The Subaru SVX World Network   SVX Network Forums
Live Chat!
SVX or Subaru Links
Old Lockers
Photo Post
How-To Documents
Message Archive
SVX Shop Search
IRC users:

Go Back   The Subaru SVX World Network > SVX Main Forums > MOD Mania > Other Mods

Reply
 
Thread Tools Display Modes
  #16  
Old 12-15-2004, 08:16 PM
THAWA
Guest
 
Posts: n/a
well to put something in the jacket and not disrupt flow would be a physical impossibility. It's probable to do it with minimal disruptance. And yes Closing the deck is possible. Dunno how reliable it is though.
Reply With Quote
  #17  
Old 12-15-2004, 08:26 PM
Wreckless
Guest
 
Posts: n/a
So has anyone been having trouble with headgaskets, blocks or cylinder walls at elevated power levels?
Reply With Quote
  #18  
Old 12-15-2004, 08:35 PM
THAWA
Guest
 
Posts: n/a
I think a better question would be, who is at elevated power levels
Reply With Quote
  #19  
Old 12-15-2004, 08:47 PM
SVXer95 SVXer95 is offline
Word to Yo Motha
 
Join Date: Dec 2002
Location: Valparaiso, IN
Posts: 1,637
Send a message via AIM to SVXer95
Quote:
Originally posted by mohrds


er, not exactly.

compression ratio formula is:

(one cylinder swept volume + deck cc + head cc)/(deck cc + head cc)

If you are increasing the volume (cylinder swept volume) it will alter the compression ratio.

Granted the change will be minimal, but it will change.

Doug
Duh...I'm stupid. For some reason I was thinking simple cycle engine examples from thermodynamics. Didn't take into account deck and head volumes...
__________________
Collin

1995 L AWD
Locker

1987 Porsche 944 turbo
80k miles. MBC + Chips. Relatively Stock
Reply With Quote
  #20  
Old 12-15-2004, 08:48 PM
SVXer95 SVXer95 is offline
Word to Yo Motha
 
Join Date: Dec 2002
Location: Valparaiso, IN
Posts: 1,637
Send a message via AIM to SVXer95
Quote:
Originally posted by tomssvx
so is there any way for us to convert to closed deck? Is it as simple to make supports without disrupting coolant flow?
I know people have converted to a semi-closed deck using some sort of epoxy filler. I would have to do some research to find details though.
__________________
Collin

1995 L AWD
Locker

1987 Porsche 944 turbo
80k miles. MBC + Chips. Relatively Stock
Reply With Quote
  #21  
Old 12-15-2004, 11:29 PM
UberRoo's Avatar
UberRoo UberRoo is offline
SVX Appeal
 
Join Date: Feb 2004
Location: Puget Sound, Washington
Posts: 843
Typically, I believe a deck is closed by welding the gap between the cylinder walls and the exterior of the block. Another method is to cut spacers from a piece of metal and press them into place.

I don't like either of these methods. The welding method seems like it would put enormous stresses on the block due to thermal expansion during the welding process. Perhaps there is a way to relieve these stresses, or perhaps it is welded with the whole block heated to a high temperature. ...or maybe it just isn't a problem. I would think it would be a fairly major concern.

The spacer method seems inadequate. Cutting adequately sized spacers accurately enough to provide even support would be very, very challenging. It does however seem like it would result in lower stresses to the block and cylinder walls.

To the best of my understanding, the primary (or only) reason to close the deck is because the cylinders tend to vibrate back and forth against the head gasket and this causes head gasket failures. This is the problem the professional Subaru rally teams encounter first. If reducing this vibration is the problem, the spacer method would be fairly straightforward and adequate.

Disrupting the coolant flow isn't really an issue unless the coolant/oil ports in the head are blocked. Placing the spacers or welds slightly lower in the block or simply putting holes in them is sufficient.

oab_au is right about cylinder sleeves. They can shift and don't have a large effect on strength. In the scenario where vibration is the primary problem, sleeves wouldn't do anything at all. A new sleeve would need to be quite thick to add any strength. You'd probably have to loose quite a bit of displacement to gain anything worthy of the trouble. The solution to preventing the sleeves from walking away from the head is to bore the cylinder a few millimeters shy of the bottom, leaving a lip for the sleeve to set on, (or over-boring the top and leaving a lip on the sleeve to hang from.)

Personally, I believe all the fittings between the block and the head should be flare fittings with crushable washers, including the cylinders themselves. Expensive, but bullet-proof.

I don't know as much about the methods, consequences, and advantages to closing the deck as I'd like to. From what I've gathered, even the experts really don't know much about it. Many believe it weakens the block or simply does nothing. Some people swear by it, and some just think it helps a little tiny bit or is only important in the most extreme circumstances. If anyone has more input on this, I'm curious. There's a lot a speculation around this subject.



Regarding how increasing the bore might affect compression ratio; in the SVX it will, but only by a very small amount. This is directly related to the combustion chamber volume (volume inside when the piston is at TDC.) If this volume does not increase with the increase in bore, the compression ratio will increase.

