Stainless Steel Side Exhaust System

[65-408]

This is a re-post from my build thread, but I figured I would post it here also...

Been working on the exhaust system for the past few weeks. It is a full 3" side exit system, made from 304 stainless steel tubing, so it should never rust... I wanted a side exit system since I figured it would be easier to build and I like the look... After extensive internet searches and you tube sound bites, I couldn't find mufflers that really fit the bill for material, sound and price. I considered spintech splitcase, Borla XR1, moroso spiral flow, race bullets, etc... but nothing seemed to really fit the bill, so I decided to make my own. Anyways, here are the details on the exhaust system/muffler build, it was a fun project...

I started by mocking up the tubes in PVC pipe and fittings, best part about this is that you can return most of it to Home Depot when you are done...

Then I measured and modeled it in SolidWorks.

Once Modeled, I made some drawings of the bent pipes and sent them to Accelerated tube in CA. I was going to fab it up from bends, but then I saw on thier website that they will make custom parts. I decided to get a quote and surprisingly, they only charge you for the bends and the tube, so buying my tail pipe, for example, with 2 bends (90 and 45) only cost slightly more than buying the individual bends (but saves tons of labor and come out better). Here is thier site:

http://www.acceltube.com/

In my muffler search I came across this thread where a bunch of cobra guys got a muffler built to replace thier rusting out side pipe cores:

http://www.clubcobra.com/forums/all-cob ... ase-i.html

Stainless specialties will build you whatever you want for inner diameter and core/case length, but they are kinda pricey at $180 each. I like this design, I think the expansion chambers at the front and back have alot to do with why these sound good. So I decided to copy it. The cobra guys really like them, but said they are pretty loud, I decided to quiet it down a bit by going to a 2.5" thru diameter with an 18" core length. I also am using stainless steel wool for the packing because I have heard that the certamic stuff breaks down over time from the vibration. Some research showed that SS wool is great for muffler packing, but it is expensive, so manufacturers don't use it. I found this chart on SS wool noise absorbtion, looks good, should only let out the nice low frequency rumble...

I got my SS wool from this place, went with the medium. I only used about 2 lbs in my (2) mufflers:

http://www.briwax-online.com/sswool.html

Here is the muffler build:

End caps and core ends made on the little mill, this sucked (hole saw+SS=lots of noise):

Perforated SS sheet (1.8" dia holes on 3/16" centers), rolled up to make the cores:

I welded everything with the mig with 308L wire and He90/Ar7.5/CO22.5 gas, it works well, but is not as good as tig...

The muffler OD is 4", with the 2.5" core, leaves 3/4" for SS wool, I did 2 layers:

Here is how the tubing came from accelerated, it took a few weeks, but they did a great job. It is all .060 wall. The 4" OD pieces in the middle are the muffler cans:

The flanges were made by Vibrant and came from Amazon.com. They are nice pieces, 3/8" thick SS.

I cut everthing on my abrasive saw, be sure to put in a new blade and all new sanding discs when working with stainless, as an old blade will embed regular steel into the SS and it will rust...

I put a giant angle onto the disc sander for truing up the cuts:

Stuffing the cans:

Borrowed some V blocks to make sure the inlet/outlet stubs were co-axial:

The welds are not perfect, but functional. The SS was fussy, was great one second, then would suddenly go bad...

The CNC pipe bender needs 6" between bends, so I had to make the drive's side pipe off the header from bends, everthing else just had to be trimmed and installed:

O2 Bungs and an 2" cross over for an H Pipe:

And it is done, I used lap type SS band clamps at the joints...

I wonder what it will sound like?

and no, I don't want a fancy angle cut at the tips, I like the brute force look...

 

[AzPete]

Looks nice. It seems to hang a bit low but being the size tubing used, that may be all the higher it would tuck up under the car.

 

[tarafied1]

very professional looking and impressive (as the whole car is)

 

[Horseplay]

Only word I can come up with to describe the work is awesome.

Question though. What are you planning to do to tie the front and rear frame rails together? With the way you have the exhaust routed you cannot use conventional subframe connectors. Are you welding it from above inside the car with something like a six or eight point cage?

 

[janschutz]

Just WoW!

 

[65-408]

Only word I can come up with to describe the work is awesome.

