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  #16  
Old 11-08-2003, 07:13 PM
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Quote:
Originally posted by wawazat??


Ok, first pistons are aluminum, not steel NikFu. Second you can forge aluminum like you can forge steel. It's a production method that utilizes massive amounts of pressure to form a cold metallic slug or billet into a roughly shaped part. This part is then machined to final dimensions. Casting starts witha molten metal which is poured in to a mold that approximates final shape, allowed to cool, and then machined into its final dimensions. Forging is typically stronger due to a more uniform grain structure in the base metal. Casting produces a random grain stucture and can introduce porosity (bad!) into the part.

Todd
innnnnnput.

i could swear that the pitsons were steel. i thought i had a crack in my block early this year so i did a lot of research because someone said cast engines cant be repaired, yet forged ones can, and i remember being relieved at finding everything was forged. also i didnt have a cracked block.

but coming from me its just hearsay. i dont usually expect to have to PROVE anything.
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  #17  
Old 11-08-2003, 08:19 PM
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Quote:
Originally posted by NikFu S.


innnnnnput.

i could swear that the pitsons were steel. i thought i had a crack in my block early this year so i did a lot of research because someone said cast engines cant be repaired, yet forged ones can, and i remember being relieved at finding everything was forged. also i didnt have a cracked block.

but coming from me its just hearsay. i dont usually expect to have to PROVE anything.
The pistons in our cars are most definitely aluminum. The engine block is aluminum with steel cylinder liners.
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  #18  
Old 11-08-2003, 08:26 PM
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hence the term "all alluminum flat-6"
phil
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  #19  
Old 11-08-2003, 08:29 PM
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i never heard the term.
whats a cylinder liner?
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  #20  
Old 11-08-2003, 09:03 PM
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Nik,
Think of a metal can with both ends cut out that has been press fit down into each aluminum cylinder. Fairly common with aluminum block engines, as they provide a harder surface for the piston rings to run/seal against. I think the Cogsworth aluminum 4 cylinder may have run without steel liners...then again, Chevy put it in Vegas
=Bill
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  #21  
Old 11-08-2003, 09:21 PM
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data logged.
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  #22  
Old 11-10-2003, 07:52 AM
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Quote:
Originally posted by SVXRide


Todd,
So, are you going to put this conversation to rest by providing "ground truth" with actual parts?
-B
One of these days Bill.

I need some specialized tools for further dis-assembly of the short block. I need more $$$ to buy those tools, and that's the issue right now. I've got a block that SVX10 helped me disassamble this summer. Not much left on it/in it other than rods, pistons, and crank.

I spent time reviewing my SVX document library this weekend and looking at cutaway pictures of the EG33. MOST show the connecting rods as having large parting lines indicative of the forging process. SOME show a thinner parting line indicative of the casting process. Nowhere could I find a statement detailing the construction method of the rods. The crank is forged according to the FHI and SOA literature I have.

Todd
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  #23  
Old 11-10-2003, 11:09 AM
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Quote:
Originally posted by Phast SVX
pistons are cast, cobb however offers forged versions Crank and rods are all forged. Right todd?
phil
I just got off the phone with Cobb Tuning, and their numerous observations of the stock pistons are that they are cast, so Phil is right. Cobb also said the crank and rods are forged. Its kind of a bummer that Subaru didn't forge the pistons too. It makes it much more difficult to boost the car to worthwhile levels without damaging the pistons.
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  #24  
Old 11-10-2003, 11:19 AM
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Todd,
Specialized tools ? Other than a piston ring compressor, I don't remember ever having to buy any specialized tools when I rebuilt my small block chevy engine
-Bill
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  #25  
Old 11-10-2003, 12:52 PM
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Quote:
Originally posted by mbtoloczko


I just got off the phone with Cobb Tuning, and their numerous observations of the stock pistons are that they are cast, so Phil is right. Cobb also said the crank and rods are forged. Its kind of a bummer that Subaru didn't forge the pistons too. It makes it much more difficult to boost the car to worthwhile levels without damaging the pistons.

