[sredwine]

I have read that BMW introduced a magnesium-clad block structure in the '06 E90. A mechanic told me they had problems with that block failing (and I've seen at least one bulletin discussing block failure-causes incurable oil leak) and reverted to a more conventional aluminum block for '07-my year, coincidentally. Anyone have any more info on this? If the blocks are aluminum, we shouldn't have to use those stupid aluminum bolts, either!

[micah_675]

To my knowledge all N52 motors are Magnesium block/Aluminum sleeved blocks. Meaning the Cylinder walls are aluminum and the outside block is magnesium. Magnesium is a very strong and light metal. FYI sikorsky MH-53 main gear boxes are made out of magnesium. If its good enough to cary a 42k pound Helo into the air, its damn sure good enough to handle your 250 hp......


From BMW's website:

Our inline six engine offers smooth power, greater acceleration and 200 lb-ft of torque at at 2750 rpms. A number of pioneering technologies make it possible. An electronically controlled water pump helps increase power output. Our patented Valvetronic system offers better fuel efficiency. And to save weight, we used a groundbreaking innovation that BMW was the first to use in a production car - an engine block made of a lightweight composite magnesium/aluminum.

[micah_675]

You sir are full of crap. TY for wasting more peoples time with more spouted off garbage you THINK you know. Guess what, NO it isn't a fire hazard. If it was why would they be able to build it? The flash point of magnesium is COMPLETELY dependent on the amount and FORM of the metal. Shavings or flakes WILL combust rather easily, however a large piece, such as an engine block, will not. Take your trash elsewhere. The block is a magnesium alloy. http://www.eurosinolink.com/pdf/sdpm020v1mg.pdf

Oh and i would like to point out Milk of Magnesia is a GREAT anti-seize and anti-corrosion device. Which is utilized as such in aircraft motors (which oddly enough doesnt catch on fire huh).

Originally Posted by TrackRat

Magnesium's biggest asset is light weight. It has many pitfalls however including brittleness, low cyclical fatigue life, corrosion issues, easily stripped machine threads, etc. Numerous car makers have used magnesium engine/trans cases over the years for production and they always revert to aluminum after a few years of Hell with the magnesium parts. Aside from the obvious fire hazard, magnesium is popular in racing for throw away parts.

IME magnesium has a very limited usefulness to date for street vehicles.

In addition to BMW using a composite engine block they decided to use aluminum cam cover bolts which regularly fracture and cause a $1000+ repair bill.

[Mike.Beale]

I agree with micah_675 that the fire hazard from magnesium is essentially non-existant. At the same time some of TrackRat's points are valid. There are issues with cracking and corrosion in magnesium. Even though mag has been used sucessfully in the past by Sikorsky and other aerospace companies, 'no magnesium' has been one of the ground rules on the aerospace programs that I have worked on. This is mainly due to the corrosion problems that the Navy and the airlines have had with mag. Note though that both the military and airlines look for a 30 year life span for their aircraft with very harsh environmental requirements. So just because its not acceptable for aerospace anymore doesn't mean it can't be used for cars.

Both VW and Porsche have used mag quite sucessfuly in their air-cooled engines. Eventually both companies went to aluminum cases. I think this was because as they increased the power and displacement of their engines they eventually needed to strengthen the cases. Switch to a stronger allow was a quicker and easier change compared with designing a whole new beefed up mag case.

[issabmw]

Originally Posted by Mike.Beale

I agree with micah_675 that the fire hazard from magnesium is essentially non-existant. At the same time some of TrackRat's points are valid. There are issues with cracking and corrosion in magnesium. Even though mag has been used sucessfully in the past by Sikorsky and other aerospace companies, 'no magnesium' has been one of the ground rules on the aerospace programs that I have worked on. This is mainly due to the corrosion problems that the Navy and the airlines have had with mag. Note though that both the military and airlines look for a 30 year life span for their aircraft with very harsh environmental requirements. So just because its not acceptable for aerospace anymore doesn't mean it can't be used for cars.

Both VW and Porsche have used mag quite sucessfuly in their air-cooled engines. Eventually both companies went to aluminum cases. I think this was because as they increased the power and displacement of their engines they eventually needed to strengthen the cases. Switch to a stronger allow was a quicker and easier change compared with designing a whole new beefed up mag case.

You make very valid points

[issabmw]

I think the OPs take on this is from a performance standpoint. The reasoning behind the magnesium block is to save weight, which I think we all can agree on.

