First Start of new 180's

quote:

Originally posted by garth66:....... Therefore, the collector flanges should not fatigue and crack since the exhaust, engine, and ZF are all joined together and move together, as one unit.

But the engine and TA don’t undergo the kind of temperature change the exhaust system does. The primaries and remaining exhaust system exhibit thermally induced growth and do so in the direction the tubes are pointing and if you anchor them rigidly, that thermal growth induces a lot of stress. An 1/8” movement of the 180s at the rear of the TA wouldn’t be unusual at all. Depending upon how you have it tied down, through cycles it adds up. Various stainless alloys maintain their strength at temperature better than carbon steel and can be more tolerant to a degree. It’s an even more significant issue in turbo systems and that’s why turbos typically are supported but not rigidly mounted. They always have expansion tolerance, at least the well designed ones do.

Best,
K

quote:

Originally posted by garth66:

quote:

I like your adapters. I don't think they are wrong but I am thinking that the mufflers have to move with the engine movement otherwise the weld on the collector flanges will eventually fatigue and crack.

Note that the engine and ZF are joined together with a whole bunch of bolts and will move together as one unit. If they're moving independent of one another or in different planes, then you have a whole lot worse problems than the risk of the exhaust flange cracking. Therefore, the collector flanges should not fatigue and crack since the exhaust, engine, and ZF are all joined together and move together, as one unit.

I understand that. It's just that the mufflers are hung way out there like diving boards and vibrate quite a bit. So much that they loosen the header bolts near the firewall.

To be honest, I just copied the design from Bob Benson and Richard Boschert, who are both running 180's with the same brackets. Both have had no issue with some pretty hard running of their cars. Not that they won't develop over time, but me thinks it's likely a non-issue...

Appreciate the input! I certainly see where something a bit better, that allows for the heat expansion would be preferred.

love it, thanks for sharing! gives me some motivation to finish mine.

I love your setup and the detail (already stated the sound was awsome).

as for the brackets at the end of the ZF supporting the muffler. I believe Brent stated they do have "flex" so in effect they are a "spring". with the mufflers unbolted, I expected the end of the plate could be pushed by hand (~100 lbf) at least a 1/4". the incorperation of the slight bend should also allow for for some vertical thermal growth.

assuming there is about 40" from the end of the block to the bracket, and assuming an extreme hot exhuast of 1000F, the flange will have to give about 0.006 X 40 X 1000 = 0.24"

quote:

Originally posted by JFB #05177:
I love your setup and the detail (already stated the sound was awsome).

as for the brackets at the end of the ZF supporting the muffler. I believe Brent stated they do have "flex" so in effect they are a "spring". with the mufflers unbolted, I expected the end of the plate could be pushed by hand (~100 lbf) at least a 1/4". the incorperation of the slight bend should also allow for for some vertical thermal growth.

assuming there is about 40" from the end of the block to the bracket, and assuming an extreme hot exhuast of 1000F, the flange will have to give about 0.006 X 40 X 1000 = 0.24"

That is EXACTLY the math I used :-)

Ah, the engineers have arrived? Now for the paramutuals? I'll bet you two bits AND give you 3 to 1 odds at least one breaks within 500 miles. Any takers?

well, I can't guess at the thickness nor the materials temper to calculate if the deflections are within the cyclic limits, but the ideal of spring support whether the spring is a coil or plate should work.

from the photo along, the suggestion to reduce the cross section as much as possible to provide support or possible add a "coil" feature at the bend