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Old 09-19-2007, 11:54 AM   #26
flycaster
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Quote:
Originally Posted by hotrod View Post
...Yes it did, you broke a piston...
In a nutshell, it's as simple as that.
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Old 09-19-2007, 05:04 PM   #27
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Ahh I see your reasoning, But I disagree.. My tune was very safe compared to how far i could have pushed things.. It made about 380whp in Arizona on 91 oct Then I moved to FL Droped 1500 ft in elevation Gained 93 octane and Hydra mist using 50/50 h20 and meth, Very good tuner.. Oh and 35 Degree temp difference. The car as it was could very well have made 450-465whp in current fourm.. It for sure wasnt living on the edge every day i drove it.. Even on race gas we left a great deal of power to be made. as the car was tuned in the 115 degree heat...

really all the cards when in my favor.. I just believe subaru motors can deal with the stress of what i was doing regardless of tune. If it knocked I would have known.. but anyhow it blew who knows why i am sure it had its reasons, I just know it would have lasted a GREAT deal longer if i had not have done what i did.. To later now... all I can do now is Rebuild and try and prevent this type of damage again, Yes also I`ll be replacing every sensor on the motor

Yes and the Hydra
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Old 09-19-2007, 05:33 PM   #28
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Originally Posted by stu View Post
he is using the hydra and hydra mist. it will moniter detonation and pull timing throughout the rpm band and resort to another safe map if needed. he would have to have a bad knock sensor to have this problem.
Does the hydra have ECT and/or IAT comp. maps? Det. comp. is after the badness has already started.
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Old 09-19-2007, 10:30 PM   #29
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the knock threshold map is very aggressive and will pull timing in fractions of a degree, it is very easy to see if it is pulling timing when connected to a laptop. but if it is really bad it will resort to a back up spark and fuel map that makes it very fat and sluggish. there is also a iat map that can be adjusted to any weather condition.I dont know how his was set but I was ther when he was tuned and there was alot left but because of the heat here in az we need tp keep things alittle rich and a little less advance on the timing here in the summer time.
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Old 09-20-2007, 01:41 AM   #30
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Originally Posted by STi_Guy04 View Post
Yes also I`ll be replacing every sensor on the motor

Yes and the Hydra
WOW, you're LOADED! $$$$$$$$$$$$$$$$$$$$$$
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Old 09-20-2007, 02:07 AM   #31
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good luck man. I would imagine with all the things you changed with your car and location the tune was off. Wouldn't it be nice if you could just build your block and be done? Makes me want a different car sometimes.
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Old 09-20-2007, 03:27 AM   #32
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Quote:
Originally Posted by STi_Guy04 View Post
Ahh I see your reasoning, But I disagree.. My tune was very safe compared to how far i could have pushed things.. It made about 380whp in Arizona on 91 oct Then I moved to FL Droped 1500 ft in elevation Gained 93 octane and Hydra mist using 50/50 h20 and meth, Very good tuner.. Oh and 35 Degree temp difference. The car as it was could very well have made 450-465whp in current fourm.. It for sure wasnt living on the edge every day i drove it.. Even on race gas we left a great deal of power to be made. as the car was tuned in the 115 degree heat...
Those are both good things, but major changes with custom tunes can create some weird situations... if the car isn't properly mapped for those conditions, you can run into problems. Long extended high speed high rpm pulls don't help either.

Seeing as you're probably going to change some stuff on the build, you'll probably get a retune... even if you don't change anything and just fix what broke, I wouldn't beat on it too hard until you get some solid data logs.
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Old 09-20-2007, 06:04 PM   #33
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Those are both good things, but major changes with custom tunes can create some weird situations... if the car isn't properly mapped for those conditions, you can run into problems. Long extended high speed high rpm pulls don't help either.

Seeing as you're probably going to change some stuff on the build, you'll probably get a retune... even if you don't change anything and just fix what broke, I wouldn't beat on it too hard until you get some solid data logs.
I can agree on this.. I`am sure things changed, But my map for sure wasnt way off... It would have knocked weeks ago doing pulls up and down the street Actually the 1st time and drive I took once I filled up with 93 was amazing drive ability was amazing she never ran better once except race gas maybe. Only thing i added on was Hydra mist, Seems like a big mod.. But it was only running 3 bars of Flow.. So I was not injecting mass amounts of Methanol and water

