Pelican Parts
Parts Catalog Accessories Catalog How To Articles Tech Forums
Call Pelican Parts at 888-280-7799
Shopping Cart Cart | Project List | Order Status | Help



Go Back   Pelican Parts Technical BBS > 1- Porsche Technical Forums > 911 / 930 Turbo & Super Charging Forum


Reply
 
LinkBack Thread Tools Rate Thread
Author
Thread Post New Thread    Reply
Registered User
 
beepbeep's Avatar
 
Join Date: Jun 2001
Location: Sweden
Posts: 5,560
The icepick

Hello!

A gentleman on another forum uploaded picture of his JE piston that has been living in 924 Turbo with slightly bad fuel injector. I tought it would be a nice picture to share, as many people ask how knock influence pistons.

This is a JE piston and it survived the treatment quite well (no edge erosion, yet) but the hacks are interesting to see. It's like someone took a icepick and wen't loose on it...

__________________
Thank you for your time,
Old 11-25-2007, 04:47 AM
  Pelican Parts Catalog | Tech Articles | Promos & Specials    Reply With Quote #1 (permalink)
Forced Induction Junkie
 
WERK I's Avatar
 
Join Date: Jan 2003
Location: Wisconsin
Posts: 3,290
Garage
Thanks Goran.
Looks like the piston is suffering from frost bite!
Interesting detonation effect. Did the spark plug electrode(s) suffer damage? It almost looks like there was a small object floating in the combustion chamber.
__________________
Dave
'85 930 Factory Special Wishes Flachbau
Werk I Zuffenhausen 3.3l/330BHP Engine with Sonderwunsch Cams, FabSpeed Headers, Kokeln IC, Twin Plugged Electromotive Crankfire, Tial Wastegate(0.8 Bar), K27 Hybrid Turbo, Ruf Twin-tip Muffler, Fikse FM-5's 8&10x17, 8:41 R&P
Old 11-25-2007, 05:22 AM
  Pelican Parts Catalog | Tech Articles | Promos & Specials    Reply With Quote #2 (permalink)
Wo ist die Rennstrecke?
 
DonE's Avatar
 
Join Date: Mar 2004
Location: Brooks, GA
Posts: 1,211
Good pic - thanks.

This was caused by a bad (lean?) injector? The rest of the engine specs would be interesting, if you have them (timing, CR, etc).
Old 11-25-2007, 06:34 AM
  Pelican Parts Catalog | Tech Articles | Promos & Specials    Reply With Quote #3 (permalink)
Registered User
 
onboost's Avatar
 
Join Date: Mar 2006
Location: Metro DC
Posts: 5,319
Alrighty now.. since we're on the topic, guess I'll share some pics from a spare motor I purchased off a frustrated individual a couple years back.

Seems this guy thought he was up shifting and insted was down shifting at speed. I bought the grenaded motor for what was salvageable from it, and was able to scrounge some other pieces to use for my EFI build down the road.

Anyway these are photos of up shifting gone bad!







__________________
RGruppe #180
So many cars..so little time!!
Old 11-25-2007, 08:04 AM
  Pelican Parts Catalog | Tech Articles | Promos & Specials    Reply With Quote #4 (permalink)
Registered User
 
beepbeep's Avatar
 
Join Date: Jun 2001
Location: Sweden
Posts: 5,560
Quote:
Originally Posted by WERK-I View Post
Thanks Goran.
Looks like the piston is suffering from frost bite!
Interesting detonation effect. Did the spark plug electrode(s) suffer damage? It almost looks like there was a small object floating in the combustion chamber.
No, picks are all done by knocking...interesting enough.

As far as I know, engine is stock 931 engine borde to 87mm and fitted with custom JE pistons. CR is unknown to me but only one cylinder suffered.
__________________
Thank you for your time,
Old 11-25-2007, 11:58 PM
  Pelican Parts Catalog | Tech Articles | Promos & Specials    Reply With Quote #5 (permalink)
Registered User
 
BoxxerSix's Avatar
 
Join Date: Jun 2006
Location: Ballston Spa, NY
Posts: 528
I can say I have NEVER seen that happen from detonation or even pre-ignition. That to me looks like foreign object impact.....scratches in the dome of a piston from detonation????

That piston looks exactly like the JE pistons that were in a mazda miata motor
that ingested a speed loaders worth of toy bb gun ammo apon startup (speedloader fell into aircleaner and was not noticed). Search the mazda forums and you'll find that old post......