Does this mean I win the "are they cast or forged?" pool?
I figured maybe cost would rear its ugly head somewhere in the engine. Go figure...10:1 compression and they run cast pistons
-B
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  #26  
Old 11-10-2003, 01:08 PM
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Quote:
Originally posted by SVXRide
Todd,
Specialized tools ? Other than a piston ring compressor, I don't remember ever having to buy any specialized tools when I rebuilt my small block chevy engine
-Bill
Yup, specialized tools required

BTW-I've still got my ring compressor from when I re-built my 327 Chebby small-block back in 1987, Bill.
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  #27  
Old 11-10-2003, 01:12 PM
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Quote:
Originally posted by SVXRide



Does this mean I win the "are they cast or forged?" pool?
I figured maybe cost would rear its ugly head somewhere in the engine. Go figure...10:1 compression and they run cast pistons
-B
I think Phil wins the pool. He said it first.

The cast pistons are not a project stopper. It will just require more aggresive techniques for keeping the cylinder temps down. Water injection with an intercooler (and a stand-alone ecu) will be the key to a reliable motor with worthwhile boost levels. I've been doing some reading on WI, and it sounds like just the ticket for this application. Both the heat capacity and the heat of vaporization of water are much much larger than gasoline. This means that cylinder temps can be brought down and a more optimum a/f ratio can be acheived while still keeping the cylinder temps down (and preventing detonation). From what I've read, about a 10% increase in HP is possible in a boosted motor just from moving the a/f ratio closer to 12.5:1 vs the more typical 11:1 for turbo applications.
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  #28  
Old 11-10-2003, 01:41 PM
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Water Injection also raises the compression a little, since water doesn't compress. It was a common thing on WWII fighters.

- Rob
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  #29  
Old 11-10-2003, 01:55 PM
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Quote:
Originally posted by mbtoloczko


I just got off the phone with Cobb Tuning, and their numerous observations of the stock pistons are that they are cast, so Phil is right. Cobb also said the crank and rods are forged. Its kind of a bummer that Subaru didn't forge the pistons too. It makes it much more difficult to boost the car to worthwhile levels without damaging the pistons.
we must take it into consideration, but we must also remember that our engine cools INCREDIBLY well, i also dont think its a project stopper, just needs addressing, and until we get an actual turbo kit and can get an EGT reading we will not know what kind of temp's were working with. Also our engine, reguardless of the cast/forge is of high quality and meticulous design.

As we say in Wi-Sconsin, "Dis is Just ona them things eh? "

phil
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  #30  
Old 11-10-2003, 02:28 PM
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When I spoke with Cobb Tuning this morning, they felt that the max acheiveable boost with the stock pistons was around 5-6 psi, contingent upon using an intercooler. I chatted with them at length about the boost potential, and according to them, the situation with the SVX is very similar to the 2.5RS. Both are 10:1 CR motors, and the piston design is fairly similar. The two main failures that occur are 1) the high cylinder temps resulting from the very high pressures due to the 10:1 CR cause the edge of the piston to melt away, and 2) the high cylinder pressures, especially if detonation occurs, causes the ring lands to break. They weren't terribly excited about WI, but they felt an IC was definitely necessary.
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:: 2006 Silver Mitsubishi Evolution 9, E85, 34 psi peak, 425wtq/505whp DJ ::
1995 Laguna Blue SVX L AWD 5MT (sold)

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SVX Mods: ND iridium spark plugs, Impreza RS fpr, afr tuned to 13.2:1 using a custom MAF bypass, custom exhaust, WRX 5MT w/ STi RA 1st-4th gear & stock WRX 5th gear, Exedy 13 lb flywheel & Sport Clutch, STi Group N tranny & engine mounts, urethane spacers in rear subframe, rear diff mounts, and pitch stopper, SVX Sport Strut Springs (185f/150r), custom 19 mm rear swaybar, urethane swaybar mounts, Rota Torque 17x8", 225/45-17 Proxes 4 tires, Axxis Deluxe Plus organic brake pads.
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