Want to put stock exhaust back on!

I bought a bike with the full FMF exhaust and all the usual crap removed.

It currently has Q4, Powerbomb header, programmer, EXUP/AIS delete, airbox opened up. I have the stock parts, except for the spring that mounts on the stock exhaust for EXUP. I'd like to keep as much useless crap off the bike, but go to stock exhaust mostly for the noise level.

The more I read, the more contradictory it sounds whether I can run the stock exhaust/header with EXUP and AIS not hooked up as I'd prefer. I'd likely keep the programmer, but maybe not. This is a 250, and all this stuff is worth $$ to me!

I did swap the exhausts and liked how it ran with stock programmer settings. Then, like I said, the more I read, the more confused I got about long term running without the EXUP/AIS so I put it back on.

I've done the research. I guess I'm looking for someone knowledgeable to sway me one way or the other.

Thanks

The conventional thought is you need the AIS junk with the stock exhaust to prevent damage to the "catalytic converter" crap.

The EXUP stuff is much less fact and more myth about it's intended purpose.

#1) it supposedly helps with increased HP at certain rev ranges

#2) it's mainly a noise/pollution reduction thingy

I know from a video a guy did once that the EXUP valve activates about 2% of the time and only for very short amounts of time. All the rest of the time it's basically wide open. The spring you're missing holds the valve in the wide-open position at all times. Unless the bike's electronics are trying to close it.


So my opinion is this.

If you return your bike's exhaust system to 100% stock, I'd think the AIS stuff needs to be put back on.

I would not worry about hooking up the EXUP stuff as much, but you should have some way of securing the valve in it's wide-open position. That's what the spring was designed to do. I have pictures of that stuff somewhere in this forum.

motokid wrote:

The conventional thought is you need the AIS junk with the stock exhaust to prevent damage to the "catalytic converter" crap.

Interesting! Much like the OP, my bike came with all the mods. I also have went back to the original exhaust, but the AIS is still blocked off. The bike has put on 3000+ miles with the original exhaust back on with no noticeable problems.

Will have to look at this some more.

IMO needing the AIS because the exhaust has a cat in it is a myth... the same amount of carbon that plugs the cat hits it with or with out the AIS. The AIS is there for a polution test, the % of polution is reduced when you put more air through the exhaust.

motokid wrote:

I know from a video a guy did once that the EXUP valve activates about 2% of the time and only for very short amounts of time.

The EXUP activates when you are running at low RPM's, while in 6th gear, going at a constant speed between 55-60 mph.

That's it.

The Exup closes during low rpm to increase torque/ widen the powerband as can be seen in this video and explained in the wiki link. If you drive in the higher rpms it will never close as can be seen in the video. Unfortunately he mostly drove 1st -4th. You might see it better in higher gears going up hills as he isn't at low rpm for any length of time.
I don't understand why the first thing people do is want to remove it. I guess if you go to redline every shift then its dead weight but otherwise it gives you a more usable tractable engine.

https://www.youtube.com/watch?v=sPeBawoIXAM

http://en.wikipedia.org/wiki/Four-stroke_power_valve_system

The AIS injects oxygen rich air into the catalytic converter so that it can finish the chemical reaction. If you don't inject air emissions will go up. I am guessing that if you don't inject air cat temperature will go down which may lead to increased soot buildup and clogging over time, but I would think it would take many miles for such a thing to occur, I am just guessing, but I wouldn't worry about it till 25,000+ miles. Now that is on a stock engine. If you have a programmer not professionally tuned on a dyno with an air fuel meter, you can easily get more raw fuel dumping into your exhaust. In that case I don't know what would happen to the cat.

beee wrote:

The Exup closes during low rpm to increase torque/ widen the powerband as can be seen in this video and explained in the wiki link.  If you drive in the higher rpms it will never close as can be seen in the video.  Unfortunately he mostly drove 1st -4th.  You might see it better in higher gears going up hills as he isn't at low rpm for any length of time.
I don't understand why the first thing people do is want to remove it.  I guess if you go to redline every shift then its dead weight but otherwise it gives you a more usable tractable engine.

https://www.youtube.com/watch?v=sPeBawoIXAM

http://en.wikipedia.org/wiki/Four-stroke_power_valve_system

The AIS injects oxygen rich air into the catalytic converter so that it can finish the chemical reaction.  If you don't inject air emissions will go up.  I am guessing that if you don't inject air cat temperature will go down which may lead to increased soot buildup and clogging over time, but I would think it would take many miles for such a thing to occur, I am just guessing, but I wouldn't worry about it till 25,000+ miles.  Now that is on a stock engine.  If you have a programmer not professionally tuned on a dyno with an air fuel meter, you can easily get more raw fuel dumping into your exhaust.  In that case I don't know what would happen to the cat.

