I still contend that most if not all of these failures have been detonation induced.

buckshot and burrita's failures involved melted areas on the pistons, this is indicitive of excess heat (duh), which may be due to the knock sensor retarding timing from excessive low level detonation. The others, where the ring lands are broken, may not have had time to melt anything, and a good, but quick bit of detonation may have been enough to cause it.
Remember, that the ring lands are typically the weakest area of a piston, and especially on a hypereutectic cast piston. These are the areas most sensitive to detonation damage.

Granted, this is just educated speculation, but I don't think there is any reason to freak out thinking these pistons are junk or anything, they are just not designed to handle the detonation that a lot of you guys are flirting with on these high compression duratecs, whether that high compression is purely static, or is dynamic (ie NA or forced induction)
If you want to make a durable motor, you have to do your homework all the way through and not just at random points.

1) When you start planning the motor, think logically about what you plan to do with it, and choose an appropriate CR, including dynamic CR (dynamic CR= static CR+ CR related to added boost) Perhaps an 11.2:1 static CR really isn't a good idea in a daily driver that runs on pump gas . . .

2) When putting your motor together, make sure you understand how the parts are interacting. One thing that has concerned me (I have no idea how well founded these concerns are though) is using 2.5L heads on a 3L block, because I have no idea what you are doing to the "squish band" because of the difference in the cylinder bore on the 3L and the 2.5L that the combustion chamber on the head is designed for. An improper squish band, as well as any hot spots induced in the combustion chamber can have a huge affect on how and when detonation occurs. As for me, I honestly don't know jack about the details of the squish band, and I wouldn't touch it myself without several very long conversations with both piston and head engineers/manufacturers/designers.

3) You can do all of your assembly and porting and other hard part work exactly right, but if you bugger the tune, you are screwed just as quickly. I think we all know Rick's (buckshot) first failure was most definately caused by a bad tune (or a tune not done yet ) just becuase Rick got a bit impatient before he could get the tune done.
Fuel and timing maps are of the utmost importance both for making optimal power and keeping your car running safely and reliably. OEMs spend thousands of hours perfecting the tune for power, driveability, durability, and emissions for every single possible powertrain combination they offer; do you really think that a simple one shot deal with an SAFC on your local backroad with a very inexperienced engine tuner (you, or most everyone you know) is enough to ensure that you have things set up safely and for optimum power?
Take the time to do it right; there are so many alternative routes to arrive at a proper tune, there really is no excuse for not doing it right. And if I hear "money" as an excuse from anyone, I will beat you about the head neck and chest with a wideband O2 sensor. It will cost you a lot more money in the long run to not do it right the first time. Ask Rick how much his one little incident of impatience has cost him . . .

There is so much more, but this is the gist of it. Now go do your own homework, the info is out there, you just have to look for it, and learn how to discern the good from the bad.

Geez, why do my technical posts always turn into books???

very well put...i plan on tuning mine to the T.....if i can just get around to droping it in....its been in the spare bedroom for months now just waiting..

Thats all very well and good, and some of it is common knowledge on here.

I did tons of homework on my motor and I think in both N/A and F/I modes it has shown itself to be a winner.
I don't know as much about engines as you guys do, but I will say that I'm trying to get to the bottom of an obvious problem. Its ok to say we're running on the edge, but that doesn't explain why its always front bank #2 and #4 pistons that are getting blown, even if it is through detonation.

I'm ok with you saying that the pistons ring lands being broken are caused by light detonation, it explains it and its the best theory by far.
I would like to point out that detonation IS causing a compressive load by the way since the pressure from the charge burning is coming on before the piston goes through TDC.
I can easily see from my temp readings that I was spiking temps of 190+ F when I cracked my pistons before, and detonation is probably what caused it. Ok.
But why always front bank?
YOu also have to see that with the thinner ring land supporting the second compression ring on the earlier pistons that it has to be the weaker link, AND that may be why they are more 'light-detonation' sensitive.
This is the gist of why I will say to use later model pistons.

tom

i would probably say that the newer pistons might be even more prone to this problem then less so.... having a higher ring pack (aka rings higher up on the piston) puts less beef between the combustion process and the rings. manufacturers use this to up the compression and to clean up emissions. that space between the top of the pistons and the top of the rings is notorious to have unburned fuel and hydrocarbons that can escape during the exaust stroke.

now if the newer pistons are a better casting with higher quality control then it may be a wash but i still belive the fact that the ring lands are thinner might agrivate this issue more then anything. it maybe the fast that less 2000 cars have a turbo that this isnt showing up

cont from my last post...

the primary ring is going to observe the most punishment in a detonation type event. where exactly are the breaking? is it at the top, or between the ring lands? what do the cooling passages look like around the block? ive never had mine apart (or never studied pics close enough) to see what they look like, how big are the cooling passages around the 2 and 4 cylinder? are they smaller or more obstructive the the rest? also how hard would it be to add piston oil squirters to our cars? as this would take a significant amount of heat out of the pistons. (i know that 3.0 and 3.5 non turbo nissans can be upgraded, however the turbo cars came with them, so that may be why)... i dont know what about those two cylinders running lean as the are closer to the throttle body? (just talking out my ass, to see what can be dreamed up). also what was the mixture like (12:1, 13:1)?

