Maybe your calculations for you mpg are off slightly?

 

Thanks for the link Kevin. Can always count on you for all the best info!

 

HD sells engines that run lean. This is a known fact. They do it to meet EPA standards and to be able to show better MPG numbers to the customer. If you do something with the intake, exhaust, map,... that increases the MPG how is the engine doing anything but running leaner? And how is this a good thing. A lean running engine runs hotter and wears out faster.


With an air cooled engine you are pretty much limited in ways to get it to run cooler. You can wire up an attic fan to blow air through the cylinder fins. You can shroud the engine with well designed air intakes and exits to improve air flow through the cylinder fins. Or you can adjust the tune to run at richer AFRs. The last is the most common method used on these engines. Run richer AFRs and you use more fuel. Use more fuel and you get lower MPGs.


Personally, if I were to see an increase in my MPG numbers rather than feeling good about my wallet, I'd be wanting to know why my engine has started running leaner and see what I could do to correct it. I would rather spend a bit more for fuel and have a cooler, longer lasting engine than save a few pennies at the pump.

 

In all my yrs of reading in here its not unusual for for Fuel Pacs to lower your bikes gas mileage. I've read in here that a lot of other members who had the FP has gotten less fuel mileage after they installed one.

The older F-Pacs also do not Re-map the Engine,, it only changes the amount of fuel added. to prevent your engine from running too lean.

The newer FP-3's I think does change some engine and fuel adjustments, but I don't know how many or how much.

 

DK does provide good information. I for one really appreciate a vendor who shares his knowledge with us, not necessarily looking for a sale, just helping fellow enthusiasts. That's the vendors I go to when I need items.

That said when I was new to the twin cam world I bought a PCIII from Fuel Moto, free tune, and cheaper than buying from dynojet direct. I was super happy with their customer service.

I noticed that the fuel map just adds fuel and I downloaded a similar map for my mods from Dynojet, and it added fuel as well.

When you add fuel you get less gas mileage. Pretty much how it works. OP try going back to stock tune and see if you get your mileage back. I bet you will.

I didn't notice any performance gain so I took it off. I recently put it back on and reduced fuel in the reversion area as I have open pipes (with thumbscrews). I've noted a slight increase in fuel mileage by taking out fuel in the reversion zone and I feel like I have a little more power by adding the fuel fuel moto did in the WOT areas. I'm always a fan of running kind of rich at WOT it's better for the pistons.

 

My micro tuner from fuel moto is great for my riding purpous albeit at the expense of a few drops of fuel per mile under normal circumstances.
Wide open roads allow me to cruise at a normal pace.
It's when congested rowds that I need to get ahead and that's where milege drops. But it's a pissa flyin past cagers that think they own the road

 

As noted, the bikes come from the factory running lean for emissions, and choked down in the exhaust for sound laws. They are also running very hot, again, for emissions.

There are many inefficiencies here-

1. The exhaust is so blocked up, the engine is constantly fighting against it. This means energy that the engine is producing to get the exhaust past all the baffling is eating gas that could be used to propel the bike forward. (which would give it better MPG)

2. The lean tune is causing low speed stumbling and poor acceleration. Many riders will then twist the throttle more to get the acceleration they want, but while twisting the throttle more to get more acceleration, it is using far more gas to get it moving than it would if it were running properly (even thought it is a lean tune)...another MPG dropper.

3. Cool air intake is something that all performance oriented cars and motorcycles need to run most efficiently. Cool air, combined with gasoline will produce much more power than hot air and gasoline. Cool air is denser, containing more oxygen, than hot air. It is oxygen and gasoline that produces power. The hotter the engine is, the hotter the intake air temperature is. Plus, all stock air cleaners, and most "Stage I" air cleaners are feeding hot oily air into the intake. Another MPG dropper.

4. Since the tune is lean, the timing advanced, and other factors, like EPA friendly cams, the engine temperature is very hot. This is done on purpose for the EPA regs. The hotter the engine, the more complete the burn of the fuel, equaling less emission. Problem is, these engine start experiencing inefficiencies at around 270* (which is a low typical since 2007, even for the waterheads). Metal expanding at unequal rates result in less compression, which results in less power for fuel used. Another MPG dropper.

There are other factors than above, and there is much more detail to the above, but that is a good snap-shot of the problems of the stock bikes in regards to power, MPG and engine longevity.

A good Stage I Upgrade will address all of these issues. The majority of Stage I Kits do Not do a good job of addressing these issues.

One popular example-

Exhaust. Many want louder exhaust, and in choosing a louder slip-on, they will get the sound they want, and the slip-on unplugs the stopped up baffling. But a new power robbing, mpg dropping issue pops up. The exhaust is so open that there is now a lot of reversion occurring. This is where the exhaust energy pulse hits the end of the pipe and some of that energy reverses direction, heading back up the exhaust tract. This slows down the exit of the exhaust gasses, and reduced the fill of the cylinder.

This results in a drop in power, which results in more throttle twisting, which results in a big MPG robber.

There are a lot more details, but I feel I may have already started to bore many.

Bottom Line is, most "Stage I" upgrades do NOT properly address the above issues.

A Good Stage I addresses all of the above issues, and when a good Stage I is used, there will be More power than stock, there will be Better MPG, and the engine will run cooler and last longer.

 

I may have screwed up the milage between fillups. I am rechecking as we speak.

 

I keep track of all mileage in a spreadsheet, and I've noticed that because our tanks are so small, .5 or even .25 gallon makes a big difference in mileage because the numerator isn't all that large at 150 miles or so. I try to fill it close to the neck each time (Don't overfill, it'll expand and dump on the ground) but it's not an exact science.

So on our bikes one tank of fuel is not a good measure, you need a larger sample size to see if things are really changing. I'd say 5 tanks is pretty good. Of course then you introduce the variable of different rides, highway vs around town...lol

 

Just to help simplify MPG AVERAGES I rely on, (my daily rides vary from one extreme to the other I get best MPG on long HWY iin non stop situations; worst in stop and go... Go figure LOL) though not heavily on my digi read outduring fills.
Understand that I have a 2" tank lift in front and 1" in back that I purchased through our good friends over at DKCustoms.

I did mod the back spacer and added an extra 1/2" so that the total out back is 1.5" and an even 2" at front, so I'm almost at the original speck by manufacturer design.
Gas prices are good ATM so it's awesome, so there's nothing to really complain about, unless like the OP and you're worried the bikes broke.

So an example... Use the trip to show you how much mileage the bikes computer estimates you will have till you're near empty or what ever zone you usually top off at. Mines between 30-60mpg The read out with a full tank is usually around 225mpg So I'm estimating that from 40mpg to 225mpg on a fill I'm getting somewhere near 175mp out of 4 gal. a fillthat= ABOUT 45mpg with a basic stage 1 install=