Under hood sound insulation

[Xess]

I really like my Sdrive X1 but found the engine to be a little noisy and not in a good way. After verifying that the underside of the hood is set up for insulation I was very disappointed to find out that none is available for the X1.
After looking around I decided to see if i could make the insulation for the 128 work. The back fit in the slot well but the holes and tabs did not line up properly so I drilled some holes in the hood sub-structure (carefully) to accept the plastic rivets that are used to mount the insulation.

I drilled additional holes (and bought additional rivets) to secure the tabs. Have to be careful that it is centered properly so it does not interfere with the seal line on each edge of the engine compartment (see additional rivet and seal line identified with arrow below).

In the end it reduced the noise by ~1/2 (down 10 db) but the best part is it attenuates the higher frequencies more so the remaining sound does not sound so tinny. You can still clearly hear the engine, especially when it is working hard, but it is quieter and sounds much better.
I am happy with the results (see photos below).

[waelspain]

Good job. From where can I have a one?

[Xess]

Originally Posted by waelspain

Good job. From where can I have a one?

From a BMW dealer. Unfortunately about $100. Should have been supplied as part of the car in my opinion.

[morski]

Can you post the part no of the insulation you used. Thanks

[Xess]

Originally Posted by morski

Can you post the part no of the insulation you used. Thanks

The insulation is part number 51489141036
The rivets are part number 51481915964

5 rivets were supplied with the insulation. I used those in the central area near where the mounting holes are but had to drill some holes to move them where they would work on the X1 hood.
I purchased another seven rivets to secure the perimeter tabs that did not line up with the slots in the sheet metal. The long rear slot / edge can be used as is.

The only suggestions I have are:
-make sure the edges of the insulation are clear of the seal lines on each side (seals are rubber strips mounted each side of the engine bay which seal to the hood when it is closed). I could see where they seated on the paint under the hood and it is a close fit from side to side
-hold a small piece of sheet metal between the support you are drilling and the hood so when the drill breaks through there is no chance of dinging the hood

It is not difficult and I am happy I did it every time I drive the car

[monfreeze]

Originally Posted by Xess

I really like my Sdrive X1 but found the engine to be a little noisy and not in a good way. After verifying that the underside of the hood is set up for insulation I was very disappointed to find out that none is available for the X1.
After looking around I decided to see if i could make the insulation for the 128 work. The back fit in the slot well but the holes and tabs did not line up properly so I drilled some holes in the hood sub-structure (carefully) to accept the plastic rivets that are used to mount the insulation.

I drilled additional holes (and bought additional rivets) to secure the tabs. Have to be careful that it is centered properly so it does not interfere with the seal line on each edge of the engine compartment (see additional rivet and seal line identified with arrow below).

In the end it reduced the noise by ~1/2 (down 10 db) but the best part is it attenuates the higher frequencies more so the remaining sound does not sound so tinny. You can still clearly hear the engine, especially when it is working hard, but it is quieter and sounds much better.
I am happy with the results (see photos below).

Great DIY
A quick question, has the noise level now decreased?

[Xess]

Originally Posted by monfreeze

Great DIY
A quick question, has the noise level now decreased?

"In the end it reduced the noise by ~1/2 (down 10 db) but the best part is it attenuates the higher frequencies more so the remaining sound does not sound so tinny. You can still clearly hear the engine, especially when it is working hard, but it is quieter and sounds much better.
I am happy with the results"


Yep. Measured the db reduction with an iPhone sound meter app.

[Fabio555]

I use this:

http://www.silentcoat.co.uk/vibratio...coat-bulk-pack

It can be used for insulate door or motor at the same...

It costs 69 euro 50cmx250cm
one roller is enought for 2 doors and motor.

[morski]

Xess- thanks

[Anguslamb]

Emm... but it might make heat accumulation which impact the engine performance at last, especially in tropical region. For me in HK, I'd even remove the engine cover for better heat lost.

[Red Bread]

Originally Posted by Anguslamb

Emm... but it might make heat accumulation which impact the engine performance at last, especially in tropical region. For me in HK, I'd even remove the engine cover for better heat lost.

Yeah, for hot climates, this would potentially be a big mistake. BMW removed underhood insulation on nearly all N54 cars and I believe most N55 cars continue not to have it. I would much rather have a cooler engine than slight noise decrease.

Even with the extra oil cooler, the N55 runs hot in TX summers and with long oil change intervals, adding even more heat is not a good plan.