Straight pipes with baffles (and I killed Santa).

[Guest]

So a buddy of mine gave me a set of louvered slip-in baffles to try on my bike. I was planning on doing a set of Emgo shorties, but I think pipes chopped at the pegs with baffles to keep the noise down will LOOK better for the style of bike I'm going for.
My question is, since these are louvered and not perforated baffles, will they give me enough back pressure to avoid a re-jet? Keep in mind the louvers directly block the flow of exhaust, and they're wrapped along the length, sealing off the louvers in the side of the pipe.
I Imagine this won't be much louder than stock, which is what I'm going for.




Here's what they look like, minus the wrap:

[BentRod]

They may be in the direct line of flow, by they do not actually form a constriction as the stock mufflers do. Hence, you will be reducing the back pressure. Wrapping them may reduce the flow area by as much as half, so you will likely be ok. Worst case you have to give the idel screw a quarter turn open, and may be increase the size of your main jets by one size.. not a huge deal. I say go for it, you should be just fine.

[Mr. Sinister]

That's what I was thinking. Since they're wrapped, it's basically the same as choking the pipe size down.

[gearheadE30]

Baffles like that actually do create a lot of backpressure, and due to the small diameter, I could see it being on the same level as what the stockers produce. Just based on pipe flows and stuff from class, that might actually be more restrictive than the stock exhaust. The bent part of the louver induces a turbulent wake and reduces flow velocity due to drag, which increases pressure. As with anything else, it's going to be a bit of trial and error.

[Mr. Sinister]

I would assume a little trial and error. If the flow feels reduced, I can unwrap or partially unwrap them. Almost like a tunable pipe.

[BentRod]

sounds like you are going to drive yourself crazy. my 400 used to run even with the pipes off completely, so you should be ok to get it running, it just might take some fiddling to get the power set just right.

It is correct that the shape produces a lot of turbulance, but only when the flow rate of the exhaust gas is highish, and then it is sort of a fun, non-linear relationship, so the back pressure will change with revs.

[Mr. Sinister]

I like to cover all the bases before a mod.
The sawzall comes out this evening........

[john82q]

The sawzall comes out this evening........

Poor Santa!

[Mr. Sinister]

Aaaannnnddd 3 of the 4 exhaust bolts broke off in the head. Good times!!
Can't say I wasn't expecting it, but dammit. Going to try a Bolt-Out before drilling. Hosed them down with penetrating oil for now.
But, I did get the mufflers cut off!!

[Mr. Sinister]

Baffles don't fit, so I'm just going to fab my own!! I cut at the mid-pipe right before the welded nuts where the covers mount, which is a tiny 1 1/4" inside diameter pipe.

[steve murdoch]

He was just wounded and now....

[Mr. Sinister]

I'm gonna turf his lawn and keep him up all night with my evil modified exhaust!!

[BentRod]

Oh yeah, I guess that would have been a good heads up that the stock exhaust pipes are stupidly thick. I think some are even double walled.

Simple fix if you've got a welder handy and an assortment of short pipe sections.

[Mr. Sinister]

I cut the pipes with a tubing cutter, after figuring I wouldn't be able to sawzall them with the exhaust on the bike without nicking the frame up. Wish I had now, with the 3 broken exhaust bolts.
Nobody makes baffles that small, so I'll make my own. Some 7/8" pipe and Chore Boy should do the job!!

[Mr. Sinister]

So, broke a hardened extractor off in the first bolt I tried removing. It just sheared off from the twisting force. Rapped my knuckles pretty good too.
It's safe to say these bolts aren't coming out. I also assume there's no drilling the extractor out, either.
So, new head, or is there something I'm not considering?