2011 FXDWG Exhaust
Outstanding HDF Member
Joined: Dec 2010
Posts: 2,036
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From: Temecula, CA
Robo,
This is good information to have. I was under the impression that the EFI on these bikes was more akin to the old school ROM based program (hence the need for a flash or download from the dealer). It sounds like the system has a closer resemblance to that of the modern day OBD-II automotive systems, wherein slight, yet progressive changes are made to the fueling and spark advance tables over the course of several hours of run time (RAM based program).
If I understand you correctly, the open loop tables are essentially interpolated or augmented from the data acquired while in closed loop operation. I would assume then that the download simply modifies the algorithm with which the fuel and spark advance values are derived from the (dynamic?) table.
As long as I am not doing irreparable damage by giving the ECM its due time to “recalibrate” itself, I can live with it.
Are we on the same page now, or am I way off base?
This is good information to have. I was under the impression that the EFI on these bikes was more akin to the old school ROM based program (hence the need for a flash or download from the dealer). It sounds like the system has a closer resemblance to that of the modern day OBD-II automotive systems, wherein slight, yet progressive changes are made to the fueling and spark advance tables over the course of several hours of run time (RAM based program).
If I understand you correctly, the open loop tables are essentially interpolated or augmented from the data acquired while in closed loop operation. I would assume then that the download simply modifies the algorithm with which the fuel and spark advance values are derived from the (dynamic?) table.
As long as I am not doing irreparable damage by giving the ECM its due time to “recalibrate” itself, I can live with it.
Are we on the same page now, or am I way off base?
Now, the ECM will look at the O2 readings and says that with F fuel the O2 reading should be Q. If it's richer than Q, then the ECM will note this and adjust F fuel by a certain amount to try and make what it thinks Q should be. Now it may be different for Harley's Delphi system, GM's Delphi system calls these tweaks in Closed Loop situations Short term Fuel Trims (SFT) and they are changing constantly as you drive based on the feedback the ECM gets from the O2s.
The ECM takes these SFT and uses them to determin fueling needs when the ECM enters Open Loop and starts ignorning the O2 sensors. In GMs Delphi systems these are called Long term Fuel Trim (LFT). When the ECM enters Open Loop, the fuel trim locks in at the LFT value. When we tune GMs, we tweak the base fuel table so that the SFTs adjustments are small and the LFT locks in as close to 0 as possible.
Now there are other things that adjust F fuel. Engine temp (for cold starting), Air Temp (hotter air is thinner air thus requires less fuel), and Barrametric pressure (for higher elevations the air is thinner thus needing less fuel) but unless modifications have been done that may have some affect on fueling needs under these conditions these tables are left alone.
Again, I've been told the Harley Delphi system opperates in a similar fashion but I don't know the details.
Last edited by Robotech; Apr 28, 2011 at 03:28 PM.
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Cruiser
Joined: Apr 2011
Posts: 184
Likes: 8
From: Georgia
Still great information to have. I understand the short term long term aspects. Thank you for the clarification. Very easy to digest. I believe it was Einstein who said that anyone could explain something to the right audience, but it takes true genius to explain something to any audience. Of course, I'm paraphrasing here.
It will be most useful to have a little more technical background on the EFI system when I speak with the dealer. I've always found it to be useful in negotiations when I know a bit more about the product (technical details anyway) than the salesman.
Anyways, I'm planning on heading in to the dealer on Friday afternoon... and hoping to come home with another Harley. Now, if only they had the 40% off merchandise deal that was going on when I bought the Nightster...
Thanks again for the explanation.
It will be most useful to have a little more technical background on the EFI system when I speak with the dealer. I've always found it to be useful in negotiations when I know a bit more about the product (technical details anyway) than the salesman.
Anyways, I'm planning on heading in to the dealer on Friday afternoon... and hoping to come home with another Harley. Now, if only they had the 40% off merchandise deal that was going on when I bought the Nightster...
Thanks again for the explanation.
Advanced
Joined: Apr 2011
Posts: 64
Likes: 1
From: Poughkeepsie, NY
I have a 3 week old 2011 FDXWG. The damn thing sounded like a lawn mower with the stock exhaust. I went with the V&H Big Radius 2 into 2 and love it. I also went with the stage 1 ac and SE super tuner. The Big Radius is not for the faint of heart, as others have said, its LOUD. Honestly, it sounds the way the bike should IMO. I love the sweeping look of the pipes, they match the curves of the 2010-2011 FDXWG very well. If you like your scoot to sound like it has some *****, go with the V&H Big Radius. Dont forget that you will have to get an ac and tune for it as you are making a considerable increase in airflow with that exhaust. I did mine with 230 miles on the clock, it was a MUST!!
Happy riding
Happy riding
Ultimate HDF Member
Joined: May 2008
Posts: 6,642
Likes: 48
From: Ogden, UT
I have a 3 week old 2011 FDXWG. The damn thing sounded like a lawn mower with the stock exhaust. I went with the V&H Big Radius 2 into 2 and love it. I also went with the stage 1 ac and SE super tuner. The Big Radius is not for the faint of heart, as others have said, its LOUD. Honestly, it sounds the way the bike should IMO. I love the sweeping look of the pipes, they match the curves of the 2010-2011 FDXWG very well. If you like your scoot to sound like it has some *****, go with the V&H Big Radius. Dont forget that you will have to get an ac and tune for it as you are making a considerable increase in airflow with that exhaust. I did mine with 230 miles on the clock, it was a MUST!!
Happy riding
Happy riding
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Cruiser
Joined: Apr 2011
Posts: 184
Likes: 8
From: Georgia
I completely and totally agree with the statement that changing only the exhaust does not significantly increase air flow. I would suspect that the effect on the air/fuel ratio would be negligible at best. I can't see that the volumetric efficiency of the engine would be adversely affected by changing only the exhaust path.
Going in tomorrow... coming home with a Sedona Orange or Vivid Black and flames Wide Glide. I probably have a week before the pipes will go on.
I did have a thought... does anyone know what the O2 sensors voltage output should be at 14.7:1? I could always check it that way. Maybe a before and after reading? It would be easy to set my Fluke for peak and hold and take a loop around the block. I could then change the exhaust and repeat. Then compare notes.
Going in tomorrow... coming home with a Sedona Orange or Vivid Black and flames Wide Glide. I probably have a week before the pipes will go on.
I did have a thought... does anyone know what the O2 sensors voltage output should be at 14.7:1? I could always check it that way. Maybe a before and after reading? It would be easy to set my Fluke for peak and hold and take a loop around the block. I could then change the exhaust and repeat. Then compare notes.
Cruiser
Joined: Oct 2010
Posts: 147
Likes: 0
Something else to consider. My 2011 FXDWG is Sudona Orange with black flames. I run a chrome thunderheader and a h-d heavy breather and a super tuner. It really, really rocks. It sound awesome. Has great bottom end and mid range torque but doesn't make the cops angry.
I have the same bike V&H staggered big shots SE tunner Highflow air, bike is fast sounds great, I'm on the throttle all the time never turned a LEO's head.
Last edited by Chris Creole; Sep 20, 2011 at 10:43 PM.
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