So I have read through a bizillion threads on crush cans. This makes one bizillion +1, sorry.

My take away (from a non-engineering standpoint) is they they are NOT connected with the airbag system in any way, right? Meaning, there is no sensor attached to them or sensor behind them that would trigger an airbag. What they are is an additional reincorcement to the bumper around the are where the bumper makes contact with the frame. Thus, when the bumper is hit, the crush cans dampen the "JOLT" that is sent from the bumper into the frame. Thus...if you remove the stock bumper and all of its hardware, you are not necessarily doing any harm if you replace the stock items with a heavy duty bumper. The airbags will still deploy in an accident. However, the MIGHT deploy at a low MPH if the bumper is not very strong and transmits too much of the JOLT to the frame. A larger more heavy-duty bumper that would absorb more of the JOLT would require more impact before the airbag system would deploy.

The crush cars only seem to be of help if in an accident they where hit. Since they guard the area of the bumper that makes contact with the frame....thus they are like a big metal vibration dampener. You can remove them so long as you put back on a heavy duty bumper.

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The airbags deploy based on a decelerometer. Basically, the faster you come to a stop, the more likely the bags will go off.

The crush cans just distribute the energy from a wreck. The force of an impact gets distributed to anything available. The energy travels from the point of impact to your body. If the energy can be absorbed by other things first, it dissipates. The goal is to dissipate the energy before it gets to your body.

i.e. crush cans, crumple zones, etc.

 

Got it....quicker the stop....more likely the chance of airbag deployment.

Crush can: similar to a crumple zone built into an OEM bumper, but has nothing to do with the airbag system. It's job is to dissapate energy transmitted from the bumper into the frame. Seemingly...a heavy duty bumper would do that as well.

 

The crush cans are mounted in front of the bumper, then the bumper is mounted to the frame.
The crush cans work only if they take the direct hit.
They have nothing to do with absorbing impact from the bumper.
It's an attempt to have a 5mph bumper in a straight on impact. A conventional 5 mph bumper would be impractical on a Jeep because people mount winches, stingers, tow hooks, etc. to the bumper.

Behind the front bumper, each frame rail has a section that is designed to crumple, possibly preventing damage to the rest of the frame.
The sections can be cut off, and new ones welded on. They are about $600 apiece.

 

Got it...5 MPH bumper is a great way to look at it.

 

Air bag deployment is based on an accelerometer mounded in the middle of the jeep. When it senses a great enough impact it electronically triggers the air bags.

 

But as far as the theory of a more rugged bumper taking the hit better and transmitting less energy to the frame, I'll have to disagree. A cheap bumper is going to bend, fold, ripple..etc during and accident. A heavier more reinforced bumper is not going to deform expending some of the impact energy, it's going to transmit more to its mounting points with a greater likelihood of hurting the frame.

 

There are two electronic accelerometers, (one mounted by each headlight), that detect frontal impact, in addition to the one in the controller mounted in the console. There is one in each B pillar on those JKs equipped with side air bags.

 

That is correct.
The likelihood of air bag deployment may be increased in a slow speed, straight-on impact, when the crush cans are not present.