You've misunderstood the issue.

The ring is a little closer to the combustion, but it isn't the rings that are breaking, it is the metal support, the ring land for the rings that is cracking.
Typically in cases where there is no melting of the aluminum present, the support for the lower compression ring is the part that is breaking. This particular support is half the thickness on the mid 99 and earlier pistons. In late 99 and up, this area was doubled in thickness by shifting the two rings upward by a couple of milimeters.
This is why under whatever loads and/or detonation that are breaking the lands is more prevalent on the earlier pistons.

As far as the two front bank pistons going out, they are the two that are furthest from the TB.

do you have a pic?

what i now understand is the second combustion rig land is the one that let go not actually the top land? would that stmt be correct? i had assumed it was the top land that had let go and that by moving the land up closer to the chamber it was going to excite the problem even more. however if its the second land that is causing the failure i can see what u mean as the 2 combustion ring land is half the thickness. that would be fixed (or better off) with newer pistons as they are much thicker in that area....

but this still sounds like a tuning issue more then anything (detonation) what was the air/fuel ratio? also you might want ti try a cooler thermostat if you havent already done so (seeing as i dont know all your mods)

in the mean time while we are still working this out.... all turbo owners might want to keep the boost low and the mixture rich just to be safe

This isn't about me really, it is about a whole series of pre-2000 motors that have cracked these rings in a similar manner, whatever the cause. Obvious the safest thing is to tune the engine properly.

Second, its about the strangeness of the fact that every single piston failure I know of both pre and post 2000 has been front bank pistons, both melted ones and just cracked ones.
Detonation induced or not, I want to know why just the forward bank pistons are breaking and never the back banks.


The general consensus is that the cracked pistons suffered from very light detonation, not necessarily lean induced that introduced a load strong enough to crack the second/lower compression ring. In one case on my piston it cracked the support for the 2nd and 1st ring, though no rings have broken.
This seems to be more prevalent on the pre mid 99 pistons with the thinner ring land support on the 2nd compression ring because it is thinner than the late 99/2000+ pistons.
So far, no one has ventured any reasonable guess to the issue of prevalence on the front bank.

It is common for boosted engine to break the ringland on the piston in between the top and second rings. At first, this seems a little strange. But the greatest loads are supporting the top ring, which is being pressed down by combustion pressure. The only thing stopping it is the ringland below it.

Yes - toplands can also break, but more from a thermal failure.

You're still missing the point.
The ring support between the second compression ring and the oil control ring is the one that is breaking. The one between the 1st and 2nd compression ring has broken, but not usually. The support between the oil control ring and the second compression ring is 1/2 the thickness of the support between the 1st and 2nd compression ring.
See pictures.

Question?

where is the water pump pickup point? is it the front bank drivers side? what i really want to know is where is the last place the coolant is before its cycle back thru the radiator? and also where is the radiator out let point connected to? maybe the coolant is super heated by the time it gets to those cylinders

That's a worthwhile though. Lets see if anyone can determine the coolant flow path and see if it bears any fruit.

Hey I see there a good debate going here about pistons but I failed to tell ya'll that my number 1 piston was the one that melted on the exhaust side and I asuming from this weakened it instantly and appeared like someone took a punch and pounded it through the piston on the side under the top ring and bottom ring.

I'm curious to what temp is required to do this. My number two cylinder next to it had little pits on the same side appearing to be next to break down. I almost looks like when the piston reaches a certain temp small pieces metal in grain form melt and fall off the piston surface and leaves small pits. Number 3 piston suffered nothing smooth finish.

i nevered pulled off the other head yet.

I ran my car yesterday with an egt and my car idles when warm at about 450 Celcius and with 8 psi it reaches right at 700 celcius and with 10.5 psi it reaches 750 celcuis my greddy gauge has the red line starting at 900 celcius to 1200 celcius.

I also have the probe in number one header one inch from head since this is the hottest cylinder being it has longest run in the intake for heat.

I don't know if this has anything to do with it but I'm also runing 30%rubbing achohol and 70% water injection system too. Does achohol affect this too?

