I just installed a thunderheader on my 2007 fxdb runs great (big horse power gain) with no power commander or similar device. Do i really need one??

 

huh... wonder how it cold make more power by not taking in more air... weird... if you do just pipes no tuner is needed. if you do stage 1 to get the most out of that pipe, you will need tuner

 

Your bike runs lean (14.7 to 1). The EPA (Tree Hugger) says that that is the optimum air/fuel ration so that all of the fuel is burned in the cylinders. You don’t want to go higher than that by adding more air.

Since you only put pipes on, more air can leave your cylinders but it can’t get in. You’re ok.

Conversely, if you put a high volume air cleaner system but didn’t get new pipes, more air would get into your cylinders but it couldn’t get out.

In either case, you don’t need a Power Commander and you won’t see a noticeable increase in power.

If you get a high volume air cleaner system in addition to your pipes, you’ll let more air in AND more are out. That’s when you’ll need the Power Commander because your bike will run too lean and ruin the engine.

I hope this helps.

 

Your logic is a little misleading. 14.7:1 a/f is only during idle and crusing. If you ran that lean under much load or wide open throttle the engine would'nt last long at all. When the computer senses load it richens the mixture probably closer to 12.5:1 in stock form. Closed loop systems "SHOULD" be able to adapt to intake and exhaust mods, and I've read that the 07 and up systems are much better at doing that, but I haven't seen any proof in the form of dynos run on a stock ECU with exhaust and intake upgrades. Bottom line is it is better to err on the side of caution. Either get it dynoed to check the a/f or get something to richen up the mixture.

 

why does a dyno run show afr through the rpm's at around 14.7:1 and not dip to 12.5:1 then? It is a wide open run.

 

It shouldn't

 

so dyno a stock bike and the afr is what people are striving for when they dial in their stage 1?

 

Not sure I'm understanding your question, but I've heard rumors that stage 1 download on 07 and ups don't even add fuel because the computer has gotten better at compensating. It's hard to get solid info on harley's eec program though. As someone who has tuned cars for years I couldn't get anybody at the dealership that could explain what exactly was changed in the download except for the rev limiter.

 

well i guess I mean to say, why is everyone reporting that the bikes are lean from the factory... People tune their bikes to get to the 13.2:1 ratio or thereabouts... from those dyno sheets, your showing us that the stock bike is already there. What do xied's/ tuners change then? AFR at idle and when your on steady throttle? Guess I got confused about this.

 

"Lean from the factory" is more than likely related to closed loop a/f. The older bikes didn't have to run at 14.7:1 during idle and cruise, so they didn't have the heat issues. XIEDS's fake the signal from the o2's and richen it up during closed loop (idle and cruise). This should help with most of the heat issues. They do next to nothing in open loop though. I say "next to nothing" becuase they may contribute to some of the adaptive learning the computer applies back during open loop.

As far as tuners, it depends on which one. SERT and PC can modify several tables to control open loop fuel along with a mutlitude of other paramaters.

Tuners like TFI intercept the signal going to the injector and add fuel before it gets there.

Fuel Pak? I have no idea how it works, and appearantly V&H is pretty tight lipped about it so I don't think many other people know either.