Bandit 1250 No Exhaust Exhaust on the Cheap

[Ves]

I was watching this video...  http://www.youtube.com/watch?v=t80JTONwbSc

So, one of the options the guys shows is just the Bandit exhaust without the muffler... just the pipe.  It's also interesting that the last option he shows is a full exhaust.  Interesting that the full exhaust with can is actually louder than the standard exhaust with just a pipe (no can).  Then I got to thinking about it.  This makes sense.   A lot of BMW R1150R owners (like I use to be and like I did) just take the muffler off and run a short stubby pipe... and it works really well... nice sound... loose about 14 lbs...  because the catalytic converter is actually doing a lot of the sound deadening and is probably a bigger resistance to flow than the muffler...

So, that got me thinking more... you could probably put just about anything on the stock 1250 header/catalytic converter and it might sound pretty good... So something like this...



All you need is a connector pipe... just a regular piece of stainless exhaust pipe bent to fit...  The obove muffler can be had for about $50 on Ebay...  custom bent pipe... $20?...  

Then I got to thinking about the fuel mapping...  The new Bandit 1250 has a closed circuit system, right?... Says in the manual, "The air/fuel ratio is compensated to the theoretical ratio from density of oxygen and exhaust gases... more fuel is supplied if detected air/fuel ratio is lean... "

so removing the muffler will cause the fuel injection to automatically compensate for any slight leanness that may result from the decrease in back pressure... right?  

Yeah, if you put a pipe on there with no muffler and no catalytic converter you'd probably increase the flow so much, and lean it out, that you'd probably be outside of the range that the control module can adjust for... but that's highly unlikely if you leave the catalytic converter in place...

Am I making sense?... am I missing anything?

[Mr Sunshine]

The computer has a range of adjustment.  It can't go wildly one way or the other.

[Ves]

The computer has a range of adjustment.  It can't go wildly one way or the other.

I almost forgot I posted this...  

Right you are, but that's the point.  The catalytic converter seems to be contributing quite a bit of the back pressure, so monkeying with just the muffler shouldn't require much compensation by the computer...

[Ves]

Nothing beats trying it...

Comparison of size... Yeah, that's a little bit smaller...


Hung it just to see how it's gong to look... Love that gray carbon fiber...


View from the back...



So, here's a soundbite of the muffler slipped onto my header, with the baffle removed...



Now all I need is the local muffler shop to make me a pipe to connect them... mmmmmmwahahahahha...

[Ves]

Well, I finally got around to finishing it... here it is in all it's glory... Still need to tighten everything up... I sanded the pipe and painted it with high heat paint... Looks a little industrial, but I don't mind that at all...  I rode it around with the baffle out and it's just a little to loud... not much, because as you get up to speed the wind is actually louder... But I don't want it to be annoying.  With the baffle in it's got just a bit of growl... I'll probably punch some small holes in the back of the baffle and strike a perfect middle ground...  Even with the baffle out it runs really well... actually seems even stronger on the bottom end, if that's possible... smoother also.. if that's possible... doesn't back fire... So I'm guessing the computer is compensating... I'll check the plugs to make sure...  It's so much smaller than the stock exhaust and really opens up the right side... I like it...  Total.. just over $100...







I still have to figure out what I want to do about the center stand... right now it hits on the bottom of the shock so I could just put a piece of plastic in there, as a bumper, and I'm done, or maybe set up a stop somewhere else.

[gunzip]

I still have to figure out what I want to do about the center stand... right now it hits on the bottom of the shock so I could just put a piece of plastic in there, as a bumper, and I'm done, or maybe set up a stop somewhere else.

 drill and tap a hole in the centerstand at the 'right' spot and screw in rubber cabinet door bumper stop , works great

[Ves]

 drill and tap a hole in the centerstand at the 'right' spot and screw in rubber cabinet door bumper stop , works great

  Wow, that really appeals to the cheap bastid in me... I like it... thanks...

[bl4ckd0g]

Meanwhile, there's Civic or WRX owner in your neighborhood all pissed off since someone stole their muffler.

[Ves]

Meanwhile, there's Civic or WRX owner in your neighborhood all pissed off since someone stole their muffler.

Shhhhhhh.... I bought it on E-bay... that's my story and I'm sticking with it...  

[Yamadavidson]

I think it looks good, has kind of a moto gp look to it. I have a scorpion on mine but also messed around with chopping up the stocker by cutting the mid pipe off it and running just that. It was too loud for me but I have a gutted cat so I'm sure with the cat in place it would be alot quieter. With just the mid pipe on mine it looked like a yosh pipes from the 70s and it retained the tab for the centerstand. The reality is that bike pipes cost way too much for what you get and finding an alternative saves you money and gives you a custom look.

[Baz]

so removing the muffler will cause the fuel injection to automatically compensate for any slight leanness that may result from the decrease in back pressure... right?  

To answer your question. This will occur to a point. It depends how your injector nozzles are sized. F.I. will compensate but not to infinity. You could reach a point where your F.I. might not keep up with increased air flow.

There is actually a lot of engineering that goes into a motorcycle (air box, exhaust system back pressure, fuel mapping) when they design the thing.

Increasing performance is not necessarily as easy as opening up the exhaust flow. In fact on the old Bandit if you modified the stock air box, piped and re-jetted the bike, (as in my case) you increased top end power but at the same time robbed mid range power, and moved it to the top RPM range.

The only way you are going to tell if you have moved in the right direction is have the bike dyno'd & analyze the exhaust gas. This should be done before and after any work.

It is quite possible to actually loose power in some modifications, or change the stock power range of the bike.

When you buy a pipe & mapping kit from the aftermarket places, you are actually paying for the work they did fine tuning things.  

You might get lucky, or you might not, just throwing parts on.

[Ves]

Of course you're right on all points.   But long before there were USB power commanders and a dyno on every corner, a lot of people tuned by making adjustments and seeing how it feels and runs.  My objectives were simple; a smaller, lighter muffler, without a drastic change, and without the need to spend gobs of money... on parts or on professional tuning.  It starts well, runs well, doesn't backfire on deceleration, and there are no perceptible changes in power characteristics, so it may no be perfect but I sure can't tell.

By the way, I finally settled on leaving the baffle in, and adding four 3/8" holes to it.  Why? because I wanted to at least match the flow outlet area of the original muffler, because the baffle outlet diameter is slightly smaller than the original Bandit 1250 muffler outlet.  Yeah, I realize that there's more to flow than area, but again, I'm working under the assumption that I want to leave things close to stock.  

I think it works, but hey, if anyone in the Chicago area has a dyno they want to give me some free time on, let's do it...  

[Yamadavidson]

You dont need to worry about remaping or buying a TFI unit for just a slipon exhaust, it will compensate just fine as is. If it pops on decel just plug the hose that runs under the tank for the PAIR system and it will stop.

[OU812]

Nice job Buddy!

[HipGnosis]

How (where) did you get the bent pipe and what did it cost you?