Contour Enthusiasts Group Archives Forums Modifications 3.0L Duratec Piston durability

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