Engine #3 For Me!

[Maxx Mazda]

Melted piston #4 again. Just needs new pistons an a hone, cylinder is not damaged. Head is fine. Marks on the piston are NOT from the missing piece. I had a magnet down the spark plug hole. It was melted and passed out the exhaust, just like before on my stock pistons. It did NOT break off.

I figured out what happened I think, but I'll get to that later tomorrow, I'm tired as ****, so please no one ask what happened. It did not run lean. I think I'm calling it quits now guys. It was fun!

 

[1moreMPH]

calling it quits.... as in, you're done with the p5??

 

[xelderx]

What is going on that is causing a repeat problem with #4?

 

[Maxx Mazda]

If you look at the path the air has to take to get to cylinder #4, it comes in through the TB, then when it gets to the intake mani, it has to take a sharp turn (more than 90*) to get into the cylinder. Now, you'd think, okay, so there is less air, so it would run rich. To a point, yes. The reduced airflow just simply cant pull in the atomized fuel fro mthe injector, as such that intake valve runs lean. Also, if you look at the water passage, it's the farthest one fro mthe water pump right in that corner, so it's gonan be running pretty hot. THere's a chance that cavitation combined with the heat created at that spot has actually boiled the water in that corner, and since there's now air in that passage, coolant that is already cooling a hot area, can no longer cool it as effectively. All of that combined with how thin the piston is around that valve pocket, and you have a recepie for disaster.

Now for the fix. I'm thinking I move the injector rim for #4 up by 5% or so, to give it that much more fuel to try and ensure this doesn't happen again.

 

[1moreMPH]

sounds plausible. and also like a decent solution. can you somehow make a different cooling route? that would probably be an pain in the asshole...

 

[aMaff]

passed out the exhaust...ok fine... but that had to go through the turbo. You check to make sure it didn't take a couple of fins with it?

 

[Maxx Mazda]

passed out the exhaust...ok fine... but that had to go through the turbo. You check to make sure it didn't take a couple of fins with it?

I'll have to check later but there is no damage whatsoever o nthe head, or exhaust valves or any evidence inside the exhaust manifold of any foreign material ever passing through there. Like before, I'm sure the piston just vaporized.

 

[xelderx]

Is it a problem specifically with the single runner manifold? I would have to study the stock manifold design again a little closer against the single runner one. I have both in my garage.

 

[Maxx Mazda]

I ran the stock mani (ported, VTCS removed) and it happened still last year...

 

[xelderx]

Interesting. I'll be paying more attention to the design of the manifold to see if there is a fix for this.

 

[CitizenPro]

Jeez.....sorry for the loss mang. These motors can be a pain in the ass.

 

[Jaysanooch]

I ran the stock mani (ported, VTCS removed) and it happened still last year...

Frigg...well that just through my idea out the window.

 

[Sveivo]

So there's no way to run a reliable boosted Protege without extensive custom work like the manifold?

 

[djarkitek]

there are many reliable boosted and built proteges running around all over the place. I'm at a loss as to how max mazda keeps hurting engines (except for when he was boostin 12lbs on his old stock block, lol) .

 

[FunkyBuddha]

LOL..nick..i think it's time you cap the boost at between 11-14psi.

ps: have you checked your valves at all?

 

[03.5MSP]

Also would getting something like a J&S help prevent a situation like this from occurring?

 

[Maxx Mazda]

I have a full standalone. Timing was no more than 14* at 18 psi. That's really retarded (literally.) I could run closer to 18*-20* but I didn't want to until it was o nthe dyno. Like I said, there was no knock. It just ran too hot and melted it. I'm at a loss...

 

[03.5MSP]

I have a full standalone. Timing was no more than 14* at 18 psi. That's really retarded (literally.) I could run closer to 18*-20* but I didn't want to until it was o nthe dyno. Like I said, there was no knock. It just ran too hot and melted it. I'm at a loss...

I'm really sorry to hear about all of this. I know when this kinda stuff happens it can really get you down about the car. I just wish you have more luck in the future.

 

[Kooldino]

If you look at the path the air has to take to get to cylinder #4, it comes in through the TB, then when it gets to the intake mani, it has to take a sharp turn (more than 90*) to get into the cylinder. Now, you'd think, okay, so there is less air, so it would run rich. To a point, yes. The reduced airflow just simply cant pull in the atomized fuel fro mthe injector, as such that intake valve runs lean. Also, if you look at the water passage, it's the farthest one fro mthe water pump right in that corner, so it's gonan be running pretty hot. THere's a chance that cavitation combined with the heat created at that spot has actually boiled the water in that corner, and since there's now air in that passage, coolant that is already cooling a hot area, can no longer cool it as effectively. All of that combined with how thin the piston is around that valve pocket, and you have a recepie for disaster.

It sounds like a fine theory, but I still don't buy it. What you described is inherent of all FS engines. So why would it happen to you twice, and not happen to others? I think you're barking up the wrong tree. Keep looking.

 

[Kooldino]

I'll have to check later but there is no damage whatsoever o nthe head, or exhaust valves or any evidence inside the exhaust manifold of any foreign material ever passing through there. Like before, I'm sure the piston just vaporized.

Vaporized? A chunk of forged aluminum would not just vaporize...not at the temps that your car runs at.