Serious question. I was running V&H Twin Slash Rounds with a stock head pipe, air cleaner, and mapping. Gas mileage was okay but I always thought it wasn't as good as when everything was stock. I even tried auto tuning with a FP3 and that was worse. This weekend, I put everything back to stock. Mufflers, pipes, air cleaner, mapping. Went on an all day ride with the group and the gas mileage was up considerably. I don't understand the connection between mufflers and gas mileage. Or, is there any connection at all? Just trying to figure out why my gas mileage is so much better stock.

 

Wow, there are really a bunch of questions in there.

Stock these bikes are mapped really lean so you would almost certainly get the best mileage when running a stock tune. It may or may not get better if you changed your air cleaner and mufflers without re-mapping, but beware. As things are running lean already further increasing air flow without increasing fuel could result in engine damage over the long haul. Long story short, when you changed the mapping and got it running right, you altered the mapping to give worse fuel mileage, but it should have been running at a lower temp and should have offered, at least, some performance boost.

in the end, you can tune strictly for mileage and emissions, or you can tune for max power, or you can tune for something in between. Autotune does not tune for the absolute best mileage and emissions. It should offer the best rideability. Smoother and cooler than the stock tune.

 

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First ,why didnt you simply tell us the actual mpg your bike was getting with the V&H mufflers etc and then when you went back to total stock setup?

So?

With that said restrictive stock mufflers can reduce fuel mileage but in your bikes case i'd bet it was returning back to stock lean fuel mapping that was most if not all of the reason mpg was significantly increased on your bike.

A person that's good at dyno tuning should have been able to give you good if not close to stock mpg with the V&H mufflers and a tuner of some sort.

Scott

 

another potential difference: are your "before" mileage numbers also from group riding? I tend to see 2 or 3 mpg improvement when riding in a group - I attribute it to the fact that I'm somewhat less "spirited" with the throttle in the middle of a group.

 

I think this indicates more that the "mapping" was incorrect.




generally a more open exhaust tract may increase MPG- with no other changes, but this is a very general statement and there are so many considerations and the result may be seen at very specific rpms- whether the machine is operated at those magic rpms is another question

mike

 

Muslims?
Oh mufflers. lololol.

 

That one went right over my head. :0( Not sure what you meant.

 

I don't think mufflers have anything to do it. I've switch from stock to the Fuel Moto micro tuner in the summer and nothing else (k&n air filter and oem mufflers) my mileage drops 2-3 mpg from averaging 39-40 to 36-37. I've tried free flowing mufflers to the oem and didn't see any noticeable difference in fuel mileage. As far as the oem's being restrictive, I have new oem pull offs on my 08 and they do much better than the original ones did. Feels like it has better torque. I very seldom ever go over half throttle. On a modified engine that runs wot I can see them being very restrictive.

 

more power takes means you're burning more fuel to make it...

but with these engines/ bikes, there are ton of factors that contribute to fuel mileage all of which you changed from from each "trial." A good and proper tune/map will be on par with stock fuel mileage maybe a few less since stock is lean (not good) and you're making a little more power when you add more fuel and open up the air flow and fiddle with the timing.

My bike gets 40+ mpg if I take it easy doing 60mph the whole time and I'm burning non-ethanol fuel. Sometimes especially in the winter mpg goes down to the low 30's. But generally I get 37-38 mpg riding pretty hard and 50/50 city/ highway driving.

 

It's the mapping. Going to get an fp3 put a tune on it give it more fuel. LOL