2 needs to go back in. Tire size and pressure correct per spec. Next remove/ limit rider and traffic influence = trip south for you, nice and steady speed - Say Loomies Cafe and back? Top of the tank first after city limit, top off second on the same petrol station on your way back. Confirm distance with satnav. Report back...

Thank you for all of your replies. Interesting and informative reading. 
I am currently waiting on the ‘hens teeth’ workshop manual for the Mk1 Crossrunner. I had to order it from Germany, who ordered it to be reprinted by Honda and it’s on its way at great cost. 
 

I don’t have any diagnostic equipment aside from a multimeter, so it’s looking like I may need to get the bike booked into a Honda garage.  Trouble is I use it daily and only have the one bike. Might just have to bite the bullet and get it looked at professionally. 

O2 sensor and old plugs

Wow! A new O2 sensor is £494....seriously hope it’s not that then. 

Not sure if manual help you in this case but why wait. There is one for 2015 non X free to download here. There should be no differences for powertrain b/w both models. 

Magneto- Tyres fairly new and correct size, pressure spot on. 
by the way I’m in UK, London. No idea where Loomies is??

Loomies is a bike cafe south of London. It is very popular with London bike crowd, similar like Rykas 

Ah! Good to know. Thanks. 
 

so I went out for a nice steady run with more open roads and some motorway miles. Filled up and zeroed everything at edge of city stuff. 
The best I saw was 10.4 miles per litre average on the dash. In 27.2 miles, consuming 2.6 litres. That’s about 48.5mpg
As I came back into traffic it started to drop down as you’d expect. But wasn’t going for long through traffic and it finished up reading 9.2 m/l average. 
 

Before setting off initially I let her warm up and the radiators were definitely getting warm at around 76 deg centigrade. The temp went up and down a bit by 1 or 2 degrees before reaching 80-82 when I set off. 
The temp when on the motorway travelling at 70-80mph sat pretty steadily at 76 deg and only climbed up when in traffic. 
Does that sound normal or should it be holding a higher operating temp of around 82-84 when in use. 
 

O2 eliminator still in place. 

Plugs still shows running way too rich. Radiator-temps shows running slightly on low end, but still within proper range.

Purpose of O2-eliminator is to allow piggybacks such as PowerCommander or Bazzaz to adjust fuel-mixture away from factory settings. With O2-sensors in place, ECU will use its feedback to adjust back to factory settings. After while, all your customizations from PC/Bazzaz will be canceled out by opposite adjustment from ECU. O2-eliminator is of no use and has no benefit with factory ECU only.

I don't like this hack of removing O2-sensor to manipulate ECU. Better to not have an adjustment layer on top of factory maps. Best way to tune is by reprogramming factory ECU with new maps. Only needed if you've got upgrades that are beyond adjustment range of factory settings.

I've seen extremely minimal gains from dyno-tuning with PC/Bazzaz, factory maps are spot-on. But huge numbers of people have worsen performance with starting/idling issues or stumbles with increasing throttle too quickly. Removing PC/Bazzaz and restoring stock ECU settings fixed all these issues.

Best step for you next, is to re-install O2-sensor to allow ECU to lean out mixtures to more appropriate AFR. I suspect this is standard zirconium flip-flop sensor. I used universal $18 Bosch unit on my Porsche instead of factory OEM version (also Bosch). Paying hundreds extra for custom connector is outrageous as sensor itself is same. Universal sensor comes with stainless crimp connectors to re-use factory connector. Soldering not allowed as sensor uses space between wire-strands to sample outside air as reference for its operation.

apparently they don't come with crimps anymore. New Smartlink compression fitting to join factory connector to new sensor.

I am watching those Germans and their cars dropping value like stones. What could go wrong! You have Denso on the other hand with their gold plated terminals on O2 sensor signal wires.... 

7 hours ago, DannoXYZ

Plugs still shows running way too rich. Radiator-temps shows running slightly on low end, but still within proper range.

Purpose of O2-eliminator is to allow piggybacks such as PowerCommander or Bazzaz to adjust fuel-mixture away from factory settings. With O2-sensors in place, ECU will use its feedback to adjust back to factory settings. After while, all your customizations from PC/Bazzaz will be canceled out by opposite adjustment from ECU. O2-eliminator is of no use and has no benefit with factory ECU only.

