Acoustic cover install

[ctrout]

I was poking around under the hood of my new 850i tonight and found something that I don't think is quite right. The acoustic engine cover is only being held on by gravity. I looked all over under the screws that appear to hold it on but there is nothing there for these fasteners to fasten to. Are there some kind of removable receptacles that they latch into that are apparently missing from my engine? Does anyone have a picture where I could see them?

[cartoonz]

#7

[smokum]

BTW as far as sound goes what is making so much noise that this cover is needed? the ticking of the injectors?

[wokke]

BTW as far as sound goes what is making so much noise that this cover is needed? the ticking of the injectors?

I'd say this is about all it covers sound wise.
And it keeps the heat nicely around the fuel rails.
I removed it on my M70 and will do so as well on the M73 which is going to be installed soon.


My M70 (removed meanwhile)


A customer's 850 after swapping the original M70 against an M73

[ctrout]

I always wondered about that thing trapping heat and warming the intake air. Looks pretty dang cool without too. I think I might just remove it. I wasn't looking forward to refurbishing the rubber seal anyway. Thanks for the info.

[olajon]

Hmmm. Could it be the other way around? That it stops heat from the exhaust pipes from coming close to the fuel rails and the cables?

If you have a close look at Wokke's second picture, you will notice that there is a part missing under the intake manifold. This part (# 5 in cartoonz's picture) is usually attached to the underside with three small screws in the u-formed recesses.

It could very well be that the acoustic cover together with those parts actually insulates the fuel rails and cable harness from excess heat. It does get hot under the hood. The air being sucked into the intake manifolds might be able to keep that area somewhat cooler....

[wokke]

Hmmm. Could it be the other way around? That it stops heat from the exhaust pipes from coming close to the fuel rails and the cables?

If you have a close look at Wokke's second picture, you will notice that there is a part missing under the intake manifold. This part (# 5 in cartoonz's picture) is usually attached to the underside with three small screws in the u-formed recesses.

It could very well be that the acoustic cover together with those parts actually insulates the fuel rails and cable harness from excess heat. It does get hot under the hood. The air being sucked into the intake manifolds might be able to keep that area somewhat cooler....

I doubt your theory because directly under the fuel rails two water pipes are running from the waterpump to the collector in the rear. And these pipes aren't insulated at all so the heat can get to the rails right away.

[X5X]

Love the \\\Wokke badges I bet some people have asked you why you put ///M badges on the wrong way

[olajon]

It was just a thought - you are right about the water pipes.... But why would a car manufacturer install useless equipment....?

[wokke]

Love the \\\Wokke badges I bet some people have asked you why you put ///M badges on the wrong way

Surprisingly no one has asked that so far. As a matter of fact the Motorsport GmbH is using MY badge the wrong way around

It was just a thought - you are right about the water pipes.... But why would a car manufacturer install useless equipment....?

I wouldn't call it useless. initially this car was designed to be a luxury V12 GT and I guess even the sound of clicking injectors is not tolerable.
But guys like me who also think that the OEM exhaust system is way to noiseless can live perfectly with this clicking sound.

[rogbmw]

Wolf - here is a photo of the heat shield on my Alpina after taking the intakes off. From what I understand from others, this did not come from BMW this way.

[cdnalpina]

Interesting photo Roger, thanks for postig that. I didn't even think to look at that on my E32 B12 5.0 when I did the intake manifold gaskets on it.

Why would Alpina put the NACA duct in on the B12 5.7, with a corresponding hole in the acoustic cover then? Isn't that to cool the fuel rails down?

[4drian]

It is to cool the injectors and rails.

Quick question: I see timing chain - thought the 5.0 was M70 based and belt?

[Omega man 1969]

I guess eventually heat will soak into the manifold from the head but it may help with hot start problems. Some data using an infra red thermometer for one with and without a cover would be interesting.

[TxGR8White]

It is to cool the injectors and rails.

Quick question: I see timing chain - thought the 5.0 was M70 based and belt?

All M70's have chains,as do S70's.

[Max Lumens]

Some alternative thoughts:

1- It's possible that the engine cover, oil drip catcher, and rubber gasket against the hood are meant to channel an accelerated air flow from the fan directly across the top of the engine and down the bell housing.

2- Water in the cooling system is considered cool to engine designers. Liquid-to-air turbo intercoolers work on this principle.

3- Alpina doesn't bat 1000. The NACA duct and the coolant pipe cover could be mistakes; how would you know? Anybody ever put temp sensors in there to test it? FWIW

[4drian]

Alpina have confirmed that the NACA duct is due to overheating of the injectors. I can't find the source of it atm, but it does work.

[rogerbrunswick]

Subscribed. Wokke...Still working on those pics of wheels.

[Max Lumens]

Alpina have confirmed that the NACA duct is due to overheating of the injectors. I can't find the source of it atm, but it does work.

I don't doubt that this is the stated reason or that Alpina believes that the solution they devised works. I speak to them occasionally and they're unfailingly obliging and informative, and I have no reason to doubt their engineering prowess. Maybe the idea is to enhance the (theoretical) existing flow under the sound cover with the venturi effect of the Naca duct? AFAIK they never did this again on any other car, such as the 6L M73 sedans.

[wokke]

Wolf - here is a photo of the heat shield on my Alpina after taking the intakes off. From what I understand from others, this did not come from BMW this way.

Thanks for this info Roger.
Without knowing this I actually thought about such a solution and the fact that ALPINA did it shows I'm on the right track.

Some alternative thoughts:

..........

2- Water in the cooling system is considered cool to engine designers. Liquid-to-air turbo intercoolers work on this principle.

..........

Agreed. But even engineers consider 80°C or whatever you have in there on a hot summer day a bit high for fuel. As a matter of fact the 850i I recently had in my shop for the M73 conversion had an alloy insulation wrapped around the fuel rails. And it definitely looked OEM and not self made. But it's not listed anywhere as a spare - or I at least can't find it.

Subscribed. Wokke...Still working on those pics of wheels.

you mean the gold OZ I have test fitted?

all m70's have chains,as do s70's.

luckily.

I knew I had taken a picture of the alloy wrap around the fuel rails.
Here it is:

[whiteghost1]

Interesting photo Roger, thanks for postig that. I didn't even think to look at that on my E32 B12 5.0 when I did the intake manifold gaskets on it.

Why would Alpina put the NACA duct in on the B12 5.7, with a corresponding hole in the acoustic cover then? Isn't that to cool the fuel rails down?

Does anyone have any pics of the said 5.7 NACA duct + hole in the acoustic cover?

Has anyone ever thought about stuffing some (fiberglass??) insulation in the valley which the coolant pipes travel through, in the M70?
I'm thinking about doing so when I do my Schrick swap.

[wokke]

I'm going to insulate the water pipes in my M73 before installing it. And I will also wrap the exhaust downpipes to reduce heat dissipation into the engine compartment.

[braincat]

[QUOTE=wokke;25337761]I'd say this is about all it covers sound wise.
And it keeps the heat nicely around the fuel rails.
I removed it on my M70 and will do so as well on the M73 which is going to be installed soon.


My M70 (removed meanwhile)



What sort of results have you observed with the adjustable fuel regulators? And how did you plumb them in?

[wokke]

I only installed them because of the 4-pintle injectors I tried out. Since I couldn't realize any benefits from that I went back to original BOSCH injectors. Since I had to modify the fuel rails for the "external" FPRs I had to keep them.

[4drian]

They do look cool!