Hypereutectic Pistons

[Celica_73]

OK quick question Currently build a 2tg/3t hybrid engine. Destroyed pistons in 6000km normal Endurotech piston fly cut to suit of coarse. So done some research to discover Hyper eutectic Piston are meant to be stronger. Other opinion is Forged. But unless I'm mistake forged piston can't be fitted to factory 2TG rods.

Ok now your probably going to say a tuning problem, timing (cam or ignition). Well the engine never sounded to be pinging. The piston failed on the ring land between 1 and 2 about 1/3 of the piston had cracks and lose pieces. The Inlet cam timimg turned out to be roughtly 10 Crank degrees retarded. Exhaust was 2 degrees (due to my incorrect timing of using Factory marks and not dialing in). Cam grind used was Camtech 401A 293 duration 241 and 372 lift @ 50. Ignition timing was set less then Factory at 13 degrees. Fuel was BP 98 Octane.

So at the current situation my options are Get the same pistons again or forged. Haven't been unable to track down any hyper eutectic piston. Has anyone been able to get some for a 3TC. If i go cast again then could some suggest what i could have done wrong to cause this. Or should i just bit the bullet and get forged.

[fixeruperer]

why cant you fit forged pistons to 2t rods ?

[Celica_73]

Well the 2TG piston are a press fit not Fully floating. all forged piston seem to be fully floating. I could be wrong but I assumed the two are not compatibly.

[oldcorollas]

maybe ytour ring gap was stuffed?

[Celica_73]

We check all gap before assembly. We actually discovered the end gap was almost twice the factory gap stated the manuals.

Thats one reason were confused over it all try to do everything to the book and still no luck. This is not a overly high compression engine compared to other I've read about both on the web and in this forum. It's just using a standard 3T-C piston fly cut. Although i have not calculated it going of others this would be roughly 10.5:1.

Cheers

[oldcorollas]

if that is the case, then something must have been terribly wrong with the tuning in order to kill pistons that quick.... or the pistons were terrible quality or fakeｓ....

first solve the issue that killed the pistons.. then get new pistons
even forged pistons will die when detonated..

[Celica_73]

Oh ok then. Everything I've read seem to point towards normal cast piston should be able do the job. Just thought I'd get some opinions on it. But about Hyper eutectic are the available for the 3TC?

Back to detonation from my understanding main causes are low octane fuel, Ignition time to advanced (possible still factory graph hence the retard static timing), High compression (176 psi measured 1500km old). Could lean mixtures also play a role? Carbies still jetted for 2TG was about to send it to the Dyno when i discovered cylinder 1 had only 50 psi.

Next question is then how many km should i get on the engine min before getting dyno tuned?

Cheers

[TA23 Racer]

Broken ring lands between 1 & 2 ring is definatly pinging (detonation). Have done a fair few pistons on my 3TG-TEU. It's just a ignition timing problem it doesn't take much with cast piston the hypo's are a little better tend not to brake the ring land but squash the crown down & jam the top ring giving excessive blowby. Forgie a tad better again but if your ignition timing is incorrect it will still shit it's self.
Programable on the run ecu, Haltech, Motec etc and a good and thorough dyno operator is the key. The cast piston can live if the mapping is correct they just have no reserve strength when tuned to the limit.

Cheers Dave.

[TA23 Racer]

Sorry Celica 73 should of read the last one of yours better.
176 psi comp sounds about 9:1 ish which is fine.
Have you changed the jetting since increasing capacity? yes lean mixtures are more spark sensitive. The advance curve for the longer stroke engine is going some what slower going through peak torque were I think your damage is occuring very hard to hear pinging with all that induction noise.
Sorry to sound like a broken record Dyno operator!
No I'm not one but when you find a good one life becomes alot easier

[Celica_73]

Carby still jetted for a 2TG didn't get to the dyno. Ignition timing was re graphed just before it died using the jarcar kit I reduce the slope of the line and stopped it earlier. Currently looking at getting a knock sensor and wiring it up to the jarcar kit. Anyone know where i could get one i see the 3tgtue have knock sensors. Guessing the thread hole probably on the 2tg block too.

Jason

[o_man_ra23]

Photos of the piston (esp the crown) and photos of the combustion chamber will help us. Sounds like she is running lean. Put a wideband oxygen sensor in the exhaust and a guage on your dash, and you will quickly find out if your mix is ok. Jaycar do a kit for an LED readout, pretty sure it reads from a narrow band sensor, should be pretty cheap to get one of them from a wrecker.

Cast pistons took a lot of pounding in my 18R-G even when I upped the compression. Always ran it on the rich side for safety, never had a problem (apart from the fuel tank draining after less than 400k )

[TA23 Racer]

Have you checked with a timing light that has an advance function that the Jcar is actually were it's sould be I mean there is no offset or somethind strange going on?
Not sure about 2TG's but the 3TG knock sensor boss is at the top of the block on the empty lifter bore side right in the middle.
I still use the cast pistons once I sorted the ignition advance probs they do the job fine, at the price of the cast ones you can afford a few broken ones but I would cry like a baby if I wrecked a forgie!
Stick at it the hybrid is worth it Cheers Dave.

