Cast Iron Vs Aluminium Alloy Engine Block

[NB4C]

Cast Iron:

Pros:

Wear resistance / Longer lifespan

More resistance to overheating

Cheaper

Cons:

Heavy

Harder to cool

Takes longer to heat up to operating temp (takes 20 minutes on a 15 degree day) - causes the engine to use more fuel when cold.

Aluminium

Pros:

LIGHT WEIGHT

Conducts heat very well - easier to cool

Heats up to operating temp quickly - reduces overall fuel consumption

Cons:

Less resistance / Shorter lifespan

Overheating damages it much faster

More expensive

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Ford's been using cast iron engines in their Falcons (and even the 2010 Shelby GT500 ). If Ford used Al. block engines in their falcons, you'd end up with a lighter / more efficient / faster accelerating vehicle. But I guess what's stopping Ford is the cost. I know GM used Al. in their new V8 engine blocks.

What are your thoughts ? How much lighter would the Falcon be with an Aluminium 4L Barra engine ?

[Adam]

This may well happen IMO with the decision to stick with the old I6.

The current engine fails the upcoming changes to the emission standards because the block doesn't heat up fast enough.

[f6rspec]

They'll just do something with the cat design to pass emission testing rather than cut into profit margins with expensive alloy blocks.

[Venom XR6]

It will stay cast iron. It costs Expensive Daewoo around $1000 extra to make an alloy block compared to an iron block due to the fact that had to source them from overseas due to Ion going bust a few years ago, and their alumium casting plant in Melbourne not being finished. Expensive Daewoo were going to source their blocks from them but it didn't end up happening.

$1000 is a massive cost to add to a car.

Ford are very close to selling their casting plant and the buyers will expect Ford to continue to buy blocks, cranks, exhaust manifolds and rods from them as part of the sale, so no alloy block.

The weight difference won't be huge anyway, maybe 15-20 kg at the most.

[PHANTMXR6]

Not to mention aluminium blocks transfer more noise.

Rising NVH is not what companies and consumers want.

[Venom XR6]

This may well happen IMO with the decision to stick with the old I6.

The current engine fails the upcoming changes to the emission standards because the block doesn't heat up fast enough.

that's incorrect. The block may take a bit longer to heat up, but it is not stopping the engine from going Euro 4. There are a hell of a lot of cast iron blocked diesels that are Euro 5 compliant. It makes it a little harder to pass but there's no rule saying it can't be done. The reason they were going to use an alloy V6 was due to the high costs of R&D to make the I6 Euro 4 compliant Vs the smaller number of engines they were making, its was becoming un-cost affective. Secretly they had a small crew working on the I6 to make it Euro 4 compliant even when the V6 development was going on, because they wanted to have a backup just in case the V6 option turned bad, which it did. It was cheaper to make the I6 Euro 4 compliant than it is to get the V6 fitted and past crash tests etc, plus the government have chipped in with some green car funding.

The current I6 doesn't not require too much work to get it Euro 4 compliant, they think they can do it with changes to injection, exhaust and calibration. The most likely thing will be moving the cat convertor really close to the head so that it heats up quicker on start up. All Euro 5 compliant engines have cats right next to the head to get heat into them quickly, which reduces cold start emmisions.

[RegSpec]

Just so we're comparing "apples with apples"..........

Does anyone know the exact weight variance between them?

[senna_T]

Well put it this way - the alloy block of a GM LS1 5.7L V8 weighs less than a cast iron Nissan RB25 2.5L 6cyl. block

[NB4C]

Yeah, Senna - that puts things into perspective. I know that Al. has a density of 2700kg/m^3 and cast iron is 7800kg/m^3, so the Al. block should have a significant weight advantage (should be a lot more than the 15-20kg Venom quoted).

It explains why a Corvette Z06 can hold a massive 7L V8 in the front, and still handle well.

Edited 30/03/09 09:21 AM by NB4C

[Venom XR6]

Yeah, Senna - that puts things into perspective. I know that Al. has a density of 2700kg/m^3 and cast iron is 7800kg/m^3, so the Al. block should have a significant weight advantage (should be a lot more than the 15-20kg Venom quoted).

It explains why a Corvette Z06 can hold a massive 7L V8 in the front, and still handle well.

How much do you think a bare I6 block weighs. I've seen people pick them up with bare hands, big guys but I've seen it. I'd say 50-60 kgs maybe?. Even if alloy was half that it would only be 25-30 less, but once you add the cast iron sleeves and main caps etc it would come down to maybe 20kgs? Plus an alloy block would need a bit more material thickness in it to retain strength.

I'm assuming the main caps in all alloy engines need to be steel or cast iron?

Edited 31/03/09 07:28 AM by Venom XR6