Fuel Pressure

[Lex]

All,

 

I've gotten poor mileage from my V11 for some time, basically since it was anything but stock. One of the things that I kept coming back to was that my fuel pressure could be too high. The little lever on the right side of the gas tank where the return line is located has been bumped around a lot. I've done everything else (set the TPS, used many maps in my PC III, leaned out the maps, changed air filters, spark plugs, checked the sensors, etc) without much improvement.

 

My best tanks (did it twice) were ~37 MP (American) G. Both done on hot days on straight, flat roads with too much police presence to ride much over the speed limit. Virtually all other tanks were 32 to 33 MPG. I even ran through a tank with the "touring restrictors" removed from my Staintunes, no improvement. It was bit too loud for me but it did sound nice on the back roads.

 

Before anyone asks why an American cares about fuel mileage, I have three reasons. First; I'm thrifty (OK, cheap), I don't mind spending money but I hate to throw it away. Second; there are places I like to go were my max range of 150 miles per tank (130 to the fuel light, in 20 miles I start to sweat) just isn't enough. Third; I hate to see any more junk get put in the air than necessary.

 

To my point, I made a simple pressure tester to check my system. The good and bad news is that the adjuster lever only adjust over a very small range. Even spinning it 360 degrees didn't put the pressure out of the "3 Bar + or - 0.3 Bar stetting. Don't waste any time worrying about the lever, put it in the middle of the range and you will be fine.

 

Conclusion: I need a custom map for my PC III. It looks like I found a semi close place (~ 50 miles) with the tuning link software. I wanted to try all the other possibilities, I'd hate to pay for a map and find my bike had a mechanical problem and the map wasn't right work when it was fixed.

 

Lex

[Guest philbo]

All,

 

I've gotten poor mileage from my V11 for some time, basically since it was anything but stock. One of the things that I kept coming back to was that my fuel pressure could be too high. The little lever on the right side of the gas tank where the return line is located has been bumped around a lot. I've done everything else (set the TPS, used many maps in my PC III, leaned out the maps, changed air filters, spark plugs, checked the sensors, etc) without much improvement.

 

My best tanks (did it twice) were ~37 MP (American) G. Both done on hot days on straight, flat roads with too much police presence to ride much over the speed limit. Virtually all other tanks were 32 to 33 MPG. I even ran through a tank with the "touring restrictors" removed from my Staintunes, no improvement. It was bit too loud for me but it did sound nice on the back roads.

 

Before anyone asks why an American cares about fuel mileage, I have three reasons. First; I'm thrifty (OK, cheap), I don't mind spending money but I hate to throw it away. Second; there are places I like to go were my max range of 150 miles per tank (130 to the fuel light, in 20 miles I start to sweat) just isn't enough. Third; I hate to see any more junk get put in the air than necessary.

 

To my point, I made a simple pressure tester to check my system. The good and bad news is that the adjuster lever only adjust over a very small range. Even spinning it 360 degrees didn't put the pressure out of the "3 Bar + or - 0.3 Bar stetting. Don't waste any time worrying about the lever, put it in the middle of the range and you will be fine.

 

Conclusion: I need a custom map for my PC III. It looks like I found a semi close place (~ 50 miles) with the tuning link software. I wanted to try all the other possibilities, I'd hate to pay for a map and find my bike had a mechanical problem and the map wasn't right work when it was fixed.

 

Lex

54861[/snapback]

 

Since the day I've owned my bike I've got almost to the mile exactly 125 miles before the warning light goes on. It started out stock and now has the Staintunes, Stucch, FBF filter kit, PC-III and a custom map. It doesn't seem to make much difference where, when or how I ride it, that just what it works out at. Maybe that's as good as it gets and it's not worth chasing ...

 

Are other people getting better milage or is this pretty much the norm?

 

Cheers

 

Phil

[BrianG]

Sounds pretty normal to me..............

 

You could put it on the dyno and program in a 15:1 section through your typical cruising RPM at partial throttle, but you might expect a bit of a flat spot there at WOT.

 

When I messed with my PCIII on the dyno, I didn't see the FULL-RICH (12:1) @ WOT that I've come to expect from a multi-dimensional EFI map.

[Lex]

Sounds pretty normal to me..............

 

You could put it on the dyno and program in a 15:1 section through your typical cruising RPM at partial throttle, but you might expect a bit of a flat spot there at WOT. 

 

When I messed with my PCIII on the dyno, I didn't see the FULL-RICH (12:1) @ WOT that I've come to expect from a multi-dimensional EFI map.