That to me looks like the piston dome was "shot peened" with nails............
__________________
Adam Hennessy
Old 11-26-2007, 10:55 AM
  Pelican Parts Catalog | Tech Articles | Promos & Specials    Reply With Quote #6 (permalink)
 
Registered User
 
Join Date: Dec 2005
Location: Atlanta, Georgia
Posts: 459
I tend to side with Adam, though further investigation is needed. The depth and total coverage of the marks look like something rattling around in the chamber. Not much carbon crust either. I wonder how the valves and cylinder dome looked?
__________________
87 930
96 BMW M3 Coupe
89 951
Peugeot moped
Old 11-26-2007, 11:16 AM
  Pelican Parts Catalog | Tech Articles | Promos & Specials    Reply With Quote #7 (permalink)
Registered User
 
BoxxerSix's Avatar
 
Join Date: Jun 2006
Location: Ballston Spa, NY
Posts: 528
Quote:
Originally Posted by William930t View Post
I tend to side with Adam, though further investigation is needed. The depth and total coverage of the marks look like something rattling around in the chamber. Not much carbon crust either. I wonder how the valves and cylinder dome looked?

Exactly. The bad injector causing the lean condition may have lead to part of the piston breaking off and causing that damage, but no way did the actual detonation shock wave do that. Preignition results in holes melted into the dome and ringland transitions. Detonation results in chunks/cracks/particles that can do the damaged pictured above....either that or some part of a(burnt) valve or plug electrode/ceramic, or foreign object ingestion.
__________________
Adam Hennessy
Old 11-26-2007, 11:26 AM
  Pelican Parts Catalog | Tech Articles | Promos & Specials    Reply With Quote #8 (permalink)
Me like track days
 
Craig 930 RS's Avatar
 
Join Date: Sep 2003
Location: Kirkland, WA
Posts: 10,196
Looks to me like a bit of ring or valve -
__________________
- Craig 3.4L, SC heads, 964 cams, B&B headers, K27 HF ZC turbo, Ruf IC. WUR & RPM switch, IA fuel head, Zork, G50/50 5 speed. 438 RWHP / 413 RWTQ -
"930 is the wild slut you sleep with who tries to kill you every time you "get it on" - Quote by Gabe
Movie: 930 on the dyno
Old 11-27-2007, 01:23 PM
  Pelican Parts Catalog | Tech Articles | Promos & Specials    Reply With Quote #9 (permalink)
Registered User
 
boxermania's Avatar
 
Join Date: Oct 2006
Location: Baton Rouge, LA
Posts: 143
beepbeep

I have seen that type damage before in both Porsches and other makes. The impingement on the top of the piston is not caused by detonation....it might have been precipitated by detonation....but that damage is caused by something that came loose, I would guess a piece of spark plug porcelain that just bounced of f the piston and the head until it finally broke appart.

Or, something came through the intake manifold and got past the intake valve.....is the head off the engine? What does it look like? If it looks the same, I rest my case.
__________________
Al Morales
77 911 S (930 steel conversion)
88 BMW M3
79 Honda CBX
Old 11-28-2007, 12:11 PM
  Pelican Parts Catalog | Tech Articles | Promos & Specials    Reply With Quote #10 (permalink)
Registered User
 
beepbeep's Avatar
 
Join Date: Jun 2001
Location: Sweden
Posts: 5,560
Just asked the owner what happened. He said that the piston knocked horribly and that damage was probably made by piece of piston itself that dislodged and bounced around in combustion chamber. He found molten aluminium in the headers and turbo as well...
__________________
Thank you for your time,
Old 11-28-2007, 12:18 PM
  Pelican Parts Catalog | Tech Articles | Promos & Specials    Reply With Quote #11 (permalink)
Wo ist die Rennstrecke?
 
DonE's Avatar
 
Join Date: Mar 2004
Location: Brooks, GA
Posts: 1,211
Quote:
Originally Posted by beepbeep View Post
No, picks are all done by knocking...interesting enough.

As far as I know, engine is stock 931 engine borde to 87mm and fitted with custom JE pistons. CR is unknown to me but only one cylinder suffered.
I have custom JE pistons and they don't look like that one. The pictured piston seems to have only 2 rings (top ring and oil ring), has a massive piston skirt (almost looks like a small diesel piston) and no cut-outs for valves.

Interesting.
Old 11-28-2007, 04:42 PM
  Pelican Parts Catalog | Tech Articles | Promos & Specials    Reply With Quote #12 (permalink)
Reply

Thread Tools
Rate This Thread
Rate This Thread:

 


All times are GMT -8. The time now is 03:38 PM.


 
Powered by vBulletin® Version 3.8.7
Copyright ©2000 - 2018, vBulletin Solutions, Inc.
Search Engine Optimization by vBSEO 3.6.0
Copyright 2018 Pelican Parts LLC - Posts may be archived for display on the Pelican Parts Website -    DMCA Registered Agent Contact Page
 

DTO Garage Plus vBulletin Plugins by Drive Thru Online, Inc.