DW 850's and the cylinder number farthest on the passenger side

 

^same one i lost way back when

 

you know i did have 3 boost spikes to 29 psi a long time ago but both chris and mitch know about this. but that has nothing to do with it, since that was six months ago.

 

I'm just throwing this out there, but you say the spark plug electrode was broken off? Sounds strikingly familiar to all the other #4 cylinder plugs being bent/compressed by contact with the piston top.

All conditions combined with this issue creates a broken spark plug electrode pinging around and blowing through a piston? Sounds very plausible to me.

I don't follow the X section, so this may have been addressed already, but we've had a few of the X's repeatedly going through plug after plug in #4 (and sometimes #1) because of bent/closed tips. Finally got curious and a friend mentioned to try adding a washer from an old plug onto a new one to double it up (I realize it's ghetto, it was just to satisfy curiosity more than anything) and lo-and-behold, no more damaged spark plugs...

It's just my opinion, but it seems almost like Mitsu either had a machine boring issue in the spark plug tubes in a batch of heads or they're just using a plug thats a hair too long for the application, or both

Related? Possibly.

 

Not trying to point any fingers at any tuner here.. just putting that out there first

So, Way back when i was testing the Dom1 turbo on my X I had one big boost spike to 30 psi the following day the motor froze up on my while cranking.... waited a minute, tried again and it turned right over and fired right up. Happened again about a week latter. about a week after that I was at the dyno and doing a few tweaks... last pull was beautiful.. zero knock retard, nice smooth plot, good power, kissed the rev limiter up top and that was all she wrote.

Turns out the spike cracked the piston and a chunk had worked loose and been floating around the cylinder to some degree or another for a couple weeks before it smashed the electrode and got wedged behind the face of a valve.

Say all that to say, just because it seemed fine for months does not mean it was.

 

very interesting, is there a difference between the X and RA plugs other than heat range?

 

[quote=Mad_SB;9239633]Not trying to point any fingers at any tuner here.. just putting that out there first



ok i understand. and thanks i appreciate the help. i will be taking the motor out saturday and will be taking pictures of the other cylinders. i really hope i figure out why this happened i will be sending my injectors out tomorow to DW to be tested.

 

YA I believe the ra plugs are range 7 and the evo ones are 8. i know there is a one range difference

 

I haven't had a chance to mic a few of each for comparison, but it'd be worth a look I think since I haven't heard of this happening with RA's

 

They looked exactly the same as the 10's when I swapped mine out, minus the heat range.

If the plugs are long enough to make piston contact it wouldn't make it out of your driveway after startup.

 

Strange coincidence that adding a washer to #4 cleared up the problem in multiple cars then?

 

If a OEM plug is contacting a OEM piston on "some" cars then something is wrong or out-of-spec in "those" cars.

Be it your theory or something else, the #1 fact is something is wrong with those cars. Perhaps a stretched timing belt that hasn't set off the sensor yet, wrong spec pistons in a certain batch? Cast-shift in a batch of heads? (Mitsu has been known for this), etc etc

Either way, even at full TDC the piston shouldn't be anyway close to the plug, it would most likely hit the valves / bowl first unless the plug used was WAY out of spec in length.

Disclaimer: I'm not an engine builder.

 

so what is the best way to prevent this from happening again? the wierdest part is i have 50k miles and this now happened. you would have thunk if my piston was going to hit my spark plug it would have happened a long time ago

 

Thanks for the clarification Bryan. That's why I made mention of the head as well, as I know there have been issues in the past. I was just thinking maybe spark plug bores too deep or offset or something along those lines if the plugs were, in fact, identical.

As I said, I hadn't taken any kind of measurements, just knew what worked to "solve" the problem and as you said, if it was a timing issue, you'd be more likely to see valve damage before the spark plug was hit.

 

so what plugs do you guys think i should get for the new motor? i know ams hass the hks plugs is anyone on here running those? oh and what heat range do you think i should get 8 or 9?