Removoing stock hood liner

[bitcore]

I've never really thought about this before nor heard much talk about it. Would it be a significant weight reduction to remove the hood liner? it apperas to be rather heavy...
What would be bad if I did remove it? It's obviously there for a reason. Fire retardent? prevent paint from cracking due to the heat? These are probably obvious reasons but I'm just curious how bad it would be...

[Autotechnica]

It's there for noise reduction. Anything else you've heard about the hood warping from the engine heat is a myth. I've had it off for the whole summer and nothing had gone wrong. My friend has had it off since he bought his car 6 years ago. The engine is noticeably louder, that's it.

If you're the kind of guy that would get into your car and wear a thinner pair of socks because it's lighter, then you should remove the hood liner for weight reduction purposes. Otherwise don't bother. I removed it because it looks cleaner and I can actually clean the underside of the hood with the hood liner removed. I don't like dirt and salt getting into places that I can't see.

The hood liner weighs as much as a car wash sponge.

Bry

[theskill]

You'll bake off the paint on your hood in a couple years if you do. And it may cause changes in the environment under the hood making your engine operate strangely.

[Autotechnica]

Originally posted by theskill@Jul 14 2004, 01:10 PM
You'll bake off the paint on your hood in a couple years if you do. And it may cause changes in the environment under the hood making your engine operate strangely.

Ummm, no it won't. That's the most ludicrous thing I've ever read. Does the car's computer sense that the hood liner is gone or something?

If it really were that hot under the hood, don't you think the paint around the shock tower would have "baked" off already?

The M3 LTW and GTR did not come with hood liners, and neither do more than half the cars out there.

Bry

[Kevin325i]

I think it looks better without it. It only weighs 2lbs if that. I removed it because I'm trying to move the weight distribution to 50/50. And in two weeks I get to have the car weighed at the track so I can see yippie

[theskill]

I see plenty of cars with baked off hood paint around and the roof looks fine.. isn't this due to engine heat? OK so it takes more than a couple years to destroy the paint but it will shorten its life. Read the white papers at dinanbmw.com for all the info on what changes in the engine's envonment can effect. I may effect it or it may not. BMW engineers are generally pretty smart people I think its there for a reason. Chill out autotech~ I've been a garage owner 23 years and have seen a few things in my day.

[Autotechnica]

Originally posted by theskill@Jul 14 2004, 02:24 PM
I see plenty of cars with baked off hood paint around and the roof looks fine.. isn't this due to engine heat? OK so it takes more than a couple years to destroy the paint but it will shorten its life. Read the white papers at dinanbmw.com for all the info on what changes in the engine's envonment can effect. I may effect it or it may not. BMW engineers are generally pretty smart people I think its there for a reason. Chill out autotech~ I've been a garage owner 23 years and have seen a few things in my day.

I know it's there for a reason. It's there for noise restriction. If there really was a problem with engine heat, the hood liner would be designed with some silver coloured material to reflect heat. I don't see how a hood liner would protect the hood from heat. Keep in mind the hood does not come in contact with the engine or manifold. If a car is poorly painted and the paint was not properly bonded to the metal, obviously heat would cause paint to chip off. My friend has an E34 525 from 1989 with over 300,000km's. He has had no hood liner since he bought the car brand new and he has never had any problems with the paint baking off. Maybe cheaper cars have crappy paint, but a BMW does not have this problem.

Bry

[bitcore]

2 lbs? I'd bet 5-10

Sound deadening material eh? OFF IT GOES!!! either way, is it too much louder?
any particular method I should use other than a firm yank and peeling motion?

[Autotechnica]

Originally posted by bitcore@Jul 14 2004, 03:50 PM
2 lbs? I'd bet 5-10

Sound deadening material eh? OFF IT GOES!!! either way, is it too much louder?
any particular method I should use other than a firm yank and peeling motion?

There's no yanking involved. You have to pop out all the plastic screws/tabs first, then the hood liner just comes off. You also have to remove the hood latches in the front.

It's definitely under 5lbs. It's paper thin and seems like it's made of some kind of cloth fibers.

