Gents,
one of my bikes (2008 TBW Ultra mildly modded) displays a decel popping that occurs say from 4000 - 1800 rpm. It is not that short pop that occurs immediately after closing the throttle (can easily be cured by decel fuel settings in TTS). It continues to pop from both pipes when the engine is coasting and stops right around 1500 -18oo rpm.
Went through the usual drill and checked exhaust leaks etc. and adjusted the AFR down to 12.8 at 20 kpa to richen up the the mix, but to no avail. I always thought that there is no fuel supply during coasting and why recommend people in the know to adjust AFR down in the relevant areas? Is there more to it than I understand (likely)? If there is popping and if there is no fuel supply by design during decel, where does it come from? I redid the vtune and the bike still shows sooty exhaust pipes, black deposits on the spark base and other giveaways of running rich, but on paper as per vtune, the world is in order.
Keep in mind that it always takes 3 things to have an exhaust pop
Unburned fuel in the exhaust. This can be from an excessive amount of fuel or a lack of fuel causing a misfire.
Unused or fresh O2 in the exhaust.. This can be from an exhaust leak or from a misfire from the previous engine cycle that has plenty of o2 in it.
An ignition source. Most likely a misfire followed by a successful firing on the next engine cycle that is still burning when the exhaust valve starts to open.
There is a 4th thing that helps is excessive heat in the exhaust.
We used to play with this stuff on other systems that I tune. All we had to do was put the motor on overrun on a long down hill run and move the fueling from fat to lean. In the middle the back popping was gone but at either extreme we had popping. This stuff is a nightmare on the high horse turbo cars. The popping plays hell on the exhaust vanes of the turbo.
Hope this helps and have fun tuning
AW
Are you sure the injectors are shutting off? I have noticed on some maps they will, some don't. I have played with different maps on my bike and with one it did not matter what I did on the afr table she popped, only thing that worked was taking the ve's up to 120 from 1500 up. This is a cable bike so it was the 0 tp column. On TBW would you try the 1,2 and 5? :nix:
Quote from: lonewolf on May 22, 2011, 09:06:30 AM
Are you sure the injectors are shutting off? I have noticed on some maps they will, some don't. I have played with different maps on my bike and with one it did not matter what I did on the afr table she popped, only thing that worked was taking the ve's up to 120 from 1500 up. This is a cable bike so it was the 0 tp column. On TBW would you try the 1,2 and 5? :nix:
That is controlled by one of the Harley Hidden Tables.
AW
Have you tried running the MT8 calibrations? There are some changes in them that may reduce this tendency. --Gary
Quoteonly thing that worked was taking the ve's up to 120 from 1500 up. This is a cable bike so it was the 0 tp column. On TBW would you try the 1,2 and 5?
:agree:
was going to suggest that also. but didn't want to hear the grief. since you stepped out there Russel, I will run with you :bike:
Used mt7 and mt8 maps (c&p tables) and no difference. I will check a data run on the activity of the injectors during decel. I appreciate a lead to a 205 level map that closes the injectors during decel.
Quote from: strokerjlk on May 22, 2011, 09:34:08 AM
Quoteonly thing that worked was taking the ve's up to 120 from 1500 up. This is a cable bike so it was the 0 tp column. On TBW would you try the 1,2 and 5?
:agree:
was going to suggest that also. but didn't want to hear the grief. since you stepped out there Russel, I will run with you :bike:
What grief? Done it myself and it works.
Ron
The TBW bikes I know idle between 3.5 and 5 % TPS. I will try the 1 and 2 % column and see what I get. So still no solid information if and why certain cals close the injectors during decel?
Quote from: ViennaHog on May 22, 2011, 10:11:43 AM
The TBW bikes I know idle between 3.5 and 5 % TPS. I will try the 1 and 2 % column and see what I get. So still no solid information if and why certain cals close the injectors during decel?
it may not end up at 120 for a ve that was just lonewolfs experience. it could take as little as +10 @ the rpm where it is doing it. might even extend to 7 %.
little at a time. if that is what is going on .the thing that sticks out in my head is you said plugs look rich and you feel the motor is running rich.
it could very well be the other way around. it could have to much fuel. hard to armchair without hearing it.
they do make a different sound when they are rich than when they are lean. (popping on decel)
Will do some road testing Tuesday and do several accel/decel data runs all the way from 5500 rpm to about idle and see if the injectors close in some areas anyway, then adjust the areas in question in 5% increments. Gonna be fun to figure it out.
The richness that I see has been around for a longer time. The base ring of the plug is always black no matter how hard or soft I run it. The electrodes are fine, white to grayish with a little coloration on the ceramics. The timing mark on the plug are spot on and the plug heat range is stock. I VEtuned the damn thing on a dyno some time ago and set the VEs via VTune software. I do see some reversion on the rear cylinder as it show abnormal VEs at lower loads and rpm. I tried to futz with this EGR tool, but that thing is not user friendly. I manually adjusted the VEs in that area to make 'em look smooth.
