I've had my Q4 on for about a week or so. It's hardly a new piece of gear on the market, but thought I would throw my impressions out there and see if they match up with what you guys noticed.

My bike:

2014 EFI, KDX200 snorkel, Iridium plug, O2 sensor bypass kit. Rest is stock.

First off, I've noticed it rev's A LOT free'er. With the stock exhaust it felt like the engine wanted to shake and fall apart past 7k. But with the Q4 it can rev way past that and still feel/sound smooth. First time I rev'd it (for the comparison vid I mentioned in another thread) I hit 10k without knowing it. Could "never" do that with the stock.

I'm wondering if the stock exhaust plugged things up so much it was making the engine work harder to get the exhaust out of there? Now with it opened up, it has to do less work? Just a guess. Point is, it revs super easy now.

As far as power, I'm not noticing much, if any, off the line. Maybe more midrange power I would say - well into 2nd gear and beyond. But I'm a heavy guy for this bike. At 240lbs I think I'll need a few more horses to notice any difference in 1st.

Noise levels...MUCH louder than stock. I'm almost done with the comparison video; you can see/hear for yourselves. The numbers don't seem a big difference, but your ears will say there is. I'm definitely going to get the Powercore plug I've seen mentioned. Though it is nice sounding as far as exhausts go. Certainly makes you feel like you're driving a larger bike.

On a side note, I'm ALREADY seeing signs of rust on some of the rivets/screws/bolts/whatever they are... Climate here is very humid and yesterday's typhoon didn't help. Still, I'm disappointed in that.

Can't think of anything else. Is that what you guys have noticed with it? Think I'll skip the Megabomb header. Or if some rich uncle on my wife's side dies...who knows.

 

q4 is great,not too loud...i stuck with oem header,351 BB kit..new bike.

 

It's kind of weird. It certainly sounds louder than stock, but if you let someone ride your bike around the block with the stock exhaust and then the q4 - you'll notice that it's actually not much louder at all in comparison. By comparison, remove the airbox lid is actually much louder over all.

While riding it though, it does seem louder!

You can get a quiet core insert that will further reduce the noise. It'll take away some of the "thump" or "bark" and have next to no impact on performance.

if you go from stock to a slip on, don't forget to adjust your pilot jet / fuel screw. I gained a TON of low end grunt when I did this and it allowed me to comfortable single track in 2nd gear without using the clutch much. Part of that is due to the MCM as well i'm sure, but there's no question the exhaust made a massive difference.

 

I have the Q4 with the quite core insert (not the one it comes with) mega bomb, KDX snork, smog gone, twin air but also did the jet kit. The bikes runs way better and throttle response is great through out the range. Try the jet kit.