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¡úRoyal Enfield? What's this?¡ú

When I visited my friend Yamaguchi-san's store, Chronicle, in Matsudo, Chiba Prefecture, I found a somewhat retro and adorable machine.
I straddled it out of curiosity and found it comfortable.
A unique sense of massiveness not found in today's domestic motorcycles.
The engine's generous torque, which is not found in today's domestic motorcycles.
Royal Enfield? What's this?
I feel good!¡¡I want it!
Huh!¡¡Already at SP Tadao Asakusa store...

SPTADAO Development Team

¡úI wonder if this is a common feature of British-born vehicles...¡ú

Oh no, it's nice, it feels good!
As soon as you start running, put the car in top 5 gears and run.
Speed is 50 Km/h. I don't want to stop flat, flat, flat.
I want to keep running flat, flat.
I feel crazy happy even though I am just running.

Yes, I recall chasing this feeling when I was developing the GB350 pipe.
Turn the large, heavy flywheel slowly.
No, it is being turned. That's how I feel.
It has something in common with the Triumphs I rode in the past.
I wonder if this is a common feature of British-born vehicles...

Oh no, it still feels good.
And it feels so good.

SPTADAO Development Team

¡úThe moment when torque characteristics are linked to human sensitivity¡ú

It maintains the same pleasant driving feel from 40Km/h to 60Km/h, and draws out a little more torque from 70Km/h.
I thought it would be more comfortable if just a slight twist of the accelerator pedal could draw out enough room to comfortably follow without a great deal of agitation.
I designed a prototype exhaust pipe with this image in mind.
This nondescript stainless steel pipe can be combined with different thicknesses, lengths, or more than one thickness to change the torque characteristics (tenacious power) of the engine.

I really enjoy this process of changing torque characteristics and have been addicted to this work for more than 50 years now.
When this torque characteristic is linked to human sensibilities, the words ¡ÈI feel so good!¡¡is the word that comes out of my mouth.
This is the purpose of our development of pipes and mufflers.
I can't stop the excitement of creating a state where you and I can say, ¡ÈI feel good!

SPTADAO Development Team

¡úYou notice that the accelerator opens completely differently.¡ú

The stock exhaust pipe of the Royal Enfield CLASSIC 350 has a very thick exhaust pipe for a powerful appearance.
But with a 350 cc single-cylinder engine of this thickness, it is impossible to apply the proper pressure to the exhaust and increase the engine's power output.
Therefore, recent neo-classic vehicles, regardless of whether they are domestic or foreign-made, have another pipe with a smaller outer diameter inserted into the thicker exterior pipe as shown in the photo, and the inner diameter of the pipe is adjusted to bring it closer to the proper exhaust gas pressure.
However, there is a problem with this: the diameter of the outer pipe is first set based on the appearance, so the diameter of the pipe inside is limited, and it is not possible to choose a variety of thicknesses.
This makes it difficult to extract the best torque and output characteristics as expected.

On the other hand, recent POWERBOX pipe products are constructed without double pipes on purpose to bring out the rider's feeling. A single genuine pipe structure is used to control torque and output characteristics.
The narrow look that naturally emerged from this philosophy is a great match for sophisticated neoclassical machines, and its superior ride quality has led to a surge in popularity.

Therefore, we have carefully selected the pipe thickness and length that we can freely choose, and are enjoying changing the settings so that the Royal Enfield CLASSIC 350 will run more comfortably and exhilaratingly in Japan than it does now.¡¢
Riding the standard vehicle every day for the past few days, I have a feeling about the traffic flow and speed zones in India, the country where these bikes are produced.
Perhaps the urban speed in India is about 5~10Km/h slower than in Japan.

It is very comfortable to drive alone in the speed range of 40~60 km/h in top gear with constant acceleration. ¤±¤ì¤É¡¢
In a situation where the car is following the car in front, when accelerating from 50 km/h, it is possible to keep up with the car without complaints.
However, I noticed that the accelerator opening was completely different from that up to 50 km/h.
To obtain the same acceleration, it is necessary to twist the grip larger than at 50 km/h or less.
From such places, we can sense the difference between the traffic environment in India and Japan, notice the slightest difference, and change the characteristics. In doing so, we will nurture the Royal Enfield CLASSIC 350 to become even prettier for you when you run it in Japan.
I always enjoy developing with such a goal in mind.
Now, let's see how the first pipe I created this time runs....

SPTADAO Development Team

¡úI need to get back to the comfort of 40Km/h to 50Km/h.¡ú

I was surprised!¡¡I didn't expect such a big response.
Maybe this machine has pretty good potential.
Usually there aren't that many vehicles that change so spectacularly in the first prototype.
And how did it change?

It was a very high-revving machine....
The standard Royal Enfield CLASSIC 350 is where I feel most comfortable, and when I am driving unconsciously, I usually feel that I am driving in the speed range of around 50 km/h.
That is just what it feels like when running at 60~70Km/h when this prototype pipe is installed.
But the problem is that the 40Km/h to 50Km/h speed range is no longer comfortable.
It is very fast, but there is not a shred of emotion in it.
The Royal Enfield CLASSIC 350 was just fast and not at all comfortable.