54897[/snapback]

 

Brian,

 

I haven't had the bike on a dyno or used a sniffer yet but I have trouble believing the mufflers being covered with black deposits of unburned fuel is normal, even for what Todd E. call "A fuel cooled" engine. The touring restrictors in my muffler look like they came out of a two-stroke. A riding buddy even commented on smelling fuel following me down a twisty road.

 

I understand this is an old fashion, air cooled, two-valve hemi engine but it is strange the mileage would be this bad. Even my R100GS (mild tuning but short gearing, horrible aerodynamics, etc.) got in the high thirties in cruise mode. Just bumping compression to 9.5 to 1 got a friend's GS solidly in the forties in touring conditions. It gets a bit twilight zone-ish when my (admittedly modern engined) behemoth K1200LT almost never get below 45 MPG and my Goose struggles to go 2/3 as far on a gallon of fuel.

 

FWIW, a friend with an identical bike reports high thirties to low forties. I expect crappy mileage with the throttle open on a fast road but it should do better on a mellow ride. I think the signs point to very rich mixture at least at some point in the map. I'll know more when I get it on a dyno.

 

Lex

[jrt]

Have you leaned it out using the PCIII or the TPS? It seems to me (I'm guessing here) that there are two factors important for fuel delivery- pressure and time the injector is open. If you can't adjust the pressure, you should be able to turn down the time interval (?).

If I'm wrong or missing something, I'd like to know.

Also, I think comparing water-cooled to 'fuel-cooled' is not fair. You can lean-burn water cooled motors and get great mileage- heck, my Toyota Prius can get 40's even without the battery assist by burning lean.

[big J]

I believe injector pulse time is controlled by ecu function, this should be adjustable if you can get someone with access to weber/marellisoftware, maybe your local dealer. There should be a "fuel trim" or similar type function.

[Guest hogjockey]

Hey guys my heart bleeds for ya, Since I have had my bike i have not had better than 23 MPG before and after Mods. So gettin milage in the thirtys sounds awesome to me....

[richard100t]

My bikes mileage varies according to how I ride it. I get as low as in the 25 mpg range. The best I've ever gotten is in the low 40's. As gas gets closer to $3 a gallon I may start to worry about mileage but not yet. If you have poor mpg try filling it up, ride 100 miles on the highway at 65mph & fill it back up. Then see how much you used, it should be around 2 to 2.5 gallons. If its more than 3 gallons in 100 miles @ LEGAL freeway speeds somethings probably wrong.

[Lex]

Thanks for the interesting comments.

 

First, Hogjocky, either you run the big wide open on the autobahn or there is something very wrong. I'm not an expert on Guzzis but if I were you I'd either start going through the normal checks (TPS adjustment, TB sync, are the sensors sending good information, etc.) or find somebody who does know what they are doing and have them look things over. It may be that I am stuck with 33 MPG but 23 MPG is ridiculous.

 

jrt: I have played with leaning out the PC III a bit and the bike does respond with a little better mileage. The problem is the adjustments on the three buttons on the PC III are so gross that I start to get pinging if I go far enough to improve the mileage. I could also mess with the map but the number of possible adjustments (128 cells, if I counted right) makes that a very long trial and error process. I think the answer is a custom map, I don't think I have many more things to try. If I'm wrong I'll be out $200 and have a bike that runs better. If I'm right I'll have a bike that runs better and I can stop sweating when gas stops are 150 miles (or more) apart.

 

You are also right comparing the 'ol Goose to the modern wonder bike isn't fair. It just seems weird to take a bike that is as big as cars in some countries (my first trip to New Zealand I had a little 850 cc triple rent-a-car, it got better mileage than the Guzzi and was a blast on dirt roads ;-) when I need more range, the tanks are not that much different but the fat bike goes much farther on a fill.

 

Big J: I have the PC III to make adjustment to the pulse width to the injectors, I don't need to get into the ECU. Since my "local" dealer is 250 miles from here that is a good thing.

 

Richard100T: I have a loop I test on, it is about 100 miles and mix tight two laners, more open two laners and a fair amount of freeway. The weird thing is that the bike gets about the same mileage riding semi-aggressively on the back roads and on the flat, straight and boring. This makes me thing the bike is rich in the small throttle/ lower RPM part of the map and not to far off at big throttle openings and higher RPM. Again, I'm just guessing. The only thing that seems to improve the mileage is a hot day, my two 37 MPG tanks were both done on days where it was over 90 degrees F.

 

Again, thanks for the input. Looks like I'll be making an appointment with the tuning link shop tomorrow. I'll let you know how it goes.

 

Lex