We're getting somewhere ...

[Lex]

Let's start off with a picture. Tell me what's wrong with this picture. (Hint: running DISI motor, look at the oil rings)

[Lex]

Exhibit #2 ... the result of oil ring failure and fuel washing down the cylinder wall. (zoom in to the full size)

BTW, this is worse than a Honda with 200k on the clock.

[socks]

the oil control ring "holes" are caked with oil.

i thought you said it had nothing to do with the oil control rings? ive suspected those since i pulled my stock motor apart.

[FreeFlyFreak]

Originally Posted by Lex Exhibit #2 ... the result of oil ring failure and fuel washing down the cylinder wall. (zoom in to the full size) BTW, this is worse than a Honda with 200k on the clock.

And solution?

[danesti]

just for a noob.. can you link a picture as to what would be more normal or acceptable? TIA

[Frequentflyer]

Not sure there's really any solution to this other than port injection. Are any of the other DI motors in the world suffering from this? Aside from using a heavier weight oil, is there a solution? Can we use the AP to lean up idle? Do low fuel pressures due to shitty pumps attribute to poor atomization of the fuel causing the wash down? To me, it's just a shitty engine design. Sometimes this stuff is trial and error and Mazda just didn't get it right. I just don't know how else you could prevent this without modifying the injection system or getting rid of the DI altogether.

[superskaterxes]

lex if u wanna spill the beans dude go ahead just make sure u give credit where its due (and im not talking about me lol)

[KayWhy]

Lex, i know you were up late last night but wake the fuck up and start explaining

[darth vader]

Miles on the motor, compression, modifications, general pattern of treatment, used oil analysis? Too many variables to draw any conclusions without further data.

Based on what I see, I'd recommend everyone go to a 10 weight oil, change it often and cut back on the short trips but, still, too little evidence to draw a meaningful conclusion from.

[whoosh@Realtune]

fuel is washing down the cylinder causing excessive heat which could lead to the piston seizing in the cylinder thus bending or breaking the rod

[Lex]

There are many things going on here. It's really a path of discovery with this motor and many have helped along the way and yes I have tried some dead end roads. If you follow a lot of the discussions on blown motors it will steer you in the right path.

Yes, oil control rings are caked. No, I don't think there's much you can do to prevent the situation . Yes, I think it's a problem for the longevity of the motor.

I will let more people chime in here before I go any further. However, the issues we have seen on this platform and motor are all related.

[superskaterxes]

heres your first hint

dun dun dun... its cursed

[clos561]

Originally Posted by superskaterxes heres your first hint dun dun dun... its cursed

maybe that is one of the reasons dcr "corrected" the forged pistons going into jumpingjacksons whip. u can see how they flattened out the top of the piston.

My Forged Engine Build

[djuosnteisn]

I don't think it has anything to do with the squish region.

[clos561]

why would dcr do that in the first place? my guess is that it helps distribute the pressure after detonation which equals less stress on the piston/rod and all the little components aka Seals and shit. tell me if im wrong, does anyone know why that is beneficial?

[superskaterxes]

darrell speaking on piston correction

DCR Machine Shop Services... - SRT Forums - SRT4, SRT6, SRT8, SRT10 & Dodge Forum

[djuosnteisn]

We also correct the side portions of the piston above the top ring land and below by reducing the O.D. to a desired diameter to increase ring seal and clearance issues for 350whp and up applications.

I guess this part of the process could help. I didn't know he was doing this. But the rest of it probably wouldn't help much for our issues.

[Lex]

One of the root causes of the issue here is fuel impingement. Who the fuck designs an injector that sprays at the cylinder wall??

Diesels have it too. But diesels have the injector at the top of the cylinder and have a dish to disperse the fuel away from the cylinder wall.

I honestly don't think ANY of us are immune to oil control rings failing, carbon buildup on the ring lands, and likely piston seizure.

Jon at PTP has said this before. On top of this, look at the piston crowns. The fuel spray is cooling parts of the piston unevenly causing hot spots and perhaps weakening the material.

Throw in a little detonation due to oil now entering the combustion chamber and lowering octane, more boost, carbon buildup, and a closed/open loop transition and you have a recipe for a seized piston. That then takes out the rod. Nothing to do with weak rods here.

It's not a coincidence you see knock after a lot of highway cruising. It's not a coincidence the car commands more fuel when knock is encountered.

Does the oil consumption issue now make sense? Thestaplegunkid said he had oil burning 4 days before it blew.

On another note, my car started smoking like a bastard maybe 4 days before she blew (it had never smoked before this, and i'm talking blue oil smoke) It did it the first time, while idling at a red light, pointing down hill.... and this corresponded with others tales of pcv fuckery. So I just figured it was that.... and the day it blew I was picking up the components for an OCC

Finally, take a look at the bore where he blew the motor. Look at the scuffing. Look at the mark on the bore. That's where the piston seized, it cracked, and the carnage proceeded.

[boardjnky4]

I have to say this is hands down the best information I have seen on this issue. Great work dude, keep it up.

