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Old 10-01-2001, 02:49 AM   #1
Eric SS
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Exclamation Who her has blown #4???

Just trying to get a fix on how has blown #4 piston? please respond!

Blown #4:

1) Imprezinator
2) AaronB (Kinda)
3) DannyAtWork
4) ImprezaRS dot com
5) M8
6) 8Complex
7) Subachad
8) Scooby South
9) Kcz
10) Fitz
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Last edited by Eric SS; 10-02-2001 at 11:08 PM.
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Old 10-01-2001, 02:53 AM   #2
Eric SS
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Doh!! can the moderators please move this to the Aftermarket forced induction forum. I accidently posted this here Thanks!

Eric
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Old 10-01-2001, 08:34 AM   #3
TaiChih
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I have and put a sunroof in the top of my motor.
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Old 10-01-2001, 09:55 AM   #4
ImprezedRS
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I broke a rod, not sure which one.
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Old 10-01-2001, 10:44 AM   #5
AaronB
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Eric,

I fragged #3, not #4.

#4 was in the second worst condition, but wasn't missing any pieces like #3.

Aaron
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Old 10-01-2001, 10:46 AM   #6
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Also I don't think kastle has fragged his motor either.

You need more work on your list

Aaron
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Old 10-01-2001, 12:23 PM   #7
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If #4 is the one closest to the firewall on the driver side then you can add my 1.8L to your list. It did last to 153,000 miles though, 30,000 of which were turbocharged.

Chad
93 1.8T
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Old 10-01-2001, 01:00 PM   #8
8Complex

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I fragged #4 pretty good.
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Old 10-01-2001, 01:02 PM   #9
M8
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i did... was just using a RRFPR @ the time.... (can't have helped matters)
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Old 10-01-2001, 01:03 PM   #10
Danny5
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#4 for me.

-Danny
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Old 10-01-2001, 01:35 PM   #11
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Chalk up 2 #4's for me..

Fitz
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Old 10-01-2001, 06:24 PM   #12
Scooby South
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ummmmmmmm....mine was number 3???? I think...the drivers side back.....
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Old 10-01-2001, 06:35 PM   #13
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Driver's side rear is #4.
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Old 10-02-2001, 01:30 AM   #14
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I toasted #4 at the strip a couple months back. You can add me to the list. Too bad they didn't all happen at the same time. We could have got a great deal on a piston GB.

Last edited by Kcz; 10-02-2001 at 01:44 AM.
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Old 10-02-2001, 07:37 AM   #15
Fitz
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Let's add a new spin to this...

Of those of you that blew up the number 4 piston (or actually any piston) what letter designation was it? A or B??

I'm going to pull a theory out of the air and guess that 90-95% of these are "B" pistons.

Fitz
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Old 10-02-2001, 09:28 AM   #16
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Quote:
Originally posted by Fitz
Let's add a new spin to this...

Of those of you that blew up the number 4 piston (or actually any piston) what letter designation was it? A or B??

I'm going to pull a theory out of the air and guess that 90-95% of these are "B" pistons.

Fitz
How do you tell the difference between an A or B?
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Old 10-02-2001, 12:33 PM   #17
Fitz
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On the top of your block, in the middle, right on the seam between the two halves, it'll have 4 letters.

Now.. follow along carefully. If you're standing on the driver side of your car, you'll be able to read two of those 4 letters. Only two of those 4 letters will be facing you. The other two will be upside down as they are meant to be read from the passenger side as they reference cylinder #'s 1 and 3.

They'll either be an "A" or a "B." It might say AB or BB or AA. This designates what kind of piston is in that cylinder. Example: If you're standing on the drivers side of the car and looking at the motor and it says "AB" then cylinder #2 is an "A" and cylinder number 4 is a "B."

I'm not sure if you can see them with everything attached.

Fitz
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Old 10-02-2001, 02:58 PM   #18
8Complex

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B, but that is irrelevant. A & B designate piston size at time of manufacturing. Since there are variances in sizing everywhere, they have to have 2 different sized pistons. IIRC, A's are within .00-.10mm over 99mm, and B's are .01-.1mm under 99mm. The B I have here measures to 98.90mm.

The cylinder bore is 99.5mm (give or take the variances), which allow .5mm to be taken up by the rings. What they do at the factory when they measure the blocks and stamp them A or B in the quadrants on top of the halves of the blocks. They're all relative to where you read them, so it's pretty easy to figure out.

Looking front the front of the engine mine read :

AB
BB

So only cylinder #3 was an A.
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Old 10-02-2001, 09:37 PM   #19
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The "Wall of Shame" at my Subaru dealership has 4 pistons on it... only one of which that came from me but all of which are "B" pistons. Coincidence.. maybe.. but I'd rather let the numbers tell me.... and by the looks of it I can chalk up a "B" for you as well....

Thanks,
Fitz
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Old 10-03-2001, 08:55 AM   #20
Fitz
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I was thinking about this last night and I realised that inquiring about the "B" piston as I was doing might insinuate that I thought there was an issue with the "B" pistons.

For the record, I'm not stating that. If it was as simple as a casting flaw or something similiar prone to the "B" pistons then why wouldn't we have blown cylinder number two, or four, or whatever cylinder you have a "B" piston in. We've established that most of the people who have replied to this thread have harmed cylinder #4. Cylinder #4 has either an "A" piston or a "B" piston. As 8complex pointed out, the cylinder letter orientation corresponds to minute differences in cylinder diameter.

Knowing how detonation is caused, maybe we can look at all the factors that go into it and try to isolate a cause. Is it fuel delievery? Does the intake manifold flow better into cylinder 4 therefore running slightly lean?? Is the compression ratio slightly higher? Does the mechanical design of the motor provide weakness in this cylinder due to varied meaurements on the crank?? Is there anything with the connecting rod for cylinder #4 that might **** the piston in the bore?

These are some of the questions we need to ask to find out what the failure mode is on this cylinder. Some of them are out in left field and can probably be eliminated; but until we ask, assess the data gathered and make a data driven decision we'll still hear theories every day of the week in regards to "weak pistons" or "frail MY00 motors."

Fitz

"steps off soapbox"
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Old 10-03-2001, 09:42 AM   #21
Clegg
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Looked at my engine and it was AA and AB

the B was for he passenger forward piston. I think.
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Old 10-03-2001, 12:01 PM   #22
Danny5
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My motor uses all A pistons except for #4.

My motor has toasted the #4 cylinder 3 times.

Twice due to piston failure, once due to rod failure.

All three times because boost exceeded 23psi. Of course, we all know my design has boost issues, but I thought it was unusual as well that #4 was the only one to go every single time.

Unfortunately, I have no theory as to why...

I am going to take a stab in the dark, and say its due to cooling issues.

Although, after looking at pictures on my chapter13 page, I really have no idea... hmm....

-Danny
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Old 10-03-2001, 01:14 PM   #23
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I actually had a theory set up for a while that #4 actually got the least fuel pressure of all 4 cylinders. Unfortunately there is no way to prove it, but I was using pretty easy concepts to prove it, so I would say that it wasn't entirely incorrect. I need more info on that damn SARD FPR...
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Old 10-03-2001, 06:18 PM   #24
Eric SS
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Very interesting, the only "B" piston is #4 humm...

Eric
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Old 10-03-2001, 06:38 PM   #25
HOK
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Umm.... I (my old friend) fragged number four too... 89 octane causing all that detonation.

dammit... i cringe when i think back.
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