Honda Power Unit Hardware & Software

[Craigy]

Cast engines are machined as well, and If your casting process is good, the structure of your metal will be as good as any forging.

Materials aren't really my area but I always thought that the point of making a forged block of metal (billet) and then machining it down to shape was stronger for a given material than casting because of how forging rearranges the crystalline structure of the material.
Am I wrong?

[MrPotatoHead]

Cast engines are machined as well, and If your casting process is good, the structure of your metal will be as good as any forging.

Materials aren't really my area but I always thought that the point of making a forged block of metal (billet) and then machining it down to shape was stronger for a given material than casting because of how forging rearranges the crystalline structure of the material.
Am I wrong?

You are correct.

A classic example is pistons.
The strongest pistons are machined from a forged near net shape billet.
Cast pistons are far weaker and serve no place in a race engine.

[godlameroso]

Yes and no. Billet blocks aren't made like swords, the aluminum isn't folded on itself a few hundred times. A billet is just a block of metal, granted not all aluminum alloys are equal. Like I said, it all depends on material and process being used, and the architecture of the block.

Cheap mass produced engines are built with cost in mind, so block structures reflect this. Thin die cast open deck blocks, heads full of casting marks, slag, thin block casing from cheap aluminum, etc. Using billet let's you rectify these shortcomings, but if all the materials and processes are of higher quality than your than a standard civic, casting is just as good.

Edit: I think the gap in communication comes from assuming all billet is forged, the two are not the same thing. Billet engine blocks aren't necessarily made from forged billet aluminum. Forging, vs casting is a different animal than casting vs billet machining.

Forged aluminum can be cast in a mold as well.

[MrPotatoHead]

Yes and no. Billet blocks aren't made like swords, the aluminum isn't folded on itself a few hundred times. A billet is just a block of metal, granted not all aluminum alloys are equal. Like I said, it all depends on material and process being used, and the architecture of the block.

Cheap mass produced engines are built with cost in mind, so block structures reflect this. Thin die cast open deck blocks, heads full of casting marks, slag, thin block casing from cheap aluminum, etc. Using billet let's you rectify these shortcomings, but if all the materials and processes are of higher quality than your than a standard civic, casting is just as good.

I totally agree on cost being the driving factor on production blocks and heads for sure. It's all about saving pennies when you make millions of an engine each year. The OEM machining tolerances leave a lot to be desired as well.
You wouldn't believe some of the loose tolerances on EM engine blocks.

As far as billet blocks go, most are made from 6061-T6, either a rolled billet or in some specific cases a forged billet.
If they have a bedplate that is typically made from 7075 or steel, otherwise they use aluminum or steel main caps.

Higher end billet race blocks will also get an additional heat treat stage curing the machining process to further increase the strength of the block.

[Tommy Cookers]

contrary to popular belief, forging is not per se beneficial
forging does not improve the material, it at best prevents the poorer bits of material being in important places
given that scale naturally develops on the surfaces of very hot metal in air
eg forging a crankshaft-shaped billet aligns the so-called 'grain' that is poorer performing material normal to the in-use stresses
in use that is after the crankshaft-shaped billet has been machined to make a crankshaft as per tradition
ie machining a crank from a cylindrical billet may even be worse (and there's a lot of waste)

Gordon Jennings said that eg forged pistons were made from forgeable alloys that were rather soft and so weak
but of course casting alloys tend to have low melting points so may be weaker in piston use
die casting certainly needs high fluidity/low melting point

a billet is quite likely cast - vacuum remelting is a good thing here
billets of fancy material are often reforged just to resize the material for the customer
we might hope in vacuum or inert atmosphere
I never questioned this, being concerned with stiffness design more than strength

heat treating can be done (or not) whether parts are made by casting or machining from 'billet'

[MrPotatoHead]

Tc I disagree with some of the things you said but I fear we are already heading off topic enough to risk a slap on the wrist, so I'll call it quits here

[godlameroso]

Yes and no. Billet blocks aren't made like swords, the aluminum isn't folded on itself a few hundred times. A billet is just a block of metal, granted not all aluminum alloys are equal. Like I said, it all depends on material and process being used, and the architecture of the block.

Cheap mass produced engines are built with cost in mind, so block structures reflect this. Thin die cast open deck blocks, heads full of casting marks, slag, thin block casing from cheap aluminum, etc. Using billet let's you rectify these shortcomings, but if all the materials and processes are of higher quality than your than a standard civic, casting is just as good.

I totally agree on cost being the driving factor on production blocks and heads for sure. It's all about saving pennies when you make millions of an engine each year. The OEM machining tolerances leave a lot to be desired as well.
You wouldn't believe some of the loose tolerances on EM engine blocks.

As far as billet blocks go, most are made from 6061-T6, either a rolled billet or in some specific cases a forged billet.
If they have a bedplate that is typically made from 7075 or steel, otherwise they use aluminum or steel main caps.

Higher end billet race blocks will also get an additional heat treat stage curing the machining process to further increase the strength of the block.

I've always found the interesting aspect of a billet engine are adding structural features to the block, like using cooling fins, thicker main girdles, re-worked coolant passages, reworked oil passages to optimize the routing, which can by itself make a big difference as far as friction in the oil pump is concerned. However, it's nothing that can't be done through casting if your materials and processes are up to snuff.

