Question Which de-cat pipe

[670cc]

Now that is a great cut away picture, thank you for getting my mind on the right track. I wonder what is inside that silencer. Do you happen to have a picture of that? I’ll be looking for a new header now lol.

Sorry, I have no muffler cutaway photo. I don’t know what all is inside the stock silencer, but it does a good job of silencing, which is why I still have mine installed.

 

[Wedders]

The Leo Vince decat pipe still has the bulge like the OEM pipe, but no internals like the cat.

 

[TacomaJD]

Now that is a great cut away picture, thank you for getting my mind on the right track. I wonder what is inside that silencer. Do you happen to have a picture of that? I’ll be looking for a new header now lol.

Silencers/mufflers/whatever you want to call them are not complicated devices. Different arrangement and designs of chambers, baffles, and packing material are all that's in there. Cats are never in the mufflers, or I'm not aware of any that are, at least.

And the difference in weight between your aftermarket can and the stock can is the difference in the materials they are made of. The OEM can is made of steel, I believe, and your aftermarket can is made mostly of carbon fiber and has less chamber wall/baffle weight on the inside as well, which is what makes it louder than stock.

 

[TheIronWarrior]

Cats are never in the mufflers, or I'm not aware of any that are, at least.

A cat in the muffler would be a pretty bad design choice. The cat needs to get hot to work, which is why they are always as upstream as you can reasonably put them.
It was discussed specifically for the NC in the promo material that the location of the cat (closer to the engine) helps it heat faster for lower emissions.

 

[dduelin]

Lots of motorcycles have the cats integral with mufflers and Honda makes that choice quite often. I think it comes down to packaging components in limited spaces. Motorcycles are generally more compact than cars and the distance from combustion chamber to muffler with catalytic converter isn't that far and there isn't much room for integrated exhaust manifolds & cats. The NC is an outlier in that regard with the cat adjacent to the engine similar to their compact and mid-size car engines - Civic, Fit/Jazz, Accord, Odyssey.

 

[senecagreen]

I ordered the Leo Vince head pipe for my 2018 NC 750X. They make quality stuff. The expansion chamber on the pipe is interesting. FMF does the same thing on thrir 4 stroke exhausts and calls the expansion chamber a " power bomb". Below is FMF's description of how it works. There is a reason Leo Vince included one on their pipe.

"The redesigned PowerBomb is a four-stroke header that incorporates FMF’s patented PowerBomb module at a precise location in the initial stage of the header. By positioning this “Bomb” at a key point in the system, increased performance and flow is achieved through the expansion and contraction of exhaust sonics through the system. Result is a flow increase of nearly 10%! The outer chamber in the Powerbomb allows the air to expand, cool and ramp back up at a higher velocity. Additionally, the PowerBomb is a “pre-muffler” of sorts which helps to lower the bikes sound output by providing more sound absorbing surface area for the sound medium (exhaust gases). On some models, you can choose between a moto or supercross version. The supercross version is designed for more low to mid-range power where the moto version is focused in the mid to upper RPM range."

 

[670cc]

I ordered the Leo Vince head pipe for my 2018 NC 750X. They make quality stuff. The expansion chamber on the pipe is interesting. FMF does the same thing on thrir 4 stroke exhausts and calls the expansion chamber a " power bomb". Below is FMF's description of how it works. There is a reason Leo Vince included one on their pipe.

"The redesigned PowerBomb is a four-stroke header that incorporates FMF’s patented PowerBomb module at a precise location in the initial stage of the header. By positioning this “Bomb” at a key point in the system, increased performance and flow is achieved through the expansion and contraction of exhaust sonics through the system. Result is a flow increase of nearly 10%! The outer chamber in the Powerbomb allows the air to expand, cool and ramp back up at a higher velocity. Additionally, the PowerBomb is a “pre-muffler” of sorts which helps to lower the bikes sound output by providing more sound absorbing surface area for the sound medium (exhaust gases). On some models, you can choose between a moto or supercross version. The supercross version is designed for more low to mid-range power where the moto version is focused in the mid to upper RPM range."

All this flow increase supposedly offered by the aftermarket exhaust makes the assumption the the stock exhaust system is a restriction. Has that been proven? Does FMF provide before and after engine data? I have no data or facts, but with the NC’s one-into-four-into-one cylinder head design, I question whether any more flow is even available.