Bry

[Kevin325i]

I couldn't notice an increase in noise at all. Maybe a little when you're outside of the car. There's a billion of these plastic rivets in it though. Make sure you get the wax out and shine it up, looks sweet. When I paint my sideskirts (yes again, yes with the right paint this time) I'm going to clear coat the underside of the hood, should look nice.

Kevin

[stationaryobserver]

Originally posted by Autotechnica+Jul 14 2004, 03:41 PM--></div><table border='0' align='center' width='95%' cellpadding='3' cellspacing='1'><tr><td>QUOTE (Autotechnica @ Jul 14 2004, 03:41 PM)</td></tr><tr><td id='QUOTE'><!--QuoteBegin-theskill@Jul 14 2004, 02:24 PM
I see plenty of cars with baked off hood paint around and the roof looks fine.. isn't this due to engine heat? OK so it takes more than a couple years to destroy the paint but it will shorten its life.* Read the white papers at dinanbmw.com for all the info on what changes in the engine's envonment can effect. I may effect it or it may not. BMW engineers are generally pretty smart people I think its there for a reason. Chill out autotech~* I've been a garage owner 23 years and have seen a few things in my day.

I know it's there for a reason. It's there for noise restriction. If there really was a problem with engine heat, the hood liner would be designed with some silver coloured material to reflect heat. I don't see how a hood liner would protect the hood from heat. Keep in mind the hood does not come in contact with the engine or manifold. If a car is poorly painted and the paint was not properly bonded to the metal, obviously heat would cause paint to chip off. My friend has an E34 525 from 1989 with over 300,000km's. He has had no hood liner since he bought the car brand new and he has never had any problems with the paint baking off. Maybe cheaper cars have crappy paint, but a BMW does not have this problem.

Bry[/b][/quote]
I definitely agree that it is there to reduce noise, but it's also quite possible that it is there to stop heat from radiating the hood.

You would need to find out the material(s) which compose the hood liner and then determine their thermal characteristics. Air is a terrible conductor, so if you're shielding the hood from that hot air with another poor conductor, then you've done a lot to stop energy transfer (heat) from the engine to the hood. How much heat the engine creates and what kind of heat the paint will withstand are also an important factors.

A silver coating might be too much insulation, causing the engine compartment to become overheated. If the hood liner is there for a thermal reason, it's likely that the BMW engineers wanted some heat to dissipate/radiate from the hood, but also didn't want an excess of direct heat on the hood. More isn't always better.

The statistic you give about having your hood liner off for three months, and your friend for five years is fallacious. We don't know how how long you drive or how often, or in what sort of environment. Same for your friend, so it's impossible to really draw any conclusions from that information.

Anyway, I think the issue is likely more complicated than you make it out to be, with no real evidence to support your opinion. If you're interested in finding out what effect the hood liner has on energy transfer, you'd need to find out what the 'specific heat' of the material is.

And now for my personal experience and opinion. heh.

Physics is how we fit a mathematic equation to what we humans experience every day. It's modeled around our perceptions. Given this fact, I'm compelled to trust the experience of 'theskill' who has owned a garage for 23 years and probably seen a lot more of the damage which nature inflicts on cars. While the paint on my car(E30) is old, and it is fading in general, the front has the worst paint. The side panels towards the top of the hood are the worst, then the hood- and my hoodliner has always been there. Sometimes the car was in a garage, other times it was outside (California, moderate temperatures..)

Since on average, the top of the car has been evenly exposed to the sun, I can't think of any reason other than heat from the engine, that would cause the paint to deteriorate in this fashion. I think the side panels are a very strong indicator- there is no 'heat shielding' to protect them. Hot air rises. The hood was protected by the hood liner. It's logical that the worst damage would be towards the tops of the side panels.

[Kevin325i]

The lightweight was equiped without it, a car made specifically for the track, so it will see higher engine temperatures than the average car will seein daily driving.

[bitcore]

But then again, they don't really care if the paint chipps and stuff.

[Kevin325i]

Never seen a lightweight with it's hood paint chipped either....

