They run hot as f##k!

Dodge trucks are the same way. Except they run so hot they burn the oil in the dip stick tube...


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But, is it their particular feature not to run the electric fan, after shutdown? As far as I know M54 has an electric fan, isn't it?
Of course, it is also not quite relaxing to have a car that is still "alive" after you leave her in the parking lot, and starts its cooling fan.

What is a little bit annoying is that all that heat, even if the engine bay is insulated, it is quite inevitable not to dissipate towards the rest of the car. And there you always find a warm (if not hot) cockpit, on warm weather, even if you parked it in the shade.

I still presume they traded engine efficiency, based on less heat loss with the overall comfort and increased lifespan of other heat sensitive parts.
After all, they really do not care what happens after your warranty expires, as they are wishing for you to come and be hooked to their stealership garages.

 

Anyone care to comment about the necessity of the hood liner? The damn things are always peeling off and falling down. Any secret to gluing them in place?

 

I personally removed it. Indeed, it looked like ****, it was storing plenty of dust and it doesn't stay stretched.

I also removed it because I prefer to have a better heat transfer, throught the metal hood and the effects are obvious, for me. I am sure they installed that insulation for fireproofing, soundproofing etc..for the daily driver.

But, I also consider the high under hood temperature is really not the right environment for all the engine's plastics, rubber and electronics...

 

Everyone needs to stop stressing about the heat under the hood. It's a freakin engine. Yeah I know it feels "right" to make things cool down faster than they do but it does not matter. The engine is absolutely designed to run that hot and removing the hood liner will not allow the engine to run any cooler. It will absolutely still run at the exact same temperature as before. The only thing you're doing is removing sound proofing and fire proofing.

 

Well, I don't totally agree with you.

Indeed, it will run within the same temperature interval but, basically, the heat exchange of the cooling system will be higher and, therefore, more efficient.

Probably, for most "commuting" driving styles, there is not much difference but, when you have a more spirited driving style or have your engine under heavy stress, as urban traffic jams, hot climate zones etc., the higher heat dissipation will sure have a positive effect.

That is one of the reasons performance / racing models have those hood vents, like the GTR version etc. Ok, I agree that we are not talking about same engines but, even a smaller engine, as the M54 can become extremely hot, when driven in a sporty manner.

Alright, we give up the fireproofing - well, I am not sure if I should worry so much, as my hood won't melt. And if I have my engine on fire, I would not wait until that insulation will supress it. I will use my on-board fire extinguisher (mandatory, here, in Romania, at least).

And about soundproofing - well, I bought my BMW for its sportiness. If I want a silent engine, I would have chosen something else..

 

Also, if you want to talk heat dissipation, having that hood mat might actually help the engine stay cooler.
Let's say theoretically you took the mat off. Then the hood would just warm up and start holding its own heat. This will actually raise temps under the hood rather than cooling them.

Think about it this way, you put tin foil in an oven and let the oven sit at 400 degrees for an hour. Then you magically instantly turn the oven temp to 74 degrees. The tin foil will follow suit very quickly and will not hold any heat to warm the air around it. There for, the oven temp will stay at relatively 74 degrees.

Now do the same thing with a block of steel. The steel will hold the heat and start to warm up the oven again. Granted they will both eventually settle but the steel holds the heat much longer.
Just like your metal hood holds the heat longer than the fabric mat. So if we really want to get technical I'm willing to bet the under hood temps are actually lower and lower more quickly after shut down with the mat installed.

 

Sorry to keep posting but this topic interests me.
You also mention the aspect of vented hoods like a gtr style. This is a totally different concept. Hoods like that create airflow, which I do agree will keep the temps down. Removing the under hood mat will not create any additional air flow. And like I said in the above post, without the mat heat is absorbed into the hood which hurts even more.

 

Now, that you mentioned weight savings. I heard many people mentioning "removing x will save weight"...indeed, it saves weight but, it is also insignificant, for low weight items, am I right?