The block is sleeved with aluminum, meaning it retains the strength of an aluminum block where it counts: the combustion chamber, while giving a lightweight housing for placement of the internals.

Now, to what degree are the blocks sleeved i.e. thickness, and how much power would it take for the block to give up is a matter of testing.

For the power we have, its a great design. I personally think that //M should give us an iron block to work with again, like the S54 in the e46, which handled extreme turbocharged setups.

[FrankiE90]

[5erman]

people keep saying aluminum is stronger-magnesium is a much stronger metal foilks--

[jaguar36]

Originally Posted by TrackRat

Please stop your inappropriate posts micah 675-

+1

Magneisum has some great properties, but the fire issue cannot be ignored. The flash point of a material is the same regardless of its form. It is 500C in a shaving or a block. (It is however alot easier to get a shaving to 500C than an engine block) It is quite difficult to get a large hunk of Magnesium to burn, however it can happen, and when you are talking about hundreds of thousands of cars, the chances of it happening are not insignificant.

Originally Posted by 5erman

people keep saying aluminum is stronger-magnesium is a much stronger metal foilks--

This is also not technically true. The tensile yield strength of Magnesium ranges from about 21-25ksi. Some Aluminum alloys have a tensile yield strength of >60ksi. (For comparison, some steels can get over 200ksi). However this doesn't tell the whole story as Magneisum is very light at only 1.7 g/cm^3 vs Aluminum at 2.7, and steel at 7.9.

Material selection is never as simple as which one is the strongest, or lightest. A whole range of features including strength, density, stiffness, fatigue, corrosion, availability, cost, machinability and so on have to be considered.

And lastly... micah_675 you lost any spec of credibility you had when you brought up Milk of Magnesia, Milk of Magnesia is Magnesium hydroxide (Mg(OH)2) and is as similar to Magnesium as Oxygen is to water.

[TSM330i]

They still use the mag/aluminum block.

Here's one of the highlights from the brand new X3 6-cylinder engine.
http://www.bmwusa.com/Standard/Conte...rformance.aspx

[sredwine]

Lots of good info here, and well-informed opinions. I'm not worried about the magnesium part of my block catching fire-if the car gets hot enough to ingnite that mass, I've probably got more than enough trouble already! The scary bulletin I found mentions an incurable oil leak between the aluminum and magensium sections (I believe) that occurs low on the right front of the bloock near the coolant pump location. New block would be only fix. The stupid, fragile aluminum bolts are used because the magnesium block has severe galvanic corrosion problems if steel is used. Now what has me posting all this is the mechanic I took the car to (pre-purchase) said they phased the magnesium block out after '06 MY but kept using the aluminum bolts to avoid confusion in the shop. He had been a mechanic at one of our top dealerships for years and had the certificates to prove it-but he could have been fed BS by BMW-anybody have some insight here?

[jaguar36]

That is partially correct. In 2006 BMW offered the 325i and the 330i, both of which used the N52 engine which has the Magnesium block with aluminum clyinder liners. In 2007 the E90s switched to the 328i and 335i. The 328i continues to use the N52 engine, while the 335i uses the less sophisticated N54 engine, which has an aluminum block with cast iron cylinder liners.

[micah_675]

@ the OP your block is still the exact same as all the N52 motors. You have the magnesium/aluminum composite block (just means they are 2 different pieces of metals pushed (mechanically fused) together). As for you worrying about your block leaking. It shouldn't be a major issue. I am sure there was defects in the metal that caused the issue.



I don't particularly care what you 2 think. The block is a magnesium alloy. Therefore let me break it down. Alloys are made of one or more metal, there is always one that makes up more of the substance than the other (typically the primary metal is what is named for the alloy). Why are alloys used? Because when properly created the strengths of the metals combined are left and typically leave the weaknesses out. Regardless, it is VERY well documented that is near impossible to ignite an ingot of magnesium. Only in its molten state does it become unstable and HIGHLY combustible.

The BMW engine uses an aluminium alloy insert for the cylinder walls and cooling jackets surrounded by a high-temperature magnesium alloy AJ62A

The makeup of our engine block is as follows, 91.7% Mg, 6% Al, 2% Sr, and 0.3% Mn. Which is a creep-resistant Mg alloy blend. Basically meaning it resists thermal and physical stress trying to tear the metal apart.