[Autotechnica]

Originally posted by stationaryobserver+Jul 14 2004, 11:23 PM--></div><table border='0' align='center' width='95%' cellpadding='3' cellspacing='1'><tr><td>QUOTE (stationaryobserver @ Jul 14 2004, 11:23 PM)</td></tr><tr><td id='QUOTE'>

I know it's there for a reason. It's there for noise restriction. If there really was a problem with engine heat, the hood liner would be designed with some silver coloured material to reflect heat. I don't see how a hood liner would protect the hood from heat. Keep in mind the hood does not come in contact with the engine or manifold. If a car is poorly painted and the paint was not properly bonded to the metal, obviously heat would cause paint to chip off. My friend has an E34 525 from 1989 with over 300,000km's. He has had no hood liner since he bought the car brand new and he has never had any problems with the paint baking off. Maybe cheaper cars have crappy paint, but a BMW does not have this problem.

Bry

I definitely agree that it is there to reduce noise, but it's also quite possible that it is there to stop heat from radiating the hood.

You would need to find out the material(s) which compose the hood liner and then determine their thermal characteristics. Air is a terrible conductor, so if you're shielding the hood from that hot air with another poor conductor, then you've done a lot to stop energy transfer (heat) from the engine to the hood. How much heat the engine creates and what kind of heat the paint will withstand are also an important factors.

A silver coating might be too much insulation, causing the engine compartment to become overheated. If the hood liner is there for a thermal reason, it's likely that the BMW engineers wanted some heat to dissipate/radiate from the hood, but also didn't want an excess of direct heat on the hood. More isn't always better.

The statistic you give about having your hood liner off for three months, and your friend for five years is fallacious. We don't know how how long you drive or how often, or in what sort of environment. Same for your friend, so it's impossible to really draw any conclusions from that information.

Anyway, I think the issue is likely more complicated than you make it out to be, with no real evidence to support your opinion. If you're interested in finding out what effect the hood liner has on energy transfer, you'd need to find out what the 'specific heat' of the material is.

And now for my personal experience and opinion. heh.

Physics is how we fit a mathematic equation to what we humans experience every day. It's modeled around our perceptions. Given this fact, I'm compelled to trust the experience of 'theskill' who has owned a garage for 23 years and probably seen a lot more of the damage which nature inflicts on cars. While the paint on my car(E30) is old, and it is fading in general, the front has the worst paint. The side panels towards the top of the hood are the worst, then the hood- and my hoodliner has always been there. Sometimes the car was in a garage, other times it was outside (California, moderate temperatures..)

Since on average, the top of the car has been evenly exposed to the sun, I can't think of any reason other than heat from the engine, that would cause the paint to deteriorate in this fashion. I think the side panels are a very strong indicator- there is no 'heat shielding' to protect them. Hot air rises. The hood was protected by the hood liner. It's logical that the worst damage would be towards the tops of the side panels. [/b][/quote]

I honestly don't care whether or not the hood liner aids in preventing heat from being transfered to the hood. The point of this thread is whether or not it's a good or bad idea to remove the hood liner, so I honestly wouldn't bother to find out how the material of the hood liner affects heat. I have never heard of anyone with a BMW without a hood liner having their paint peel because it baked off. I mentioned previously that the M3 LTW and M3 GTR which are production cars did not come with hood liners. I'm sure if there was a huge problem with heated up hoods causing paint to peel that the M3 LTW would have that extra 2-3lbs from the hood liner as stock. A lot of BMW's extra insulations and padding are there for noise reduction. If you're really anal about things like noise, heat, etc. Simple, don't remove it. BMP sells reflective "silver" coloured hood lining for their E30 race cars. The point of this is to reflect heat away from the hood to aid in keeping the engine compartment cooler, not the hood.

Now the conditions. How does 4 hours of constant intense track driving sound? I've been to the track 3 times this summer already. 25-30 degrees celcius without my hood liner. I think that's as hot as the motor will run in any condition. I don't know what other proof you need. I don't need to do all these mathematical calculations inorder to determine whether or not this will cause a problem. There are lots of BMW owners in the US with turbocharged M3's who track their cars with no hood liners. They haven't had any problems. If you go to a BMW track driving day say at Mosport, you'll notice that almost nobody has a hood liner. Even people who constantly track their cars can do without one.

I'd trust a guy who has moderate track experience over a mechanic any day. Owning a garage for 23 years doesn't make you a BMW specialist. Obviously I don't know everything, but I believe what I see.

Bry