Ducati.ms - The Ultimate Ducati Forum banner
  • Hey Everyone! Enter your bike HERE to be a part of this months Bike of the Month Challenge!
1 - 17 of 17 Posts

·
Registered
Joined
·
209 Posts
Discussion Starter · #1 ·
Hello everyone,

I have a '95 916 that I ride pretty much every day. It's a beautiful bike that feels amazing to ride, and even though I don't have any previous experience with any other Ducatis to compare it to, everything feels OK with this bike.

So here's my concern, kind of: I'm getting an average of 10.5 km/l. Which would translate to about 25 mpg or so, no?

From a FULL tank I see around 78 miles until the light is on.

Is this mileage about right? I can't complain, the bike is amazing and never did I have fuel economy as an argument to buy it, but the number seems a tad low, and I worry that this could act as a symptom of something else.

Some context to better judge my situation:

-Trips are usually short, around 4 miles each way.
-Temperatures are pretty low, around 48F average, never much above 60F.
-Cross winds are common (35mph or so is not rare)
-Fuel is 93 octanes chilean...the lowest number here.
-New fuel filter and lines are installed.
-Air filter was installed by the previous owner inside the airbox, covering the trumpets. It's completely rubbish, but luckily I've just received some stock air screens that I will install instead of this.
-New sparkplugs; old ones were black (but who know how long they were there).
-Riding pace is always "happy".


Reading this list, I know to expect dccreased fuel economy, I know, but this thing almost eats more fuel than my car!

Thanks :)
 

·
Registered
Joined
·
5,164 Posts
Something's not right; My 916, which has been tuned to give around 15% power increase, even riding hard will go 110 - 120 miles to light on, which is around 35-40 (Imperial) or 30 - 35 (US) mpg.

On a steady highway run it will easily do 45 (Imperial) or 38 (US) mpg.
 

·
Registered
Joined
·
588 Posts
Yeah, something's not right. My 95 916 regularly goes to 110 miles til low fuel light comes on.

The bike has high compression pistons, big Arrow exaust, performance chip and madduc filter pods.

The worst mileage ever was riding at the Dragon (very happy speeds) and the light came on at 85 miles.

Start at the beginning and go through everything. These bikes aren't that complicated.

Good luck.
 

·
Registered
Joined
·
940 Posts
Definitely something wrong. I see anywhere from 40-50 mpg on my '95 with slip ons, custom map, degreed cams and stock gearing.
 

·
Registered
Joined
·
209 Posts
Discussion Starter · #5 ·
Damn, seems like I was right to worry.

I'll get on it. Any specific tips or things to look for that a new owner might not know about?
 

·
Registered
Joined
·
940 Posts
It sounds like you don't have allot of the bike's history.

I'd check the gearing to see whether it is stock or geared down. Aggressive gearing down could easily account for the poor fuel economy.

When was the last time the bike was serviced? Out of balance throttle bodies, coupled with out of spec valve clearances, and the crappy air filter together could also reduce fuel economy.
 

·
Old Wizard
Joined
·
3,006 Posts
Your fuel mileage is reduced because the computer is adding fuel until the coolant temperature is over 150°F, so on most cool days, and given your short rides, the coolant doesn't get up to temperature. The computer also adds fuel based on the air temperature because cooler air holds more air molecules and more fuel is needed to compensate. Black plugs means that the above factors are placing you in a continuous rich fuel mixture condition. A dirty air filter will also make things worse.

As it turns out, the '95 916 P8 ECU has a fuel trimmer. (The 916 biposto is different).

On these ECUs there is an external screw adjuster located next to the 35 pin harness connector. This is usually under a grey plastic cap which can be removed for access. The screw adjuster has a range of four turns, or plus/minus two turns. The default position is in the middle of the range. When you screw the adjuster clockwise the mixture is richened. The adjuster has no end stop, so if you over-adjust the screw the trimmer just rolls over at the maximum or minimum setting, without damaging the trimmer. Each time the trimmer rolls over a tiny click is just audible.

To set the default position, all you need to do is turn the screw clockwise five times, and listen for the tiny click when the trimmer rolls over. Note the position of the screwdriver blade, and then turn counterclockwise for two turns. The trimmer is now in the default position.

Try moving the current trimmer position an 1/8th of a turn at a time to lean out your fueling. Go too far and you'll experience some starting and idling issues. Monitor your tailpipe color to see the effect.
 

·
Registered
Joined
·
1,008 Posts
I wonder if the coolant temperature sendor is working properly? Perhaps it always thinks the bike is cold and is running way too rich at normal temps. Not sure if fiddling with the P8 will completely rectify this if the sensor is bad.
 

·
Registered
Joined
·
209 Posts
Discussion Starter · #9 ·
It sounds like you don't have allot of the bike's history.

