The Project Pad

a friends S6 started knocking so he proceeded to tear it down and see what exactly failed. rod bearing on cylinder 5 is telling the knock knock joke but after an inspection down in each cylinder with a bore scope we discovered a few of the pistons where missing material from them! here's some pictures of the damage. no one has any idea what caused this and thats why im asking for input from you guys to see if you can explain why this happened of if you've seen it before.

the car itself is stock less an MTM 1+ chip set. the car was over heated pretty bad by a previous owner but we have since replaced the head with another AAN head and refreshed the whole top end with a new metal head gasket, redid the valve train, and just a good cleaning along with an ARP head stud kit.

Too much boost and or not enough fuel. Pretty much looks like a lot of detonation. Does he have a manual boost controller or something extra on the car?

bummer, looks like detonation to me.

My guess would be det brought on by not enough fuel (edge of the piston became a hot spot).

no MBC or anything on it, just the MTM 1+ chips that we all have used over the years and everything else is bone stock. the car did run freakishly well, it would outrun my avant that has far more done to it. i wondered if it being severely over heated at one point had something to do with it? made the aluminum weak or something. im not even sure thats possible but with this engine im learning anything is possible lol.

also there was a good bit of oil in the crossover pipe, i wonder if it burning oil could have caused this? i was thinking of a kind of hydro lock with oil, the car did smoke but we just though it was because the turbo was cooked when it was over heated and some oil was passing into the turbine housing and being burned.

I thought the MTM chips were known for this. Wouldn't you think that if it's freakishly faster than others you've experienced that maybe it is running a little too close to the ragged edge? You aren't learning anything about this engine, you're learning what happens when you, specifically, touch mechanical things. Don't you ever ask yourself why these things only happen to you and not anyone else? Quit trying to blame the engine

it didnt happen to me, i never touched this car other than looking it over when my friend bought it. i opened up the ECU and seen it had aftermarket chips and an OEM looking 3 BAR MAP sensor. i pulled the chips and read the data on them and discovered they are MTM 1+ because i already have that chip set in my database of tunes and it matched perfectly. when i stopped messing with the stock motronic i installed these chips in my car over a year ago but i removed 5 to 8 degrees of timing over the whole map for fear of this happening to my car and i have no problems.

I'd rebuild it and get a wideband on the car. Something is way off

now im starting to think its the MTM chips that are in the car after loxxrider pointing out about them causing this. here's the stock MTM 1+ mapping in black and my revised timing map thats in my car in red under it. i just went and pulled the chips off of my car and re-read them to refresh my memory on what i had in there. it turns out i did adjust the problematic MTM chip sets timing to make me more friendly. at full load on the top of the RPM range the the MTM shows 21.75 degrees advance and my revision at the same point shows 18.00 degrees even.

Yeah, that looks like knock city.

I'd agree it was knocking. The oil ingestion could be part of that. Ingesting oil significantly advances knocking.

I'm glad you take my harsh words in stride so well lol. I think you did well to reduce the timing in that map though. I agree with Jim, every one of these old cars should have a wideband, even if it's not on standalone.

loxxrider wrote:I'm glad you take my harsh words in stride so well lol. I think you did well to reduce the timing in that map though. I agree with Jim, every one of these old cars should have a wideband, even if it's not on standalone.

i totally agree they should have a wideband! unless the person with it has no idea what they are looking at or how to use it. i had a couple people wanting them installed just for the blinky light show and all the fancy numbers that are displayed on it.

audifreakjim wrote:Yeah, that looks like knock city.

are you referring to my mapping or the original MTM?

Mtm, that's a big bump in timing at peak torque

audifreakjim wrote:Mtm, that's a big bump in timing at peak torque

thats what i thought too. after loxxrider saying about the MTM tune killing engines that reminded me about a few threads i read on quattroworld about it a looong time ago. no one ever had any actual pictures of the mapping or anything showing what the ignition map actually looked like so i didnt know what to watch out for because i know there's a good version of the MTM 1+ out there too. i think one is the original german MTM 1+ which is the killer and the other is a later hoppen MTM 1+ which is the safe tune. here's the the 2D map of the original MTM main ignition map for everyone to see what it actually looks like. cell values are BTDC, RPM is on the left and load is on the top.

actually here is the is the original timing/fuel BIN, my revised timing/fuel BIN and the tunerpro XDF that i created to go along with it for anyone that whats to analyze it further or is just curious about it.

FWIW, this was my old car (like 3 owners ago now?). That tune was on the car for the entirety of my ownership, never had any issues with det. I had the stock injectors ultrasonically cleaned and flow matched a few years ago, and I believe I changed the fuel filter at that point. Never touched the fuel pump.

Yes, the MTM 1+ tunes are not the best, but something else failed to cause this damage. There are a ba-zillion MTM 1+ tunes running on UrS cars out there... the software doesn't melt pistons on it's own.

When you pulled the head after the overheating, the pistons were fine at that point?

Weird stuff happens... fuel pump gets hot and loses flow at the top end, bad tank of fuel (it happens... "Hey I got an extra 1000 gallons of 87, you want it?" "yeah, put it in the 93 tank"), who knows?

They don't call it the scary edge of tuning because it is safe after all If you want a safe happy tune, leave it stock.

(note: this offer not applicable to '08-up Subaru 2.5)

I think Pete has it right, something is just far enough off to make it go south. Could have been overheating related, fuel, wrong plugs. My point is, rebuild it and make sure fueling is good and it isn't knocking.

audifreakjim wrote:I think Pete has it right, something is just far enough off to make it go south. Could have been overheating related, fuel, wrong plugs. My point is, rebuild it and make sure fueling is good and it isn't knocking.

a full rebuild is being done now and my buddy decided we're going to install my revised MTM 1+ timing/fuel chip in there just to be on the safe side. i've been running on it with no problems and so has another local URS4 owner. i thought about the over heat thing and i wondered if that could have done something to the pistons like weakening the material on the top? who knows really but i figured i'd pick you guys brains to see if a cause for this could be found for future reference and prevention of this happening again.

Why does the load axis only go to 206kpa? A stock urs6 will pass that. You sure that's the right map?

Nonetheless, I'm also in the "something external caused this" camp. Bad fuel, unregulated overboost, not enough fuel, etc...

The load axis is strictly load % only. Has nothing to with boost pressure directly. There are multiple values that create the load value. Boost is one of them along with several others.

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Ya I was thinking how boring 206 kPa and 18° is lol. Must still run well enough to keep your interest in the chassis anyway

Just to confirm, what MAP sensor is in the ECU?

When live map tracing, what cells do a WOT pull with decent loading go through on this map, at what boost levels?