I bet she just knocked a few times and poped or somthing... as wells but for replacing every sensor... lol Spur of the moment comment hehe I dunno If its that expensive.. Maybe just replace all the Important one. Knock, Cam, Crank, Ect, For sure get a knew boost gauge... Seems most of them never read right any way... I have loooked at logs between what my boost gauge sees and hydra actually sees... and its Way off!! Anyone else run into this.. my gauges are greedy electrical ones.

ohh one more thing anyone know where you can get a decent Laptop that has a serial port? for cheap I`ll never boost my car without watchin that crap again!

thanks for the help and I`ll keep you all posted.. I`am skipping the Cylinder leak test.. Just going to tear her down and see what I find
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Old 09-20-2007, 06:20 PM   #34
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Originally Posted by STi_Guy04 View Post
. as wells but for replacing every sensor... lol Spur of the moment comment hehe I dunno If its that expensive.. Maybe just replace all the Important one. Knock, Cam, Crank, Ect,

meh, you're only looking at $1,000.00 or so. Should be worth it



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Old 09-20-2007, 06:35 PM   #35
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Damn really.. Well Yeah if she doesnt blow in like another 4,000 miles I`d say it would be worth it.. I`ll check into it..

Subaru`s and I have a bad relation ship
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Old 10-13-2007, 12:45 AM   #36
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4032 Mahle's, huh? If you broke one, I think that makes 5 so far. Let us know.
Well Got the the heads off the block... As i thought broke the top ringland of cylinder number 4..

All let the pics speak!

here you can see the damage to piston in cylinder 4


a shot of cylinder 2 & 4


a shot of the cylinder head in question


cylinder 1 & 3


cylinder head for 1 & 3



The block when it was fresh


those where some quick pics... If there is any other things you would like to see let me know I`ll post them up.. Both head gaskets looked fine. Had a Slight issue getting cam sprockets off... only the plastic ones though... other than that it was a smooth tear down to this point,
And these where the mahle pistons
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Old 10-13-2007, 01:14 AM   #37
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Quote:
If there is any other things you would like to see let me know I`ll post them up..
Yes I would like to see a good sharp closeup of the #4 cylinder head showing the area just between the intake valves that matches up with that broken piston. A very high percentage of the engines that have blown, which I have had the chance to look at, appear to detonate and kill the piston at that 1:00 postion in the cylinder just adjacent to the rear most intake valve on the head.

I personally believe our cylinder heads develop a hot spot there (or something) under high power condtions so it tends to detonate there.

On my car when I was drag racing it hard and trying to find out how much octane it needed to prevent detonation I saw exactly the same thing when I was reading the plugs. When it had detonation events you could see that direction of the aluminum splattered on the plug was coming from that 1:00 postion every time.

If we can fix that tendency to detonate there, we can push the limits up on the whole engine because that is the first point to detonate it appears.

Larry
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Old 10-13-2007, 01:30 AM   #38
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Well, the land beneath the crown is probably broken, but I've never seen a crown and edge erode like that before. That looks to me like it was happening over a period of time, not just an "event" - I've only seen a clean break or hairline fracture with the Mahle, other than one catastrophic failure which scattered piston "bb's" throughout the entire motor. Also, #4 isn't the only piston with hot spots...it suggests a really lean tune, or perhaps an intake leak.

[edit] Just a thought, but Ed and Vaus (other tuners too) have tuned at altitude and both have stated that an aggressive tune up in thin air can become dangerous at sea-level. I dunno if 1,500' is enough to trigger this, but just thought I'd throw it out for consideration.

Last edited by flycaster; 10-13-2007 at 01:40 AM.
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Old 10-13-2007, 04:36 AM   #39
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That sort of "erosion" is classic long term low intensity detonation damage, it slowly blows bits of aluminum off the piston crown giving it a sandblasted look.
That is why I want to see a good picture of the head, I would like to see if there is a matching erosion site on the head that would give a hint of exactly where the detonation is occuring on the cylinder head.

Larry
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Old 10-13-2007, 10:17 AM   #40
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this my not be any help , but i have heard from a tech from element tuning, that perrin fuel rails sometimes lean out the # 4 cylinder i have a very similar set up to yours to include the rails and i am now very concerned.
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Old 10-13-2007, 12:34 PM   #41
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Quote:
Originally Posted by hotrod View Post
That sort of "erosion" is classic long term low intensity detonation damage, it slowly blows bits of aluminum off the piston crown giving it a sandblasted look.
That is why I want to see a good picture of the head, I would like to see if there is a matching erosion site on the head that would give a hint of exactly where the detonation is occuring on the cylinder head.

