Popping on Deceleration

[JeffOlson]

What causes it? What can be done to reduce it?

I am no mechanic, but some say that it is due to the engine running lean, causing the engine to run hotter and allowing unburned fuel to ignite in the hot exhaust system as the exhaust exits the engine.

On my Triumph EFI Thruxton, I was able to eliminate popping on deceleration entirely with a combination of mods, so I am not sure if any one of them would have done the trick (replaced the quiet, stock sewing-machine cans with loud, open BC Predator cans, removed the secondary air injection system entirely and plugged in a resister inline to fool the ECU, removed the oxygen sensors and plugged in resisters inline to fool the ECU, and had the Harley-Triumph dealer install the richer map for the Arrow cans).

On my Norge, I don't think it would be that easy. I suspect a more open silencer would automatically cause the ECU to run a bit richer but not entirely eliminate the popping. (That is my recollection from my previous Norge with an Agostini can, sans DB killer, but without a new map.) I imagine replacing the compensator box between the exhaust header pipes and the muffler with an open Y-pipe would help reduce the exhaust system temperature. Finally, I imagine installing a new map with GuzziDiag might help.

How about you? What are your thoughts? Do you care? If so, what has worked for you on your EFI Guzzi?

[rbm]

On my V7, I installed a Power Commander V with Autotune that modifies the fuel mapping.  I have programmed it to enrichen the mixture throughout, which resulted in elimination of the decel popping as well as overall a better behaving motorcycle.  It was necessary for me to turn off the O2 sensor in the ECU using Guzzidiag so that the PC-V had access to the lower 40% throttle values in the map.

The same outcome I got with the PC-V can be achieved by buying the ECU Reflash tool for the V7 from Guzzitech.  It will load the ECU with a custom map that eliminates decel popping and improves the bike's engine performance overall.

[guzziboy66]

I kinda like a little popping on decel...

Eric

[kirkemon]

I kinda like a little popping on decel...

Eric

Me too - makes my bike a little more bad-ass than a sewing machine.

[Scud]

My sewing machine K75s pops a little on deceleration. I find it a little annoying, but have figured out how to ride around it (ease off the throttle, don't chop it). The conventional wisdom is that it's often corrected by valve adjustments.

So far, have not had the problem on my Guzzis.

[canuguzzi]

I kinda like a little popping on decel...

Eric

Yup and those in the know says it isn't harmful.

Running the modded map (do try it) TBs set just right, valves good, fresh plugs, good air filter, the works, idle all that, still pops a bit.

Thought I'd never say it but it does lend soul/character or that stuff and cals out rather than the quiet the Norge presents most of the time.

Jeff, make the ride next week to SF for that love of motorcycling show and you can have the map loaded on the spot.

[Cool Runnings]

Does the Norge 'pop' if half the DB killer is cut and left it place?

[Dukedesmo]

Does it have an 'air into the exhaust port' valve that opens on the over run? Because I've seen a few bikes that pop due to this. My Son had a Yamaha YBR125 that would pop like crazy until I disconnected the valve & blanked off the air port - ran much smoother afterwards.

[RANDM]

R1150's have the same thing going on as part of their
surging problems. When I was working through that I
found a guy on Adv who actually ran tests via the 911
and an Innovative Motorsports LC-1 hooked up to his
laptop and logged/posted the Data.

He found it was going too lean causing incomplete
combustion, the left over unburnt fuel caused popping
in the exhaust - a richer mix eliminated it. The richer
mix also stopped the lurch that's caused by the fuel
cutoff in the EFI which is programmed to cut the fuel
until you get down to around 1800 ruppums when it
Comes back on just as your setting up for a corner.

Personally I wouldn't want to "ride around it" as I think
engine braking is great and use it a lot.

Cheers Maurie.

[canuguzzi]

Might be worth the read


http://wildguzzi.com/forum/index.php?topic=69633.0

[Cool Runnings]

My head is popping now. 

[rbm]

My sewing machine K75s pops a little on deceleration. I find it a little annoying, but have figured out how to ride around it (ease off the throttle, don't chop it). The conventional wisdom is that it's often corrected by valve adjustments.

Backfiring on the K75 can be cured by making sure the exhaust side of the engine is airtight.  That means:
- check exhaust valve clearances are in spec
- check and replace any defective exhaust gaskets at the headers (just do this as a matter of course since they are so cheap)
- check exhaust nut torque and re-torque if necessary
- check for air leaks in the headers, header/muffler joint and muffler.  Use exhaust sealant to seal the muffler to the header instead of the OEM mica gasket.  The OEM gasket deteriorates quickly.

Being diligent on all of these points will cure the backfiring.

[Cool Runnings]

Maybe I will just pound a 1/2 inch rod through the stock can and get the same sound as a $700 custom spaghetti can? 

[Cool Runnings]

Process involved with removing stock baffles on a Harley Davidson 2013 Street Glide

https://www.youtube.com/watch?v=m7eoFXeUJsQ

https://www.youtube.com/watch?v=o87CnmdyMZg

Wonder if I could do the same with the stock Norge can?

[SED]

Usually popping is a result of an air leak into the exhaust system.  Exhaust should have not have any oxygen left in it to cause the pop.  Often the seal between the pipe and the head, but sometimes pipe joints.

