Hypereutectic pistons

[akauf]

So I made it about 250 miles in my new starion before busting up some ringlands. The car has a stack of reciepts that came in it including one from a machine shop noting installation of hypereutectic pistons. The old owner also has a list of parts and numbers and on there are listed Keith Black Hypereutectic pistons. What I'm wondering is how I identify these things. Upon inspection I only found the pistons to be .5mm over stock bore. Anything to look for here?

[lionbull]

So I made it about 250 miles in my new starion before busting up some ringlands. The car has a stack of reciepts that came in it including one from a machine shop noting installation of hypereutectic pistons. The old owner also has a list of parts and numbers and on there are listed Keith Black Hypereutectic pistons. What I'm wondering is how I identify these things. Upon inspection I only found the pistons to be .5mm over stock bore. Anything to look for here?

 

yeah you need confirm the compression ratio of those pistons. keith black makes a quality piston but you should not put a N/A piston in a turbo car.

Edited January 12, 2010 by lionbull

[Technology]

Did you take the pistons out to confirm they are broken? And how bad was the car misfiring before it broke?

[maxboost87]

Hypereutectic pistons dont expand as much as a cast or forged piston to seal the rings and lets flame go by the ring gap like a blow-torch. if the block was not machined to fit those particular pistons. Hypereutectic pistons are made of an alloy of aluminum which has much more silicon present than is soluble in aluminum at the operating temperature. Hypereutectic aluminum has a lower coefficient of thermal expansion, which allows engine designers to specify much tighter tolerances. There is 16-19% Silicon in the aluminum of one of these pistons. With this said the engine must be to full operating temperature before they seal. Another this about this alloy is that it is very very hard but because of that it makes them very very brittle. They do not like anything but perfect ignition timing and high octane fuel. (Detonation and Pre-Ignition) If your bore is 5mm over stock that would be the same as a .020" Overbore, If the shop bored the block out .020" and put hyper -U's in it without realizing the bore had to be smaller to compensate for the un-expansion of the pistons. Check block's bore diameter to be sure, you might be able to just throw forged or stock cast's back in it if its sized right. get the piston to cylinder wall clearance specs along with the ring-gap. that is if you want it back to stock specs, i don't know what else is done to your car as far as what your running: boost pressure injector size and what not, stock specs can handle quite a bit.

 

 

Some carnage from my personnel file;)

 

http://www.axcessmypics.com/photos/photo05/65/9f/5057cc5c0ef6.jpg

Edited January 12, 2010 by maxboost87

[Indiana]

You have torn it down and looked at the pistons or are assuming this? Could have been from several reasons. Why was it for sale? What were you told? What was done to it other than the motor and what did you do to it.

[akauf]

Yeah I have had it torn down for a little while now the car is just sitting on the side burner for now. I guess I need to get out the bore gauge next.

 

I got the car through a local kid and I knew it had some issues as it used a good deal of oil but once it warmed up it ran great. In my normal impatience I decided to up the boost as the previous kid had it down at 8 psi. I added some fuel with the afc and all was well to about one bar where I would get a massive fuel cut. Not just running out of fuel just no fuel at all suddenly for a second or two. The second time it fuel cut it had a wicked detonation. I backed off the boost a bit and changed the plugs and it seemed fine. After another day or two it started blowing through more oil than before and it was obvious a cylinder was down. Compression was 100-80-35-80 after idling the car up to operating temp. So I tore it down and sure enough #3 piston ringlands were cracked up pretty good. Now I'm not sure about the low comp on the other cylinders as I only visually inspected the wall gap, ring gap and condition of the parts but nothing jumped out at me as being an issue.

 

Here some pics and receipts that came with the car. The head work isn't listed on these but it looks like a Schneider 274 custom grind, and Schneider springs is all that's up top. The car has a 50 trim turbo and stock fuel injectors at stock pressure. The rods appear to be stock though I was told they were shot peened with arp bolts.

 

*Edit: The kid I got the car from did not do the engine work. The guy before him installed the larger turbo and inter cooler. The guy before that was Frank Melfa. He had the motor work done and was running a 16g. These are the actual receipts of what was bought (I have one more not listed here specifying cam and springs). Anything else is a list that I believe Frank assembled as a sort of wish list so I can only assume from there that the pistons are keith black .