We have a pretty good fuel (still) over here with max 5% ethanol in it. Could that be a reason for running rich through the rpm range?
"I VEtuned the damn thing on a dyno some time ago and set the VEs via VTune software. I do see some reversion on the rear cylinder as it show abnormal VEs at lower loads and rpm. I tried to futz with this EGR tool, but that thing is not user friendly. I manually adjusted the VEs in that area to make 'em look smooth."
The AFV is going to take over and the other tables relying on the VE tables are going to be skewd. Smoothing needs to be done with the EGR tables.
Quote from: ViennaHog on May 22, 2011, 11:44:51 AM
Will do some road testing Tuesday and do several accel/decel data runs all the way from 5500 rpm to about idle and see if the injectors close in some areas anyway, then adjust the areas in question in 5% increments. Gonna be fun to figure it out.
The richness that I see has been around for a longer time. The base ring of the plug is always black no matter how hard or soft I run it. The electrodes are fine, white to grayish with a little coloration on the ceramics. The timing mark on the plug are spot on and the plug heat range is stock. I VEtuned the damn thing on a dyno some time ago and set the VEs via VTune software. I do see some reversion on the rear cylinder as it show abnormal VEs at lower loads and rpm. I tried to futz with this EGR tool, but that thing is not user friendly. I manually adjusted the VEs in that area to make 'em look smooth.
We have a pretty good fuel (still) over here with max 5% ethanol in it. Could that be a reason for running rich through the rpm range?
Don't think the 5% will hurt much. I'm tuned on 10e without issues. I have to agree the 60 kpa runs to obtain data for egr adjustments are brutal on the bike, but it's the only way possibly to keep the AFV in line with the ve's. Manual adjustments of ve's without going the egr route will not keep it stable in closed loop. No problem with open loop but afrs need to be monitored to dial them in acurately, which you have done already.
One thing you can try is data log what kpa the acual popping is happening. Sometimes it's not where you think and you could be working the wrong afr tables to eliminate it.
Ron
VH,
Take a look at the exhaust on a 'up to 2008 touring' and you will see a problem.
The left side pipe will feed 'clean' air into the rear exhaust down pipe.
This will cause the rear 02 sensor read uncorrect (this is the reason why you see abnormal high VE's) and it can help to get a highly explosive mixture in the right side exhaust.
:agree:
Makes sense to me. Its been awhile any of us had stock exhausts! HAHA.
The bike in questions has the stock headpipes and ST Megaphones. So much for stock exhaust. I went through the exercise of adding backpressure to left exhaust and ran 8 disks left and 12 right, no significant difference.
The bike has an exup valve (HDI) which I would like to be able to control. On decel close it and run the entire gas flow through the left muffler, problem solved.............
and come to think about it, why would one add fuel during decel to begin with? I saw anything from 1-3 ms injector time during decel, it is not just one fixed amount, it varies with rpm or map. Any logical explanation for this?
Quote from: VosselmanPerformance on May 23, 2011, 10:37:17 AM
VH,
Take a look at the exhaust on a 'up to 2008 touring' and you will see a problem.
The left side pipe will feed 'clean' air into the rear exhaust down pipe.
This will cause the rear 02 sensor read uncorrect (this is the reason why you see abnormal high VE's) and it can help to get a highly explosive mixture in the right side exhaust.
I used an 1 5/8" freeze plug with a 7/8" hole drilled in the center in the left header pipe ahead of V&H mufflers on an '08 to control popping.
Looks like this:
http://www.zippersperformance.com/catalogue/showproduct.asp?cat=813&prod=2206 (http://www.zippersperformance.com/catalogue/showproduct.asp?cat=813&prod=2206)
Quote from: Ajayrk on May 23, 2011, 01:10:46 PM
Quote from: VosselmanPerformance on May 23, 2011, 10:37:17 AM
VH,
Take a look at the exhaust on a 'up to 2008 touring' and you will see a problem.
The left side pipe will feed 'clean' air into the rear exhaust down pipe.
This will cause the rear 02 sensor read uncorrect (this is the reason why you see abnormal high VE's) and it can help to get a highly explosive mixture in the right side exhaust.
I used an 1 5/8" freeze plug with a 7/8" hole drilled in the center in the left header pipe ahead of V&H mufflers on an '08 to control popping.
Looks like this:
http://www.zippersperformance.com/catalogue/showproduct.asp?cat=813&prod=2206 (http://www.zippersperformance.com/catalogue/showproduct.asp?cat=813&prod=2206)
on the list of things to tinker with. I like it and thanks for the lead.
I posed this very scenario on the V-Twin forum and no one had heard of it. The Kury website says when installing the Crusher mufflers on stock headers you are supposed to use the supplied block off plate to stop that from happening - but it is solid - no hole in it so you would totally block off the left muffler. That is the main reason I changed headers so I wouldn't have to do that. I wish I would have known about this forum a long time ago!
