Noise insulation, Engineer types opinions needed Options

[nivekdodge]

Just a thought

There's another thread today discussing using perlon for the back pad and if it was quieter or not. Something I've notice is Some GM hood have their inner surface looking like a golf ball. There are 3" round divots and when asked about it I was told it reflects the sound back to the motor and that kills the sound.Anyone know if there is truth to this?

This would of course be in the engine compartment.

Kevin

[vitamin914]

Just a thought

There's another thread today discussing using perlon for the back pad and if it was quieter or not. Something I've notice is Some GM hood have their inner surface looking like a golf ball. There are 3" round divots and when asked about it I was told it reflects the sound back to the motor and that kills the sound.Anyone know if there is truth to this?

This would of course be in the engine compartment.

Kevin

Last week I was at a dealer looking at a Mercedes GLB since I need a new SUV. Popped the hood to look at the engine. The sales guy pointed out the divots in the underhood bracing without my asking (I was interested in the engine - didn't even notice the hood). He said they are designed to reduce head impact forces in a collision with a pedestrian. That is a bit more believable than the reflecting sound theory... but I don't know the real answer either.

[Superhawk996]

… designed to reduce head impact forces in a collision with a pedestrian.

(IMG:style_emoticons/default/agree.gif) This

All of automotive design has turned into an abomination of government mandates.

Pedestrian impacts are increasing due to wide A-pillar and high belt lines that obscure visibility. Not to mention due to dolts walking around and stepping into traffic while looking at their phones. So now cars are designed for hitting pedestrians. (IMG:style_emoticons/default/chair.gif) I think it was one of the German OEMs was even playing with pedestrian air bags .

If you pay attention, you’ll notice hood lines moving up. This is to provide more space between the hood and top of the engine to cushion pedestrian impacts.

A-pillars have grown very thick to meet roll over requirement. These wide A-pillars obscure pedestrian visibility.

Belt lines are rising due to side impact requirements. Ever driven a Camaro? It’s like looking out of a port hole. Outward visibility in that car is among the worst out there.

Rear deck lids are rising and rearward visibility is reduced due to rear impact requirements. Result, more children and pedestrians being run over while vehicle is backing up. Government mandated solution: add a useless rear camera that is easily obscured by water, ice/snow, mud, dust. There were other more elegant solutions but that is what was mandated with full compliance required by 2018.

Meanwhile NHTSA basically just proposed mandating light duty trucks out of existence with a 58 mpg CAFE average. Of course that sort of fuel economy is completely at odds with all the weight that keeps being added to vehicles to meet the impact requirements.

https://www.nhtsa.gov/laws-regulations/corp...ge-fuel-economy

Vehicles no longer really designed with the consumer in mind. OEMs just trying to keep up with and meet the endless mandates that are often at odds with other mandates as noted above.