Originally Posted by Baggrmark

I guess I will maybe look into the PC III.Price doesn't seem to bad @ fuel moto,will I have to have it dynoed also if I go with the PCIII.

Originally Posted by Mr. Wizard

Hey Mark

Nice look'n 6 btw

Since you have already read many of the post about decel then you understand this is a gremlin that some can't shake. Since you already have duals then you've gotten rid of the one thing that causes the majority of decel pop IMO, the crossover pipe.

Other causes are not only leaks in the slip joints but leaks at the exhaust port and the intake port/throttle body too. To find these you warm up your bike and spray carburetor cleaner or WD40 around the intake connections. If you hear your motor rev up a little then there's a leak. This leak will lean out your fuel ratio. It's hard to find and you must be patient.

Another issue is air reverberation. This is when the sonic pulse of the exhaust comes back into the mufflers drawing air with it. This added air mixes with unburned fuel in the pipes then gets it's ignition source from the exhaust port spark....pop. This is more common with open pipes or baffles 2.0 or larger.

You can seal all of your slip on joints with Hi temp Copper RTV. Apply to the inside of the female joint about the thickness of a business card and as wide as a cigarette and about 3/4" just inside the joint. Slip the joint together and wait 24 hours before tightening. Don't cheat.

If your head gaskets weren't replaced when you converted to TD's then go ahead and replace them now when fixing the slip joints.

If this doesn't cure the decel pop you should look at adding fuel to your 0 to throttle position at the RPM's you get the pop at, normally starting at 1750 to 3500 RPM. Unfortunately the only way to do that is to purchase and install a fuel management system such as a PC, SEST or TTS. Note: the auto tune systems will require you to install 02 sensor bungs in your head pipes.

You also ask if your pop will simply go away. It is rare this will go away on a pre 02 sensor bike it's own but rest assured it will not hurt your motor, just your ego.

Originally Posted by malibuexpress44

Hello Mr. Wiz,
Much appreciated insight on this decel pop issue. I'm having a similar problem. Got a 2010 Fat Bob and just installed a heavy breather and 2 into 1 D&D exhaust. The decel is at basically the rpms you described and it's never there before the engine gets fully warmed up. I have a super tuner and wanted to ask if I were to adjust the AFR for those particular rpms do I do it across the MAP spectrum? If I'm at 14.6 where would you recommend starting?

Thanks very much for the advice!

Originally Posted by Mr. Wizard

Congrats on the '10 FB. The D&D sound is wonderful.

If your decel pop is not there when the motor is cold then the warm up enrichment is working properly, adding fuel until your motor is warm. When your motor warms up, these calibrations lean out as designed. When the motor gets too warm it richens up again to help cool the motor.

I will be taking for granted that you have had a Dyno tune or you did the manual Smart Tune to calibrate your VE tables. If you haven't calibrated your VE tables first then do so before any other adjustments are made. This is very important.

There are several ways to work out decel pop with the SEST. The two most common are the Decel Enleanment and the AFR Table.

Deceleration Enleanment straight out of the SEST Manual.

Decel exhaust popping is combustion occurring in the exhaust. Since combustion occurs over a narrow range of A/F ratios, popping can be cured by either richening or leaning the unburned mixture in the exhaust so it cannot combust.

Any changes made to the Decel Enleanment table increase or decrease the amount of fuel delivered while the Deceleration Enleanment mode is in effect.

• Use this Tuning Table to increase or decrease the fuel removed during a Deceleration event
so that it runs properly.

• If exhaust smells of fuel on throttle roll-off – increase the Decel Enleanment cells to increase the amount of fuel Enleanment. In other words, the higher the numbers in this table the less fuel, lower numbers = more fuel (richer)

AFR Table

You are dealing with a kPa (vacuum) not throttle position on your SEST map. You can increase the second column cells on the left (27 kPa) between 1750 and 3500 simply to see if the decel pop goes away. Drop these cell numbers a few tenths at a time until your decel pop goes away. Example... drop the cells from 14.6 to 14.4 then to 14.2. Lowering your cell numbers will take your red cells out of closed loop and the ECM will richen your mixture without 02 sensor intervention. (See Decel Enleanment information above)

Caution: Adjusting your 27 kPa tables will cause your fuel mileage to drop. Make small adjustments and only when necessary. Be sure to save your original map and each adjusted map by naming it in numerical order, saved in its own folder. This way you will have a back up in case something goes wrong.

Originally Posted by malibuexpress44

Thanks very much Mr. Wizard! It sounds as though these changes should be done subtly. Unfortunately I think I have been making changes that vary too wildly (Decel enleanment from .34 at 160 to .18 - still heard popping but only lower rpm. Then up to .68 - still popped but all through the rpm range (1500+)). I have used the smart tune to get the VE tables recalibrated. Still need to do some more of that but have taken 4 runs thus far and have 1/3 -1/2 of the table revised.

Because the popping isn't apparent when the engine is cold, should I assume that exhaust gasket/leak aren't the issue?

Thanks again - this is all a huge help!

Cody A

Originally Posted by Mr. Wizard

Cody

Assume...You know what hyphenated assume means. Seems if I loosen a screw on a bar switch the back wheel falls off. I assume that won't happen. Several years ago there was an interoffice memo sent to all concerning the word "Oops". It read; the word Oops would not be used anymore and is to be replace by the word "there". The memo was a NASA memo. I also assume they don't loosen bar switches.

Being a '10 bike I wouldn't think there would be an intake leak but with the installation of new 2-1, I would suspect an exhaust leak at the head until verified none existed. Hopefully you replaced the exhaust gaskets during the install and check torque on all four 1/2" nuts after 100 miles or so.

VE calibration... you will not be able to calibrate all cells. Get the ones you ride in for the most part and a portion of the WOT areas then call it a day. If your wish is to calibrate all areas then you would need a Dyno and several hours to touch all the cells. This is really not needed unless you race. The areas you will calibrate will look like a " \ "through the VE map table.

Decel Enleanment... Although I am aware of others hitting this table hard I don't believe that is good practice. Small changes are more effective than killing a fly with a shotgun, patience is key. I would suggest putting the DE back to the original and starting over. Remember 16C is about 60*F and 112C is about 233*F. Start with the 80C and adjust through 128C.

AFR Table... If you have no luck with the DE then go to the AFR table as do as directed above.


-wiz