That well written marketing hype will surely convince some people to get out their wallets. If the FMF exhaust pleases the buyer in some way(s), real or imagined, that’s all that really matters.

 

[senecagreen]

The NC basically has a exhaust manifold built into the head. Whatever is used after the exhaust port will not provide a significant bump because of that.

Modern oem header pipes on most bikes now are so good from the factory that on a 155 hp bike you might get 5-8 more hp peak replacing it on your typical sportbike.

I would assume when Honda designed the built in exhaust manifold into the head that they put some thought into it and that it is probably optimized for the design of this particular engine.

That said what comes after it still has a effect. With no exhaust at all after the 02 sensor it probably would lose power and rideability. (zero restriction)

The intrigueing thing about exhaust design is how the engineers factor in the sonic waves not just exhaust pulses and air flow and the effect all this has on reversion (Im not an engineer so I dont understand how when doing the design you manipulate it to affect these things and optimize the result)

So while there may be no increase in peak power with the Leo Vince head pipe maybe the design improves the power across the powerband or shifts the power in a positive way giving more in the low to mid without hurting the peak?

I don't know but I do know Leo Vince has been successful in racing for a long time and they understand those terms and how to manipulate the design to shift and enhance the power or rideability in a positive way more where the bike design category is actually intended to be used.

I was intrigued why they would add an expansion chamber where with a black widow headpipe is just straight pipe. Maybe its just for a acoustic effect or maybe it keeps velocity of the exhaust pulse high or maybe it affects the sonic wave? I don't know because the sonic wave effect is what I least understand.

I thought for $240 it was worth putting on to see. If it pulls the front wheel up easier in 1st gear I will know it had a positive effect. I don't expect more peak power for sure. Even with only 58hp this bike is very entertaining. Im looking forward to wheelieing out of the 1st gear corners we find on the roads we ride in AR. Riding a slow bike pretend fast makes for a lot of fun on those kinds of roads.

I rode my sons 2024 Gsxr750 yesterday and it is pretty thrilling the acceleration on that bike and Im sure it will be a blast in AR but it requires a lot more concentration and throttle control whereas wheelieng out of corners on the NC will just be grins and laughs.

A long answer to say Im being realistic in my expectations with the Leo Vince head pipe

 

[gary]

The NC basically has a exhaust manifold built into the head. Whatever is used after the exhaust port will not provide a significant bump because of that.

Modern oem header pipes on most bikes now are so good from the factory that on a 155 hp bike you might get 5-8 more hp peak replacing it on your typical sportbike.

I would assume when Honda designed the built in exhaust manifold into the head that they put some thought into it and that it is probably optimized for the design of this particular engine.

That said what comes after it still has a effect. With no exhaust at all after the 02 sensor it probably would lose power and rideability. (zero restriction)

The intrigueing thing about exhaust design is how the engineers factor in the sonic waves not just exhaust pulses and air flow and the effect all this has on reversion (Im not an engineer so I dont understand how when doing the design you manipulate it to affect these things and optimize the result)

So while there may be no increase in peak power with the Leo Vince head pipe maybe the design improves the power across the powerband or shifts the power in a positive way giving more in the low to mid without hurting the peak?

I don't know but I do know Leo Vince has been successful in racing for a long time and they understand those terms and how to manipulate the design to shift and enhance the power or rideability in a positive way more where the bike design category is actually intended to be used.

I was intrigued why they would add an expansion chamber where with a black widow headpipe is just straight pipe. Maybe its just for a acoustic effect or maybe it keeps velocity of the exhaust pulse high or maybe it affects the sonic wave? I don't know because the sonic wave effect is what I least understand.

I thought for $240 it was worth putting on to see. If it pulls the front wheel up easier in 1st gear I will know it had a positive effect. I don't expect more peak power for sure. Even with only 58hp this bike is very entertaining. Im looking forward to wheelieing out of the 1st gear corners we find on the roads we ride in AR. Riding a slow bike pretend fast makes for a lot of fun on those kinds of roads.

I rode my sons 2024 Gsxr750 yesterday and it is pretty thrilling the acceleration on that bike and Im sure it will be a blast in AR but it requires a lot more concentration and throttle control whereas wheelieng out of corners on the NC will just be grins and laughs.

A long answer to say Im being realistic in my expectations with the Leo Vince head pipe

when installed, share your thoughts on the install process, sound, aesthetics, performance, etc.
good luck.