In the exup vid you posted the exup valve is open at low rpm then closes at higher rpm, you have it backwards.

You cant compare the exup valve on the wrr/x to the ones on 4 cylinder sport bikes, they work the oppisite to each other.
The sport bike ones are closed at low rpm, it boost tq on small 4 cylinder motors, it only works on motors with 4 into 1 pipes.
On a single the more open the exhaust with the proper sized pipe the more low end tq you have.
Adding a straight through pipe like the fmf power core gives you the most low end posible, anything that blocks flow hurts the low end on a single, thats why mx bikes have straight through loud pipes.
The exup valve is on the wrr/x to make it quieter for some sound test it needs to pass, thats all!

I admit the video is confusing because I don't think he is wide open throttle in every gear, and he isn't pulling any hills so it happens fast.

Here is the play by play:  starting at 2 min 12 seconds in the video, ending at 2 min, 15 seconds.
1. valve starts OPEN, throttle is closed.
2. valve closes as he twists the throttle to wide open (this only occurs IF the engine is below a certain rpm)
3. rpms climb and valve opens opens back up.

You can also google "what does exup mean"

I think you maybe the only one confused by the vid lol.

The vid shows the valve working like I tried to describe it...
Open at low rpms, closed at the rpms they sound test the bike at ( mid range were you would want max exhaust flow lol ) then open at higher rpms.
Its not doing anything to help power at all, its all about noise!

If chokeing the exhaust off makes the bike run better why do you need to put an open free flowing pipe on the bike with no exup to get more power? lol.

googling "what does exup mean" wont tell you anything!
I tired to explain this in my last post...
4 cylinder motors have way different exhaust needs than singles! You cant compare the wrrs exup to a sport bikes.

Do u have any links to back u up big lake? Where does it say power valves dont work on thumpers?

Biglake wrote:

IMO needing the AIS because the exhaust has a cat in it is a myth... the same amount of carbon that plugs the cat hits it with or with out the AIS. The AIS is there for a polution test, the % of polution is reduced when you put more air through the exhaust.

Actually, the AIS (air injection system) on the WR is there to introduce oxygen into the exhaust at the port to extend the burning process of the unburned fuel vapors before it reaches the cat. This reduces the amount of "work" the cat has to do to remove the remaining fuel vapors before exiting the muffler. Without the AIS, the cat works harder & will cause it to increase in operating temperature which shortens it's useful life. Not all vehicles have an AIS system, it depends on the engine efficiency & design whether they need one or not. If you have ever seen a car running really rich due to a sensor or fuel system malfunction, the cat will begin to glow orange if run that way for an extended period of time.

Don't ya like how you ask a pretty simple question and you get multiple contradictory answers. Well you don't have to take my word for it, (though I like my answer the best). You can simply google something like air injection catalytic converter to find out exactly what it does. It has been used on many many vehicles during the 80s and early 90s. And I can ensure you just cause a car has multiple cylinders and this bike only has one has no effect on how a catalytic converter works lol.

beee wrote:

Do u have any links to back u up big lake?  Where does it say power valves dont work on thumpers?

I dont have a link or need one lol.

Straight from your link... This is achieved by partial closing of an internal butterfly valve within the exhaust at the point where the four primary pipes from the cylinders join.

It says its for 4 cylinders lol.

Have you ever seen a exup on any other single cylinder bike? If it worked other bikes would have em!

Most 4 cylinder sport bikes have them because they work in that applacation.

Ya gotta let it go... the exup is extra unessicary weight just like the airbox flapper, they're both there to make the bike quieter for some third gear 50 km/h drive by noise test thats all!

Well the original poster has enough info to decide to do whatever he wants. This is my last post in this thread.

^^ Come on mate.....one more for the road hey !   lol

 

lol