Newbie, help with 20V turbo build

[10k 20v]

with 20v pistons yes they are.
but the gze pistons don't have the valve relifes in the right places so they touch, but only if your timings seriously out.

[NZ_AE86]

GZE pistons have not valve cuts in them as they are concave domes! They will not hit if timed right. And GZE pistons are much stronger and will give you a better comp ratio for a turbo engine.

[Chickenman]

Why does it have to be 20Volts for a turbo?









Toby is a member of the "I'm just $&#$% with ya" club

[sergei]

early GZE pistons do not have cut outs and are not forged, late model have cutouts, higher compression, and are forged...

[10k 20v]

yes, gze pistons have cut outs but for 16valve, not 20volts, i mean valve

[4ageturbs]

All gze pistons are forged the older 1s are just lower compresion, which means you can run more boost, Y bother with the 20v head your pistons will only handle a certain amount of hp personly id stick with the 16v spend ur money in another area like biger turbo,nos,lsd,petrol

[NZ_AE86]

All GZE pistons are Semi forged not fully forged, still stronger then a fully cast piston. GZE pistons do not have any valve cuts outs in them!!

[vvega]

sorry guys
both old and new have cutouts

i have bothe standerds and oversize in front of me
they are hyperutetic pistions
meaning they have a high silicon content
and they are ceramic coated for overous reasons

if you want pics i will if i have too


v

[NZ_AE86]

Must be some oddball GZE pistons as I have built a few and used brand new TGP pistons and never seen any with valve cut outs in them! Could you please put some pics up?

Cheers

[EVLGTZ]

In regards to semi forged vs forged debate, ya might wanan check out the link below, some detailed analysis has been carried out on ze pistons

http://forums.club4ag.com/topic.asp?TOPIC_ID=74570

[Al]

semi forged? you mean hyperuretic (sp)

its either forged or it isnt.

[NZ_AE86]

In regards to semi forged vs forged debate, ya might wanan check out the link below, some detailed analysis has been carried out on ze pistons

http://forums.club4ag.com/topic.asp?TOPIC_ID=74570

Now thats some interesting reading! Cheers.

[vvega]

[NZ_AE86]

yep, that is a 101 GZE piston, I just found one! early ones are quite different!

[20vpsi]

true that is a 101ze piston. im running early ae92ze pistons and are really dished i mean i could eat my soup out of then with bread of course ive fitted then to 20v rods and crank so infact it's just a 20v motor with low compression pistons hope that sums it up for you..

[vvega]

if youve ever started a motor with forged pistons in it your know that when cold they rattle
this is due to the greater clearances needed for the thermel expansion of the higher desity material used in the forged pistons

after 2-3 mins the pistions grow to fit the rattles and blowby stop and your ready for bussness

hyperutectic pistons however have a almost identical grain structure to forged are lighter and do not have the same issues with thermal expansion

they are also used in mazda gtx,nissan gtr,mitsi gto

the only production car i know of to have ever been fiiltred with forged pistons is the mazda gtr
if youve owened one youll know they rattle when cold and if drivin while cold they use a shitpile of oil

hyperutectic pistons can handle simalar condidtions as forged pistons and are made from a 6000 series alloy (t6) and are then tempered to t89? i think thats the temper

just my thoughts

v

[4ageturbs]

wow, what he said

[Mr Revhead]

he only production car i know of to have ever been fiiltred with forged pistons is the mazda gtr

well add levins/truenos and MR2s to that list....

i myself have just been holding a brand new aw11 4agze piston in my hand. i took it round to AGR (engine builders here) who do ALOT of performance engines. and he confirmed that they are most definitly forged pistons not cast, not hyperutectic. that came from an expert with 20 odd years expericene in building hot engines. thus confirming what the techies here said and what iv always beleived

also do a search on the web, from all the info i found hyperutectic were closer to cast than forged in appearance, something that was mentioned to me by AGR aswell.

