is exhaust performance even noticeable?

[JA50N]

So, can somebody answer this question:
 
Why, if the FZ-07 has no air injection on decal and also cuts the fuel to the injectors, does it backfire on decal? How is their unburnt fuel in the exhaust if the injectors are off?

[bmwpowere36m3]

Decel popping is usually a lean condition and NOT rich… some carburetors have a "coast enricher" circuit for closed throttle/decel. Adding an aftermarket exhaust/intake only makes the problem worse. Now it's entirely possible to have a rich condition… but I'd say that's NOT the norm and its sound is different from a lean decel popping.
 
To a degree, some decel popping is normal and to be expected with a straight-through/glass-pack muffler… which is freer-flowing and thus emits more "noises". If you richen up the mixture too much, to eliminate all decel popping, there is a good chance that the off-idle/part throttle mixture will be too rich.

[howworkclutch]

So, can somebody answer this question: 
Why, if the FZ-07 has no air injection on decal and also cuts the fuel to the injectors, does it backfire on decal? How is their unburnt fuel in the exhaust if the injectors are off?

 
 
Even under lean conditions there is unburned fuels in the exhaust. With the throttle closed you will have reverse exhaust flow for brief periods between cycles because of valve overlap.
 
Keep in mind that these modern engines make way more power than same-displacement engines made 20 years ago. Those older engines were made before the existence of evironmental regulations.
 
I mention this because there are people who will tell you that regulations have robbed us all of performance and those people are totally incorrect. Today's engines run better for longer and do so with much tighter emissions restrictions. That's a fact. But the myths or obviously more fun to believe I guess.

[norcal616]

I feel the performance increase from using an aftermarket exhaust is only noticed in the mid to upper RPMs ranges...if you really want a performance increase get a ECU reflash...stock exhaust is still good exhaust with an ECU reflash unless you are after sound and race...exhaust sounds are tricky to read( think crotch rocket with loud exhaust going down the road at high rpms and you think boy it's going fast like 80mph by the sounds of it but when the bike rolls by its only doing 35mph)...I tend to listen to exhaust sounds under WOT
race/drag conditions to tell when the motor is flatling...my leovince exhaust has some crackles and crackle pops under certain circumstances but it is a high flow exhaust due to no baffle or "cat"... If I use the baffle and "cat" the exhaust has no odd sounds that I hear... If you really wanna hear some exhaust noise YouTube " rotary drag cars"...I have yet to hear my exhaust with an ECU reflash or fuel. Tuner. Installed..

[gregjet]

"If you really wanna hear some exhaust noise YouTube " rotary drag cars".
Sooooooo true
 

[FZWes]

Full system, OEM system, tuner, ECM map, the debate will rage till the end of time.

Most riders replace their OEM exhaust two reasons, their buddy's all did, and sound. Years ago some manufactures would tell you put our pipes, enrich the fuel air mixture and you could add 5 hp! Hogwash!

[klx678]

On 6/3/2015 at 11:00 PM, bmwpowere36m3 said:

Decel popping is usually a lean condition and NOT rich… some carburetors have a "coast enricher" circuit for closed throttle/decel. Adding an aftermarket exhaust/intake only makes the problem worse. Now it's entirely possible to have a rich condition… but I'd say that's NOT the norm and its sound is different from a lean decel popping.
 
To a degree, some decel popping is normal and to be expected with a straight-through/glass-pack muffler… which is freer-flowing and thus emits more "noises". If you richen up the mixture too much, to eliminate all decel popping, there is a good chance that the off-idle/part throttle mixture will be too rich.

What is called exhaust crackle is very common and exactly as you say, a lean condition when the throttle is closed.  Crack the throttle slightly and it usually goes away.  It is never any loud bang.  Funny part to me is most motorcyclists want to stop the crackle, but if you google it and go to places like the Corvette forums, the drivers want to know how to make their Vettes crackle under deceleration.

Mikuni has an article on it relating to carbureted bikes, but closed throttle is closed throttle.  click here 

Quote

It is normal for many high performance exhaust systems to moderately backfire or pop when the throttle is closed from mid-to-high rpm. In fact, one should expect a well-tuned high performance engine to "pop" and "crackle" when the throttle is closed at high rpm.

The popping is a result of the air/fuel mixture becoming very lean when the throttle is closed and the engine is rotating well above idle speed. It is also necessary that the exhaust system have rather open mufflers.

 I figure if the people who make the carbs says it's normal they must know what they're talking about.   Any attempt to eliminate it is simply making the closed throttle fuel mix overly rich.

The way most EFI bikes eliminate it is to shut off fuel completely when the throttle is closed down to a certain rpm.   My 96 Ford Ranger even does it in 5-3 gears, but not in 2-1 gears to avoid stalling.   You let off the throttle and it just drones down to the rpm point or the clutch is pushed in, then it will feed fuel to stay running.    

I may be wrong, but at least on the XSR that is one complaint, about the fuel shut off when the throttle is closed.  Riders experience some jerkiness when they are transitioning from full closed throttle in a corner to opening the throttle.   Doesn't bug me at all. I usually am in a lower gear with a touch of throttle, just the way I ride.

 

11 hours ago, FZWes said:

Full system, OEM system, tuner, ECM map, the debate will rage till the end of time.

Most riders replace their OEM exhaust two reasons, their buddy's all did, and sound. Years ago some manufactures would tell you put our pipes, enrich the fuel air mixture and you could add 5 hp! Hogwash!

Used to be some exhaust change could make a significant difference, but even in the 80s anytime a comparison was made on most sport bikes, the gain might be 3 hp at the very top, but usually worse performance through the middle.   Made that hit feel stronger than it actually was.

The only good reason to buy an exhaust is for looks or for better tone.  Worst reason is to be blatantly loud and obnoxious.  Most will not gain enough power to make it worth doing.   From every I've seen, the gain is only good if all the other peripheral work is done to maximize the exhaust. 

I did an exhaust on my bike for the look and tone.  Not volume, but tone.   The system I got sounds so much better and is only around 5 dB louder than stock according to the decible meter app on my phone.   It shows around 78 dB idle and around 89 dB when reved.  I think it's pretty close, because it shows my son-in-law's FTR with the S&S Grand Nationals high pipes at around 97 dB with the inserts.

[Triple Jim]

Since I got my MT-07 last year and kept it stock, several people have told me they like the way it's so quiet.  One approached me in a parking lot just to tell me.  I had a 1989 Moto Guzzi Mille GT for about 8 years.  It had a stock exhaust system, but it was fairly loud.  Its mufflers were straight-through, packed with some sort of absorbent material that was probably stainless steel wool.  I never once had anyone approach me to say it sounded good.   What we think is a sound improvement may not be perceived that way by everyone else.  In effect we're a bunch of kids who put cards in the spokes of our bicycles to make noise.

I left a camera on the side of the road so I could hear the Guzzi from that point if view and I thought it sounded pretty good, yet in 8 years no one complimented me about its sound.

 

 

 

Edited October 24, 2021 by Triple Jim

[Dash]

My 2015 airbox removed. Two brothers full exhaust. Power commander. By the seat of my pants I would say there is a little less torque down low. But more pull up top higher in the RPM range.