What are these bags under the engine manifold?
 

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Was this car used to smuggle heroin? What the hell are those things?

My money's on heroin because I just checked my X and nothing.

Sorry to say it man, but get rid of your car ASAP because it's a drug dealers car. haha jk. I had these in under my manifold and it looks like it was Jag's attempt at heat insulation and trying to keep engine heat away from the air intake manifold. Probably not too important IMO.

My X also has them. I took a little pinch of the brown stuff in the bags, but it doesn't smoke too well. Burns throat, very harsh!

So it's probably just insulating material.... Honestly, anything that keeps heat away from the intake manifold is welcomed!

My s v8 has them except where the rats nibbled, I suspect noise insulation ...because I didn't hear the vermin at work.

very interesting... I at first thought heroin, but now I just think you may need to change your spark plugs because it doesn't look like your intake has been off since the last time it crossed the border :D

Bulletproofing.

(I was thinking of adding more)

Yep, it's just boring old insulation, nothing more nefarious than that.

It is supposed to be noise insulation and also is molded on the bottom to keep the valley hoses in their place.

Dang. I was hoping for a score I could sell to my Colombian cousins for big money. Ah well, have to settle for a day job.

Mine does not have it...maybe removed by previous owners...

The area where these bags sit gets very hot, what do you think? 200°F plus? If you were going to replace them, I imagine you'd have to get them from the dealer because that plastic can handle the high temps.

So the functionality is
Sound insulator
Heat spread away from the intake manifold
and keeps the hoses in place

Not bad!

I had mine removed while at the shop for a new door clip. They said its better not to have them so air can move around and cool under the intake.

I think removing them or keeping them depends on the weather. Today it was 118F in Scottsdale AZ and I was driving on surface streets with the AC on. The outside temp was so hot that I doubt these thermal insulators were able to do much in the way of suppressing, or diverting heat from the lower half of the engine from getting to the Aluminum cast intake.

On the other hand, in moderate temps (70-80F), they are probably effective at keeping the heat away from the manifold. In even lower temps, including snow conditions, they keep the heat from radiating away from the lower half of the engine, and this is good. A combustion engine loves heat, to a point.

So, I think it 'depends', but for most conditions, they do serve to keep useful heat at the engine block and slow its convection to the intake manifold. Therefor, the manifold may run a little bit cooler for it.

In extremely cold conditions, they are very useful. In moderate weather/temps, they serve well. However, in Scottsdale and Phoenix today where the outside temp was 118F, the heat insulator bags are not doing much. Hot is Hot.
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