Quote from: Ajayrk on May 23, 2011, 01:10:46 PM
I used an 1 5/8" freeze plug with a 7/8" hole drilled in the center in the left header pipe ahead of V&H mufflers on an '08 to control popping.
Did you notice any change in engine temperature while cruising or at idle after you installed the freeze plug?
No change in temperature on the '08 or '03, both bikes have fuel management systems. The '03 has TMax and the '08 has the V&H Fuelpak
Quote from: VosselmanPerformance on May 23, 2011, 10:37:17 AM
VH,
Take a look at the exhaust on a 'up to 2008 touring' and you will see a problem.
The left side pipe will feed 'clean' air into the rear exhaust down pipe.
This will cause the rear 02 sensor read incorrect (this is the reason why you see abnormal high VE's) and it can help to get a highly explosive mixture in the right side exhaust.
:up: :up:
Bob
Quote from: ViennaHog on May 23, 2011, 12:59:58 PM
and come to think about it, why would one add fuel during decel to begin with? I saw anything from 1-3 ms injector time during decel, it is not just one fixed amount, it varies with rpm or map. Any logical explanation for this?
You're targeting a specific air/fuel ratio in the exhaust. It can't get there without fuel. If there was a carburetor on the bike you'd have fuel being introduced on closed throttle events, too. :D
so why would you target a specific exhaust AFR during decel? On a stock carb it is impossible to turn idle fuel off, so it by design. In the old days some cars had a decel fuel cut off, that used an electromagnetic idle jet. So again what is the reason behind adding fuel on decel?
Quote from: ViennaHog on May 29, 2011, 10:26:30 PM
so why would you target a specific exhaust AFR during decel? On a stock carb it is impossible to turn idle fuel off, so it by design. In the old days some cars had a decel fuel cut off, that used an electromagnetic idle jet. So again what is the reason behind adding fuel on decel?
Adding a small amount of fuel raises the chamber pressure slightly so a little more mixture is burnt before the exhaust valve opens and dumps it into the exhaust pipe where the after fire takes place. After-market pipes are often a big factor in making this bang louder as a lot of them have significant reversion bringing fresh air to the burning ejected mixture. The stock headers and mufflers hide this reaction and also lesson the the air available to the ejected mixture.
Thats my understanding of it anyway.
Hilly
Why wouldn't I cut the fuel entirely and avoid decel popping altogether? Bring it back on-line when the engine gets closer to to idle speed
Quote from: ViennaHog on May 30, 2011, 02:33:41 AM
Why wouldn't I cut the fuel entirely and avoid decel popping altogether? Bring it back on-line when the engine gets closer to to idle speed
If you let the throttle off completely and the TPS is registering zero then you have shut it off, its perfect, still goes bang though, the vacume created when you back of sucks in anything thats there, limited fresh air as the butterfly is closed, reciculated exhaust gasses, whatever fuel that is around, this mixture does not burn well, so the mixture is ejected into the exhaust, on a stock engine this is still happening its just covered up.
Quote from: ViennaHog on May 30, 2011, 02:33:41 AM
Why wouldn't I cut the fuel entirely and avoid decel popping altogether? Bring it back on-line when the engine gets closer to to idle speed
It'll ride poorly if you shut the injectors off on every single tipout, and it's not good for emissions either. The new bikes do cut fuel when off throttle for more than a brief instant, but there are specific entry conditions for it, and when you reintroduce fuel at a lower engine speed it's just as easy to get pops through the exhaust.
3 things need to be present for a decel backfire, pop, or gurgle.
We, as tuners can control 2 of these ingredients...Fuel and Timing.
We can retard or advance closed throttle timing...which can help in certain circumstances.
Fueling adjustment is really the most effective method we've found for minimizing, if not eliminating the irritating decel backfire/pop.
The above said, there are 2 schools of thought with fueling:
1) Cut all the fuel.
Upside: Eliminates 100% chance of decel backfiring.
Downside: As mentioned by blusmbl, when the rider tips back into the throttle the fuel gets "turned back on" which almost always creates a hesitation in that transition further irritating the rider.
2) Add to the decel fueling.
Upside: Greatly reduces/eliminates the loud backfiring and leaves a bit of a mellow gurgle as the engine returns to idle.
Downside: Uses a minute amount more fuel to enrichen the decel mixture.
There are other techniques used by OEM/emissions calibrators that can help to control decel backfiring but for most of the tuners out there using the above mentioned techniques have been most effective to reduce/eliminate decel backfiring.
A question some ask about possible damage caused by decel backfiring. AFAIK there is nothing but muffler packing, if present, that would be affected by backfire/pop.
Bob
Bob and bluesmbl,
thanks for letting me in on the details of decel fueling, makes sense now. Would one change the AFR at closed throttle or rather VEs at low maps (205 level cals)? And I think I will do the freeze plug fix and see what that does to reduce fresh air leakage.
Great advice as always