 

here's the piston and receipts:

 

http://i645.photobucket.com/albums/uu171/akauf/IMG_0112.jpg

 

http://i645.photobucket.com/albums/uu171/akauf/IMG_0115.jpg

 

http://i645.photobucket.com/albums/uu171/akauf/IMG_0116.jpg

 

http://i645.photobucket.com/albums/uu171/akauf/IMG_0117.jpg

 

http://i645.photobucket.com/albums/uu171/akauf/IMG_0120.jpg

Edited January 13, 2010 by akauf

[Dad]

Hypereutectic pistons dont expand as much as a cast or forged piston to seal the rings and lets flame go by the ring gap like a blow-torch. if the block was not machined to fit those particular pistons. Hypereutectic pistons are made of an alloy of aluminum which has much more silicon present than is soluble in aluminum at the operating temperature. Hypereutectic aluminum has a lower coefficient of thermal expansion, which allows engine designers to specify much tighter tolerances. There is 16-19% Silicon in the aluminum of one of these pistons. With this said the engine must be to full operating temperature before they seal. Another this about this alloy is that it is very very hard but because of that it makes them very very brittle. They do not like anything but perfect ignition timing and high octane fuel. (Detonation and Pre-Ignition) If your bore is 5mm over stock that would be the same as a .020" Overbore, If the shop bored the block out .020" and put hyper -U's in it without realizing the bore had to be smaller to compensate for the un-expansion of the pistons. Check block's bore diameter to be sure, you might be able to just throw forged or stock cast's back in it if its sized right. get the piston to cylinder wall clearance specs along with the ring-gap. that is if you want it back to stock specs, i don't know what else is done to your car as far as what your running: boost pressure injector size and what not, stock specs can handle quite a bit.

 

 

 

I'm not quite sure about the statement in bold. piston to wall clearance is the skirt clearance. He has broken ring lands from detonation, lean conditions not scored, scuffed skirts.

 

Dad

[akauf]

I'm not quite sure about the statement in bold. piston to wall clearance is the skirt clearance. He has broken ring lands from detonation, lean conditions not scored, scuffed skirts.

 

Dad

 

 

Any chance you could identify the broken piston and send me a replacement if I shipped it out to you?

[maxboost87]

A year or so ago the same thing happened to me on no. 2 cyl. after i swapped the stock for hyper-u's. lasted a few days and there went no.2 bought a single replacement, same thing happened again after a few days this time on no.3. put a new set of stock replacement in and they are still fine. the reason for going with hyper-u's is because i originally broke a land on no. 4 piston (bad boost retard act. "vacuumm advance" not retarding the timing under boost) on 20 psi boost and mpi. The hyper-u's i had running on 12psi, till everything broke in, which they never had a chance to. You would think that the hyper-u manufacturers would compensate for the un-expansion of the high silicon content piston to work in a standard overbore size, this i am not sure of, but they do need less clearance then stock or forged. At the time, I did not have the tools to do any exact measuring. I just measured the difference between a stock cast with a .50mm overbore and a Sealed power hyper ".50mm overbore" and came up with the same measurement of 3.580". So if that's the case, those pistons would act as if the engine never warmed up to expand the pistons to take up the clearance and close the ring gap enough for a boosted engine. Also if the clearance is too much it is very hard on the top ring/and ring-land because the pressure is not applied evenly to the ring-land and is more centered on the outside of the land making it break easier than they already do.

 

 

Just my thoughts...hope it makes sense lol

Edited January 13, 2010 by maxboost87

[akauf]

I see what your saying here. I'm not going to make any purchases until I gt this measured up so I know why the compression was so low across all cylinders and be sure this won't happen again.

[MrWOT]

All hypereutectics aren't created equal, and those are cast, not forged. World of difference, I've pushed over 200hp/L on Mahle 4032 slugs. The difference is in the tuning requirements, the high silicon content means they don't appreciate high shock loads.

[Dad]

Any chance you could identify the broken piston and send me a replacement if I shipped it out to you?

 

 

There may be a part # on the inside of the piston.

 

Dad

[gofastredstar]

All hypereutectics aren't created equal, and those are cast, not forged. World of difference, I've pushed over 200hp/L on Mahle 4032 slugs. The difference is in the tuning requirements, the high silicon content means they don't appreciate high shock loads.

 

True statement. I have sealed power hypers in mine. The engine has about 15k on it and dynoed at 306. 21 degrees of timing and 11.8 afr has kept it together.

[Tim_C.]

Hyper-U's don't like boost. They don't like the heat, they can't withstand detonation like OEM or forged can, etc... I would never put a hyper u piston in a boosted engine myself. IMHO

In many cases, by the time you get the engine tuned, its already blown up. However, you do need to tune better, and with the right monitoring devices to keep that from happening. It's just that hyper u's are less forgiving there, so you need to have tuning experience, and no equipment failures to keep a performance, bossted hyper-u engine on the road for more than 20K miles.

[ragdoll_unlimited]

strange that randy (dad) runs them in his car? why not ask him?

[lionbull]

True statement. I have sealed power hypers in mine. The engine has about 15k on it and dynoed at 306. 21 degrees of timing and 11.8 afr has kept it together.

 

was that on pump or rece fuel?

[lionbull]

All hypereutectics aren't created equal, and those are cast, not forged. World of difference, I've pushed over 200hp/L on Mahle 4032 slugs. The difference is in the tuning requirements, the high silicon content means they don't appreciate high shock loads.

 

hmmm, are you implying there are forged hyperu pistons out there?

