homemade exhaust silencers

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I can only assume it was a loud/std pipe of his to start. It was pretty loud.

I wish I could find another way to adjust it, though. 18 screws is a bit much.

I've been swamped with work, girlfriend, and friend stuff lately. I can probably play around with some more ideas next week.
 
Nice design, simple and effective.

I must tip in on the backpressure issue though...
I've been reading the forums for a little while now and love all the useful and real world info, but backpressure is always popping up.

Backpressure is the enemy of power, and torque. You want high gas velocity, usually achieved with small tuned-diameter systems, and often lost with open, gutted stock and poor aftermarket systems.
This often leads people to the (incorrect) conclusion that backpressure=torque, it is simply not true. It is true that high torque systems often have a little back pressure, but it is only a by-product.

Look at a drummer exhaust, which are renowned for low-down torue, they are a large open chamber with a tuned diameter exit, i.e. high velocity, but very low backpressure, probably only 2 or 3 psi. Whereas the stock system would be more like 10psi of backpressure. The 'silencers' would cause huge back pressure and likely rob a lot of power up top, but possibly increase scavenging down low with more reversion and result in more torque, but this does not mean that the torque is the result of backpressure, it's much more complex than that.


Pheww. Sorry, i needed to get that off my chest.
 
I love a loud pipe but I guess it might be cool to have somthing to make it quiet if I were going to kill someone and needed a ninja stealth mode.:D
 
Hey Paniller how're those things holding up? I love my exhaust but sometimes get tired of feeling like my ears are about the bleed and I think I'm 1 or 2 rides away from going back to the stock exhaust. If those silencers are working out well for you still I'll probably check out Mcmaster's site and see about ordering some of the parts for myself.

What's your final recommendation on the inside diameter that would be ideal? I don't need it as quiet as stock, I think I'd be happy with half way between stock and Hawk for when I have them in.
 
Oh, and also, when you ordered the extra set screws, which type of tip did you get on them? The pointed ones so they held the best, or some smoother ones so they didn't rip up the inside of your exhaust tip too bad? I wasn't sure what kind even came with the shaft collar to begin with. I'll have to sit down and do some math to make sure I get the right length and all of that. It looks like if I get the 1-1/4, the shaft will be 3/8 thick.

Do these look like the right parts?

http://www.mcmaster.com/#shaft-collars/=8x2en6

http://www.mcmaster.com/#set-screws/=8x2jww

I don't think I'm going to thread the other 9 holes yet. I'd just drill them for now and see how it goes. I actually think all of my taps are metric anyway, so I'd have to find some of those before I got very far anyway.
 
Sorry for disappearing guys. It's been hectic. Hopefully I can make a few and send them out to soothe bleeding ears.

Maiden, those look like the correct parts. I went with the set screw shaft collar (upper left on the page at the moment). I ordered cupped set screws. I just kept turning them until I could feel a slight bump forming on the outside of my exhaust tips. Nothing visible, you can just feel a slight bump forming, like a pimple under the skin the night before the prom.

The shaft is a little thick/wide. I'd almost consider buying aluminum stock so I could cut them thinner than the shaft collar is. The weight drops with added holes, but it's all still a bit excessive.

I wrote some misleading information that I can't edit. I didn't use the 1.25" ID, I used the 1.1875" (1 3/16"). I added 9 13/64" holes. I tapped them, but honestly never tried set screws. It feels like it'd be too much backpressure/restriction.

I'd probably do it all again with 1.25", a slightly larger ID, less resistance. With the 1.1875" and 9 holes open, it's been perfect for me in terms of volume. However, that's at full blast, so I'd rather it louder, then add a few screws for this volume.

Powerwise, it feels a little more smoother and powerful down low. I'm assuming this is because it flows less, and is running slightly richer and resulting in a little more power. Up top, I definitely feel it drop off or level out in the top 1000 rpms. This is why I'd say definitely go larger ID. I've been riding mine hard the whole time, so it's not bad, but I feel it could be better.

I'm not sure if the 13/64" side holes still works with the larger ID. If it doesn't, I'd shoot for a little more than my previous ~1.4 in^2 open area (total of the 1.1875 and 9 holes). A fully open outlet is 3.14in^2, I'd bet 2in^2 would be what most people want, 1.5 at the smallest.
 
So, conclusions so far:

1.1875" ID with nine 13/64" holes is ~1.4 in^2. The sound level is great, a hair above stock, but power suffers up high.

1.25" ID resulting in ~1.5 would be better for this simple design, yet still bulky and not adjustable to be loud enough

A narrower shaft collar with different design that varies from 2.5 to 1.5 in^2 would probably be ideal.
 
I put my stock exhaust back on for the time being since I was having problems getting the race map to load. I'll probably try to sort out all the computer stuff over winter, so maybe I'll make some of the silencers as a winter project.
 
and those were the pieces I was looking at, I didn't check the links so I didn't realize it just took you back to the main page anyway, not actually a link to the shaft collars.
 
Ok so I just did this to my xb9 and it doesn't seem to make my exhaust quieter at all if anything maybe a little more throaty. I used the 1 1/4 inner diameter with no holes drilled. It seems the only thing it has done is not make my rpm's climb as quick as before. Anyone have any ideas?
 
Probably too much restriction? Strange that it's not quieter, though.

That's strange, you'd think you'd see the opposite results.

I'll have to take mine out again to confirm the changes I've felt. The power could be mainly placebo effect, but I know it got quieter.
 
I'm starting to have my doubts here. I took these things out to try to widen/open them more to restore top end. I was startled to see how much power was regained by removing them. It was just choked out above 4k rpm. Even below that is healthier, it idles 200rpm higher, for example. The only difference is a little less from 1000-2200rpm, where it was smoother with the inserts(not necessarily faster).

So, obviously these things are not a feasible option. I really can't recommend them anymore, as you'd have to drastically open them up from what I used. At which point, they'd probably be just as loud as before.

I wish I could edit previous posts, but hopefully people make it this far. Don't use my previous design, unless you want to experiment and open it up more. Maybe a thinner thickness or better tune would work.

Post up if you have results for other sizes or designs. I hear of better results from people using 3 thinner washers with tons of holes, then lining the washers up with a gap, holes offset. Maybe someone can try that, we need to block sound waves with minimal resistance.
 
Anyone come up with any other options for the hawk exhausts yet? I was really looking forward to trying this before spring, but I see it doesn't look like it helps much. I would really like something a mid step between stock and loud.
 

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