I mean, if some will remove this insulation, for example, for "weight loss"...in my opinion, it has less than 2kg (probably, even not more than 1 kg). And you carry a 2 liter bottle of water, in your car or even worse, the driver weighs over 100 kg that would not help much, wouldn't it? Or carry a full trunk of (usually) useless stuff...

Anyway, back to my initial question - do your car have no cooling fan on, after having ignition off? I am asking as all my previous cars had this feature and I find it strange to have the engine hot, even after 1-2 hours in the parking lot.

 

Well with the idea of weight savings, it all adds up. So a few small things can add up to be significant. But yes I agree, you're never going to notice any difference in acceleration just by removing something that insignificant.

No my car does not have the fan run after shut off.
I don't really see any advantage of it being on after shut off because the engine is not heating up, and the cooling system is no longer circulating. So pulling air through the radiator is just a waste of energy.

And yeah my engine stays warm for a while. More so than other cars. Even my e30 cools down pretty quick. I honestly think that is an advantage because starting a warm engine puts less wear on it. So maybe they did that on purpose. Idk

 

I doubt removing that liner will do anything for engine bay temperatures. It's all of the rubber seals and plastic guards that are holding that heat in. Besides, I'm pretty sure that liner is just there so it doesn't scorch the paint...

 

What I am referring to was that the uninsulated hood acts as a heat exchanger, in my opinion - as a radiant heat panel or, if I compare it that way, similar to a frying pan.
Of course, this would work only if the outside temperature is low enough to allow a rapid heat exchange. And then, comes the reverse side, of having high efficiency of an engine at higher temperature so, decreasing it will be detrimental to its efficiency, while having relative positive effects to certain heat-sensible parts.

However, I am sure, as most German engineering, every detail has been planned with function over form and I agree that those heat-sensible parts are tolerant to the normal under hood temperature intervals.

I removed the insulation as, when my engine cools down quicker (when parked), the "epic mysterious" warm / semi-hot sluggish engine startup problems almost disappear, in my case.

Indeed, you can toast bread on my hood, after a more intense ride but, until I will identify that mysterious "heat-loving gremlin", I will keep it that way.

 

Removing the hood insulation will allow more heat to escape than leaving it on there. That is simple thermodynamics. Whether it is enough heat loss to affect the performance or longevity of engine components is another question.

Having the electric fan and perhaps even the auxiliary heater/electric coolant pump run after engine shutdown would serve a very valuable purpose, to mitigate the engine compartment temperature surge that inevitably happens when you shut down. This happens because a lot of heat is still inside the engine but the cooling has stopped. Whether the temperature surge is high enough and long enough to affect the life of components is, again, another question.

 

Just open the hood if you want to dissipate heat.

The fan will run with the motor off if you get it hot enough.

 

Yup, I sure could stay with my hood open, in a parking lot, while I go have some lunch.

 

Bottom line being read the forums BMWs run hot period.


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I really like the fact that the engine bay stays warm. I can drive to work at 9, and when I go to lunch at 1145 the temp gauge is still at high noon (though probably at the bottom of the range). thermal cycling and cold starts are the things that create the most wear, so the heat retention property is a feature, not a bug. The only time it's annoying is when you drive to a buddy's place to work on the car, but then you can open the hood to let it cool. As far as the insulating mat is concerned, it a) insulates (see previous point) and b) keeps the hood slightly cooler, which prolongs the hood's life (think about a very warm hood getting rained on unevenly, and having paint/metal of various local temperatures and thermal expansion coefficients).

 

...so the heat retention property is a feature, not a bug...

Dude, you have soooooo just outed yourself as a software engineer. Ha ha...

 

Okay, QA then?

 

Market research, including some surveying of our own customers.

 

My B6 S4, through years of time and mileage, has such a crammed engine bay with the V8 that it literally cooks hoses, PS lines, etc. I worry about this much less on the ZHP given that the motor actually fits in the engine bay and there's space to allow for avoiding things like routing PS lines directly atop exhaust manifolds. Bottom line - I trust my hot-running BMW way more than radioactive triple-radiatored Audi.