Question though. What are you planning to do to tie the front and rear frame rails together? With the way you have the exhaust routed you cannot use conventional subframe connectors. Are you welding it from above inside the car with something like a six or eight point cage?

I am using the factory designed Ford parts called torque boxes... Probably not the popular opinion around here, but I'm not a big believer in subframe connectors. I have asked a few of the sub-frame manufacturers for test data (torsional and beam) and was not surprised to find out that they have none... Not to mention that the front of almost all subframe connectors tie into an essentially non-structural part (the floor support). This thread has some very interesting data to support:

http://www.stangnet.com/mustang-forums/ ... coupe.html

I think adding the 67/68 front torque boxes are much more effective, further stiffening of the rockers (like adding the convertible inner rocker, would be next on my list, but I'm not sure I will do that. I will likely stiffen the weakest part (torsionally) of the mustang unibody (the shock towers) by adding tubing back to the A pillars, like these guys did:

http://sn65.com/Fire%20&%20Ice%20unibod ... cement.htm

You are right though, an internal cage is very effective, but I don't really want one in my car...

 

[Horseplay]

I have no engineering data for support but I can tell you from experience that the danger of twisting a unibody 60's muscle car is very real. The level of power your car will be producing is more than adequate to do serious damage if you are able to hook it up. You can do a search on Youtube or the like and find a few videos. I recall one of a white firebird that really did a number on itself.

The tower to pillar idea is solid in lieu of using tubing to tie it into a full cage but without connecting the front to the rear you will still have issues with flex and the very real possibility of torsional "twist". I have seen countless pics (and firsthand) of damage done to unibodies that did not have framework in place to tie the front to the rear.

If you are never going to take it to the track you will probably be OK as hooking on the street is not the same.

 

[Anonymous]

I never thought I'd say this, but I agree with T E R R Y. These cars are fairly flexible without anything tying the front to back and side to side.

I have a 6 pt cage in my 66 and wish I would've added SFC's through the floor during the resto.

 

[Horseplay]

I never thought I'd say this, but I agree with T E R R Y.

It's OK to be right once and a while, Mark. We all have to experience new things occasionally.

 

[65-408]

Don't get me wrong, I agree that these bodies are flexible. I debated and researched sub-frame connectors for a while, but once I found good data that shows that they added very little, I decided to not change my desired exhaust routing to incorporate them.

I believe there are more effective ways to stiffen these unibodies than sub-frame connectors and since I wanted side exhaust, I will utilize those other methods.

Also, when you add both front torque boxes, you are very effectively tying the front and rear sub-frames together, I think time will be better spent stiffening the other known weak areas...

 

[Horseplay]

FWIW, I installed torque boxes in my 65 along with subframe connectors and was ( it looks as though I am selling now) installing a 6 point cage/system that will be strategically welded to the upper roof/door framework to unitize the entire body.

Why do all this? Because if you are going to build a car to go fast why would you waste a large amount of that expensive power in body flex? Have you ever been to the track and seen a severely over-matched car out run the high H.P. opponent? Drag racing is all about getting the power to the pavement. That means chassis is everything.

You can still tie yours together by doing it above the floor and maintain your exhaust. Again though, if you are not going to take it to the strip you're probably all good.

 

[apollard]

About the subframe connectors -

The ones tested in the link were bolted in. IMO, this will offer little if anything, since the bolted connection will move. Even the tightest bolt hole will allow .04" or more at the hole, which translated over the distance to the corners will be much larger. In addition, bolt holes will enlongate. I would be very suprised if you got no improvement with good solid welded in connectors. However, adding torque boxes is clearly the biggest bang for the buck.

SF connectors aren't designed and don't provide the most rigidity in the torsional direction IMO. They provide much mor in the flex between the front and back suspensions when going over bumps, etc in a straight line.

However, you can get the benefits w/o SF connectors by using the vert inner rockers.

Reinforcing the space behind the rear seat should be done also IMO, and will do more for torsional stiffness then connectors. Every BMW I've owned had major structure there, and they are know for the stiffness of thier bodies. For example, on my 91 M5, you can't jack the front tire off the ground w/o lifting the back tire to the limit of the suspension travel (and that's alot of travel). The wifes' X5 has no rear seat reinforcement, but you should see the structure around there in the roof and floor area.

BTW, nice job on the exhaust!