Well, thanks to this pipe, I have a tendency to know where to tweak to draw more power in the 60Km/h~70Km/h speed range.

Next time I need to pull down the torque timing a bit more to get back to the comfort level of 40Km/h to 50Km/h.
Now, what part of this pipe shall we tinker with?

SPTADAO Development Team

¡úI'd like to do something about it, imagine how it will run when it's all set up nicely.¡ú

The previous prototype was measured on a chassis dynamometer (power characteristic measuring instrument), and it was found that the torque does not drop from 40 to 50 km/h, but that the shape of the torque line during this period is problematic.
So now we tinkered thoroughly with the goal of making the torque line a little flatter while increasing torque further from 40 km/h to 50 km/h.

What can be tweaked in this simple pipe to pinpoint and increase torque?
The project will be finished based on 50 years of accumulated data.
This time, we focused on the expansion capacity created behind the catalyst and the angle of the taper.¡¡
Now, what's the result?

I see, you are going in the right direction.
The comfortable torque feeling from 40Km/h to 50Km/h that was present in the stock system has returned.
On top of that, it still has an exhilarating RPM increase from 60 km/h, which is not present in the stock model.
This exhilarating stretch of speed is essential to make the Royal Enfield CLASSIC 350 feel good in Japan. This part of the car seems to be fine.

The other thing that bothered me from the beginning was the torque line from 50Km/h to 60Km/h.

There is a slight trough occurring here, and I can't keep the right hand and the engine in sync.
Yes, this torque line causes the gas pedal opening to be much larger when trying to accelerate from 50 km/h.
This has compromised the comfort of the Royal Enfield CLASSIC 350 in the Japanese traffic flow.

Even in its current state, it's getting much better than standard, but I can't help but imagine what it will be like when the torque line at 50 to 60 km/h is nicely set up.
I just can't stand it like this.

SPTADAO Development Team

¡úI didn't want to put a sub-chamber on it and adjust its characteristics.¡ú

Difficult, really difficult.
When preparing a torque line with pinpoint accuracy, attach a sub-chamber in the middle of the pipe.
It is a common practice to tweak the characteristics of the pipe at its installation position, but considering the simple beauty of the Royal Enfield CLASSIC 350, we would like to make the powerbox pipe to be installed as simple in structure as possible, with an essential beauty of form.
So I didn't want to put a sub-chamber on it and adjust its characteristics.
The development staff suffered because of this.
The prototype was built by changing the settings over and over again.
Basically, the only things that can be adjusted are the subtle capacity of the case, which also serves as the expansion quality containing the catalyst, and the length and thickness of the front and rear pipes.
We were particular about the detailed feeling and compared it with the stock one over and over again.
We changed the settings endlessly to bring out a beautiful torque line from 50 to 60 km/h, and thoroughly searched for the characteristics that the rider would feel comfortable with.

While repeating measurements with the chassis dynamometer and actual driving, the important thing toward the ideal is whether the rider can say ¡Èit feels good¡É or not.
All we ask for is just that.

SPTADAO Development Team

¡úThis POWERBOX pipe feels great! That's all.¡ú

It's amazing! I really feel good!
It turned out perfectly and performed exactly as I imagined. It's really amazing!
Connect the clutch and shift smoothly into top gear.
From 40Km/h, the engine comfortably follows the twists of the right hand. This is good.
It's like a lighter, more comfortable version of the standard. Very good.¡¡
The speed is increased to 50Km/h.
Yes, it is also robust and comfortable. Very nice.
And the challenge was 50Km/h to 60Km/h.¡¡
It's a relief, this feeling.
The acceleration that could only be obtained with a big twist of the right hand in the standard model, can be obtained with just a slight twist of the right hand, and the heartbeat of the engine follows.
It accelerates pleasantly.
The feeling of the right hand and engine working together to create a sense of oneness between the rider and the Royal Enfield CLASSIC 350 is impressive.
Royal Enfield CLASSIC 350 will love it.
And here's where it gets even more amazing.
In the standard, the speed increase is somewhat staggered after 60 km/h, and it is not advisable to increase the speed too much.
I feel that kind of feeling, but the POWERBOX pipe is completely different.
The Royal Enfield CLASSIC 350 maintains its original comfortable feel as it exhilaratingly increases its speed toward 120Km/h, the highest speed in Japanese traffic.
I want to keep driving at that leisurely speed of around 50 km/h for as long and as far as I can.
It retains the unique comfort of the Royal Enfield CLASSIC 350 that is hard to find on other bikes. No, it's more than that.
And I feel a feeling that I will be able to stay with them for a long time, eliminating one by one all the stress I had felt in the Japanese traffic.¡¡
Good. Very good.¡¡

This POWERBOX pipe 'feels great!' That's it.¡¡

In addition, a test drive campaign will be held at various locations, so all Royal Enfield CLASSIC 350 owners are encouraged to come and experience this famous car. For users in distant locations, POWERBOX pipes for trial fitting are available for rent on a store-by-store basis, so please consult with the store where you purchased the product.

SPTADAO Development Team