4 to 1 Exhaust... what's the truth?

[TheCafeKid]

I went to the 4-1 (MAC) because it was the only unit I could get for my 650 to replace the stocker that was falling apart. I still have the stock air intake setup and with that no rejetting was needed. Besides a trimmer look to the bike, the sound is great. Haven't really noticed a power increase.

Doing it again, I'd go for the black headers if they were available, because the MAC chrome isn't very good-a lot of surface rusting that constantly needs attention.

Personally I have never cared for MAC pipes because I always thought they sounded a lil "tin canny" to me. But overall, this seems to be a constant complaint about thier product...

[andrewclaycomb]

I just traded in my Bandit for a new 2nd gen FZ1. It's fuel injected and has a similar moto GP type of exhaust. It's odd though because there is a servo motor in the exhaust that operates a valve electronically like the older ones did with a cable hooked to the carbs. I wonder if something like that could be integrated into the GS. with the servo you wouldn't need the specific carbs off an FZ1. you might be able to just modify the headers and have a simple exhaust swap. I also think it looks kinda cool.

[BigDaddyD]

So here's another question...
What's the best way to get the most performance out of a 4-2 system?
Are there performance engineered 4-2 systems available?

My only real reason for asking is that I'm not particularly a fan of the unbalanced look that a 4-1 gives. I know it sounds silly... but having those 2 big shiny megaphone pipes on either side of my ride just looks damn-cool! ;-)

[Mark M]

So here's another question...
What's the best way to get the most performance out of a 4-2 system?
Are there performance engineered 4-2 systems available?

Same as for a 4-1. You need to size the primary and secondary pipes (diameter and length) to suit your engine (valve sizes, cam timing, port sizes, etc.) and intended operating range.

Note that you can't buy any really good performance exhaust in 4-1, 4-2, or 4-2-1 configuration, the good ones are hand made to suit your application. The V&H dragracing megaphones are good systems, but they kill cornering clearance on the RH side. If they would use those numbers and re-bend to suit a typical 4-1 street system arrangement, then they would have something...

I don't know of any off the shelf 4-2 systems that are aimed at performance markets. You may be able to fit a Busa exhaust or maybe a Bandit 1200 system, they should be better than the typical aftermarket stuff for our bikes.

Mark
Mark

[BigDaddyD]

Sounds like a lot of technical stuff....
Don't know if I gots the smarts for all that.
;-)

[Nessism]

Sounds like a lot of technical stuff....
Don't know if I gots the smarts for all that.
;-)

What's wrong with the mufflers you currently have? If they are rotted out you can have some aftermarket mufflers grafted onto your current headpipes. JC Whitney sells a couple of different models that should flow more than stock and give you a more throaty sound. Not exactly a tuned system but it will flow more than stock.

[Jethro]

I just traded in my Bandit for a new 2nd gen FZ1. It's fuel injected and has a similar moto GP type of exhaust. It's odd though because there is a servo motor in the exhaust that operates a valve electronically like the older ones did with a cable hooked to the carbs. I wonder if something like that could be integrated into the GS. with the servo you wouldn't need the specific carbs off an FZ1. you might be able to just modify the headers and have a simple exhaust swap. I also think it looks kinda cool.

Nice choice on the FZ1! I am loving my '06, and have modded it to the max. If you need any advice, let me know, I did all the work myself. Open that airbox and let it breathe! The bike comes stock with a serious case of asthma...

[Old Colt]

Nice thread here, allot of info in it. I build custom headers for part of my living. I can say there is quite a difference between what is sold commercially and what can be made for a specific application.
A few notes.
A 4-2 exhaust needs to pair cylinders properly. To make any gains in power the firing pulses should oppose each other. This would mean 1&4 and 2&3 need to share collectors. Generally these systems pair each side with uneven pulses going in them. You will not get much power from this but it is easy to package.
The reason a 4 into 1 with a flat collector does not show a flat spot in a power band is simply due to the fact that it does not make any gain in the powerband anywhere. The flat collector has to much volume within to provide any scavenging. The flat collectors are considered an untuned system.
The current technology in exhaust systems has been centered around the collector. The system builder can do allot with the engines character by changing dimensions withing this small area of an exhaust. Loss of low end power can be a thing of the past by paying attention to the length of the merge, volume of the collector and outlet size and divergence into the tailpipe. Defiantly not something found with off the shelf systems that cost less than one collector does.

The most economical way to get good power gain and a visual balance may be to get a 4 into 1 header that is centered under the bike and then have a center pipe made bringing the exhaust out each side into two mufflers of your choice. This can give you the most use of off the shelf parts with the minimal of custom work done local to you.

[BigDaddyD]

What's wrong with the mufflers you currently have? If they are rotted out you can have some aftermarket mufflers grafted onto your current headpipes. JC Whitney sells a couple of different models that should flow more than stock and give you a more throaty sound. Not exactly a tuned system but it will flow more than stock.

They're starting to rot at the ends. Nothing too bad, just a few small cracks starting.
I'm sure I can still get plenty of usage out of them, they're not in horrible shape. A little scratched up here and there and the right muffler and #4 header tube are badly discolored from a broken Exhaust Manifold bolt and a missing exhaust seal where the muffler meets the header tube.

Nice thread here, allot of info in it. I build custom headers for part of my living. I can say there is quite a difference between what is sold commercially and what can be made for a specific application.
A few notes.
A 4-2 exhaust needs to pair cylinders properly. To make any gains in power the firing pulses should oppose each other. This would mean 1&4 and 2&3 need to share collectors. Generally these systems pair each side with uneven pulses going in them. You will not get much power from this but it is easy to package.
The reason a 4 into 1 with a flat collector does not show a flat spot in a power band is simply due to the fact that it does not make any gain in the powerband anywhere. The flat collector has to much volume within to provide any scavenging. The flat collectors are considered an untuned system.
The current technology in exhaust systems has been centered around the collector. The system builder can do allot with the engines character by changing dimensions withing this small area of an exhaust. Loss of low end power can be a thing of the past by paying attention to the length of the merge, volume of the collector and outlet size and divergence into the tailpipe. Defiantly not something found with off the shelf systems that cost less than one collector does.

The most economical way to get good power gain and a visual balance may be to get a 4 into 1 header that is centered under the bike and then have a center pipe made bringing the exhaust out each side into two mufflers of your choice. This can give you the most use of off the shelf parts with the minimal of custom work done local to you.

I actually thought of that, running a 4-1 header and then splitting it at the collector. But all the talk I hear about the loss of ground clearance and possible oil filter issues... I'm just not sure if I even want to mess with a 4-1. Plus, wouldn't running the extra tubing to the 2nd muffler on the left side unbalance the flow of exhaust? Or is it not a concern since it would be after the collector?
That weird X-pipe that is mentioned earlier in this post SEEMs kool... I just haven't heard of anyone using one just yet. Don't quite know if they're even real at this point ;-) Any thoughts on those?

For the moment the stock 4-2 is working well. I was having some troubles w/my mixture b/t all the carbs (my #1 and 2 plugs kept fouling but I couldn't lean out those carbs anymore since they were already significantly dialed out farther then my #3 and 4 carbs), but upon inspecting my system the other day, I noticed that the baffles on the right side muffler were practicality blown out yet the left side was still in tact. Needless to say there were some definite exhaust-flow issues occurring, so I knocked out the remaining baffles in both mufflers and she's running quite a bit smoother now. The tubes and packing are still in there so it's just slightly louder, (and actually a quite nice low tone) so we'll see if that helps me get the mixture dialed in more evenly across all the carbs being's they're all flowing the same amount of exhaust now.