Stock v. Aftermarket Headers

[Scarabsport]

These stock mufflers have to go and go soon.

If slip-ons add relatively little power over stock then those huge ugly stock mufflers must really be efficient. What is it about the stock headers then that are so restrictive? Does it have like an exxup valve or something? Or is it that they have too many turns or sloppy welds or something?

 

[thebbbusa]

There is a combination of many things mostly involving compromises for EPA regs and such.

The factory has to meet many restrictions including but not limited to sound levels and emissions.  As a result, their pipe sizes are smaller, the mufflers are larger and the bikes now have something like a catalytic converter in them.  Additionally the headers are usually made from less expensive heavier materials.

The aftermarket systems will usually offer a dramatic weight reduction and are tuned with varying diameter sizes for maximum flow efficiency.  To do this from the factory would increase the sticker price a lot.  Also each quality mfr will tune their system to make power at certain rpms vs others based on the intent of use.  The aftermarket systems also do not have catalytic converters in them and as a result technically are for offroad (as in on the track) use only.  If you read the fine print, most if not all aftermarket systems are not street legal.

So to directly answer your question the stock headers are restrictve because they usually use bending methods that will reduce the diameter size, joints may not be welded as cleanly, have an overall smaller diameter, have cats, and cans that are very restrictive and weigh a ton.

 

[Eagle747]

I understand the cat in the new Busa is in the collector box. Maybe a bit of surgery would help?

 

[Bo_]

no exup, but if you pull one of your stock mufflers, (remove the hanger bolt and loosen the hose clamp, not the flange bolts), then shine a light into the catalytic converter and you will see the honeycomb, the honeycomb is the most restrictive part of the stock header system other than the muffler. So if you install a free flowing slip-on can it will uncork it a bunch, an after market air filter a little more, and an after market full system even more.

 

[Professor]

There is a great exhaust thread showing the different on the early version pipes. .. Someone point it out. I can't get there from here. It is pinned in one of the performance or mod areas. I believe War Baby was the author. You might have to turn on display all threads from the beginning to see it.

 

[Eagle747]

no exup, but if you pull one of your stock mufflers, (remove the hanger bolt and loosen the hose clamp, not the flange bolts), then shine a light into the catalytic converter and you will see the honeycomb, the honeycomb is the most restrictive part of the stock header system other than the muffler. So if you install a free flowing slip-on can it will uncork it a bunch, an after market air filter a little more, and an after market full system even more.

Is that for the 'old' Busa? I though the new one had the cat in the collector box! But I'm often wrong....

 

[Ride_or_Fish]

About 25 - 30 lbs, depending on what you system you pick!

 

[Eagle747]

What about the O2 sensor? I know there is one but don't know where it is.... A new full system would mean no sensor. What would that do to fuelling?

 

[Got-Busa?]

The PC for the 08+ BUSA has a dummy plug that eliminates the o2 sensor...

Heck just take one off and compare them side by side. It's a night and day difference over stock. Not to mention you save 30lbs+ and pick up 5-20+ rwhp depending on your setup with just a pipe....

 

[Commuta_Busa]

read thebbbusa post

 

[rocktober]

yea,... but how do these after market fit , i heard some nightmares about most of them, not only that but the quality of the way there built, like not fitting

 

[Commuta_Busa]

a good quality name brand full system will not have any issues. I cheap fleabay knockoff might.

 

[rocktober]

have you personally installed an aftermarket header, and if so what kind fits the best without any issues

 

[Scarabsport]

Okay, so if I understand it right the catalytic convertor is actually in the pipes and not the muffler, and that is at least in part the reason for the restriction?

If so then one of my bikes (R1?, FZ1?, I'm getting old, memory is going) I remember punching the catalytic convertor out of the pipe, it was a slip fit that pulled right out, and as I remember it uncorked the exhaust system and greatly reduced the heat that was coming off the pipe in that area.

So my question then is can the cat(s) be pulled out of the'08 pipe? Kind of a poor man's full system?

 

[Commuta_Busa]

full muzzy no install problems
full akra no install problem
full brock/hindle no install problems
full hmf no install problems
full tiforce had problem with can mounting point, was resolved in later models

those are the only ones I've actually done. The headers have never been an issue but the mid pipe can sometimes need a little fairing spacer put in for clearance and to reduce the risk of melting the fairings.

I think the hardest header install I had was with a damn turbo. Those bolts were a nightmare to get my sausage fingers to turn.

 

[Bo_]

Okay, so if I understand it right the catalytic convertor is actually in the pipes and not the muffler, and that is at least in part the reason for the restriction?

So my question then is can the cat(s) be pulled out of the'08 pipe?  Kind of a poor man's full system?

On the 4 to 2 to 1 to 2 system, the cat honeycomb is in the 1 part, and no it cannot be removed by simply pulling it out, I'm sure it could be chopped out but it is like 4 inches in diameter and the only way out is two 2 inch holes/spigots.

 

[Professor]

Here is the thread I was referring to Click Here

 

[Scarabsport]

Prof, thank you for that link, very informative. That post would be an excellent one to pin, especially with the Gen II driving so may questions on exhausts (like my questions)

 

[Professor]

Prof, thank you for that link, very informative.  That post would be an excellent one to pin, especially with the Gen II driving so may questions on exhausts (like my questions)

It is pinned in the engine and performance section. However due to a bug in the board software it is not visible if you are filter to view threads in the last 30 days.

One of my favorite threads here.