What might cause poor fuel consumption, Norge

[Brian UK]

When I got my Norge last August, I was getting a readout of 46mpg (US) average.
Then it went in for a service. Since I have almost never got it over 36mpg average.
Last weekend I went to the Pioneer run in Brighton, and came back on the motorway, steady 70mph, no hard accelleration etc, and a flat road too. Average was 35.6. Ambient temperature 13 celsius/55 farenheit. Two up, but both of us are lightweights.

Now the plugs do look quite dark, and the exhaust has black soot in it, so I think it runs a bit rich now.
Have been back to dealer, who installed new map, and checked all the settings. For a short time it was better, but no longer.

I now have VDSTS, and have checked settings on that, but all seems correct. Also checked balance with a vacuum guage, again OK.
The engine temp sensor is bedded in heat conducting mastic, and I have also checked the resistance against temp, and it tracks OK.

So, my learned friends, what else can I check?

 

[londonrob]

Take it out late one night, find an empty motorway, and thrash the nuts off it.
When i first got my B11 its previous owner kept to the speed limits and consequently it ran a bit rough.
A regular dose of throttle does them a world of good.
Just watch out for cameras....and police helicopters.
If you have checked everything and it all is ok, it might just need a blast to clear the crap out of the engine.

 

[john zibell]

Brian,

55 degrees F is still a bit cool for these engines. They won't get good mileage until over 75 degrees F. That said, try making the trim more negative. You can do that with the VDSTS. At first go 20 points at a time, then reduce to 10-15 until it is where you want it.

These engines should be clean burning. Have you checked air filter and Lambda operation? You can view lambda volts with the VDSTS (there is a channel you can select for that). It should be changing rapidly.

 

[Brian UK]

Thanks for that John.
The Lambda operation was checked on Axone when the new map was installed. Bike has only done 4500 miles, and the air filter looks as new still. However, the one thing which did happen at the service was that the oil was overfilled, I drained about 100 ml out of the air box drain, and another 600 ml from the sump to get it to the right level. (it was 15mm above the full mark with the dip stick NOT screwed in). So maybe that oil has partially blocked the filter, though the breather parts are all downstream of the filter.
Does the trim on VDSTS control the whole range, or just the closed loop bit do you know?
But I will try that bit by bit.
It also seems things are not quite as bad as I thought, when i filled up - 200 miles from full to light coming on, I put in 19.5 litres, which equates to avout 42 mpg (US)
But I reset the trip when I filled up, and a few miles later it showed 46 mpg average. Went out again last night, and sure enough it's down to 36 again.
So some of the problem is the computer giving inconsistent readings.

 

[draidt]

I generally don't pay too much attention to the bike's MPG calculations, but what John Z says is correct for my Norge as far as being a temperature sensitive beast. I consider it broken in now and ran it hard yesterday for almost 300 miles in varying conditions some twisties, some interstate blasting at 75+ with head and crosswinds and some about town stop and go. left with a full tank filled it twice at the midpoint and when I got home for the first time I averaged above 45 MPG this was at 80+ degree temps. If it was 65 or below I bet it would have barely broke above 35 MPG. As far as the plugs looking black I believe I would take the trouble and bother and look at the filter and air box. The bike's calculations were 2-3 MPG too low.

 

[ncassidy]

The mpg reading on the computer will change as your driving. Depends on whether your horsing the bike or not. Best thing to do is a manual mpg test to find out what your actually getting. Driving around town the mpg will be not so great according to the computer. Get it out on the open road at a constant speed of say 70 mph and the computer should read somewhere in the low forties mpg.

 

[Chuck in Indiana]

From what I've read, and my experience, the bike computer will be around 3 mpg lower than actual.

 

[NeroGuzzi]

Mine usually reads 4-5 mpg below actual.

 

[Joe breva1100]

NeroGuzzi wrote:

Mine usually reads 4-5 mpg below actual.

Mine too.

If your Breva is still no better try changing the plugs, inner one too.

I've had my B11 from new and I'm now up to 26,000 miles. I did'nt change the inner plugs until it had done more than 20,000 because NKG regards them as being long life premium items. But when I did change them boy did it make a difference to how the bike ran, much smoother and beter fuel consuption.

I'll be doing them every other service from now on.

 

[Holt]

Don't forget to check your driving habits as well.

You might feel a bit more - well, confident - with the bike after a year on the road. :laugh:

What John Z said also! I remember from my childhood when motorcycles actually were used for commercial use, that the drivers would put chardboard shields in front of the cylinders to keep a decent motor temperature. Air cooled motors can be a bit difficult to regulate.
I don't know, since I'm a smallblock man, if there's a thermostate in the oil-cooler line, or if it's possible to place one, but if; it might be a way to obtain a more even motor temperature?

 

[RJVB]

I've had a similar thing on mine, in october last year or so. Belated 20k km service. Of course there had been a temperature drop between the time I brought it in and I got it out, but they'd also done a thorough bit of work: install of the upgraded rearshock the "official way" (from above, requires to remove the ABS and all).
I had significantly higher consumption for a few 100 km, until I gunned her good a couple of times (that's what toll stations are great for )

Anyway, no one has yet mentioned the engine temperature sensor. Check (or have checked) that it has good thermal contact with the engine, and if necessary, put in some thermal (heat-conducting) paste. That's a simple remedy against a number of ailments.