[maxboost87]

It has a lot to do with the "clearance requirements" to how long they hold up, the engine must be machined around the type of pistons if this is the route you want to take. There are different grades of hyper-u's. 4032 has a silicon content of around 11% which makes them brittle and not expand much at all at warmed up running temperature, the reason for this is new car manufactures have gotten into using them alot to reduce cold-start smog emissions. Now im not a machinist but have read quite a few books on metallurgy, and engine performance and cant seem to find specs anywhere for the clearance these pistons need to be reliable...maybe you must call the manufacturer?? idk. I would think you go by the % of silicon in the alloy "there are different grades"...but if it was 15% you would need to reduce the clearance by that much...?? BTW yes there are forged versions...they begin as a formed casting and then hydraulically compacted(FORGED) and then machined into perfect shape "keep in mind they still have large amounts of that implant stuff in there". There are also "2618" alloy with 2% silicon which are far more forgiving and actually expand as they warm up. Why would you want a piston so brittle?? Strength of metals comes from flexibility not hardness In my opinion hyper-u's were made for one thing that's to reduce smog emissions.

 

This is a very interesting topic i enjoy discussing these things and speaking my mind and this forum is the only place i have to talk about things of this nature...most people i'm around laugh when things like this are brought up cuz there lame and somewhat ignorant when it comes to this kind of stuff so bare with me lol...

[Indiana]

Some just refuse to accept facts.

[dstar88]

strange that randy (dad) runs them in his car? why not ask him?

 

 

i was waiting sooooo long for someone to say that! lol why'd you have to let the cat outa the bag man!?? hahaha

 

right you are my friend! right you are!

 

 

 

Daniel

[Indiana]

to prove a point or to save money why don't you ask him

[MrWOT]

hmmm, are you implying there are forged hyperu pistons out there?

 

The only hyper forged pistons I have seen are 4032, and yes a few manufacturers (highly recommend Mahle, good QC). They require much less piston to wall clearance than 2618 and will take all the power you will ever use on the street, ever. Only reason you break them is if something in your combination is terminally wrong anyway.

Edited January 15, 2010 by MrWOT

[Dad]

The Hyper U pistons that I sell are by sealed power. the minimum clearance specified on the package is .001. I normally go about .0015-.002 so I don't see where the piston to wall clearance causes the problem of ring lands breaking. Forged pistons by far will be stronger than Hyper pistons. Seems like cast pistons are getting harder to findand that Hypers are always getting a bad rap.

 

Yes it's true I run the same hypers in my car that I sell, the car was put on the road about 3-4 yrs ago and now has just over 7500 miles on them. I run a 12a at about13-14 lbs boost, I have a walbro fuel pump, trilogy injectors, maft translator and more important a wideband gauge.

 

For the longest time I ran a 1G mass but I did not raise any boost levels until I had a wideband to monitor whats going on. This motor will be replaced with a much stronger build in the future. If the pistons hold up that will be great, if they fail. no biggie. For those thatknow me I drive the car pretty hard from light to light so I have put the pistons thru quite a bit of strain. This past year with the addition of the injectors of course had wooried me as I have had a few lean issues at times and I KNOW that the hypers don't like that at all. but so far things are good. Guess time will tell.

 

Dad

[Couth'nize]

I had ran Hyper-U from Dad before with no issues and yes the clearance is tight. The car I'm driving now has Hyper-U (not from Dad). I don't know what kind of build or how you guys ran your car to blow it up so quick. This current car I'm driving is the one I install the Megasquirt on so ya'll know how it is on the Tuning process, rich/lean condition, still holding up (3000 miles plus) pushing 15lbs daily.

 

Back on subject: Please see about getting the piston and wall measurment, I'm curious also. From reading your post, seems the car has trouble before you took over.

[lionbull]

The only hyper forged pistons I have seen are 4032, and yes a few manufacturers (highly recommend Mahle, good QC). They require much less piston to wall clearance than 2618 and will take all the power you will ever use on the street, ever. Only reason you break them is if something in your combination is terminally wrong anyway.

 

seems like like both of these are good. the 2618 is supposed to be stronger though.

below is what i pasted from some site.

 

“4032” performance piston alloy has an approximate Silicon content of 11%. This means that it expands from heat less than a piston with no Silicon, but since its eutectic level of Silicon is fully alloyed on a molecular level, this alloy is less brittle and more flexible than a stock Hypereutectic “smog” piston. These pistons can survive mild detonation with less damage than stock pistons.

 

The “2618” performance piston alloy has less than 2% Silicon and could be described as Hypo (under) eutectic. This alloy is capable of experiencing the most detonation and abuse while suffering the least amount of damage. Pistons made of this alloy are also typically made thicker and heavier because of their most common applications. Because of the higher than normal temperatures these pistons experience in their usual application, and also the low-Silicon content allowing the maximum possible Aluminum heat-expansion, these pistons have their cylinders bored to a very loose cold-fit. This leads to a condition known as “piston slap” which is when the piston rocks in the cylinder, and it causes an audible tapping noise that continues until the engine has warmed to operational temperatures. These engines should not be revved when cold, or excessive scuffing can occur