[styler]

hey

2tg (2tg pistons and 2tg crank):

cast pistons are avaliable in:
standard (rare if even avaliable?)
oversize either +20 or +40 thou (ie 0.5 or 1mm) (rare if even avaliable?)
custom made oversize ($800)

forged are avaliable in:
some oversize premade with different compression volumes (rare but obtainable)
custom made oversize ($1200)

3tc (3tc crank and 3tc pistons)
cast pistons are avaliable in:
standard ($300)
oversize either +20 or +40 thou (ie 0.5 or 1mm) ($300)
custom made oversize ($800)

forged are avaliable in:
many oversize premade with different compression volumes ($600)
custom made oversize ($1200)

2tg hybrids ie a 3tg (3tc crank and 3tc pistons)

cast pistons are avaliable in:
*same as 3tc* ie
cast pistons are avaliable in:
standard ($300)
oversize either +20 or +40 thou (ie 0.5 or 1mm) ($300)
custom made oversize ($800)

forged are avaliable in:
*same as 3tc* ie
many oversize premade with different compression volumes ($600)
custom made oversize ($1200)

notes:

1. you must use 2tg pistons with 2tg crank
2. you must use 3tc pistons with 3tc crank
3. cast 3tc pistons need flycutting for 2tg use
4. some brands of cast pistons dont have enough material left after flycutting and are too weak in the crown or ringland area. this is due to the crown not being thick enough.
4. forged 3tc pistons usually have oversize valve reliefs as stock and the crown
is thicker from factory to compensate for it. they dont need flycutting.
5. most forged pistons have floating pin, the rods need to be floating to suit.
stock rods can be converted but sometimes dont have enough meat in the small
end, plus they need to be resized and prepared and balanced/weighed too $400 or
so. which makes sense to buy aftermarket 3tc forged rods all prepared and floating end
from factory for about $600.
6. check piston height after decking block
7. bore. lol... the short version is

90mm is when you get the block sleeved and this is expensive plus only custom
forged pistons or custom cast.

89mm is the 1940cc "2 litre kit". i have had one, it works for NA but only on some blocks or if you can use offset boring to suit. it does leave the walls very thin and while not breaking through it can cause bore distortion.

88.5 is 1920cc and is the safe NA overbore but no premade forged pistons suit, only custom forged or custom cast.

88mm is the 1900cc capacity and has no premade forged pistons to suit either, only custom forged or custom cast. it suits NA and maybe the lower end of forced induction

87mm has premade forged pistons suitable for NA or forced induction or custom
forged or custom cast

86mm has premade forged and cast pistons as well as custom forged and custom
cast.

8. its not worth going custom cast when premade forged is the same price or
custom forged is a few hundred more.

9. piston compression figures dont mean shite when they are for another motor
with a different chamber volume eg 3tc pistons are for the 3tc with 63cc chamber volume not your 2tg at 45cc to 55cc! and the 3tc motor specs quoted probably runs a stock 1mm headgasket and has not been decked on block or head which also increases compression. see? always do your own calculations!!!

10. compression ratios. lol. ok the short version is. get your head cc'd. decide
what capacity ie overbore you want and what cams you want to run as longer
duration require a higher static compression ratio. do your own calculations with different headgasket thicknesses and dome volumes until your ratio suits.

11. Hypereutectic is mean to be stronger but some sources say its not much different.
that and the fact they arent very avaliable in many sizes...

thats all for now, havent read it through much

[w810sc]

Ok now your probably going to say a tuning problem, timing (cam or ignition). Well the engine never sounded to be pinging. The piston failed on the ring land between 1 and 2 about 1/3 of the piston had cracks and lose pieces. The Inlet cam timimg turned out to be roughtly 10 Crank degrees retarded. Exhaust was 2 degrees (due to my incorrect timing of using Factory marks and not dialing in). Cam grind used was Camtech 401A 293 duration 241 and 372 lift @ 50. Ignition timing was set less then Factory at 13 degrees. Fuel was BP 98 Octane.

Next time, I recommend you set your intake cam to be more advanced than your exhaust or say set the intake valve to (roughly) open 20 thou more than the exhaust depending in your cam specs when you degree it. (It doesn't have to be, its just to guide you)

Styler is on the money, to re-enforce his information here are some links on pistons for 2T-G/3T hybrid.

http://www.kameariusa.com/2TG_Piston.php
http://www.ariaspistons.com/products/toyota.html
http://www.paradiseracing.com/pistons.htm
http://brdracing.com/2tc_3tc_wiseco_pistons.htm

But I believe 3T-C forged pistons "need" to be fly cut. The ones that "don't need" to be fly cut are the ones that state they are for the "G" series head (DOHC performance oriented wide-angle valve placement) eg: 2/3T-G and 2000cc 2T-G applications. When I find the link that says this guy had to fly cut his forged 3T-C pistons I'll post it up.

You can use forged pistons on standard rods. Not modifying the rod to accept a floating pin simply defeats the purpose of the pin being able to rotate freely ie: "floating". It's costly to modify the standard rod to accept a floating pin but It's been done before. Please refer to this thread as it's been covered:
http://www.toymods.net/forums/showthread.php?t=34574

fonz

[jeffro ra28]

Correction, forged pistons can be used with a press fit conrod.
I would say lean mixtures is your cause.