Forum Freak
Nice clean internals, BS still in place, but we can't see where the damage originated.
Interesting observation about the carbon deposits in the heads. Was it on the piston tops and combustion chambers? Accumulating enough of it there will alter the compression ration and put the engine into detonation territory.
Naturally Awesome
We have seen carbon "caking" affect 2 stroke motors like that, builds up until they change compression all together, but that also usually takes a while and something else usually goes wrong first.
There has to be something else which is causing that piston to seize and rod to go "Splits-ville"
DJ NOM NOM in da house
The piston tops were well coated (carbon black). The chamber walls were pretty clean. I didnt get to see the top of the chamber or the valves.. If it was detonation related, the valve stems would be black as well. Interesting to note the colour of the oil in the sump - Dark coloured & thick with carbon also, so one would have to assume it had been a long time between oil changes...Originally Posted by kmh001
Naturally Awesome
If that isn't a good reason to change your oil regularly I don't know what is!
DJ NOM NOM in da house
If you're looking at this in first principles, if you imagine the piston rod as a paddlepop, and hold it between 2 fingers. If you squeeze your fingers together, the top and bottom stay in a fixed position, but the middle of the paddle pop bows/bends outward. If you squeeze and hold long enough, the paddlepop stays bent. Steel acts in this very way. It can resist pressure up to its "yield" point on a regular occassion, but after time, it will fatigue, and eventually it will stay in the bent position..
The tollerance in the piston chamber is extremely small. If you pressurise the piston head with enough force on the downward stroke on a fatigued rod, the rod will bend, putting the piston out of alignment and thus you've got a seized piston (in the best case). You could argue, that the rods are being bent slightly in the first action - downward stroke - but allowing the piston to complete the downward stroke. But when it has to complete the upward stroke, its so far out of alignment and seizes in the chamber, resulting in a bang -> you've got bent rods; or depending on the brittleness of the rod which could happen by increased heat in the sump by addition of fuel in the oil - shattered rods, and thus a blown motor....
Again the above is theory. At the end of the day, the rods are metal - forged maybe, but still metal. Given enough pressure over time, metal fatigues resulting in failure. Elements such as heat will accellerate this fatigue. Maybe certain factors such as hydro locking, detonation, etc are advancing the fatigue and causing over pressure on the rods.
As a Structural Engineer, I think if we're going to get into nitty gritty of whats happening to the rods, we must first get a few good condition rods from a blown motor, and carry out compression and tension tests to find the yield point. Then we need to work out the Nm force being created in the chamber to failure, and then we will know how far these motors can be pushed.
To do the testing, we'll need at least 10 samples (thats 2.5 motors!), and average out the results. If there are any Mazda Techs reading this thread, maybe they can provide the details on the rods. I would hazard a guess that this info is "TOP SECRET"..
Last edited by Wardski; 08-05-2009 at 09:12 AM.
Naturally Awesome
Nice info Ward, I had a basic understanding of how a motor seizes (due to working in the jetski industry) but that made me understand alot more.
You then have to think, if you do go fully forged internals would that stress anything else in the motor? Would that move your weak link in the chain to somewhere else?
I agree too, it would be interesting to test out some stock rods and see what "breaking" point is on them.
DJ NOM NOM in da house
To date, ive not seen any damage to any of the crank shafts. However, if I was to get forged rods, I'd like to know the info on the standard rods so that I know the new ones would be rated higher. In any case, I'd replace both Crank (and bearings), Rods and piston heads, rings, seals etc at the same time to start new. God knows what that would cost!
Thinking about fuel/injector cleaners, these are supposed to remove carbon deposits throughout the firing chamber, injectors, etc. I'm wondering if this could be a simple remedy to clean the piston heads.. Maybe someone else could shed some light on this subject?
You know, its all sounding like good maintenance is the key to saving our motors. Changing the oil regularily, using fuel cleaners, etc could all be benificial to a healthy motor and lengthy operation (100,000km+) I think Duggy is testimant to this. While he's running a stockie, he's done almost 70-80,000km in his MPS, used only BP ultimate fuel, changed his oil every 5000km, and by no means has he driven it like a wuss.. He's also avoided (so far) having to replace his turbo....
I'd be interested to find out Cosmic's habits as well.
Last edited by Wardski; 08-05-2009 at 10:19 AM.
Naturally Awesome
Cost would be a fair amount then there is labour involved in installing it all, god knows I wouldn't be able to do it myself so that means paying someone else...you would have to think is it worth it?
Forum Freak
Why not just post the relevant links from MSF I dont think Rowan or Doug will mind, after all this isnt OMC, and I'm sure you wont get any dramas from Hal at MSF either, its for the good of the community after all.
DJ NOM NOM in da house
In addition to my comments in post #86, the pictures of the blown motor is one of the V3 flashed ones. I am thinking that the reason for the blackened piston tops was probably due to the fact that the V3 flash allowed 100% WOT. I think from memory, the standard Maz ECU only allows up to between 50-75% WOT and no where near 100% WOT. With a 100% wide open throttle, surely this would cause the 2.3ltr MZR motor to run extremely rich, and could account for the carbon on the pistons.
This may have also caused detonation. eg. flooded chamber, lots of heat, boom??
Last edited by Wardski; 08-05-2009 at 12:45 PM.
Senior Member
I have just updated my dashhawk profile with one of the popular US ones. Alarms have been set up for knock, temps etc. It is very good and someone else has done all of the hard work. i have also made a couple of small tweeks on my own. You will need to download the latest firmware to use it, (v2.51). This is the profile if anyone is interested (may just save you from blowing a motor):
DashHawkProfile.zip
Lazy postwhore
My understanding was the throttle plate directly controls the amount of air coming in, the ecu then can increase the fuel going in to meet the preset AFR. It should be no richer with the throttle plate flash than without as the ecu is still trying to meet the preset AFR.
Nuliaj: Hatches are only really half a car anyway.
shinslinger66: And you forgot to add that they are also a girls car!
DJ NOM NOM in da house
Interesting. So would the turbo pressure @ 100% WOT be greater than @ 50-75% WOT? I assume yes, and therefore what effect would that have on the combustion chamber for each piston?
Forum Freak
The effect on the CC would depend on what the PCM is programmed to do with the injector pulse width and ignition timing after reading the boost pressure, boost air temp, throttle position etc etc.
This could for example reveal a flaw in the software that results in excessive cylinder pressure.
Naturally Awesome
so it could be software related...confusing itself and thus incorrectly changing things which don't need to be changed.
Could we be onto something?
Forum Freak
Yeah, but I don't think it's a revelation. I've always believed the cause would be found in the software because detonation is usually resolved by proper tuning. Clearly the rods aren't weak as some initially claimed. The rods are breaking because they are being belted beyond their design load.
The work being done by the Ukrainians seems to show that most US tuners have only accessed and understood a tiny fraction of the PCM. Add to that the fact that these engines represent a bunch of new technologies for Mazda and are notorious for doing wacky things, and I reckon it's no surprise that they aren't happy being operated outside their original parameters.
The truth is that no one outside Hiroshima knows what these engines are really doing, yet. Until the programming is fully understood any modifications have to be considered experimental.
I reckon if you took away the Mazda PCM and ran the engine on a stand alone Motec it would make an easy and reliable 400 crank hp.
Gone to Volvo
Naturally Awesome
MoTec isn't cheap though and then there is time to tune it properly using it...pretty much going back to basics and going from there.
Forum Freak
Do motecs and the like even support DI yet?
Naturally Awesome
DI? As in Direct Injection??
Forum Freak
Yes_
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