Frankly if you have a good process, casting is every bit as good as raw block machining and pieces can be churned out in half the time.

As far as waste is concerned, I don't think it matters, you collect as many shavings and "wasted" metal as you can and you recycle 95% of what you machine away.

[Craigy]

Tc I disagree with some of the things you said but I fear we are already heading off topic enough to risk a slap on the wrist, so I'll call it quits here

I wonder if Honda were creating so many heads/blocks that casting made more sense..?

This isn't a joke based on Honda's reliability record - I am wondering how many of the things they had to make for dyno and development work in Sakura as well as the track engines. It could literally be hundreds.

[ncassi22]

Tc I disagree with some of the things you said but I fear we are already heading off topic enough to risk a slap on the wrist, so I'll call it quits here

I wonder if Honda were creating so many heads/blocks that casting made more sense..?

This isn't a joke based on Honda's reliability record - I am wondering how many of the things they had to make for dyno and development work in Sakura as well as the track engines. It could literally be hundreds.

I honestly think it just has to do with expertise (knowledge i.t.o design/software/mfg/logistics etc). They cast their other racing engines as well. WTCC, SuperGT/SF, motogp, F1.

[PlatinumZealot]

What the benefit of using machined valve cover and head ala merc compared to casted ala honda? I think machined head is overhype, no need to do that at all. Merc is doing germany, overengineered

It's probably easier for Mercedes HPP to make that way. Casting requires a Kiln that's always hot. You need be to pushing through a lot of parts to make it viable. So instead of firing up a big ole furnace for a few valve covers, or outsourcing the part, HPP just machines it out of block. Honda, and Renault and Ferrari make a truck load of engines right through the time, ao it is easier for them to just cast things. Just my take on it.

Edit: I think the casted material they use to make cylinder heads is much, much stiffer than T6? Aluminum? Some of those alloy formulations are even kept secret. Magnesium and some other elements are used. The artisan pots made from recycled cylinder heads are ridiculously strong.

[ncassi22]

As an aside a few years back I read cosworth designs as much of their engine to milled by a 3-axis cnc mill. Saves them a lot of money whereas Honda’s budgets are bigger usually

[godlameroso]

What the benefit of using machined valve cover and head ala merc compared to casted ala honda? I think machined head is overhype, no need to do that at all. Merc is doing germany, overengineered

It's probably easier for Mercedes HPP to make that way. Casting requires a Kiln that's always hot. You need to pushing through a lot of parts to make it viable. So instead of firing up a big ole furnace for a few cylinder heads, or outsourcing the part, HPP just machines it out of block. Honda, and Renault and Ferrari make a truck load of engines right through the time, so it is easier for them to just cast things. Just my take on it.

Kilns are super old school, no one uses stuff like that any more, it's all electric arc, modern ones will melt just about any metal in short order, that's to say if Honda uses full melt casting, maybe they use something more advanced not that I know such information.

[PlatinumZealot]

Electric arc furnaces are very power hungry, even if they can be fired up relatively quickly.

It makes me ponder if there is such a thing as an induction heating oven?

[ncassi22]

What the benefit of using machined valve cover and head ala merc compared to casted ala honda? I think machined head is overhype, no need to do that at all. Merc is doing germany, overengineered

It's probably easier for Mercedes HPP to make that way. Casting requires a Kiln that's always hot. You need be to pushing through a lot of parts to make it viable. So instead of firing up a big ole furnace for a few valve covers, or outsourcing the part, HPP just machines it out of block. Honda, and Renault and Ferrari make a truck load of engines right through the time, ao it is easier for them to just cast things. Just my take on it.

Edit: I think the casted material they use to make cylinder heads is much, much stiffer than T6? Aluminum? Some of those alloy formulations are even kept secret. Magnesium and some other elements are used. The artisan pots made from recycled cylinder heads are ridiculously strong.

Possibly but I think they are quite rigid with keeping racing and mass production engines separate. Even the very low volume NSX engine is cast by COSWORTH

[63l8qrrfy6]

Forgings are typicall stronger as the grain is forced to flow parallel to the faces of the part. The forged part will exhibit anisotropic properties which can be taken advantage of - for example a shaft will be stronger in bending if the grain flow is parallel to the neutral axis.

An as-forged fillet will always be stronger than an as-cast/machined fillet. An engine valve for example experiences high stresses at the blend radius between the head and the stem so it is quite common to forge nickel-alloy exhaust valves in high performance engines for this particular reason. It is important to note that the sections of the forging that are machined (where the cutter goes throgh the grain) can lose most if not all of the advantage over a casting/ billet machined part.

I know that in V8 days Cosworth used a sump machined from cold rolled 7075 billet that had high directional strength in one plane. Interestingly they experienced failures and had to move to an isotropic alloy.

Cast surfaces have poor profile tolerances compared to billet machined parts, as a result it is almost impossible to maintain a low uniform wall thickness. Secondly, machining allows the creation of highly undercut pockets which save considerable amount of weight. It's impossible to have the same sort of pockets on a casting as it can't be removed from the mold. The pockets can't be machined in the casting either as the extra material required would create shrinkage and porosity issues.

Generally the surface finish is low on a casting which decreases the endurance strength. Of course, the same is true for billet machined parts with massive cusp height.