Exhaust Brackets and Engine Torque

[topherchrisb]

This morning I wrapped up installing the left side pipe exhaust bracket that FFR provides. I have a gen4x coyote with the catalytic converter headers that have no ball flange for the flexible adjustment. My engine torques pretty hard under full acceleration with the FFR provided poly engine mounts. I have been slowly enlarging my exhaust hole on the body as I notice contact being made through out my test runs. I have the hole large enough now it is not making contact but I'm going to go another 3/8" larger just to make getting to that upper bolt easier when installing the pipes. You can see in the picture below where the paint has been rubbed off the pipes during contact.

When installing the bracket I put the hanger under a little load so it would relieve under slight torque and probably end up with downward pressure as the engine reached full torque. On the passenger side as the engine torques that hanger will be adding additional upward load on the pipe which I think would be more of a cause for cracking somewhere than just allowing them to hang under their weight. I'm debating on trimming material out of the hanger to reduce the help on the load it's providing or possibly leaving the brackets off entirely as I don't think I would enjoy solid engine mounts.

Am I crazy with the thinking here?

Engine torques paint comes off:
https://thefactoryfiveforum.com/attachment.php?attachmentid=221791&d=1763579582

Exhaust bracket current fitment:
https://thefactoryfiveforum.com/attachment.php?attachmentid=221790&d=1763579582

I'm also going to have to test if under full torque this bracket starts to make contact with the body.

[John Ibele]

Hey, good to see your name pop up! Your thinking went along the same lines as mine.

I thought of the side pipes as inducers of torque on the headers - first with their static weight, then adding additional torque when they bounced down, and reducing torque or even inducing torque in the opposite direction when they bounced up.

The header bolts can more than handle the static load plus some. But the greater impact is the tendency for the side pipes to act as a torsion spring, winding up with torque in one direction when bouncing down, then bouncing back up and reversing torque …with every bump, until the spring settles down. So the side brackets limit travel and limit that extended response to a single bump.

On the other hand, you don’t want to lock things down completely, as you say. Leave the fastener a little loose that attaches the bracket to the side pipe. The ny-loc nut shouldn’t move any.

That’s my thinking and I think it’s sound, but it’s not based on a lot of practical experience. As usual one of the folks with oodles of the latter will chime in if I’m off base.

[topherchrisb]

Hey, good to see your name pop up! Your thinking went along the same lines as mine.

I thought of the side pipes as inducers of torque on the headers - first with their static weight, then adding additional torque when they bounced down, and reducing torque or even inducing torque in the opposite direction when they bounced up.

The header bolts can more than handle the static load plus some. But the greater impact is the tendency for the side pipes to act as a torsion spring, winding up with torque in one direction when bouncing down, then bouncing back up and reversing torque …with every bump, until the spring settles down. So the side brackets limit travel and limit that extended response to a single bump.

On the other hand, you don’t want to lock things down completely, as you say. Leave the fastener a little loose that attaches the bracket to the side pipe. The ny-loc nut shouldn’t move any.

That’s my thinking and I think it’s sound, but it’s not based on a lot of practical experience. As usual one of the folks with oodles of the latter will chime in if I’m off base.

I forgot to get back to this after I had thought about your post for a bit. I do think you have a point. I wasn't really thinking about the load on the pipes as you hit bumps. Living in CO the snow plows tear up the road pretty good. Then the 60 during the day and freezing at night allows the freezing water to cause more damage and heaving. Those bumps definitely add to that torsional momentum. So I decided to add the passenger side. I did cut a couple small reliefs in the rubber to reduce the load though. I figure they are a wear item and I can get replacements easily enough for them due to the quicker aging.

It's usually one of the first things I notice when I go to a southern state... feel how smooth the roads are!?

[Presdough]

I alsoput a hose clamp aroung the rubber hanger to manage flex. you can tighten or loosen the clamp and get the height correct. Youcan also tighten the clamp to compensate for stretch. My loast set have been on for four years now...

[CraigS]

I am not familiar w/ your exact exhaust setup so I will ask a question. Is it all solidly bolted together from head to sidepipe tip? I think it is as you stated no ball flange. So my experience on my old MkII may be helpful. Forget completely about hangers. They are not needed. I had my car for 15 yrs w/o any hangers. At one point I realized that one pipe was a 1/2" high at the tip and the other was about the same but low. Ah, no problem. I will jump up and down on the high one and jack the side of the car off the ground at the tip of the low one. I got about 1/4" movement on each. They are STRONG. On the rocking engine you have a few choices. What I did was clearance the fiberglass a little more until it didn't get hit by the pipe. I thought about solid mounts and a torque strap frame to head. I actually tried a quickie mockup strap but I could hear an extra not particularly nice sound on full accel so took it off after maybe a month. Thought about incorporating some rubber into the strap but it just wasn't worth it vs an extra 1/4" of fiberglass grinding.