I don't like this hack of removing O2-sensor to manipulate ECU. Better to not have an adjustment layer on top of factory maps. Best way to tune is by reprogramming factory ECU with new maps. Only needed if you've got upgrades that are beyond adjustment range of factory settings.

I've seen extremely minimal gains from dyno-tuning with PC/Bazzaz, factory maps are spot-on. But huge numbers of people have worsen performance with starting/idling issues or stumbles with increasing throttle too quickly. Removing PC/Bazzaz and restoring stock ECU settings fixed all these issues.

Best step for you next, is to re-install O2-sensor to allow ECU to lean out mixtures to more appropriate AFR. I suspect this is standard zirconium flip-flop sensor. I used universal $18 Bosch unit on my Porsche instead of factory OEM version (also Bosch). Paying hundreds extra for custom connector is outrageous as sensor itself is same. Universal sensor comes with stainless crimp connectors to re-use factory connector. Soldering not allowed as sensor uses space between wire-strands to sample outside air as reference for its operation.

the plugs picture is the old plugs from a few months ago. New plugs were installed when I upgraded the suspension. I had the tank up, so decided to do it at the same time. 

the O2 eliminator is being used as a test to see if the sensor is malfunctioning. 
I will refit if I can ascertain if it is still operating normally. Waiting for workshop manual to test this. 
 

So are you saying I could buy a universal sensor and fit it to the Honda connector. 
 

I’m thinking it’s the thermostat. Surely the rads shouldn’t be getting hot at 76 degrees. It’s only supposed to open at 80-82 degrees. 
The presence of a milky haze in the oil window when I first bought the bike also points to low operating temperature and moisture. 
If the stat is stuck open it would cause constant cold running signal and rich mixture wouldn’t it? 
 

Plot thickens. The old plugs are iridium and not original to the bike. So PO was trying to fix something on 10k miles motorcycle with 100 dollars worth of plugs...

I’m pretty certain the Crossrunner came with these as standard from the factory

I am not keeping up with progress, great surprise. On the other hand I would not have excuse to mess with them for another 5 years.... 

21 hours ago, Bikespod

the O2 eliminator is being used as a test to see if the sensor is malfunctioning. 
I will refit if I can ascertain if it is still operating normally. Waiting for workshop manual to test this. 
 

So are you saying I could buy a universal sensor and fit it to the Honda connector.

You can test for malfunctioning O2-sensor by just disconnecting it. Bypass/eliminators just connects heater-circuit so ECU doesn't throw code. But functionally exactly same as disconnecting O2-sensor since there's no useful data going to ECU in either case. Better disconnected rather than having bad O2-sensor reporting "lean" full-time because ECU would use rich base-map AND add additional petrol on top to compensate for "lean" signal. So you're halfway there on this issue by disconnecting bad O2-sensor.

I'm not sure of on-board diagnostics capability of this ECU and how it detects malfunctioning O2. On autos with OBD-2, you can connect scanner and actually get live-data from ECU of O2-sensor output. Or use an oscilloscope, output should be sine-wave with centre around 0.45v. I'm not aware of any other way to positively diagnose O2-sensor for proper output.

[image: uc?export=download&id=16ILGQKS95QkKXYQoj]

Since you're getting improved mileage with O2 disconnected, we can positively conclude that it is defective.

You have 3 options for replacement sensors:

1. factory Honda-brand sensor $$$
2. OEM sensor made by Denso $$
3. generic/universal sensor made by Denso/Bosch $

I haven't fully tracked down #2 to a compatible unit, but there appears to be many Denso units that may fit. Such as this Denso-DAC234-4400 unit. This might be easiest option, get one and try out. If connector doesn't fit, return it. Amazon's really good about that.

Last option if not able to find suitable connector is generic/universal route. At my tuning-shoppe, I only carried universal Denso/Bosch units since I didn't want to stock hundreds of different sensors. Our primary focus is on dyno-tuning turbo cars, which is impossible to do with failed O2-sensor. We'd confirm O2-sensor was working before tuning, and if not, generic/universal unit was spliced in to get going on job. I've used Denso on Porsche/Mercedes/BMW and Bosch on Toyota/Subarus without any issues, their outputs as measured on oscilloscope is exactly same.