Because the combustion chamber volume is primarily in the cylinder head dome, increasing the cylinder bore will not have a large effect on the combustion chamber volume. If the piston had a concave top and was replaced with a larger piston with a larger concave top, this would tend to keep the compression ratio the same as before.

The only way to reduce compression ratio is to increase the combustion chamber volume by increasing the size of the cylinder head dome or making the piston head concave (or just a little shorter.)
__________________
1994 LSi, Laguna Blue SVX Appeal
1992 LS-L, Ebony Pearl SVX-Rated
UberLocker
Reply With Quote
  #22  
Old 12-15-2004, 11:54 PM
Phast SVX's Avatar
Phast SVX Phast SVX is offline
BOOOOOOOOOOOOOOOOOST
 
Join Date: Feb 2001
Location: Madison, WI
Posts: 2,800
Send a message via AIM to Phast SVX
Re: reducing the swept volume?

Quote:
Originally posted by oab_au
Boring and then sleeving the block will change the ratio. But why? You will then need different pistons, so why not use a piston with a lower ratio, and leave the block as it is. Boring and sleeving will leave the block weaker than it is now.

The liners are cast in, they can't move, pressed sleeves can and do.

Harvey.
i was thinking more in terms of a brace, a "blockguard" adapter as many hondas used(in their fully open deck alum block) in turbo applications that we do.
phil
__________________
~Phil
Teal 1992 Subaru SVX Turbo - Sold in May 2011 to peace-frog.
Reply With Quote
  #23  
Old 12-15-2004, 11:56 PM
Phast SVX's Avatar
Phast SVX Phast SVX is offline
BOOOOOOOOOOOOOOOOOST
 
Join Date: Feb 2001
Location: Madison, WI
Posts: 2,800
Send a message via AIM to Phast SVX
Re: Re: reducing the swept volume?

Quote:
Originally posted by Phast SVX


i was thinking more in terms of a brace, a "blockguard" adapter as many hondas used(in their fully open deck alum block) in turbo applications that we do.
phil
http://www.prostreetonline.com/buy/r...g_block_guard/
__________________
~Phil
Teal 1992 Subaru SVX Turbo - Sold in May 2011 to peace-frog.
Reply With Quote
  #24  
Old 12-16-2004, 02:40 AM
SilverSpear's Avatar
SilverSpear SilverSpear is offline
Still 1.7K to go...
Subaru Silver Contributor
 
Join Date: Oct 2004
Location: Lebanon, Middle East
Posts: 7,563
Send a message via AIM to SilverSpear Send a message via MSN to SilverSpear Send a message via Skype™ to SilverSpear
Registered SVX
Quote:
Originally posted by mohrds


It could, but realistically not.

In order to decrease compression, the sleeve would have to be thinner than the amount you bore the cylinder out. You start boring that much and you'll probably get into some coolant passages.

Doug
I was thinking more of slightly larger diameter pirtons. they won't even get near the water passages... can it lower the compression?
__________________
Danny

1994 Silver SVX in hybernation, awaiting for the monsterous awakening (Lebanon)
1967 Mercedes-Benz 250SL Euro Specs, Hard/Softtop, White/Red. Under Complete Restoration
2013 Mercedes-Benz SL350 Euro Specs, White/Red. Mint... Another step into SL Collection.
Reply With Quote
  #25  
Old 12-16-2004, 02:45 AM
SilverSpear's Avatar
SilverSpear SilverSpear is offline
Still 1.7K to go...
Subaru Silver Contributor
 
Join Date: Oct 2004
Location: Lebanon, Middle East
Posts: 7,563
Send a message via AIM to SilverSpear Send a message via MSN to SilverSpear Send a message via Skype™ to SilverSpear
Registered SVX
Quote:
Originally posted by SVXer95

You still wouldn't change compression ratio by changing bore. The volumes would be different, but the ratio would stay the same. CR is a affected by height/length of the combustion chamber, not volume of diameter.

When a small glass is half empty a big glass of the same height is half empty, but with more beer.
man but the pressure made from burned fuel would disperse in a larger volume, so the pressure on say 1 cubic inch space is greater than say 1.1 cubic inch space, so the compression on 1.1 is lower than that of 1. isn't it logical???
__________________
Danny

1994 Silver SVX in hybernation, awaiting for the monsterous awakening (Lebanon)
1967 Mercedes-Benz 250SL Euro Specs, Hard/Softtop, White/Red. Under Complete Restoration
2013 Mercedes-Benz SL350 Euro Specs, White/Red. Mint... Another step into SL Collection.
Reply With Quote
  #26  
Old 12-16-2004, 03:58 AM
SilverSpear's Avatar
SilverSpear SilverSpear is offline
Still 1.7K to go...
Subaru Silver Contributor
 
Join Date: Oct 2004
Location: Lebanon, Middle East
Posts: 7,563
Send a message via AIM to SilverSpear Send a message via MSN to SilverSpear Send a message via Skype™ to SilverSpear
Registered SVX
guys I was thinking of something, if stroking an engine will make the metal gap between piston chamber and water passages thinner. this in fact will heat up the engine more than usual and will cause its wear to happen quicker... unless proper cooling is adjusted to this mod.
Is there by any chance a way to upgrade the water pump to spin quicker same as upgrading the turbo bearings to spin more...???
__________________
Danny

1994 Silver SVX in hybernation, awaiting for the monsterous awakening (Lebanon)
1967 Mercedes-Benz 250SL Euro Specs, Hard/Softtop, White/Red. Under Complete Restoration
2013 Mercedes-Benz SL350 Euro Specs, White/Red. Mint... Another step into SL Collection.
Reply With Quote
  #27  
Old 12-16-2004, 07:38 AM
mohrds's Avatar
mohrds mohrds is offline
Fight Eminent Domain Abuse!
 
