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TurboS10 03-24-2004 09:38 AM

Building a muffler
Hey guys,

I have a weird project and thought I would get some input. I am going to build a muffler for my wastegate dump on the S-10. It is open to atmosphere and makes it impossible to hear detonation when it opens while tuning so I am going to build a muffler.

I got some reducers and a small pipe from auto zone so that I can build a tiny little dynomax bullet style muffler. The question is with gas routing. I plan on drilling a bunch of holes in the inner tube to start. I have two ideas on what to do next: I can cut the inner tube a little short and plug it so that the gases will be forced to flow to the open chamber around the tube and then back through the holes and out...OR...I can pack the chamber with steel wool and just let it dampen the noise like the dynomax design.

Keep in mind this is not a real high flow application and the main goal is to make it more quiet. I am wanting to stick to the basic design because of packaging and looks. I looked for a lawnmower muffler, but they were ugly as hell.



k2mooch 03-24-2004 09:46 AM

Sounds like a good plan, but be careful with steel wool. We learned to start fires with it in boy scouts by touching a 9v battery to it. If you stretch it out and get one end going, it's really cool to watch closely at night on the floor in the garage.

Anyway, just make sure no sparks are traveling in that tube.

Why don't you use the guts of a lawnmower one and just spruce up the cover?:D


TurboS10 03-24-2004 10:30 AM

The lawn mower mufflers are just not the right shape. They are really just an empty chamber with some holes......not much there.

Thanks on thr steel wool. Maybe fiberglass would be better. Anyone know the melting temp?


gt2betubbed 03-24-2004 10:56 AM

Is this muffler temporary?
I don't know much at all about turbos, but I believe that the wastegate is what regulates the boost. Wouldn't putting a muffler (restricting airflow) on it effect the boost? I know you do your research, and you would know a million times better than me, but it's just a thought. The reason I ask if it's temporary, is if it is, then just baffle it, and the looks really don't matter.

TurboS10 03-24-2004 11:01 AM

True GT about restriction. It is something I am going to try. I have not really read anything on this, it is my own trial and error. If boost creep is a problem it will come off to test if it is a problem. If I do the straight through design there will be no restriction to speak of. The other would have a little, but I think would make it quieter also....


astroracer 03-24-2004 11:19 AM

Just throwing stuff out here but could you plumb the wastegate into the exhaust on the outlet side of the turbo? I don't know how much higher pressure the bled off boost will be over the exhaust gas but it may be worth checking out...

TurboS10 03-24-2004 12:08 PM


I could do this, but my downpipe is on the small side at 3.5 inches. Adding the turbulent flow off of the wastegate will impact flow a good bit or I would do that. If I had room for a larger downpipe, I would have done that to start.


k2mooch 03-24-2004 12:31 PM

Call up a local muffler shop and see if they ahve any high temp fiberglass left from a glasspack. You could make a smaller scale one out or perforated exhaust pipe housed in a larger diameter one.

You can either drill the perforations or have some fun with it and hang it from a tree and break out the 'ol .22 rifle. Now we're talking perforations. :thumbup:


astroracer 03-24-2004 12:53 PM

If the wastegate only operates at intermittent times I don't think it will impact the flow through your 3.5" pipe. And, when it is open the motor will be feeling the lost boost more then it will the added turbulance. I think you should look into it...

TurboS10 03-24-2004 01:05 PM


You have to realize that once an engine reaches a boost level the wastegate will remain open to maintain the boost level. Although it does modulate a little, it will pretty much be open the whole time the engine is under load. As RPM goes up, pressure and flow goes up both in the downpipe and on the wastegate dump. In non linear flow is entering the downpipe via the wastegate it will hurt flow. The real question is how much??? I dont know, but I would rather not have to redo it later if it presented a problem. I may end up fabricating a 5 inch race only downpipe and I can integrate the wastegate to that. Of course at that point noise is a mute point:). I will probably not do that until the engine is tuned and I have some kind of electronic knock sensing.


The small version is what I am basically building. I might check for a damaged new muffer and just cut it up for the packing.


mustangman1968 03-24-2004 02:06 PM

there should be no worrie about the back pressure because a lot of turbos have internal watgates(in the exaust)so its just a little less restrictive then a internal wastegate

TurboS10 03-24-2004 02:24 PM

Not trying to be rude, but I am not going to change the design. It is well researched....I promise. I just need to quiet the wastegate dump....thats all.


astroracer 03-24-2004 02:59 PM

Yea... I see. Shows to go ya how much I know about turbos... Well, I know a little bit more now...:thumbup:

gt2betubbed 03-24-2004 03:26 PM

I didn't see if you were doing this on a temporary basis yet. I think you already know which way you are going to go with this, but if it's temp. you can just plump the wastegate further towards the rear and out of the engine bay. If you are building a "glasspack" type muffler, and a very small one at that, I don't know how much quieter it's going to make it. Giving that glasspacks are one of the loudest mufflers on the market, you might end up doing a lot of work for nothing...just my 1/2 cents worth.

TurboS10 03-24-2004 03:48 PM

That is a good point GT on the noise level. I am thinking that redirecting the gases where they have to go through the perforations in the tube might make it quieter. I could also add some baffle easily.

As far as time, I can whip this thing up in a half hour pretty easily. I already got the shell and inner tube. Just trying to figure out how to route the gas. I have a PM going with someone who has done some small muffler design so we'll see what he comes up with.



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