[superskaterxes]

AAAAAAAAAAAAAANNNDDD the shit has hit the fan.

see you guys in the FS section lol

[802MS3]

fuck my couch.

[boardjnky4]

safe to say that my car is staying stock and being sold before that drivetrain warranty is up

[Deadman]

Evo be in my driveway within the next 2 months. I will make sure of that... somehow someway.

[AndyMS3]

Originally Posted by opt_ms3 fuck my couch.

I concur.

Good work Lex, keep the information coming.

[NRSpeed]

Lex, I would like to thank you for all the time you are putting into figuring out the problem with the engine.

But, you are making it sound grim.

[djuosnteisn]

this is pretty condemning information.

is there any strategy or hope for a long term disi mzr other than building?

[subparpunk03]

Lets just say we live in fantasyland for a minute...

if somehow we were able to pick up a set of hitachi injectors that fit the stock fuel rail, but changed the angle at which the fuel sprayed into the combustion chamber, would that really alleviate the problem?

Sounds to me like the issue is the rings themselves. Maybe instead of spending a ton of money on new rods and pistons its possible to JUST replace the oil rings with a 3 piece design on the stock pistons?

[jwdp54]

just when i remembered why i bought my car you give me the reason why i wanted to sell it....

mazda engineers suck, not that we didn't already know that

[Darksun280]

Damn thats the first indepth theory that makes sense to me. I really wish I could get in contact with P3 and ask them what my motor looked like when they pulled it apart.

[clos561]

so where the piston seized, is where the injector is spraying fuel or is that the opposite of where the fuel is sprayed? that would be the "hotspot" cause by un even cooling from fuel spraying to only one side?

does that expain why lilguys piston crack like that? it was the opposite side of the fuel spraying

[_Toxic_]

I ceep mine stock.. if it blows it does... (not that i think it will but..) the car is great! faster then most equal cars anyway...can use it on the track and daily driving, i put my money on suspension and rims etc...

[Darksun280]

If the mazda gods would allow me their fallen hero to have back only an intake and not blow that would please me.

[spheed3]

If this was the case wouldn't we see CX7s blowing like crazy too? Most other DI cars are very similar in design (IS250s come to mind) wouldn't they be chucking rods too? Also if carbon build up is the issue, which I see everyday it is in DI cars, isn't that something that simpley running quality fuels and oils would fix? When I take apart any of our DI cars I can CLEARLY tell wether the owner has been using quality fluids or not.

[superskaterxes]

ugh the problem lies with the EXPANSION of the piston from over heating. this in turn binds the rings against the walls and seizes the piston. if you were to ceramic coat the entire cylinder and piston id be willing to be we'd never seen another blown motor that wasent from sheer power.

[Lex]

There are many things working against this motor. However injector location is a big one. We (unlike diesels) are limited to that location because the spark plug is in the middle.

Original Mitsu DI engine designs did have the injector in the middle.

Yes, maintenance helps, keeping heat down helps, keeping boost down helps, but in the end the flaw in the design is blaring and it is bound to cause many more cars to fail on top of reducing overall engine life for everyone. The VW and N54 engines run a lot less boost.

[FreeFlyFreak]

Thats it!
Im gonna start throwing some 2 stroke oil in my gas. LOL

But seriously, what is the stuff gunking up the oil control. Carbon build up?
Maybe some serious leaning out would do the trick.
OT:
Travis @ Cobb indicated 12.7 AFR was ideal for our engine, I dont know if this came from testing they have done with their own car or what:
http://forums.cobbtuning.com/forums/...07&postcount=5

[IshiKage]

this car sucks but im still going to mod the shit out of it and get a new motor if it blows. haha

ill be looking to get rid of this shit in the next 2 years and get a Coyote Mustang

[_Toxic_]

Originally Posted by Lex There are many things working against this motor. However injector location is a big one. We (unlike diesels) are limited to that location because the spark plug is in the middle. Original Mitsu DI engine designs did have the injector in the middle. Yes, maintenance helps, keeping heat down helps, keeping boost down helps, but in the end the flaw in the design is blaring and it is bound to cause many more cars to fail on top of reducing overall engine life for everyone. The VW and N54 engines run a lot less boost.

I want to see how many STOCK engines who has blown. Considering all of the engines here had has some kind of mod/tune.. perhaps that if it is many stock engines who has blown they maybe arent telling that here.. but if there were as many stock blow up´s as Tuned/modded blow up, mazda shurely would investigate in that. Dont think they will have a rep. of building bad cars!

[NRSpeed]

Just below the red circle that shows the scrapes, you can see a ring that looks like where the piston had seized. Or is that likely just the impression made from when the rod was chucked?


I also love how the angle just shows how the rod went right through everything

[Lex]

The lower line is likely where it had already broken.

Also, I would certainly use the highest quality synthetic oil in this car and change is often.

The VW FSI 2.0T motors also deal with oil burning issues. Do a little bit of searching.