 

[Brian UK]

RJVB wrote:

Anyway, no one has yet mentioned the engine temperature sensor. Check (or have checked) that it has good thermal contact with the engine, and if necessary, put in some thermal (heat-conducting) paste. That's a simple remedy against a number of ailments.

I did,
The engine temp sensor is bedded in heat conducting mastic, and I have also checked the resistance against temp, and it tracks OK.

Has anyone noticed how the on board average fuel reading goes down drastically if the bike is left at tickover, but stationary? It's as if it thinks, fuel being used, but speed zero, so fuel consumption in MPG must be infinite. I think that's what causes the inaccurate reading.
Haven't had a fiddle with VDSTS yet, as I was in France for the weekend, though not with the Guzzi.

 

[NPS]

I have a breva 1100 and have now done about 12k miles over the last 18 months.

Mine has the addition of a Bosch wide-band lambda from which I monitor the air fuel ratio in real time while a second signal mimics the original narrow band lambda to the ECU.

My experiance is that my bike runs rich most of the time. It is meant to run from the feedback of the lambda when hot enough ( never in winter but after 10 mins from start up in summer). The air fuel ratio then ocsllates around 14.7 for the benefit of the catalyst to work properly. When you open the throttle quickly it uses the map and on mine that means between 11 to 12 to 1 air fuel ratio. My engine bulks at this on the motorway where anything over about 45% throttle opening makes it run off the fuel map and far to rich. It hessitates every 10 seconds or so as presumably the plugs foul or the combustion conditions are far from ideal. The exhaust is always sooty.

A change of air filter makes no difference and the bike is completely standard otherwise. My fuel trim is running about -25 but perhaps I should try some different settings.

I would be grateful for anyone else who has experimented with the fuel trim and what values they are using. I susspect that my particular problem is down to either the pressure sensor not correctly calibrated or perhaps even the ECU not correctly optimised for a range of operating conditions and transducer reading tollerances.

Sorry for any spellings mistakes
Nigel

 

[RJVB]

A friend just discovered the reason for the high consumption on his V11, when all of a sudden he no longer had a rear brake. Pads must have dragged, causing the whole rear brake system to overheat (up to and including the switch that controls the brake light?!)

 

[john zibell]

Nigel,

Since you pipe is sooty, go more negative on the trim. I'm running about -65 on my 1100 Breva and she is doing well. 48-50 mpg in warm weather (75 F / 24 C and higher), and no soot in the pipe. Also don't forget thermal mastic under the engine temperature sensor.

 

[RJVB]

Brian: ever watched the instantaneous consumption read-out while pushing the bike backwards with the engine idling? Here the value (in liters per 100km) indeed goes towards infinity, as one would expect (well, with the bike stationnary).

However, this weekend I had my needle go below the 1/8 full mark and the reserve light come on, only to see the needle go up to 1/4 full and the light off a bit later during the ride. This annoyed me a bit because usually the reserve light has been reliable ... but at least the dashboard showed it wasn't *that* stupid (i.e. it clearly knows liters don't reappear in the tank while riding) ^^

 

[Brian UK]

Well, since I had an empty tank yesterday, I removed it to check the intake air temp sensor. It was working fine of couse, but while I was there, decided to look again at the air filter.
The bike has done only 5k miles, so it looks clean, but just to be sure (hadn't got a spare to hand) I washed it in a bath of paint thinners (acetone), and dried it very thoroughly afterwards. The acetone did turn yellow.
Filled the tank and off, and the fuel consumption average is now showing 39 mpg, as against the 34 mpg previously. I did reset the trip.
So had the overfilling of the sump clogged the filter with oil? Only a new filter will prove the point which is the next thing to do.
Teach me to check the bleeding obvious first.:angry:

 

[RJVB]

That's not really a significant difference, I think - could be wind, could be ambiant temperature that make you get 39 or 34 mpg.

How's your idle? Maybe you "simply" have an issue with your TPS (if the TPS voltage can get off, that suggests there's a component that could fail though I have no idea what that could be).

 

[Geordie]

RJVB wrote:

That's not really a significant difference, I think - could be wind, could be ambiant temperature that make you get 39 or 34 mpg..

It's ~15%!

 

[Brian UK]

The point is it got very abruptly worse immediately after the service. So either something suddenly failed to work properly, or something in the service affected things.
I have also ahd a new fuel map installed in the mean time, and have no idea what effect that might have had.
I do know that the air box had a large amount of oil in it shortly after the service, due to the sump being overfilled.
Also the temp last night was from 14 down to 10 degrees celcius, which is lower than the previous ride so if it was down to temp, I would have expected the fuel consumption to be worse.
I now need to have a trip on a warm day just to see what happens, and to put a new filter in.
15% in the right direction is a good start as far as I am concerned. And I know the real, or true figure will probably be better still.