Virgin baffles...

[diamond_jim]

Looky, looky-


I got a local muffler guy to make these for my V&H straight shots. It took him all of 5 minutes to make them. He said no charge but I gave him $10 anyways. Now I can start modding these and see what I can come up with.

[diamond_jim]

Mod #1.

I simply wrapped the inside narrower section with the fiberglass muffler packing.

The good- Wow, it's sounds great at idle. Like with the fibrosleeves, it attenuates high frequencies such as natural pipe resonances. It sounds absolutely awesome.

The bad- too loud at any rpm above idle. It's as loud as having no baffles but a good bit deeper sound.

I'll try another idea later.

[NateHarris]

yeah, I had to go with stock pipes again. Those drilled pipes were just too damn loud! My ears would be ringing for hours after a long day of riding.

[diamond_jim]

Rode some today with the first mod of the baffles. It's not quite as loud as I thought but still a little louder than I'd like.

[mbgraham2000]

What gage steel do you use for baffles? I want to attenuate my Jardines a little. Will rivets hold up in the exhaust?

[diamond_jim]

I'm not sure what gauge steel mine are. It is the standard stuff that exhaust and muffler shops use. The guy simply measured the inside diameter of my pipes, found some pipe that was about a 3/8" smaller in diameter, put it on his cool machine and expanded the ends so they slide perfectly into the pipes. Took less than 5 minutes.

[diamond_jim]

Step 2.

I went back to the muffler guy and had him weld a washer in the inside end of the baffles (the washer side will slide in first).

[diamond_jim]

Wow! Much better. It cut the volume quite a bit but still sounds deep just like I was hoping it would. There is still a good bit of pipe length after the washer to help keep that deep sound. Very nice. A definite mod recommendation for anyone with custom pipes and the desire to change the volume while on a budget.

[Purplefern]

Is the change significant enough to re-jet/ try a new map now?

[diamond_jim]

Hmmm... good question. I can definitely feel the added backpressure. The engine doesn't wind up as fast or feel as free-breathing when accelerating hard.

There were some posts on here somewhere recently discussing changes in backpressure affecting engine braking. Well, no engine braking change with the addition of the noticable packpressure.

Here's the good and the bad.

Good- it's half as loud as straight pipes and sounds pretty darn good at idle and about half way up the rpm range.

Bad- it's starts to sound exponentially more crappy the higher the rpms. At 75mph it sounds like a 250 engine at redline.

Time for mod #3...

[mbgraham2000]

Maybe you can open up the hole in the washer a little. There may be an optimum size you need to find.

[diamond_jim]

That's what I'm gonna do. Also, when I tested it, I didn't have the narrower portion wrapped with fiberglass. So I'm gonna open the washer hole a tad, perforate the narrow section with a bunch of holes, wrap them with fiberglass and try it again. I think it will be just about perfect then.

[Thundurburd]

The acoustics of this is such that a hole will have properties of mass and enclosed volumes will have a stiffness, probably something like loudspeaker design. A mass and stiffness will have a corresponding resonant frequency and in fact the muffler/exhaust system will have many natural frequencies relating to pipe diameters, length, standing waves and so on. All this is fairly complicated I suppose.

Possible ideas might be to (and I'm no expert) change hole size, add another washer with a different hole size, drill holes in the wall of the tapered section, and so on, trial and error.

Sounds like fun. I'm going to try later this summer to quiet down my V&H Classic IIs on my S50. They sound good but are a little louder than I wanted. On the other hand some days they sound just right.

[diamond_jim]

You're right, Tburd, whatever all that meant. Just kiddin'.

I drilled holes in the narrow section which I've since wrapped with fiberglass packing. I've also drilled 4 additional small holes in the washer in attempt to relieve some backpressure while still trying to capture most of the volume. It is noticeably better.

[Thundurburd]

That looks good to me, hope it improves your sound.

[diamond_jim]

Just got back from a ride. It sounds much better now with the extra holes and fiberglass wrapping. The 4 smaller holes in the washer relieved enough back pressure so that it rides better.

[Thundurburd]

I think the long exhaust with just one hole basically "tuned" the pipe which could have caused then to "sound more crappy the higher the rpms." As you said the additional holes should release more back pressure but should also cause the pipes to be tuned differently. Fiberglass packing adds friction which is most effective with higher frequencies perhaps leaving a lower rumble which it seems we all like. Good luck with your experimenting.

However as I've heard said several times, free advice is priced just about right. IOW, what do I know?

[mbgraham2000]

Did you drill all those hole by hand? Man that's a lot of drillin'. I can't drill a straght hole to save my life.

I usually have to drill one hole and make one slot when I go to mount something. That way I can adjust out my lack of skill.

Looks good. I will be stealing your idea for this as well.

[diamond_jim]

Originally Posted by mbgraham2000

Did you drill all those hole by hand? Man that's a lot of drillin'. I can't drill a straght hole to save my life.

I usually have to drill one hole and make one slot when I go to mount something. That way I can adjust out my lack of skill.

Looks good. I will be stealing your idea for this as well.

Yes, by hand, turning the crank on the drill press!

[07M50Limited]

That looks good...wish I could put some like that in mine, had to settle on 4" long ones inside the header pipes.