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The cure for your exhaust drone

Anak said:
I have yet to see an exhaust shop with a mandrel bender. All that I have ever seen are press benders.

A mandrel bender takes up nearly as much floor space as an automobile.

Here is an example of what a mandrel bender looks like:

https://www.youtube.com/watch?v=gdtrTaY7yfk

That long bar that runs the length of the machine is the support for the mandrel. Around the 40 to 45 second mark you can get a decent sense of the mandrel itself. It is comprised of several jointed segments which are able to follow the bend and support the pipe from the inside.

I cannot see a mandrel bender making sense for an exhaust shop. Just the time to change over the tooling from one tube diameter/bend radius to another would be prohibitive, never mind the setup time to go between patterns.
Click to expand...

While that's a true mandrel bender, a good tubing bender doesn't "ripple/indent" the pipe
 
RCP Phx said:
While that's a true mandrel bender, a good tubing bender doesn't "ripple/indent" the pipe
Click to expand...

That is mostly a function of bend radius and degree of bend.

As long as you don't need to re-shape the pipe much you don't need as much support in order to keep it round.

Once you really get into mandrel bending you might as well start viewing it as an extrusion process.
 
I checked every shop within 10 miles (which is over 100 shops) nobody does true mandrel bends. I ordered mine from summit, jegs, etc.
 
I just had the muffler shop down the street do my entire system from the header back with a new downpipe/cat/muffer/tailpipe and all the bends were beautiful !!!
 
Thanks for posting this, and the link to your site. It's very interesting, and I see you have the education to back this stuff up.

Now I just need to find a good muffler with a nice tone at idle and cruise, but a bark at WOT.

Flowmaster need not apply...
 
Green XJ Jeep said:
That would be Borla
Click to expand...

Yup, that's my thinking, or maybe Magnaflow.

But then I get to thinking how outright comical it is to weld those nice mufflers to aluminized pipe.....
 
I liked the sound my Dynomax ultra-flow welded made on my '86. (It would even shoot flames when I had it on the test pipe! lol)

The can was aluminized so it didn't look stupid when welded onto aluminized pipe.
 
Yes, but that's pretty much just a flowmaster. Pass.
 
the TURD said:
Just did a little internet research to find those values. They are based on the physical properties of exhaust gas.
Click to expand...

I am assuming that the temp is for exhaust gas and is there a reason you used the incorrect value for 2E?

Speed of sound is 340.29m/s and with the correct value entered it does change the length.
After playing with google docs it looks like anyone can modify the doc so you might want to include your values you used on your blog
 
Green XJ Jeep said:
Cant go wrong with either Borla or Magnaflow.
I prefer Borla's on 4 and 6cyl engines and Magnaflows on v8's
Click to expand...

To a degree, that is true. Even borla makes some stuff that sounds like Joe Dirt would be a fan.
 
Green XJ Jeep said:
I am assuming that the temp is for exhaust gas and is there a reason you used the incorrect value for 2E?

Speed of sound is 340.29m/s and with the correct value entered it does change the length.
After playing with google docs it looks like anyone can modify the doc so you might want to include your values you used on your blog
Click to expand...

Speed of sound depends on the temperature in the pipe. Coming out of the head, it will probably be between 300C and 500C. Inside a catalytic converter, the temperature is upwards of 500C. Of course all of this depends on the engine and the exhaust setup. There is no actual flow through the resonator, so it's going to be cooler than the flow in the actual exhaust pipe. I don't recall what I used as an assumption, I could find it in the original excel sheet I created for this.

I want to allow others to modify the doc so they can use the tool themselves. can you do me a favor and verify that you are ONLY able to input target frequency and temperature. I want it to be useable, but I don't want anyone to be able to screw up the calculations for others.
 
So I'm seriously looking into replacing the flanges on my exhaust manifolds with v-band flanges, but I'm finding there is apparently a serious issue with warping of the flange during welding, in which case you'll never get them to seal.

How do you address this when you weld? It certainly seems as though there isn't much to the flanges to keep them from distorting during welding- and the suppliers I've found say the flanges are guaranteed leak free, unless they've been welded.. This seems rather stupid, what am I supposed to do, glue them on?

Apparently there is a solutin- the Marman flange. It was literally invented by one of the Marx brothers.
Info here: http://www.gbemandrel.com/marman-flanges.html

I know nothing of the company, but the flange does seem to be more robust and a better product.
 
I just use Summit or Columbia River brand. Never had any real issues with warping. Just extend the pipe a little bit through the joint as shown below for extra strength and sealing.

V-BandDetails.gif


I've heard of Marman flanges but never used them. I'm sure they are great, but v-band works really well for me.
 
the TURD said:
Speed of sound depends on the temperature in the pipe. Coming out of the head, it will probably be between 300C and 500C. Inside a catalytic converter, the temperature is upwards of 500C. Of course all of this depends on the engine and the exhaust setup. There is no actual flow through the resonator, so it's going to be cooler than the flow in the actual exhaust pipe. I don't recall what I used as an assumption, I could find it in the original excel sheet I created for this.

I want to allow others to modify the doc so they can use the tool themselves. can you do me a favor and verify that you are ONLY able to input target frequency and temperature. I want it to be useable, but I don't want anyone to be able to screw up the calculations for others.
Click to expand...

I can edit target freq. temp and speed.

It is indeed useful and something I most definitely going to play around with and research further
 
the TURD said:
I just use Summit or Columbia River brand. Never had any real issues with warping. Just extend the pipe a little bit through the joint as shown below for extra strength and sealing.

V-BandDetails.gif


I've heard of Marman flanges but never used them. I'm sure they are great, but v-band works really well for me.
Click to expand...

How far would you say you extend the pipe through, about 3/16"? This makes something I ran across make sense.
 
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