I'd check the gearing to see whether it is stock or geared down. Aggressive gearing down could easily account for the poor fuel economy.

When was the last time the bike was serviced? Out of balance throttle bodies, coupled with out of spec valve clearances, and the crappy air filter together could also reduce fuel economy.
Well, you are right. This bike comes with a funny story, in fact:

PO tells me the bike has always been maintained at a Ducati shop, and that its last service (belts, valves, etc. with new tires) was a little under 2k miles ago, and that he has the records.

When we received the bike, it had a stuck tachometer and the tires looked old. I checked their code, and they were from 1999!!! But everything else checked out ok, so we decided to ride it a little before changing belts and everything..

And last week I received the owner manual, which had got lost on the way from the US somehow. It includes records, and indeed the last full service was at 10xxx miles (bought the bike with 12000 now around 13500), but that last service was 12 YEARS AGO!

Way to feel stupid about not asking the right questions. Sometimes omissions are worse than lies. So, belts have been changed, same with filters and lines. And this fuel economy issue is just part of the lists of things I suddenly realize NEED TO BE DONE.

Valves and gearing are within spec. Throttle bodies will be checked, and air filter will be changed. Even if not for all, I'm sure this crappy air filter accounts for something...

Your fuel mileage is reduced because the computer is adding fuel until the coolant temperature is over 150°F, so on most cool days, and given your short rides, the coolant doesn't get up to temperature. The computer also adds fuel based on the air temperature because cooler air holds more air molecules and more fuel is needed to compensate. Black plugs means that the above factors are placing you in a continuous rich fuel mixture condition. A dirty air filter will also make things worse.

As it turns out, the '95 916 P8 ECU has a fuel trimmer. (The 916 biposto is different).

On these ECUs there is an external screw adjuster located next to the 35 pin harness connector. This is usually under a grey plastic cap which can be removed for access. The screw adjuster has a range of four turns, or plus/minus two turns. The default position is in the middle of the range. When you screw the adjuster clockwise the mixture is richened. The adjuster has no end stop, so if you over-adjust the screw the trimmer just rolls over at the maximum or minimum setting, without damaging the trimmer. Each time the trimmer rolls over a tiny click is just audible.

To set the default position, all you need to do is turn the screw clockwise five times, and listen for the tiny click when the trimmer rolls over. Note the position of the screwdriver blade, and then turn counterclockwise for two turns. The trimmer is now in the default position.

Try moving the current trimmer position an 1/8th of a turn at a time to lean out your fueling. Go too far and you'll experience some starting and idling issues. Monitor your tailpipe color to see the effect.
GREAT!! This seems like EXACTLY what's going on with my bike.

Will check everything ASAP.

Thanks so much, once again
 

·
Registered
Joined
·
209 Posts
Discussion Starter · #10 ·
I wonder if the coolant temperature sendor is working properly? Perhaps it always thinks the bike is cold and is running way too rich at normal temps. Not sure if fiddling with the P8 will completely rectify this if the sensor is bad.
I could be mistaken, but I feel the sensor is working. The bike seems to react to the temperature change in a manner that feels right, compared to other bikes I've ridden in this temperature.
 

·
Registered
Joined
·
209 Posts
Discussion Starter · #12 ·
Gas should be around 0.6-0.7 litres per 10kms.
If youre experiencing over 1 liter and it still runs ok, not all is getting into the engine, imo.
Are you implying that I should not leave the bike at my father's garage anymore, as he is stealing my gas?

More seriously, could you please elaborate? What worries me about your post is that it DOES run ok. I guess it could run a little smoother, but I use the word "guess" to mean that I'm quite content with the power delivery; everything feels pretty much right, and the only thing that started to bug me is the mpg number. I guess it could be "more perfect", but until I started thinking about mpg, the bike feels right.

I took a look at the pipes, and sure they are pretty black on the inside. I feel I am definitely running rich, but my question is the following:

If the bike feels right, can I assume the TB and TPS are fairly on tune, and simply fiddle with the fuel trim screw to lean the mix a bit? Is it safe to do it this way?

I ask because to balance TB I would have to fabricate or buy some tools, and I'd like to do it all the right way, and if fiddling with the fuel trim will risk this -albeit imperfect- balance, I prefer to wait until I have everything before touching anything.

Thanks so much!
 

·
Senior Narcissista
Joined
·
5,737 Posts
To have that kind of mileage it would be rich to the extent of blurring, or very close to atleast. Im thinking maybe it leaks?

Under 10:1 afr it will start running uneven, have a friend run after you if its pig rich you can smell it.

You can try the adjuster screw nothing bad will happen, it just adds a fixed amount of opening time to what the ecu figured out by the mapping, +/- 200ms at whatever the opening time already is, 2ms to 12ms, so it (obviously) will have the most impact at short openings and very little on long.

