Engine Block Question 3

[jax79]

I'm a 4th year Mechanical Engineering student who is doing a project on engine blocks. Basically, I have to talk about the different types of materials used for engine blocks, critique them (pros/cons), and then try to design a new material for engine blocks. There are a couple of things I'm not too sure about, and was wondering is somebody could fill in all the blanks:

1. Why use iron instead of steel? I know steels in general have a higher hardness then irons, so I thought that would be an important factor in making engine blocks. Is it that iron is easier to cast then steel?

2. I here ceramics are the new big thing, as soon as they figure out how to cure it w/o any bubbles or cracks. Are there any websites that say how they're curing it? Theoretically, could you do some kind of layering process like laser sintering to make engine blocks?

3. The "New Steel" vs Aluminum... if a company could design an engine block out of steel that would be just as light as aluminum, would they use it? Also, would you still need piston rings?

4. One of my group members was telling me about the corrosion factor of steel, but I was wondering why companies wouldn't just use stainless steel if it was such a big problem.

That's all... any help would be greatly appreciated. Please note, I'm not trying to get anybody to write my project for me, I just need some answers to my many questions so i can do my project.

Thanks

 

[GregLocock]

1) Don't know, but hardness (=yield strength) is not the dominant requirement. Most block designs for passenger cars are stiffness limited. Incidentally the stiffness of the complete engine is largely controlled by the head, and the detail design of the head bolts, rather than the block.

2) There did used to be a ceramic engine - the so-called adiabatic diesel engine. I think GM made it for the US army. Stopping cracks forming in ceramics is, and always has been, the hardest thing.

3) My current boss designed a new engine block 15 years ago and thinks that his cast iron block was within 15% of an equivalent aluminium block, for weight. I don't understand your rings comment - aluminium blocks use steel liners in the bores.

4) Corrosion isn't much of an issue in the block itself, there are far more fragile components in the cooling circuit. Stainless steels are expensive and have comparitively poor mechanical properties. Cheers

Greg Locock

 

[jax79]

Thanks for the response... you filled in a lot of blanks that I've been having lately about the pros and cons.

Out of curiosity... did your boss's iron engine block go into production? I remember someone telling me that an old nascar mechanic wrote a book about why iron blocks are better then Aluminum.

This topic has really sparked an interest in me, cause one of my profs told us a story of how the "new steel" was implemented into car frames. I'm not sure if you know the story or not, but basically the engineers put the design of the frame into a CAD program, and it optimized the shape of the steel frame so that it was lighter then Aluminum, but still had higher impact strength.

I thought it was interesting, so I thought I'd share.

Thanks again.

 

[GregLocock]

Yes, we have built about half a million of 'his' engines. We use cast iron cos it's cheap, no better reason is needed!

I think you are talking about the ULSAB body (trying to remember the acronym). They got about 25% weight reduction. I'm pretty sure that the optimisation method was a bit more elaborate than meshing it all up and hitting the optimise button! What would have been interesting is to optimise an aluminium structure in the same way, and come up with a true comparison.
Cheers

Greg Locock

 

[gdodd]

In addition cast iron, particularly flake graphite cast iron contains better sound deadening properties, a lower melting point and has better fluidity than steel castings.

The new engine block material is cast aluminium using steel inserts, hard alloy plating or preferential microstructural treatments that produce a wear resistant surface in the bore.

ULSAB - Ultra light steel auto body developed by Porshe engineering and supported by the steel industry to slow the potential development and adoption of aluminium alloys and composites being used on the body in white.

Corrosion in the modern car engine is less of a problem since chemical inhibiters were introduced into the cooling system.

 

[Grelling]

Flake graphite cast iron can be cast very thin walled which reduces weight of the motor block close to motor blocks made of aluminum, because the composition and metallurgy of flake grey iron can be adjusted to be nearly no need of risering. This can't be done with steel castings nor with aluminum castings. Steel castings usually also need welding because of cracks, inclusions etc. Therfore production cost will be 3 and more times of that of flake grey iron. In case of leaking, castings can be efficiently sealed.

A further advantage is that the graphite and its cavities serve as small containers for oil or graphite which is suitable for lubrication at start of the engine and lubrification at emergency situations.

 

[MaxRaceSoftware]

A few additional comments;
Aluminum block
The dyno test I 've done on aluminum blocks for
Chevy small block and big block ...the results were
significant Torque and HP Losses, along with slightly reduced ring seal and increased blowby CFM under full-load
acceleration. On the small block Chevy , all parts were switched over to new cast-iron Bowtie block machined to same dimensions, and Torque and HP were very much improved

The aluminum block acted like a giant heat-sink
reducing HP ....the same effects were observed by my dyno testing Chrysler Hemi heads in aluminum VS cast-iron versions for NHRA Super Stockers ..as much as 12 to 15 HP losses were seen with aluminum heads, and on small block Chevy engine ...10 to 12 hp losses between seemingly similiar ports/porting in aluminum VS cast-iron heads Larry Meaux (meauxrace2@aol.com)
Meaux Racing Heads
MaxRace Software
ET_Analyst for DragRacers

 

[truck]

Iron vs. Aluminum Castings:

In backyard discussion accuracy, aluminum has about half the density of cast iron and about half the mechanical strength. For equivalent parts, therefore, the iron and aluminum parts will weigh about the same.

Your weight save comes in the area of being able to tailor size to material necessity (e.g., runner size). A well optimized cast iron block will not be all that much heavier than aluminum and will come out way ahead in the 'bang for the buck' department. Truck

 

[wroberts]

While I am all for the Iron block. I would like like to point out some advantages of Aluminum. The manufacturing process for Iron is Dirty, Hot, bad on your body and equipment. Trust me I've worked in an Iron foundry producing Truck Blocks. It's shear hell. Iron needs to be produced on site. Aluminum can be shipped in hot and held in holding tanks. Iron must be poured into a mold. Aluminum can be pumped into a mold. Aluminum foundries can be Air Condioned, Iron you live in 100+ degree heat all day long. There is an enormous amount of pollution produced making Iron. Two eqivalent plants both proding engine blocks, Iron 2000 people, Aluminum 500 people.
I'd rather drive an Iron block, but much rather work in a plant making aluminum ones.
Will Roberts

 

[Grelling]

Hi,
regarding dirt in iron foundries. I worked in several iron foundries many years, the job is dirty but people are friendlier, because the white collar types stay outside. And if they try to enter with "management games", the foundry will show red figures because quality depends on too many workers and demotivated workers may harm extremely. In central Europe there is a larger group of companies, with mechanical shops, engineering departments and they had also a foundry (10'000 tpy). The retirement founds are also for the foundry employees still at this group. Statistically the longest lifes after retirement are those of the foundry workers.
The dirt of the foundry you can wash after work. The traces of fight for survival in cleaner areas burn your mind.

regards
grelling

 

[evelrod]

Amen




Rod