Sources

Makeup of the alloy on page 681 (also goes in depth about creep testing on the alloys mentioned in the article including AJ62A (our engine block))

http://books.google.com/books?id=WIG...page&q&f=false

mathematical formula for computation of creep characteristics and description of creep

http://personnel.mcgill.ca/files/mih...uz/kayaadv.pdf

Any questions? I would like to point out that cracking is not going to be a major issue. Why? Because your actual cylinder walls are Aluminum NOT the magnesium alloy.

A good fact sheet about magnesium

http://www.magnesium.com/w3/data-bank/index.php?mgw=222

Magnesium is an excellent conductor of heat, and, as a practical matter, the entire piece must be brought to a temperature near the melting point before ignition will occur. Normally, this will not occur unless the solid magnesium piece is surrounded by a general conflagration from other sources.

[Dirnegrey]

Originally Posted by micah_675

You sir are full of crap. TY for wasting more peoples time with more spouted off garbage you THINK you know. Guess what, NO it isn't a fire hazard. If it was why would they be able to build it? The flash point of magnesium is COMPLETELY dependent on the amount and FORM of the metal. Shavings or flakes WILL combust rather easily, however a large piece, such as an engine block, will not. Take your trash elsewhere. The block is a magnesium alloy. http://www.eurosinolink.com/pdf/sdpm020v1mg.pdf

Oh and i would like to point out Milk of Magnesia is a GREAT anti-seize and anti-corrosion device. Which is utilized as such in aircraft motors (which oddly enough doesnt catch on fire huh).

Magnesium IS fire hazard. even little kid know that.

[jaguar36]

It is certainly possible for a magnesium engine block to ignite. It is also highly unlikely. However like I said before when you have hundreds of thousands of them running around, a one in a million chance becomes pretty likely.

Regardless its pretty irrelevant for the car owner, by the time the block would go up you'd be long dead if you were in the car. Its really only an issue for firefighters (and the guys who would have to come fix the road after your engine block melted a hole through it). Firefighters have to know not to use water on a magnesium fire as magnesium burns so hot that it will decompose the water into hydrogen and oxygen, which will just make the fire worse.

[Gavin@MMW]

Originally Posted by micah_675

@ the OP your block is still the exact same as all the N52 motors. You have the magnesium/aluminum composite block (just means they are 2 different pieces of metals pushed (mechanically fused) together). As for you worrying about your block leaking. It shouldn't be a major issue. I am sure there was defects in the metal that caused the issue.



I don't particularly care what you 2 think. The block is a magnesium alloy. Therefore let me break it down. Alloys are made of one or more metal, there is always one that makes up more of the substance than the other (typically the primary metal is what is named for the alloy). Why are alloys used? Because when properly created the strengths of the metals combined are left and typically leave the weaknesses out. Regardless, it is VERY well documented that is near impossible to ignite an ingot of magnesium. Only in its molten state does it become unstable and HIGHLY combustible.



The makeup of our engine block is as follows, 91.7% Mg, 6% Al, 2% Sr, and 0.3% Mn. Which is a creep-resistant Mg alloy blend. Basically meaning it resists thermal and physical stress trying to tear the metal apart.

Sources

Makeup of the alloy on page 681 (also goes in depth about creep testing on the alloys mentioned in the article including AJ62A (our engine block))

http://books.google.com/books?id=WIG...page&q&f=false

mathematical formula for computation of creep characteristics and description of creep

http://personnel.mcgill.ca/files/mih...uz/kayaadv.pdf

Any questions? I would like to point out that cracking is not going to be a major issue. Why? Because your actual cylinder walls are Aluminum NOT the magnesium alloy.

A good fact sheet about magnesium

http://www.magnesium.com/w3/data-bank/index.php?mgw=222

This is good information right here^^

[Spitfirocks]

I love lighting magnesium strips on fire! It is a beautiful sight(or lack of, because you can never look directly at it)

[philsteroni]

This topic makes me laugh because 20 years ago BMW introduced aluminum blocks to the car industry with the e36 model. They had a recall on them and everyone started to put in their 2 cents about how BMW was stupid for using aluminum blocks... Now every car manufacturer uses aluminum for their engine blocks. Why don't we all learn from history and let the BMW (industry leading) engineers do the thinking.

[superduty]

I hope you aren't saying that BMW was the first manufacturer to produce aluminum blocks.

Originally Posted by philsteroni

This topic makes me laugh because 20 years ago BMW introduced aluminum blocks to the car industry with the e36 model. They had a recall on them and everyone started to put in their 2 cents about how BMW was stupid for using aluminum blocks... Now every car manufacturer uses aluminum for their engine blocks. Why don't we all learn from history and let the BMW (industry leading) engineers do the thinking.