de cat de baffle exhaust after needs

hia, i plan on taking out the baffles in muffler and hollowing out the 3 cats for the little extra performance gain and some more noise. i have sevral questions and i am a auto tech so if your are a motorcycle tech please dont hesitat to go into detail, here goes.

1. i asked my local shop about the 02 sensor, wanted to know what it does (if its like a car pre cat o2 will try to compensate (pcm)fuel mixture for a rich /lean condition) he didnt know if it worked the same, So does it?

2. i have seen other posts that say i would need a power commander because of the lean condition i would be creating, ok... the o2/ pcm wont compensate enough then? I have seen another product befor hopefully you can point me to it, it was pretty much a resistor you put in line with your Iat (intake air temp) sensor to fool the pcm that it was really cold out, hence it would make your air fuel ratio richer. would this inline resistor be enough to keep me from running to lean, after the exhaust mods? i know i wouldnt gain the extra hp from the power commander but untill i got one, just dont want to burn up my valves.

3. lets say i did the exhaust mods and did nothing about a commander/ inline resistor, wouldnt it thou a check engine light due to the o2 sensor/block learn intergrater going fuel rich for a extened amount of time? and same question about the resistor, if i remember right it made the pcm see a -40 value, wouldnt that set a light to?

4. for anyone who has actually debaffled (not drilled) there muffler----what way cutting it open works best, in half or making a large hole on the top/bottom? are the pipes and baffles welded inside?

thanks in advance for your help, like i said i am a auto tech, trying to find out the theroy of the motorcycle side of pcm controls.
:thumbup:

As for number 4.

I had my muffler off today - looking at it, it seems that each layer of baffles is pretty well welded on all around the case. So you'll probably have to cut the muffler in half/thirds and cut them out. Just a guess based on the weld marks coming through the outside of the muffler.

Thank you, that's why I have torchs for. To cut out welded baffles.

Someone gutted a muffler as you intend about a year ago, on this forum. Do a search, there were pictures posted too.

IMHO, I'd gut the muffler first before doing anything else, it should get considerably louder and have close to the same back pressure as most aftermarket pipes which are pretty much flow thru. You can leave the cat and O2 sensor connected for now so it can do its thing. I know with the cat out, it does get increasingly louder.

With just my open Scorps (cat still in) the sound is about right. I could NOT take it any louder.

I looked and couldn't find the thread. Pretty much, they cut three large cuts on one side of the muffler and bent that "panel" back. They went to town with a torch cutting away all the innerds. Bent the panel back, tig welded it back tight, GUTTED MUFFLER. Also just doing this, you likely don't have to worry about any O2 issues as your still hooked up before the muffler.

TownsendsFJR1300 said:

Someone gutted a muffler as you intend about a year ago, on this forum. Do a search, there were pictures posted too.

IMHO, I'd gut the muffler first before doing anything else, it should get considerably louder and have close to the same back pressure as most aftermarket pipes which are pretty much flow thru. You can leave the cat and O2 sensor connected for now so it can do its thing. I know with the cat out, it does get increasingly louder.

With just my open Scorps (cat still in) the sound is about right. I could NOT take it any louder.

I looked and couldn't find the thread. Pretty much, they cut three large cuts on one side of the muffler and bent that "panel" back. They went to town with a torch cutting away all the innerds. Bent the panel back, tig welded it back tight, GUTTED MUFFLER. Also just doing this, you likely don't have to worry about any O2 issues as your still hooked up before the muffler.

Click to expand...

I found this one, Scott. Hope this is the one you were looking for, or at least can help:thumbup:http://www.600riders.com/forum/fz6-m...k-exhaust.html (Heavily modded stock exhaust)

motojoe122 said:

I found this one, Scott. Hope this is the one you were looking for, or at least can help:thumbup:http://www.600riders.com/forum/fz6-m...k-exhaust.html (Heavily modded stock exhaust)

Click to expand...

Yepper, that's it, didn't think it was that long ago. Thanks!

My open Scorps are considerably louder than the modded pipe (W/O DB killers)

Thanks for the link. One question about the muffler he made. Why did he put in the insulation? Would it of been louder if he didn't. Or a different tone?

GravisMaximus said:

Thanks for the link. One question about the muffler he made. Why did he put in the insulation? Would it of been louder if he didn't. Or a different tone?

Click to expand...

Dunno.

I would think, the insulation would get rid of any "tininess" in the muffler.

Almost all aftermarket pipes have "packing it them.

Might be worth your while, if doing this mod, to invest in a re-packing kit. Speaking with a rep from one of those companies can probably let you know the effects of packing vs no packing.

TownsendsFJR1300 said:

Dunno.

I would think, the insulation would get rid of any "tininess" in the muffler.

Almost all aftermarket pipes have "packing it them.

Might be worth your while, if doing this mod, to invest in a re-packing kit. Speaking with a rep from one of those companies can probably let you know the effects of packing vs no packing.

Click to expand...

What you said - is right.


The fiberglass or metal thread/string that is in aftermarket exhausts works to absorb the high frequency sound. This leaves the rumble that people look for in a deep exhaust. If you just did a straight pipe, there would be a lot more of the tinny, ricey cracking sound.
For MC exhaust, most companies use metal packing material, as it does a better job than fiberglass at removing the noise. I've been pretty happy with my glasspack though.