My 2 pistons failed in the rear bank.....

One thing that i think most people are negating are the effects of the cams on dynamic as well as cylinder filling/scavaging. On a high end car something as simple as a header change can bring the car into detonation because of the increased vacuum generated by negative exhaust pressure on the intake ports. So in order to determine what is the exact cause of these pistons splintering and going everywhere you need to know whats done to the car. Intake manifold/header/cat/exhaust/cam/porting.

If the heads have been home ported this is a huge factor. Home ported heads never flow anywhere close from port to port and often the combination of gasses have MANY rich/lean pockets then when left in stock port. There are so many variables. And i dont nessasarily think its pre 99 engines only that do this. Im not sure of all the factors in these engines yet. But need to take some pics of the top of the pistons as well as the cylinder head to find the rich/lean pockets in the chamber. and see if where those are are on the side where the lans are cracked/broken. Alot of lan damage is caused by the uneven heating of the piston. If one side expands more then the other and runs tighter on the ring it causes alot more stress.

Also what chamber is being used in general is important as well. Because of the quenching at the top of the head This also has alot to do with what detonates and what doesnt.

There has to be some specific modification that people are doing to cause this. Also anyone have the intake events/exhaust events on the svt and 2.5 l standard cam as well as whats on the 3.0l . I could drop these into some equations and figure out if the dynamics you guys are running are too high or not. If someone could supply me with the maf read outs with a dyno run and what that converts to in pounds of air thatd be great too.

1382* is packing alot of heat. Most of the time you start to loose valve seats in production between 1300-1400 Thats really hot. The turbo zetecs are running much cooler mid to low 1200 in toms 400 whp t3/t4 hybrid.probably need more fuel or reduce boost or if it also can be caused by excessive retardation of timing. Could advance ignition timing if its been retarded signifigantly. Cant help but think youv got a little detonation going on. IMO anyways. i cant think of a case where your exhaust gasses should reach 900 degrees c 1652 degrees f is way too hot. You hit that and your engine is already gone

My engine in N/A form used to run 800 Celsius at 6700 rpm! This was after it was dyno tuned into the correct 12.5:1 A/F at 6700 rpm. I ran it a bit leaner in the lower rpm range but as it got up in rpm the temp still would climb. These engines just run hotter and they are made of more advanced materials than the average ford pushrod motors.
Turbo Tom's zetec is turbo so he is probably using fuel to keep the mixture cooler.
I try to run 12:1 or 12.5:1 with my turbo unit right now.
The only modifications that most of these people have made to their motors is boost. Some cracked pistons without having a dyno tune, like me.
-The hand porting jobs can be hit or miss I agree.
-BTW, I used the same tuning before and after the intercooler on my car. BEFORE I put on the intercooler I cracked two pistons. I put new pistons in the motor and then carefully drove it to the dyno in AZ to get the intercooler fitted and dyno'd with A/F.
The very first run with the intercooler on it and THE EXACT SAME A/F curve as previously when I cracked the pistons!! I put down 300 wHP and the A/F was 12.5:1

Therefore, the problem was in high combustion pressures/temps and possible that threw the A/F off enough along with the excess heat to make light detonation or it was just plain too much pressure.

Since then I have been running 50% more boost and no problems that I know of.

All your points are good except that:
1. Duratecs in good tune run high combustion temps.
2. The 99 and earlier pistons are definitely a weaker design...we have the pictures of the two types of pistons to prove it.

Well is there anyway you could give me some specs on these engines? I dont have one or id figure it out myself. Im looking for a replacement for my zetec. Kinda figuring out what i want. It detonated the diffrential and while the tranny was on the floor i decided to upgrade engines while i was at it. So while im figuring my choice thought id learn about there weaknesses and this was a good place to start.

SO if youv got like a big data sheet on compression ratio`s valve sizes port flow data and everything else i could figure out what i could figure out and see if any of it could help you all find the solution.

Question for you all. Would I run into this problem if I have replaced my Rods and Pistons with Forged ones?

Most likly not...You may encounter this if you use an OE replacment aftermarket brand.


Lupe

Hey what psi were you guys running and for how long before the pistons broke? Did you have the turbo for a while or just after it was running?

The non-revised pistons are not suitable for boost.

It is really that simple.

I have maintained 8 psi for about 12,000 miles on a 98 with no problems.

So a late model 3.0L duratec (production date 6/99) would have the thiker thing and in theory should be okay?

Originally posted by {Kontofosho}:

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I have maintained 8 psi for about 12,000 miles on a 98 with no problems.

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Then consider yourself lucky. I have pictures of broken ring lands from a cougar, a 3L (my own) and two 98 SVT's.