[RedMist]

Mr Revhead, I'll have to start the Bunderson in front of you some time. It's got Aries forged pistions and sounds damn awful when it's cold. The pistons slap the bore so hard and ring with a high pitched twang you sware the engine is screaming at you to stop the pain. I've never heard that from a ZE, that's why I suspect that VVEGA is correct. Either that or Toyota have some new form of metalurgy that makes a forging not expand?

There is definately something fishy about the ZE pistons!

[fivebob]

Ahh the bullsh*t is strong in this thread

Firstly some definitions;

Forging, casting and sintering all processes, hypereutectic refers to the composition of the material, specifically the concentration of a minor component in this case silicon.

Hypereutectic alloys contain more of the minor component in a mixture or alloy than in the mixture of the same elements that has the lowest melting point, the opposite of this is hypoeutectic which of course means having less of the minor component than the alloy with the lowest melting point, and of course eutectic alloys are the ones with the lowest melting point. In the case of aluminium silicon alloys the eutectic point corresponds to the point of saturation of the silicon (around 12%). The higher the silicon content the lower the expansion rate of the alloy.

Hypereutectic pistons are supersaturated and as such have undissolved silicon crystal structures spread throughout the alloy. Provided these are evenly distributed they add to the strength, silicon inclusions with have a detrimental effect on the strength of the alloy so a special flux is used in the casting process. Note all alloys are cast, whether it be into billets, or their final shape, so use of this term doesn’t imply the final finishing process in this case.

Hypereutectic Al/Si alloys are brittle, so the can’t be formed with the traditional cold forging techniques and they have to be heated to a state between solidus and liquidus before than can be press into the mould, this is known as semi-solid forming (or thixoforming) hence the misnomer of semi-forged.

Solidus is that temperature at which an alloy begins to melt. Liquidus is the temperature above which an alloy is completely molten. Between the solidus and liquidus temperatures, the alloy will be a mixture of solid and liquid phases. Just above the solidus temperature, the mixture will be mostly solid with some liquid phases (like the consistency of snow, but hotter!). Just below the liquidus temperature, the mixture will be mostly liquid with some solid phases (like sleet).

Most common forged pistons are made from 2618 alloy, which contains virtually no silicon hence has a high expansion rate, necessitating a high piston to bore clearance. They can be hot or cold forged and are mechanically stronger than eutectic or hypereutectic and will resist detonation better as they surface erodes/deforms and doesn’t form stress cracks as easily as higher silicon alloys will. However they are thermally weaker so in a high heat situation, like a forced induction engine, they require more clearance and more in cylinder cooling than a high silicon alloy piston or they may melt.

The most common high silicon alloy used for forging pistons is 4032, though strictly speaking this is usually regarded as eutectic, as it has between 11 & 13.5% silicon. If you can find a manufacturer that forges 4032 pistons these are probably the best ones to use in a forced induction engine, especially a street driven one, they don’t have the expansion problems of 2618, and are not as brittle as hypereutectic pistons, so they don’t exhibit the common Toyota problem of broken ring lands as readily.

NB 6000 series alloys are not used for pistons as vvega stated and certainly not in the T89 temper which involves cold working (hard to do on a finished item), they are not Hypereutectic and usually have less 1.5% silicon in them, the main alloying element in 6000 series is magnesium (to form magnesium silicate) and it’s not suitable for pistons, 6061 is the most common of the high strength 6000 series. Both 4032 and 6061 are typically hot die forged and 6061 can be cold forged.

Hypereutectic pistons usually have 16-24% silicon content and are either produced as a casting, like Mercedes Benz truck pistons, or are hot forged like the Toyota items. The higher the silicon content the harder it is to avoid silicon inclusions, therefore alloys with a higher silicon content, up to around 35%, are sintered to avoid this. The sintering process involves mixing powdered aluminium and silicon in a mould and subjecting it to extremely high pressure and heat, this process is not AFAIK used for automotive pistons, though I do have a few extremely high performance model aircraft engines in my collection that have these pistons. You can also buy this Sintered Al/Si as bar , but the cost is astronomical and it has poor machining qualities.

***Edited to add reference to semi-solid forming + the following references to the properties of the common alloys

2618
4032
6061


Now I'll leave all the x-spurts to continue their discussion