They are sensitive units, so care must be taken not to contaminate them. NEVER, EVER use any fuel-additives such as over-the-countre octane "boosters". Aside from being snake-oil and not working, they contain organo-metallics that will destroy O2-sensor and catalytics. And use silicone sealants sparingly, just enough to get seal, but never enough to ooze out of seam on either side. Silicone will destroy O2-sensors. One or more of these issues may be why your O2-sensor is dead after only 12000 miles.

11 hours ago, Bikespod

I’m thinking it’s the thermostat. Surely the rads shouldn’t be getting hot at 76 degrees. It’s only supposed to open at 80-82 degrees. 

The presence of a milky haze in the oil window when I first bought the bike also points to low operating temperature and moisture. 
If the stat is stuck open it would cause constant cold running signal and rich mixture wouldn’t it? 
 

Replacing thermostat is good idea; never know when those suckers will fail. They are not binary units, but have temp-ranges. They start to open at certain temp, and are fully-open at some higher temperature. So it's possible yours is operating correctly, although at low-end of specs.

White condensation in crankcase could be from short-trips. Could also be headgasket. Do compression-test to gather additional data.

Also measure ECT, IAT, intake vacuum and MAP-sensor output voltage at idle. Computers are stupid, garbage-in, garbage-out.

Thanks Danno. That all makes sense. I’ll look into O2 sensors. 
stat and new o ring are already ordered. 
When I’m doing the stat, I’m going to replace the pairs covers that have blind ended tubes on them with proper milled ally covers to remove the possibility of any leaks at those points. 

First 3 images are the Honda sensor and connector

Last image is what I’ve found on Amazon. 
Question is will the sensor fit the exhaust. The wiring connector looks perfect, even down to the wire colours 

Then there’s these with strange name / branding. But the similarities are startling. Both the original and this one have Japan written on them same font, same construction ( probe end aside )

Different connector but could attach the one from the original. 

Or maybe this is a better bet?

I suspect that all major makers and their suppliers are outsourcing production to 3rd parties. So you can pretty much pick any sensor, snip off connector and crimp on OEM connector and it should work fine. 

Try to find Denso if you can for its narrower body. I had some clearance issues with Bosch on a Toyota Supra where sensor had clearance issues with AC line. If there's room on VFR, then either should work fine.

I’ve gone for a Bosch universal for £46 delivered. Can return if no good. 
it has to fit here, so hopefully it’ll be ok

I bought a low mileage (3700 miles ) VFR800 2017 used sensor for £11 on eBay as a backup plan. 
Honda are taking the mick with their pricing. Unforgivable. 

DannoXYZ, 4/4/2021 at 10:02 PM

I suspect that all major makers and their suppliers are outsourcing production to 3rd parties. So you can pretty much pick any sensor, snip off connector and crimp on OEM connector and it should work fine. 

Try to find Denso if you can for its narrower body. I had some clearance issues with Bosch on a Toyota Supra where sensor had clearance issues with AC line. If there's room on VFR, then either should work fine.

I’ve fitted the used sensor and it’s a pretty tight fit. No fault codes. 
Don’t think the Bosch unit will fit. I’ll have to return it. 
I tested the warm up cycle again and the rads are definitely starting to get warm at temperatures below 70. I’m more convinced it’s the thermostat. I’ll definitely replace this when it arrives and update the thread if there is an improvement in mpg and warm up cycle. 

Good to hear. I would clean old sensor and keep it as a spare. 

5 hours ago, Bikespod

I’ve fitted the used sensor and it’s a pretty tight fit. No fault codes. 
Don’t think the Bosch unit will fit. I’ll have to return it. 
I tested the warm up cycle again and the rads are definitely starting to get warm at temperatures below 70. I’m more convinced it’s the thermostat. I’ll definitely replace this when it arrives and update the thread if there is an improvement in mpg and warm up cycle. 

Just check the temp gradients. The rads do heat up before the thermostat opens due the the coolant bypass circuit. You need to check the coolant path temps, if hose above right rad heats first then definitely thermostat. 

10 hours ago, Mohawk

Just check the temp gradients. The rads do heat up before the thermostat opens due the the coolant bypass circuit. You need to check the coolant path temps, if hose above right rad heats first then definitely thermostat. 

Thanks Mohawk. That is very useful information. I’ll double check the manual for the paths. 

Bosch universal is much bigger. It’s not going to fit. 

Any further updates?