BREAKING: new 4 in 4 exhaust

[franov_imp]

Hello guys!

guess what.. our friends from Busso Silencers just wrote in the Italian CB1100 owners Facebook group that they'll be working during the upcoming winter season on a new 4 in 4 exhaust system!

really hope they'll make it "cb 750 four style" and of course with the possibility to maintain the center stand: it would be the only one in the world with those properties!

fingers crossed...

 

[peterbaron]

Good luck and fingers crossed.
Update us accordingly!

 

[Houtman_imp]

That would nice and another option.

 

[PowerDubs_imp]

My favorite style is the Moriwaki 4-4. It has the cleanest lines and angles.

I don't want a sandcast style flange seamed muffler.

I will not buy an exhaust that makes me loose the center stand. There is no reason it can't be done.

If they were able to include not only the 2 OEM sized O2 bungs- but also 2 smaller WBO2 bungs to give us the option to install the Dynojet power commander without having to custom weld- they will have my sale, and a writeup not only on the install but dyno result comparisons as well.

Pass that on.....

 

[franov_imp]

I'll tell them! btw I think that currently the best looking ones are the wyverns with their classic look, but still didn't buy them mostly because center stand had to go, and I would never be able to give up on it as I think it's one of the most important accessories to be fitted to every motorcycle, both for maintenance and security.

 

[whizzle_dizzler_imp]

Any word on pricing?

 

[franov_imp]

still nothing for the moment: only thing I can tell is that the slip on silencers (4 in 2, similar to the stock ones) are about €600 VAT included; don't know how much the same ones cost in the USA with the monetary exchange, taxes etc.
I don't think they'll make the 4 in 4 cost more than €800 (if just slip on silencers) or about €1200 (complete with headers) as they are generally quite good with their prices even if the product is 100% artisanal, therefore taking a lot of craftsmanship

 

[Charlie Bravo_imp]

I'd be interested in a 4 into 2 like on the early 90s 750 Nighthawks. Hmm, a search may be in order...

 

[Paris_imp]

I'd be interested in a 4 into 2 like on the early 90s 750 Nighthawks. Hmm, a search may be in order...

I saw a huge jump in torque and an extension of the power curve when I replaced the 2 into 2 stock exhaust on an '81 CB750F with a 4 into 1. As I understand it, there is a big advantage using a 4 into 1 over even straight pipes if it is tuned correctly. The exhaust pulses traveling down the header create a vacuum which scavenges more exhaust out of other cylinders.

 

[Roper_imp]

I'd be interested in a 4 into 2 like on the early 90s 750 Nighthawks. Hmm, a search may be in order...

I saw a huge jump in torque and an extension of the power curve when I replaced the 2 into 2 stock exhaust on an '81 CB750F with a 4 into 1. As I understand it, there is a big advantage using a 4 into 1 over even straight pipes if it is tuned correctly. The exhaust pulses traveling down the header create a vacuum which scavenges more exhaust out of other cylinders.

I have heard this before, but I have a hard time visualizing it.

As exhaust travels through the headers, it remains in discrete pipes until the collector. So any vacuum created in the header behind the exhaust pulses wouldn't affect the other cylinders, whether it's 4-1 or 2-2.

In an I-4 engine, the outer two cylinders move together and the inner two cylinders move together.

With a 2-2 exhaust, when one cylinder is on its exhaust stroke, the other is on its power stroke. I suppose there could be a vacuum created in the collector to help "scavenge" exhaust from the other cylinder in the millisecond the valves are open. The exact same thing is happening on the other side.

With a 4-1 exhaust, the same thing is happening, but in pairs. Sure, there is double the exhaust volume which may create a larger vacuum, but it's also "scavenging" exhaust from double the cylinder volume at the same time. The ratios don't change.

So, I'm either misunderstanding something, or there's something else going on that I haven't taken into consideration.

 

[the Ferret]

Tuned exhaust - Wikipedia

 

[Lord Popgun]

Do I get to say Helmholtz resonator again? Cause I like to say Helmholtz resonator!

 

[peterbaron]

Not Helmholtz but Helmut holds

 

[Roper_imp]

Tuned exhaust - Wikipedia

Thanks ferret. I also read the link to exhaust scavenging. This part "The purpose of a 4-2-1 exhaust system is to increase scavenging by merging the exhaust paths of specific pairs of cylinders," makes me think that the "2" part of the equation is merging cylinders differently from what I was envisioning. Also, the information about primary tube lengths and diameters is fascinating--making me realize that there's a heck of a lot of engineering involved in designing an exhaust system, and that drilling holes, removing stuff, swapping parts, etc. could have a huge negative effect on engine performance if you don't know exactly what you're doing.

 

[the Ferret]

Yea that's why I trust the engineers and dont make many changes to modern Japanese motorcycle that aren't strictly for aesthetics.

 

[mrichi_imp]

If the 4into1 system is more efficient , how come dragsters just have straight out pipes ?

 

[Roper_imp]

Because dragsters are all about raw power, not efficiency.

With belt-driven blowers and Nitromethane, the only purpose for exhaust pipes is to get the still-burning gas out and away as quickly and safely as possible.

 

[Paris_imp]

If the 4into1 system is more efficient , how come dragsters just have straight out pipes ?

I took the exhaust system off my '81 CB750F just to see what would happen. It was so loud, it sounded like a helicopter.

 

[whizzle_dizzler_imp]

If the 4into1 system is more efficient , how come dragsters just have straight out pipes ?

I took the exhaust system off my '81 CB750F just to see what would happen. It was so loud, it sounded like a helicopter.

BLOP BLOP BLOP BLOP BLOP BLOP BLOP BLOP BLOP BLOP BLOP BLOP BLOP BLOP BLOP BLOP BLOP BLOP BLOP BLOP BLOP BLOP BLOP BLOP BLOP BLOP BLOP BLOP BLOP BLOP BLOP BLOP BLOP BLOP BLOP BLOP BLOP BLOP BLOP BLOP BLOP BLOP BLOP BLOP BLOP BLOP BLOP BLOP BLOP BLOP BLOP BLOP BLOP BLOP BLOP BLOP BLOP BLOP BLOP BLOP BLOP BLOP BLOP BLOP BLOP

 

[Houtman_imp]

It does not sound as if the bike runs well , it missed two BLOBS !