Larry
Good point Larry... I agree that it is detonation damage...
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Old 10-13-2007, 01:25 PM   #42
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Well I agree. It could be detonation damage, With that said.. why would the Hydra not pick up on this detonation?

Also If it has anything to do with it.. my afr on pump gas is 10.2, But I shall get those pics up in the next few minutes

one other thing about the long term detonation, The car did not smoke at all before it fully blew... the thing i would say did not burn any oil.. with in reason all cars burn a degree but. For sure we shall figure this out!

Thanks for the insight!!

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Old 10-13-2007, 01:48 PM   #43
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It wont burn much more oil until the second compression and oil rings warp...
The hydra might not have picked it up because of the frequency of the knock..
Your knock sensors might not "hear" that frequency...
You can also get a rich knock as well as a lean one...
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Old 10-13-2007, 05:03 PM   #44
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Pics






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Old 10-13-2007, 05:08 PM   #45
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That sort of "erosion" is classic long term low intensity detonation damage, it slowly blows bits of aluminum off the piston crown giving it a sandblasted look.
Agreed, and that is what I was implying. I've just never seen det damage like that on a piston edge before - on the crown, a bunch. I learn soemthing new here every day, cool.

I dunno, but it sure doesn't look like that cylinder was running 10.2:1 AFR's, at least not all the time.
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Old 10-13-2007, 05:41 PM   #46
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right... Yeah IT sucks but I guess I`ll have to go though everything and Find out . I`am pretty new to building motors for say... this would be the seconds one i took apart,

So would you guys say send out the fuel injectors get flow tested, Set Hydra Knock threshold as low as it can go. I got shots of the other cylinders I`ll post them up and see if you guys can spot other detonation issues
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Old 10-14-2007, 12:36 AM   #47
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...send out the fuel injectors get flow tested...
Not a bad place to start. You can get them cleaned and flow tested, with new seals, for less than $20 each. Number them, so you know which came from what jug. If #4 is off, that would make your search a whole lot more simple.
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Old 10-14-2007, 02:55 AM   #48
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Wait, he dropped 1500ft in altitude without a re-tune on Hydra?! Hello change in VE!

With the increased WGDC (reduced in backwards Subie nomenclature), the more open wastegate would increase the flow into the cylinders per pound of boost. That throws MAP sensor systems way off and would have made the engine run lean until the Hydra could adapt.

But, unless the Hydra adaptation occurs while the wastegate is being used, the change in requisite WGDC at high boost is going to throw the A/F ratio off (to the lean as you decrease altitude) under full load. (I'm assuming Hydra is open loop at full load like most ECU's.)

All that crud around the exhaust valves makes me think it even more likely that the tune lean-ed out as the altitude decreased (classic over-cooking the exhaust valves with insufficient fuel+water). If the detonation originated there, it could setup a detonation mode like the first, or last, one here, which would put almost as much stress on the intake (top) side of the ring land as the bottom (exhaust) as the pressure spike "rings" back and forth between the two regions:



-Adrian
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Old 10-14-2007, 03:06 AM   #49
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I am inclined to think the "crud" on the exhaust valve is aluminum blown off the intake side of the piston toward the exhaust side of the cylinder. That is what I saw on my plugs. If you indexed the plug you could see that all the aluminum spray was coming from about 1:00 on the intake side of the cylinder and blowing across the combustion chamber toward the exhaust side where I would expect it to bond to the surfaces there just as it does on the spark plug electrodes and insulator.

Larry
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Old 10-14-2007, 03:14 AM   #50
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I am inclined to think the "crud" on the exhaust valve is aluminum blown off the intake side of the piston toward the exhaust side of the cylinder. That is what I saw on my plugs. If you indexed the plug you could see that all the aluminum spray was coming from about 1:00 on the intake side of the cylinder and blowing across the combustion chamber toward the exhaust side where I would expect it to bond to the surfaces there just as it does on the spark plug electrodes and insulator.

Larry
In either case, they could both be strong indicators of running lean under full boost.

Given that, although part-throttle changes in VE are taken into account by almost any ECM, full throttle changes due to change in WGDC at each fuel load point are NOT taken into account (without built-in wideband, full throttle closed loop, and lots of time to adapt), it does seem fairly likely that the engine thought less air was entering than was in actuality.

I wonder what the "tales of the wideband" have to say.
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