 

[senecagreen]

I actually have a decibel meter so will measure sound at idle and max db revved with
stock headpipe with delkevic slip on
Leo Vince headpipe with stock muffler
Leo Vince headpipe with delkevic muffler

all same distance and angle from outlet of muffler

and of course if any noticeable difference riding

 

[Dan German]

I actually have a decibel meter so will measure sound at idle and max db revved with
stock headpipe with delkevic slip on
Leo Vince headpipe with stock muffler
Leo Vince headpipe with delkevic muffler

all same distance and angle from outlet of muffler

and of course if any noticeable difference riding

I look forward to something more than seat-of-the-pants/calibrated-ear. I have a Leo Vince header pipe on order. For the record, I did not choose to purchase it because I want more power, or because I’m replacing the exhaust (call me strange, but I have no issue with the look of the stock muffler.) They had me at stainless steel. The bulge/expansion chamber makes me curious, though. Leo Vince would not spend the money to put that there if there weren’t a good reason, I figure. I have heard that the LV header makes a slight difference to the exhaust sound, which is OK with me. I rather like the stock exhaust note, but if I can get a bit more of the rumble it already has, I’m down with that. I had a LV slip-on on my last bike (CBR300R, although the slip-on was meant for a 500), and it was very nicely made for the price, if a bit loud.

 

[Wedders]

I have a full Leo Vince system. Decat pipe and carbon end can bought off eBay like new for £300. I like it deepish and throaty.

 

[senecagreen]

I will go ahead and measure the stock muffler on the stock headpipe too will I'm at it just for reference. I usually measure about 6ft behind the outlet of the muffler and in this case I will put the meter on a folding chair directly behind. The meter has a max setting so it shows what the loudest level achieved was. Thats where I rev it to check for that.

 

[senecagreen]

I look forward to something more than seat-of-the-pants/calibrated-ear. I have a Leo Vince header pipe on order. For the record, I did not choose to purchase it because I want more power, or because I’m replacing the exhaust (call me strange, but I have no issue with the look of the stock muffler.) They had me at stainless steel. The bulge/expansion chamber makes me curious, though. Leo Vince would not spend the money to put that there if there weren’t a good reason, I figure. I have heard that the LV header makes a slight difference to the exhaust sound, which is OK with me. I rather like the stock exhaust note, but if I can get a bit more of the rumble it already has, I’m down with that. I had a LV slip-on on my last bike (CBR300R, although the slip-on was meant for a 500), and it was very nicely made for the price, if a bit loud.

I emailed Leo Vince about the bulge in the headpipe for the NC750X and below is their reply.

"It is not an expansion chamber, it is a pre-muffler. Inside is a perforated tube with packing material around it, just like a muffler. It helps reduce noise before the exhaust gases get to the muffler."

Aha, that solves the mystery and that is cool with me because I didn't want it too loud with my delkevic slip on. Perforated tubes give better flow than louvered tube/baffles and dont get loud till you give it the gas. Will be interesting what the max db will be revved vs the stock headpipe. I can even include db at 4000 rpm which is where I spend my time at highway speed.

 

[Dan German]

I emailed Leo Vince about the bulge in the headpipe for the NC750X and below is their reply.

"It is not an expansion chamber, it is a pre-muffler. Inside is a perforated tube with packing material around it, just like a muffler. It helps reduce noise before the exhaust gases get to the muffler."

Aha, that solves the mystery and that is cool with me because I didn't want it too loud with my delkevic slip on. Perforated tubes give better flow than louvered tube/baffles and dont get loud till you give it the gas. Will be interesting what the max db will be revved vs the stock headpipe. I can even include db at 4000 rpm which is where I spend my time at highway speed.

Thanks! Interesting that they would do that, when the LV Corsa GP I bought needed a longer db killer and a metric s**t-ton of packing to be even close to neighbour-friendly. Don’t get me wrong, I loved the muffler on my CBR300R, but I’m keeping the stock NC muffler with the LV header.

 

[senecagreen]

It probably also has to do with the tone. It might have sounded crappy/ raspy / harsh with their LV slip on before they added the pre muffler. I bet it sounds good with my delkevic and by measuring the db's with the stock muffler on it you will have data on how much louder it is with your stock muffler vs the stock headpipe.

 

[senecagreen]

Get my Leo Vince head pipe Thursday. Will also include when I do db measurements stock headpipe no muffler, Leo Vince headpipe no muffler to see how much louder Leo Vince is by itself.