Join Date: Mar 2001
Location: Milwaukee, WI
Posts: 3,175
Send a message via AIM to mohrds Send a message via Yahoo to mohrds
Quote:
Originally posted by SVXer95

Duh...I'm stupid. For some reason I was thinking simple cycle engine examples from thermodynamics. Didn't take into account deck and head volumes...
No Prob. If you search on my old posts, you will see many instances where I forgot things ranging from engineering to basic math.

Doug
__________________
1992 LS Touring (6/91) - Currently undergoing a five speed swap
Black over Claret with spoiler; 235,000 miles; Mods: 2002 Legacy 5 speed, ACT Pressure Plate, Excedy Clutch, Short Throw Shifter, Aussie Powerchip
1992 LS Touring (6/91)
Black over Claret with 2.5" setback spoiler; 202,000 miles; Mods: B&M Cooler
1994 LSi (4/93)
Bordeaux Pearl; 198,000 miles; Mods: Weight reduction.

1969 Mustang GT Convertible
1970 Mustang Convertible
2000 Ford Excursion
Sola lingua bona est lingua mortua.

My Locker
Reply With Quote
  #28  
Old 12-16-2004, 07:46 AM
SVXer95 SVXer95 is offline
Word to Yo Motha
 
Join Date: Dec 2002
Location: Valparaiso, IN
Posts: 1,637
Send a message via AIM to SVXer95
Quote:
Originally posted by mohrds


No Prob. If you search on my old posts, you will see many instances where I forgot things ranging from engineering to basic math.

Doug
Yeah...it happens. The funny part is that I was completely convinced that I was correct.
__________________
Collin

1995 L AWD
Locker

1987 Porsche 944 turbo
80k miles. MBC + Chips. Relatively Stock
Reply With Quote
  #29  
Old 12-16-2004, 07:51 AM
mohrds's Avatar
mohrds mohrds is offline
Fight Eminent Domain Abuse!
 
Join Date: Mar 2001
Location: Milwaukee, WI
Posts: 3,175
Send a message via AIM to mohrds Send a message via Yahoo to mohrds
Quote:
Originally posted by SilverSpear


I was thinking more of slightly larger diameter piton's. they won't even get near the water passages... can it lower the compression?
What are the consequences of using a custom built head spacer? I was thinking that if you lengthen the intake runners to accommodate it, you would have to re-tune the iris system, but it may be a good way to lower compression.

Just a morning coffee thought.

Doug
__________________
1992 LS Touring (6/91) - Currently undergoing a five speed swap
Black over Claret with spoiler; 235,000 miles; Mods: 2002 Legacy 5 speed, ACT Pressure Plate, Excedy Clutch, Short Throw Shifter, Aussie Powerchip
1992 LS Touring (6/91)
Black over Claret with 2.5" setback spoiler; 202,000 miles; Mods: B&M Cooler
1994 LSi (4/93)
Bordeaux Pearl; 198,000 miles; Mods: Weight reduction.

1969 Mustang GT Convertible
1970 Mustang Convertible
2000 Ford Excursion
Sola lingua bona est lingua mortua.

My Locker
Reply With Quote
  #30  
Old 12-16-2004, 08:46 AM
SVXer95 SVXer95 is offline
Word to Yo Motha
 
Join Date: Dec 2002
Location: Valparaiso, IN
Posts: 1,637
Send a message via AIM to SVXer95
Quote:
Originally posted by mohrds


What are the consequences of using a custom built head spacer? I was thinking that if you lengthen the intake runners to accommodate it, you would have to re-tune the iris system, but it may be a good way to lower compression.

Just a morning coffee thought.

Doug
I think it would be easier to do a custom intake. While the IRIS system makes for good low end, the power increase from a turbo or s/c would more than make up for it.

After looking at the pics of LAN's intake cutting and welding, it looks very difficult to make modifications to the stock intake because of the flowpath and shape of the runners. If you don't want to mess with internals, I think this woould be a great way to do it.
__________________
Collin

1995 L AWD
Locker

1987 Porsche 944 turbo
80k miles. MBC + Chips. Relatively Stock
Reply With Quote
Reply

Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off

Forum Jump


All times are GMT -6. The time now is 02:35 PM.


Powered by vBulletin® Version 3.8.7
Copyright ©2000 - 2024, vBulletin Solutions, Inc.
© 2001-2015 SVX World Network
(208)-906-1122