Tinny ricey cracking noise?? Like a Indy car while it decelerates? Notice I said like I now its never gonna sound just like it. :BLAA:

ok did a lot more research, so i have more questions. the co adjustment that can be unlocked by grounding- i suspect a scanner like the rmt 7 in 1 connector for yamaha. RMT-7 in 1 Motorcycle Scanner -Motorcycle Scanner-obd2 tools, ELM327 interface, VAG diagnostic interface, vehicle diagnostic tool, OBD code reader, car diagnsotic scanner, obd scanner, auto diagnostic cables this would plug into the same connector you brake apart to get to the empty pin. the scanner conector has a ground wire and states that it can make co adjustments, i bet its grounding the same wire like you do manualy to unlock it. anybody know this to be true or not. there are several different scanners with the same looking yamaha connector, has the green wire.

After i do these mods one of my questions was about the o2 sensor being able to compensate for the lean mixture (it wont do it enough i was told), after my research i see many posts about having to unplug the o2 because when you hook up a pc3-5 or a juice box naturaly it will run rich due to changing the maps, but the o2 will try to lean it back to the stock settings. so it will not fix the lean condition but will lean it out due to the power commander? that dont make sense. i understand its trying to adjust it to a stock setting, but if it can trim enough away to void the benifits of the power commander, shouldnt it be able to add enogh no to run rich. a little help here.....
where would you recomend getting this 02 disconnect kit i have read about. here are just some of the links ive been looking at.
http://www.600riders.com/forum/fz6-mods/36620-dynojet-oxygen-sensor-eliminator-kit-fz6.html
http://www.600riders.com/forum/fz6-mods/4809-dyno-tune-co-adjustment-leo-vince.html
http://www.600riders.com/forum/fz6-mods/7801-verifying-what-ive-learned-about-efi-fz6.html

I don't know if you have been able to find any pics of the cats but they flow incredibly well. They are a very open honeycomb design and you won't gain too much power for the work involved. That being said I had a 04 and gutted the single cat which did make it a bit louder. As for gutting the muffler you won't be able to use a torch it's all stainless steal. Cut off wheels are your best bet unless you have and are real good with a plasma cutter but even then the muffler walls have 3 layers so again cutoff wheels are your best bet. As for a power commander, depending on how much you gut your muffler and if you change the openings you would be fine with out it. If you simple gut the muffler and don't direct the exhaust flow any towards the outlets you will most likely loose power, just something to keep in mind.

I'll also add that by looking at the pics in the posted link it looks deceivingly easy to gut the muffler, it's not, it's a huge pain in the ass the way it is made with some baffles welded as well as folded over and crimped onto one another

Do an experiment for all of man kind.....

See the two outlets in the OEM muffler - Remove them, replace them WITH A NEW DIAMETER OF 1.45" (1.25" to 1.5" I.D.) and put it back together.

I bet you get the sound you want, pass emissions, and it costs you time and some short chunks of SS pipe. Bolt it back up and call it done!

PS - leave the baffles and simply increase the flow at points of restriction - i.e. increase hole diameter ONLY!

Final impact. Your suggestion would basicly be straight pipeing the muffler correct? Which brings up a question/ your opinions. What would the difference be in the sound between straight pipeing the muffler and just removing all the baffles and increasing the outlets to 1.5.

Whatever you do I wouldn't eliminate the CAT as it's an expensive fix if you ever have to replace them. The other thing I'm wondering is how you're going to attain a known, healthy A:F ratio without a sniffer especially if you open up the back.

I've modded a stock can and it's not that easy because it has chambers and there's an outer skin then fiberglass then a perf metal section. The metal is spot welded so it's not as straight forward as it seems. It sounded 100 % better than stock but it was a lot of work with out a welder. I use a cutting wheel for opening it all up. Getting rid of the output pipes and swapping them for a larger bore pipe would have made the lower frequency component more prominent so consider making that part larger for better tone.
Good luck with your mod!

The hope is to be able to hook up a scanner and read live data. Then set the co levels to richen the mixture. The scanner I've refers to in other posts. Rmt 7 in 1 says it works with Yamaha fi . Now after calling multi dealers in the area only one said I could hook up a scanner to my bike. The others say it only uses the on board diag. I really find this hard to believe, I've seen the hand held Yamaha scanners on videos, so what Yamaha's does it work on?
Today as I was checking my stock co levels I found a 4 pin plug wrapped up tape next to the ecm, wonder what its for. I will upload a pic if it tomorrow, maybe its the scanner plug???

i will start a new thread for this plug in the electrical section

GravisMaximus said:

Final impact. Your suggestion would basicly be straight pipeing the muffler correct? Which brings up a question/ your opinions. What would the difference be in the sound between straight pipeing the muffler and just removing all the baffles and increasing the outlets to 1.5.

Click to expand...

Not at all. But it would be a painful extraction unless you have access to a plasma cutter. Look at the OEM pipe, that tiny outlet is likely the hold up. The muffles itself has lots of volume to keep the tones low (desired effect), but the tiny outlet forces the sound waves into a high velocity single file exit. Opening it by increasing the diameter may be the ticket bit it'll be a serious PITA to do it.
Use a cut off wheel to open and extract the old pipe and a die grinder to open the dia up. Leave the baffles in.

Finished the exhaust mod, heres what I did i removed the header pipe cut the outlet off and removed the precats welded it back together. Removed the mid cat and reinstalled. Removed the muffler, debaffled it increased the outlets to 1 3/8 welded the muffler and reinstalled.
The sound is a much deeper tone, nice. I took a db reading of before and after, before the mod at idle I measured 90db at the muffler and 104db at 12k rpm. After the mod 104 db at idle and 115 db at 12k rpm.
I've taken milivolt readings at the o2 sensor after the mod, .835mv at idle and .875mv at 8k rpm. So I will be rechecking this after I remove the AIS and adjust the CO to try to bring the reading closer to .450mv. Having to do it this way due to the scanner I got (7 in 1) does not hook up to our bikes. I spent many hours trying to get it to communicate with the ecu.
I have pics of the muffler if your interested.