Muffler Ideas For The Mighty Red Truck, FreeEMS #2

[Fred]

My current setup is efficient, sounds good, and isn't horribly loud, but is for sure louder than I'd like it to be. It looks like this:






















My plan, for years, was to double back, and add one or two more mufflers, then exit much as it currently does. Today out of chance I found a muffler design that I kinda liked and searched around a bit to find similar stuff. Turns out they call them "twin loop" mufflers, and are HOT with the JDM, YO crowd. I don't mind that. I'm not a ricer, and I know it, so I don't care what others think. The benefit to these designs is full straight through flow and more muffling, but the draw backs are more length, more bends, and more weight.
























What I might try to do is fabricate my own up to save weight, as standard mufflers use quite thick steel and are pretty heavy. The thing with going lighter gauge is that if there is much pressure in the thing, it can blow the sides out. I've seen this done to an HKS muffler with 160hp, not cool. To mitigate that is as simple as using only round tube to do the body. Be it one big round tube rolled from s/s sheet, or three small ones isn't too important.

Thoughts, ideas, and abuse welcome.

Fred.

[eraser87]

I just thought about this, the only thing you can probably do without compromising flow is add a bigger straight-through muffler. Those double-pass mufflers-yo add a lot of really tight bends to your exhaust and that would be a shame considering how straight your exhaust is now.
Now the Miata crowd seems to be really pleased with that really big magnaflow, video here: http://www.youtube.com/watch?v=_XErfrMrdU0
Replacing your back muffler with something like this would quiet things down but add some weight, in the right place though (imo), as your truck is probably light in the back

[Fred]

Fair point about the straightness and ruining it. There are other aspects which I might explore too. EG, spread out into a flat slot to pass over the battery box and out the back into the low pressure zone. Maybe another muffler could be inserted there depending upon how things go.

Baldur also said "bigger volume = better muffling". I'll have to see how mufflers fit into my new fuel tank plan.

I may also be able to put another coby in the straight section under the cab. I wanted to put a flexi there, but I might be able to put that in the down pipe somewhere instead. If I put two flexis in, one up front, one at the rear, then I could pretty much solid mount the stuff after the second flexi. This would help make the rear exit a reality. I don't like that it dumps large quantities of gas under the rear, even if the lift effect is small.

As for the miata crowd and that vid. Firstly, I have little respect for the guy in that vid, both personally and technically. Secondly, my exhaust doesn't sound much different to that as it is! :-) How it is right now: http://www.youtube.com/watch?v=Edy5-1YW8sc

It's not bad as it is, really, I just want it to be even more quiet so as to be more stealthy. The worst part is the low frequency component. For example, if you have it parked in a garage and fire it up, you can feel it in the floor above, etc.

And yeah, the truck is a little light in the back, but not much. My solution to that is to remove more weight from the front and shift what weight I can backward. I have an overall plan :-) I don't mind adding a bit at the rear, though. I added a tow bar bracket with replaceable fittings, for example.

Fred.

[eraser87]

Weight moving plans sound good
I also didnt mean to advertise (nor hate) "Braineack engineering", just saying that a bigger muffler would quieten it down further.
That "low frequency wobble" you talk about cant be dealt with imo, without dampening the exhaust pulses and restricting flow greatly. Especially if you say its not that loud in higher revs. I cannot really back that up in scientific terms, but i once had a i4 opel (yes, haha) with only straight through mufflers (and a cat) on it, it was extremely quiet, yet made garage floors vibrate...
So basically if you can feel the pulses at the tailpipe (good flow!), they're going to make stuff wobble, no?

[Fred]

Yeah, fair call(s). The other "quiet" use cases are:

• Cruising near a cop < done this, up shifted, laboured engine, sounded like a gutless ute with a worn out exhaust.
• Going fast within a mile of a cop < done this, by accident, right past one at double the 80kph limit, expected to be handcuffed, didn't even come after me even though I slowed down.
• Pulling into/out of drive ways late at night < this likely doesn't really matter too much, but it's certainly audible to neighbours when going for a 3am skid session.

I'll see what I can come up with once I get clos to it again, see what will fit, what will work, how it'll work, etc.

[Fred]

Re fitment, looks like I can move the location of the flange in order to pick up space for another coby at the front as well as a flexi, maybe. This might be enough. Pics of downpipe: