What are SEMI FORGED PISTONS?

www.mrpltd.co.nz/
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What is up engine heads! Today we're talking about semi-forged piston and we will try to clear away some of the miscronceptions surrounding semi-forged pistons, and even other semi-forged stuff like semi-forged wheels.
To understand what semi forged pistons are we first have to understand how they're made. So how are they made? Well...they aren't. There's no such thing as semi-forged pistons. It is physically impossible to semi-forge something. It's impossible to forge things half-way. A piston, just like pretty much anything else, is either forged or cast.
In many cases when people speak about semi-forged pistons they actually speak about hypereutectic cast pistons. The term semi forged is common in the Subaru community and many people also like to call the 2JZ-GTE oem stock pistons semi forged. In reality they're cast hypereutectic pistons. Hypereutectic pistons are usually a step up from the more common gravity cast eutectic pistons because they do have a higher silicon content (more than 12.5%) which gives them better wear resistance, enables a tighter piston to bore fit and reduces emissions and blow-by). Although hypereutectic pistons need high pressure casting to be made properly, there is still zero forging going on during their manufacturing process. A molten aluminum alloy is fed under pressure into a mold. So the term semi-forged, although used often is definitely unjustified in the case of high pressure cast hypereutectic pistons.
So what about semi-forged wheels? Well, in their case the semi forged term is sort of justified. A semi forged wheel starts as a cast wheel with a thinner than specified rim. After it's cast it's set into a special machine that rolls the rim section into the final width of the wheel. This gives the rim section forged-like properties, however the segment of the wheel where the spokes are remains fully cast with cast mechanical properties.
What about pistons where the semi forged term is sort of justified? Well, the OEM 4AGZE Toyota pistons are one such case. These pistons aren't made using conventional low or high pressure casting methods. Instead, they are made using semi-solid casting. Semi solid casting relies on thixotropy, a property of certain fluids to be more viscous when agitated and less viscous when at rest. Aluminum is also thixotropic at certain temperatures and the semi solid casting process relies on this property to create parts of very high quality, great surface finish and excellent mechanical properties. Because aluminum is forced into the mould when semi solid there is no slushing or slurring of the liquid which results in zero porosity for the final product. On top of this semi solid parts have an excellent grain flow and a very fine micro structure, similar to that of forged pistons. The process also creates parts with a very smooth finish that don't shrink as they cool. This is why the undersides of semi solid cast pistons look very similar to that of forged pistons, without any parting lines or crosshatches.
This makes semi solid cast pistons excellent all-rounders giving them properties of both cast and forged pistons. They are usually made from a hypereutectic alloy with around 17% silicon in it, so they have low thermal expansion, but are strong thanks to their excellent micro-structure. Of course. a fully forged piston made from the 2618 alloy will still take more abuse and be stronger and more ductile, but semi solid cast pistons are much better all rounders.
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[@d4a]

www.mrpltd.co.nz/ Rock the AW11: amzn.to/2G1fL8L Rock the GZE: amzn.to/304HP1V See the action: amzn.to/32XhGEb

[@emanuelnamseth1469]

Isn't MAHLE the biggest OEM piston manufacturer?

[@trumanhw]

I thought it meant forged then machined. How lame that they're embarrassed to admit bc we won't like "the words."

[@codyblea3638]

Another one down, another one down, another misconception hits the floor. Man, you have a damn talent for this. These videos are reference material grade. I mean, intro level in a lot of cases. However a good spring board to launch from is invaluable in a topic as vast as engines. I learn so much from these videos. Thank you.

[@GaurdianAzzar]

+1 My thoughts exactly

[@MrWita]

I couldnt say it better

[@adrianolacerda3410]

Great my semi-machined-titanium-hypereutetic-cast-aluminium alloy engine head cover just arrived

[@nikolai502]

Tough luck! 🤣

[@bryanst.martin7134]

Semi machined 3D printing, aka "drill the holes where they're supposed to be!"

[@adrianolacerda3410]

@@bryanst.martin7134 too hard, lemme get my 672 axis diamond welding mill

[@aterack833]

What do you have valves in block or something?

[@adrianolacerda3410]

@@aterack833 i have 16 valves in my exhaust header

[@davidcoghill8612]

For the wheels, "semi-wrought" is probably a much more accurate description than "semi-forged". Forged generally implies high temperatures above the recrystallisation temperature of the alloy, whereas wrought is a more generalised word to describe any time you're shaping a metal by using brute force to deform it below the melting temperature. More specifically in industry you'd typically call a lump of material shaped whilst red-hot "forged" and a piece of metal shaped while cold (like stamping car bodywork out of sheet) "wrought". Although to add even more confusion "cold-forged" is a term that also exists. Engineering speak can be very messy sometimes, with words going back hundreds or even thousands of years. And then the Germans have an entire dictionary of their own engineering terms which don't translate well into English at all.

[@hermanman8235]

Thanks for the info.because of my poor performance in my English vocabularies and grammar I really don't understand the term "forged" .for me (incorrectly) it meant more towards cheating and/or producing something in a bad way.thanks again.

[@cr10001]

@@hermanman8235 Well, if you forge banknotes or paintings then your interpretation of the meaning is absolutely correct. So 'forged' has come to mean two very different things in English. One, something fake (also known as a forgery). Two, a metal item produced by hammering in a forge (and usually of higher strength than a cast one).

[@asherdie]

It's called roll forging, edumacate yoseff

[@mceajc]

Ah, I remember learning about thixotropic metal forming many years ago - nice to know more about its applications. Curious to know more about the coatings that pistons get!

[@d4a]

I'll do a video on coatings soon

[@1crazypj]

I've been 'playing' with engines about 50 years and this is the best video explanation I've seen. Any time I learn something new is always good. I had never heard of semi solid casting before although I had an idea of high pressure die cast parts due to various places my father worked. I thank you and wish I was in a better position so I could send some cash your way

[@d4a]

Don't worry, no need for cash, words like that are more than enough 😉

[@michaelfortier7726]

Nothing beats an engineer who loves cars when it comes to explaining anything related to a car. The quality of the information is next level. Most of this stuff you teach took me years of gaining parcels of information here and there to learn properly.

[@RmJhoe]

man! I've learning so much in this channel. This is very helpful to me specially I'm having a automotive class

[@25kmgb]

There simply is no other place on the net to find information like this presented in like this. I've been racing and building motors for 40 years and find these presentations absolutely ilumating! They have been invaluable in preparing for my next rebuild. Thank you so much.

[@lauraiss1027]

Don't care about cars or motorcycles, I don't even change oil in my car by myself, but I watch your videos just because they are really entertaining. And while I won't be disassembling any engines or repairing vehicles in nearest future, it's a cool bonus to learn something while enjoying good video. Thank you!

[@adanjuarezjr5135]

The growth you’ve done with your channel is amazing asf I’ve learned so much over the years

[@bryanst.martin7134]

I remember when Honda was introducing pressure cast Aluminum. It was similar in strength to forged. Not bad for Aluminum. This would probably be where the the diffusion began.

[@mohammadaran9274]

I follow all your programs from Iran. Excellent and informative.

[@scunnerdarkly4929]

The term “semi-forged” was probably coined by the same marketing goons that came up with “CAN Bus LEDs”. People who like buzzwords without understanding what they’re actually trying to describe.

[@NatePrikkel]

Just like "99% fat free" It's actually 0% fat free, because it still has fat in it.

[@Hydrazine1000]

No, there is a valid point here. Both semi-sold casting and high pressure hyper-eutectic casting involve a slurry, so a mix of molten phase and solid phase. Semi-solid casting starts with a slurry, hyper-eutectic alloys turn into slush before they solidify as they cool. Proper forging involves forming a soft solid phase. If you're dealing with a mix of liquid phase and solid phase, and it behaves like very high viscosity liquid, then there is some truth in calling it semi-forging.

[@Pork-Chopper]

@@Hydrazine1000 sounds half-assed to me...

[@Pork-Chopper]

Or like "dipped in Chrome"! No such thing. How bout if pistons are run over by a "semi"! Does that make them "semi pistons"?

[@jamescaley9942]

Saying your engine has "hypereutectic pistons" sounds much better when bluffing you are an expert.

[@sefutho]

On of the best if not the best channel as far as automobile industry is concerned 🤔👍🏽

[@JosephArata]

Injection molding casting has been a thing for decades in plastics, it's even been a thing for metals for many years. Most compacted grey iron engine blocks for diesel engines are cast under injection pressure because they are mechanically stronger than your typical gravity cast block.

[@pospc2]

Mrp is a great. Have bought from them a number of times. Excellent communication as well! Also they price match. Makes it hard to justify shopping anywhere else.

[@802Garage]

This video is amazing man! You're an absolute asset to the greater car community. :)

[@aywall5905]

I love how you called out the bullshit on the forums I hate when people miss educate ppl like Lauren Hill

[@CableWrestler]

Can you explain SHOT PEENED gears please? I love the channel, you're a pioneer.

[@AmaroqStarwind]

My first guess is a combination of casting and forging. Something that I would probably do try to do (and I wouldn't call it sem-forged) is start off with a combination of advanced casting processes, and then utilize a combination of ultrasonic frequencies and aerogel-based thermal insulation within the mould/die to maximize the evenness of the entire alloy and crystal structure. I would follow up with some precise machining, and finish off with a combination of inductive heat treating and surface treating.

[@snap_oversteer]

Nice to see this explained, recently bought the same set from MRP too and wondered what they really are :D

[@Dethjingles995]

Been wondering how a piston can be semi-forged for so long. Thank you so much

[@SirRaventheSecond]

Hello all, First of all - thanks for great videos. You can explain so complex problems in such way that it is so easy to understand. Secondly: based on your videos i realised, that such pistons would be most suitable for my use (casual driving with very ocasional track days). But how to search for pistons like this? Go for “semi-forged”, “hyper eutectic” or something different? I know that it is about looking at the specs but how to specify searching for semi-solid casted hyper eutectic pistons? Thanks a Lot in advance and thanks for a great content once again.

[@charleslowe522]

Great video, I didn't know such terminology existed. Keep up the good work my friend.

[@abhishekchaudhary9542]

I think this guy knows so much about cars, that he can start his own automobile company.

[@franklinmora1709]

Congratulations man!!!! what a master piece of video haha, great information and explanation!!!!!

[@tfsupp]

Just plain old pressure die casting with the wheels its just metal spinning on a casting - thank you very well presented

[@generaldart6567]

Perfect channel for a car nerd and for me

[@maxsinventions8913]

You should do a podcast. I like listening to you talk.

[@jdmking4776]

Same pistons I have on my 7AGE. Perfect video

[@pabitrikalita3940]

I really fell for it at first 😅,

[@jackiejoe8930]

All die cast hyperutectect pistons are strong and might be marketed as semi forged. Truly semi forged possums are really also semi die cast pistons. Thanks for providing great technical information.

[@drewwill2650]

Dude I cant believe you only have 200k subs... you're gonna blow up soon, I can tell.

[@TurboHappyCar]

Really good stuff man! Dropping a comment to help out the algorithm.

[@kenlipper874]

Great explanation as usual - keep it up mate!

[@samcoote9653]

As always, i enjoyed it, found it useful, and entertaining man! Never knew the difference but now I do, cheers!

[@chregu2]

I'm very disappointed, I really loved your sword fairy tale! :-D Excellent, brilliant, clear as always!

[@ViewThis.]

I recently read an online article about Hypereutectic pistons. It said "One manufacturer claims it's Hyper pistons can handle 2hp per cubic inch" yet they didn't mention which manufacturer that was. Another manufacturer claimed 1000 hp/Hypereutectics with a proper tune but no manufacturer name was given for that either.

[@jozsefizsak]

Very interesting, informative and entertaining. Thank you, good sir.

[@eTiMaGo]

learned a lot again, thank you Professor D4A!

[@scottchladek1770]

Very impressive video, informative and entertaining.

[@laurabasuki2841]

This video really good, simple explanation...

[@MrWita]

Great work my Dear 👍🏻 Greetings from Unkel ,Germany

[@nikolai502]

I like your videos, they are very information heavy!

[@nicholaschriss1706]

Yes I remember the time I got my girlfriend semi pregnant.

[@d4a]

😂😂😂🤣

[@boostfrog]

She was actually hypereuknockedup.

[@clannishkobra8965]

🤣🤣 good my friend

[@aurelianpetre93]

Yea.. +1.... And now I'm a semi father. The kid is mine so she claims 😁😂😂😂 and my job is a semi truck driver. So everything just interconnects.......

[@bigbothoee8617]

What happened was it half a baby

[@georgelincolnrockwell14]

lots of great new information, thanks!

[@phillgizmo8934]

Same thing about semi-automatic hand guns, they are all automatic but with different trigger selectors (single, burst, full auto).

[@stevenmitchell6347]

High pressure casting of an oversized part "blank" that is subsequently pressed to final size in a secondary mold similar to the wheel analogy. This process reduces the size of the voids in the cast blank and creates some strengthening grain flow. In other words, semi-forged/thixotropic. Semi-forged is easier for layman to understand than thixotropic.

[@grzybair]

Love your vids. Keep em going

[@megaman992]

A die is placed between two semi trucks at full speed. The impact forges the pistons, but not quite fully, allowing for a little more ductility

[@acurarl9929]

We want and need a video on piston quality’s. Like how many different forged pistons are there. How many different hyper and how many different cast. How do we know.

[@ChristnThms]

Loved the intro. I was like WTF?! I was like 15 the last time I used the "halfway in" lie. I guess it still works.

[@holmesteadready]

I for one, am very glad that John Snow knows his shit

[@richardcaldwell6159]

I always learn something from your videos, generally even when I revisit them. And yeah, semi-forged sounds like marketing hype. I kept thinking of a "semi-forged cheque". And I have to admit I was befuzzled at first, going, "Huh?" Then I remembered you did this sort of hoax before....

[@CL9k24a3]

Do a video on polishing heads. There are still people that do thet on intake part and believe that increase performance when in reality it does opposite.

[@hlbcarlito1]

GREAT VIDEOS!! KEEP ON GOING!

[@GrabnerMotorsport]

Are you gonna make a video about camshafts too? Keep up the good work!

[@TheJademan85]

"Once upon a time!, sir! start the vids with that!

[@johncunningham4820]

So calling them Semi-Forged is a Forgery in itself ? The Thixotropic Casting explanation was Excellent . The Process IS actually similar to Cold Forging without the Violence and Risk .

[@marcusquinones1634]

🇵🇷 💘 ur teaching methods,great job

[@Wydarr]

Random guy with access to an electron microscope: "This piston is forged!" Driving 4 Answers: Emm... not quite, let me explain it to you 😁 Great channel, very informative, keep up the good work!

[@d4a]

😁

[@SteamCheese1]

I actually know a situation where semi-forged is actually a justifiable term. If you cast a piston blank and then hammer or press forge it too spec.

[@johnzapper1652]

Hypereutectic = Pressure injection molded piston machined finished. Semi forged wheels = Cast wheel with Cold rolled alloy rims. Forged wheel = stamped billet machined.

[@josediazasmr6014]

You are a master teacher 👨‍🏫

[@ΘωμάςΤσιλίκας]

you are so comprehensive! Thank you!

[@liamholcroft7212]

I thought it was a cast piston with a forged steel head

[@Scuterist]

i learn so mutch from you , thank you !!

[@graham2631]

In ww2 the Allies looked at a German downed fighter plane and where shocked to realize they couldn't make some of the parts. The main strut was lighter and stronger than anything the Allies had and made in one piece. This was something they didn't even know how to do. Germany had developed manufacturing technique using 15,000T presses. The Russians and the Americans both took presses home as war prizes. Then came the heavy press program and well still use these 50,000T presses today in forging structural parts.

[@d4a]

Nice one, love pieces of information like this.

[@justmemyselfandi5532]

Thank you for the video, excellent! though you forgot to mention one thing. These days CNC is quite accessible and cheap to use, so many pistons are machined all over. how do you recognise piston manufacturing process than and not to be forced to trust manufacturer :) That is tricky question. usually it goes like this "machined all over = forged piston" Also funny thing that Mhale has very similar designation for cast and forged piston M124 - cast according to you, though M142 forged. Big LOL, easy to confuse your self :)

[@Euphoria0011]

Likely will buy your stickers to put on my tuning laptop and tool boxes :)

[@douglaswilliam3978]

O melhor vídeo sobre o assunto ❤❤❤

[@whoknowsu9097]

The trick piston almost fooled me but I saw the undercuts in it then I was pretty sure it was cast! Forging is something that 99% of the world believe has an almost supernatural quality when it's more like it's man behind the curtain in the Wizard of Oz. Forging was a necessary evil that man had to do when we first discovered metals alloys and came out of the stone age. Impurities in the alloys caused numerous problems and forging helped minimize those issues but centuries later you can now get alloys straight from the foundry that are as strong and far stronger than what any forge smith could ever have produced 50 years ago hell 20 years ago. Forging steel and other alloys today has far less to do with the part being stronger than it has to do with the how much it cost to forge it vs machining it from a blank billet. As for forging vs casting here to is less an issue with which one is stronger but which way is cheaper and I've been out of the forging business for over a decade now I still believe that forging is the cheapest way to get a high quality highly complexed automotive part to the market but I could be wrong I am bias to forging! Forged piston/wheels have the mythical status to car guys today that Ninja's and Bruce Lee had to martial arts enthusiast during the 1970-80s. But who knows I could be wrong

[@codymoncrief8478]

All I heard was “Toyota-something-something-something-SUPERCHARGED.” Although I could see an attempt being made at, say, forging a piston top for greater strength, then casting the rest of the piston around this forged “biscuit,” resulting in lower outward expansion of the main body of the piston, combined with higher impact strength and density of the forged head. I could see that working correctly if the expansion rates were carefully accounted for. Also, doing a “two-piece” construction may allow for a crown-oil-cooling-passage to be carefully incorporated into the design. Alternately, a forging could be made where only the crown area of the piston is actually subjected to the forging compression, leaving the rest of the piston at a lighter density, although I would still worry about internal stresses from the differential expansion and contraction.

[@jackdaniel4977]

I’m using this toyota piston in to mivec 4g92 turbo with 480hp at 1.8bar no issue.. Worth for budget

[@kawardeep_sidhu]

I swear I had never missed my single class if he was teacher ❤

[@ИванИванов-м6ч1о]

IMO semi-cast pistons can be made by firs casting a rough piston shape, then putting it in a press and forging it to almost the perfect shape needed. This method may be better than basic forging since the part coming out of a press will need less machining than a piston cast from a solid chunk of metal.

[@someguy8094]

You should do a video on magnesium engines

[@c.n.h4841]

ultrasonic welding or sonic welding can be used to connect forged and cast part but i know they don't use it in engines yet but could be possible

[@patrickwendling6759]

Thank you for your knowledge and videos USA 🇺🇸 USA 🇺🇸

[@bluewanderer9903]

Honda K series can also take over 500hp with stock oem pistons, just wondering if these really are "just" cast?

[@christoskapareliotis4425]

These videos are so interesting that I'm wanting to do my post-grad in automotive engineering rather than mechatronics or do you think that I could incorporate mechatronics with the automobile industry? (Currently studying Mechanical Engineering)

[@kilianortmann9979]

tl,dr you can work in automotive as mechatronics engineer, but try applying in a company that does process control as an automotive engineer. That's only half the truth though. Engineering is so complex and applications so specialized, that you will always have to keep learning. Even applying for the same job, at a different company, might mean things are done differently. So choose what you like, cause chances are, you will have more fun during your masters. If you are good and your courses, or past work experience, are at least halfway relevant, you will find a job. I've met an engineer who went from Porsche to Airbus to RedBull F1. That being said mechatronics is still a bit more universally applicable.

[@christoskapareliotis4425]

@@kilianortmann9979 thank you for the advice!

[@cerseonbrassmann5222]

Ah... That explains a lot. Thanks lad. Question: could you make a video about water injection systems? Are there mechanical ways to inject them? Or are there any usage against knocking without turbocharger? Are there such for motorcycles?

[@34SV]

brillant, thanks

[@drewwill2650]

Great video! Thanks.

[@bowez9]

The process described on "semi forged" wheels is called work hardened.

