[Hockey13]

I know many are leaving the engine cover off but can this present a heat issue with the hood and paint?

[AWSAWS]

Originally Posted by Hockey13

I know many are leaving the engine cover off but can this present a heat issue with the hood and paint?

I highly doubt it. The main reason for me keeping mine on is to mask the noise of the dam ticking high pressure injectors.

About a third of the engine is covered by the cowl. Some people recommend removing that to aid cooling by not trapping the heat in the bay.

[shnaggs]

I don't see why It would pose a problem. Diesel engines don't run as hot as gas engines...typically. But if you still have all the emissions stuff intact, the regens definitely cause a lot of localized heat, but the heat is not fully covered by the engine cover.

I personally have ABC delete a run the cover during winter months, then I run with out it during summer months.

[Needbmwpartzz]

Why would you want to keep cover off?

[tek4tex]

Originally Posted by Needbmwpartzz

Why would you want to keep cover off?

Better engine bay cooling that can extend component part life on hoses and other heat sensitive items. Less power loss in high heat conditions could be a benefit as well

[Needbmwpartzz]

Originally Posted by tek4tex

Better engine bay cooling that can extend component part life on hoses and other heat sensitive items. Less power loss in high heat conditions could be a benefit as well

N54-55?
I know on the N52 it's way too loud with it off....it actually really quiets the mechanical noises of the engine to tolerable levels.

[BB_cuda]

Yes, I've run a couple summers with the cover off. Now that I have switched to the M3 cowl, it is noisier when cover is off. I never realized the standard E90 cowl blocked the engine noise.

[JOHNNYBRAVO1]

If you want it quieter just put some dynamat under the hood. I keep mine off. A lot easier to work on plus keep an eye on everything.

[335dsleeper]

I've had my cover off since I installed my water injection set up. It's a tad bit louder but there's no issues with excess heat.

[Persian Whisperjet]

Mine has been off for over a year no issues. As Cuda says it is a little louder.

[logandeere]

Took mine off at first and swore there was something wrong with my engine until I got around a few other 57s without a cover and realized it's ok to sound like that

[Thecastle]

Just an opinion

Honestly, given the large number of people reporting running 100K+ miles with hardly any issues with the engine cover on. My opinion would be, they designed the car to run with the cover on, and any benefit of removing it would likely by minor, and frankly who knows if the insulation helps protect some components from radiant heat. Just my opinion, its not likely to make a huge difference either way. I'm not sure anyone could measure much of any difference. A little weight loss and possible better cooling, at the expense of more noise and possibly more radiant heat on certain components, seems a toss.

I've seen enough things happen on cars over the years I question mods that don't really offer a measurable improvement. I've seen folks add catch cans hoping to improve "performance" who ended up blowing their supercharger as their supercharge depended on the lubrication of the PCV system... (ford lightening)

My only point being is that there can always be unintended consequences of a mod, but I think this one is real safe, just not sure about the benefit.

[logandeere]

Originally Posted by Thecastle

Just an opinion

Honestly, given the large number of people reporting running 100K+ miles with hardly any issues with the engine cover on. My opinion would be, they designed the car to run with the cover on, and any benefit of removing it would likely by minor, and frankly who knows if the insulation helps protect some components from radiant heat. Just my opinion, its not likely to make a huge difference either way. I'm not sure anyone could measure much of any difference. A little weight loss and possible better cooling, at the expense of more noise and possibly more radiant heat on certain components, seems a toss.

I've seen enough things happen on cars over the years I question mods that don't really offer a measurable improvement. I've seen folks add catch cans hoping to improve "performance" who ended up blowing their supercharger as their supercharge depended on the lubrication of the PCV system... (ford lightening)

My only point being is that there can always be unintended consequences of a mod, but I think this one is real safe, just not sure about the benefit.

i agree 100% but on the other hand i think and correct me if I'm wrong but bmw designed that engine cover for noise because the D wasn't originally built to be much of a "race car" as a majority of people would buy it to be a classy quiet fuel efficient family size sedan

[shnaggs]

I do know that tdiwyse has taken under hood temps both with the cover in place, and removed. He saw enough of a temperature differential to warent leaving it off during the summer months.

[BB_cuda]

Purpose of cover is to shield acoustic noise. It is foam under there and it is certainly a thermal insulator. Hottest area of engine (turbo and exhaust area) isn't insulated. It does let heat out better and top of engine's temp doesn't pose harm to sensitive things. I don't see this as a mod for mod's sake as engine is better "dressed" with cover on. My opinion though.

[BB_cuda]

A different angle to consider on the cover. A couple guys have a different path for catch can hoses over to dip stick area and have cover off. Their setup wouldn't fit under the cover.

[temporaptor]

On the X5 35d a couple of people took off their engine cover foam insulation, because it would hold water from a bad cowl seal / cracked cowl, causing injector #5 to rust and start throwing fault codes.....

http://www.bimmerfest.com/forums/sho...7&postcount=56

[Chief Orman]

Took mine off over a year ago. Engine slightly noisier, but can't stand doing anything that would help to trap heat in the under-hood inferno that is the 335d.

[sukutash]

I've had mine off since day one and 5+ years later still going strong. Everyone has posted some good pro's, con's and opinions and now I offer mine. The purpose of this thing was to suppress noise and aesthetics. An engine bay is for an engine, not cosmetics or facades. Noise, whoever buys this car and doesn't want anyone to know it's diesel then leave the cover on.

[runbyu1]

So the question is does the engine sound more powerful, better, more exciting with the cover off when accelerating? Or is it mostly just more noisy while idling?

[logandeere]

Originally Posted by runbyu1

So the question is does the engine sound more powerful, better, more exciting with the cover off when accelerating? Or is it mostly just more noisy while idling?

As far as I'm concerned it's just more noisy at idle nothing crazy when you get up to speed