And a note on stealing fuel. A friend bought a new car, and another friend had access to the garage aswell as the keys to the car, so each day he had ridden his new car the other guy would check the milage and add gas in it, for a good month. The car owner was so thrilled about how little gas the new garage queen was pulling and bragged hard about it, then they stopped filling it...
 

·
Idiot Savant
Joined
·
1,187 Posts
After your bike warms up does the exhaust still smell like gas?
If so you are running too rich. Granted, it has to be WAY off the mark for you to smell it.

Either way, I'm betting on clogged injectors. An uneven spray means a poor burn which means perfectly good gas is being flushed down the tubes, literally.

Best of luck finding the cause.
 

·
Registered
Joined
·
133 Posts
I think that the length of your trips and that you live in a climate that is completely devoid of heat are likely all or a big part of the high fuel use. Punta Arenas summers have temperatures that are about the same as Seattle in November. Spring there (now), is about the same as Seattle or Ashville N.C. in the dead of winter. You warm up the bike for three minute and ride for another 7 minutes (to go 4 miles) it is going to have bad mileage (not to mention the fact as has been previosly noted, it will run fat due to the low temps). I would be more concerned about having future children after riding in that climate for too long (cross country ski breifs provide good protection). Maybe others can chime in on their mileage in the cold, but I don't bother checking because I know it's bad.
 

·
Registered
Joined
·
209 Posts
Discussion Starter · #17 ·
To have that kind of mileage it would be rich to the extent of blurring, or very close to atleast. Im thinking maybe it leaks?

Under 10:1 afr it will start running uneven, have a friend run after you if its pig rich you can smell it.

You can try the adjuster screw nothing bad will happen, it just adds a fixed amount of opening time to what the ecu figured out by the mapping, +/- 200ms at whatever the opening time already is, 2ms to 12ms, so it (obviously) will have the most impact at short openings and very little on long.

And a note on stealing fuel. A friend bought a new car, and another friend had access to the garage aswell as the keys to the car, so each day he had ridden his new car the other guy would check the milage and add gas in it, for a good month. The car owner was so thrilled about how little gas the new garage queen was pulling and bragged hard about it, then they stopped filling it...
So, today I got a chance to work on the bike. I checked thoroughly and there are no fuel leaks, and the bike has been staying at my house, so no suspicions about my father :D That's a pretty cruel story on the car guy, by the way! haha


After your bike warms up does the exhaust still smell like gas?
If so you are running too rich. Granted, it has to be WAY off the mark for you to smell it.

Either way, I'm betting on clogged injectors. An uneven spray means a poor burn which means perfectly good gas is being flushed down the tubes, literally.

Best of luck finding the cause.
Thanks. It doesn't seem to smell like gas after warming it up properly...but the exhaust IS pretty black!

I guess some injector cleaner wouldn't hurt my case, I'll look into that.

Did anyone catch that his trips are on 4 miles each way?
I think that the length of your trips and that you live in a climate that is completely devoid of heat are likely all or a big part of the high fuel use. Punta Arenas summers have temperatures that are about the same as Seattle in November. Spring there (now), is about the same as Seattle or Ashville N.C. in the dead of winter. You warm up the bike for three minute and ride for another 7 minutes (to go 4 miles) it is going to have bad mileage (not to mention the fact as has been previosly noted, it will run fat due to the low temps). I would be more concerned about having future children after riding in that climate for too long (cross country ski breifs provide good protection). Maybe others can chime in on their mileage in the cold, but I don't bother checking because I know it's bad.
haha thanks Montanan, you just described this weather perfectly. A few weeks ago I even got some light snow...in november (!!?!?). It's a pretty unwelcoming climate, that's for sure.

I already have a son, so I'm settled for now, by the way.

Anyway, I had the chance to change the crappy air filter with OEM filters. I went for a short ride and the difference is NOTICEABLE! Throttle instantly got smoother from the bottom of the rev range, and it feels a LOT less "twitchy". I was expecting some change, but I'm amazed by the difference. Seems like that damn filter was as bad as it looked.

I wanted to play with the trimmer screw, but just couldn't figure out how to get the protection plug out without risking breaking something. I was expecting a rubber cap, but it's a pretty sealed rubber plug :( Any tips?

I guess I'll have to measure mileage now with the change in air filter. I am expecting at least a little difference, as it certainly rides better. And, I guess Montanan (and my father) is right, and in this context I just can't expect decent mileage, given that I don't seem to have leaks and the bike feels GREAT to ride (even better now).

I'll just relax and get on with due maintenance (tb sync, tps reset, etc.). It's really fun working on this bike.

Thank you all so much

Nico
 
1 - 17 of 17 Posts
Top