[@panchonorthmann6408]

So, yes, a wheel can definitely be semi-forged. Here are two ways: 1) you cast a wheel face with a heavy rim that you then attach to a spinning lathe and draw out the barrel. This is a form of forging, and it is done both hot and cold industrially. The end product is a single-piece wheel with a cast face and a forged barrel... SEMI-FORGED. 2) a peculiar process from Japan where a roughly finished shape wheel casting still in its semi-liquid phase is then struck with high force to refine the grain structure. The shape of the wheel was cast, but it was treated via a form of forging... SEMI-FORGED. Perhaps we need to look at the purpose of forging and determine if that goal has been met in any product purporting to have been forged. I know you can buy a wheel made by cutting a shape out of a forged aluminum billet and it's called a forged wheel. Same for a forged piston. But in the same vein you can grind a knife out of a bar of (definitely by any measure forged) hot or cold rolled mill steel and nobody would call that a forged knife. Semantics, maybe?

[@bikernaut1]

Great piston

[@jackdaniel4977]

4agze piston are very popular for mitsubishi 4g9X turbo

[@jamescarver9273]

Would you mind do a video explaining how to calculate wheel fender and tire fitment?

[@d4a]

There really is no formula, and there's a million variables. Only way around it is to measure and test fit until you get the desired fitment.

[@fastinradfordable]

Measure your oem wheel. Compare measurement of new wheel Measure available space around oem rim. Is that difference larger than space available? Your welcome.

[@jameshaulenbeek5931]

Another option is to go to the Fitment Industries website and see what they have in their gallery. They have a massive gallery and provide wheel and tire specs depending on what type of fitment you're looking for. It simplifies the whole process

[@AsiAzzy]

@@fastinradfordable Agree! For weird projects and unanticiapted problems a good way to measure clearences of the wheel and suspension arms, steering and other bits is to have the car suspended by the frame and whte springs removed. This allows the wheels to be put at full steering lock and full stroke up and down to better asses the clearances available in all possible positions. In case of double wishbone suspension is really easy to just unbolt the whole spring-damper combo. On macpherson struts is a bit more complicated. Removing the spring and reasamble the strut on the car without the spring is pretty hard and time consuming but well worth it. The alternative is a lethal danger lurking if the spring is just in compressed state by clamps. In theory it works, in practice is a big no-no. A car spring has a lot of force and energy stored in it. A J hook clamp can slip and slide, or the spring buckles and slips out, is a waiting danger. If that happens while taking measurements around the wheel expect the wheel to go full force in down position and can and will kill you or break and sever limbs cought in suspension arms. So don't skimp on this!

[@jamescarver9273]

I know there are many variables, I have checked out fitment industries I just wanted to hear you're explanation @driving 4 answers

[@hectorae86]

Semi forged means they drove over it with a semi truck in order to forge it. True story

[@BigGroupHug]

Damn buddy, can you explain your research procedure?

[@d4a]

It's pretty simple 😊 Step 1. Get on the PC Step 2. Spend an eternity combing through everything and fact checking.

[@OmarOmar-wd5cq]

The 15 dislikes are from the managers

[@Baard2000]

Who almost choked in their choco mocca soy latte after hearing the truth...

[@davegt27]

thanks next 2 piston rings vs 3 piston rings ??

[@saurabhnanoti8925]

its just a simple die casting process nothing more improves massproduction rate and give semi finished product quality is modrate air pockets are to be emilinated by controling temp. n flowability of molten metal reduce oxidation in manufacturing process clean n give better repeatability through out production so implimented by manufacturer for cutting cost and improve production rate n quality parts with less machining trust mi i am certified mechanical engineer☺☺☺

[@saurabhnanoti8925]

there is no term called semi-forged its HOT METAL DIE CASTING just like plastic molding its slang just used by noobs n non technical persons or mechanics😂😂😂😂😂😂😂😂

[@mituc]

Ok, up until 1:51 I was like ... Ww... wot... wwwwot the phawk?! :))

[@d4a]

That was the goal 😂

[@km6832]

Still waiting on that video about valves and valve included angles

[@ronnieboucherthecrystalcraftsm]

i chose a subaru engine with hyperutectic pistons = ej207 spec c ra sti jdm = instead of forged pistons - just a street 300hp .

[@arthurdombroskie3083]

I just subscribed to the channel..