An exhaust gas analyzer can usually tell you if you have an airleak by measuring CO2 in the pipe (as I recall).

Did your Norge always pop?

If popping is due to a lean mix it is probably just lean at idle and an adjustment or new map could take care of it.

 

[Cool Runnings]

Usually popping is a result of an air leak into the exhaust system.  Exhaust should have not have any oxygen left in it to cause the pop.  Often the seal between the pipe and the head, but sometimes pipe joints.

An exhaust gas analyzer can usually tell you if you have an airleak by measuring CO2 in the pipe (as I recall).

Did your Norge always pop?

If popping is due to a lean mix it is probably just lean at idle and an adjustment or new map could take care of it.

Jeff has one of those LOUD cans.

[JeffOlson]

If the popping is indeed caused by unburned fuel igniting in the exhaust system, then presumably the only ways to eliminate it would be to (1) make the engine run more efficiently so it burns up all of the fuel in the combustion chamber  and/or (2) cool the exhaust system somehow so the unburned fuel cannot ignite.

Enriching the air-fuel mixture, thereby causing the exhaust system to run cooler, is probably the easier of the two methods.

However, I am not a mechanic, let alone an engineer or physicist.

[JeffOlson]

Usually popping is a result of an air leak into the exhaust system.  Exhaust should have not have any oxygen left in it to cause the pop.  Often the seal between the pipe and the head, but sometimes pipe joints.

An exhaust gas analyzer can usually tell you if you have an airleak by measuring CO2 in the pipe (as I recall).

Did your Norge always pop?

If popping is due to a lean mix it is probably just lean at idle and an adjustment or new map could take care of it.

Both of my Norges always popped on deceleration. So, too, my Ducati and both of my Triumphs. I believe it is simply because the bikes are made to run lean from the factory, leading to extreme temperatures in the exhaust system. Triumph, if fact, has a secondary air injection system, where air is pumped into the exhaust headers to cause the unburned fuel to ignite!

As for my current can, it is stock. Sadly, I sold the Agostini can with my prior Norge when the reckless driver's insurance company bought it from me.

[Cool Runnings]

If the popping is indeed caused by unburned fuel igniting in the exhaust system, then presumably the only ways to eliminate it would be to (1) make the engine run more efficiently so it burns up all of the fuel in the combustion chamber  and/or (2) cool the exhaust system somehow so the unburned fuel cannot ignite.

Enriching the air-fuel mixture, thereby causing the exhaust system to run cooler, is probably the easier of the two methods.

However, I am not a mechanic, let alone an engineer or physicist.

Asked my dealer about custom exhausts, they didn't know anyone with a custom map for the 8V?

[JeffOlson]

Asked my dealer about custom exhausts, they didn't know anyone with a custom map for the 8V?

Some people on this board have custom maps that they create with their computers based on real-world riding. They then upload them to the ECU with GuzziDiag, a laptop, and some cables.

[canuguzzi]

Yup^

Dealer might not be allowed to load a custom map.

??

[Cool Runnings]

Some people on this board have custom maps that they create with their computers based on real-world riding. They then upload them to the ECU with GuzziDiag, a laptop, and some cables.

Sounds scary, think I'll hang onto that two year warranty. 

[Cool Runnings]

Yup^

Dealer might not be allowed to load a custom map.

??

HD does it all the time! 

[JeffOlson]

Sounds scary, think I'll hang onto that two year warranty. 

Check out this thread: http://wildguzzi.com/forum/index.php?topic=69168.0.

I am about to go outside and give it a try.

[canuguzzi]

HD does it all the time! 

Are those maps supplied by the factory?

I only stated that because I'm not sure if a dealer could load a map which you bring to them to load onto a new bike since that map might not have EPA or whatever approved.

From prior threads, no one can tell if you loaded a different map but that is different than having a dealer do it from a source the factory hasn't authorized.

We can and do all kinds of things but the map directly affects emissions. Like asking the dealer to bypass the cat on a new bike under warranty.

The question to which I don't have the answer is " would an authorized MG dealer load a different than OEM map onto a new bike still under warranty if that map was given to them by the customer?"

Dealers might know.

[beetle]

Popping with the 8V (assuming no air leaks or other freaky things) can be cured by adding fuel to the map between 2500-3500 RPM in the 4.6-5.2 TPS range. The extra fuel cools and floods the zorst enough to quench the pops.

[Cool Runnings]

Check out this thread: http://wildguzzi.com/forum/index.php?topic=69168.0.

I am about to go outside and give it a try.

Bookmarked, let me know. 

[Cool Runnings]

Are those maps supplied by the factory?

I only stated that because I'm not sure if a dealer could load a map which you bring to them to load onto a new bike since that map might not have EPA or whatever approved.

From prior threads, no one can tell if you loaded a different map but that is different than having a dealer do it from a source the factory hasn't authorized.

We can and do all kinds of things but the map directly affects emissions. Like asking the dealer to bypass the cat on a new bike under warranty.

The question to which I don't have the answer is " would an authorized MG dealer load a different than OEM map onto a new bike still under warranty if that map was given to them by the customer?"

Dealers might know.

Want to give my Dodge a 'tune' with 'hemifever'. 

[Cool Runnings]

pooping on deceleration, oh shit. 

[canuguzzi]

Cool Runnings, the map for the Norge works.