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  #31  
Old 05-30-2012, 04:13 PM
bazza bazza is offline
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Re: Increasing Compression

Quote:
Originally Posted by Dessertrunner View Post
Two questions
If shaving the head is the way to go how much needs to be shave to increase it to 14:1.

Does any one know were to get the piston if thats the way to go.

Harvey the higher compression is for the race car.
Tony
Sps pistons in melbs
Cp in USA

Will do whatever you wish after you send em your stock piston for base. $$$$ though
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  #32  
Old 05-30-2012, 05:38 PM
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icingdeath88 icingdeath88 is offline
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Re: Increasing Compression

Quote:
Originally Posted by bazza View Post
Sps pistons in melbs
Cp in USA

Will do whatever you wish after you send em your stock piston for base. $$$$ though
CP pistons doesn't need a base any more, they have done enough EG33 pistons by now.
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  #33  
Old 05-30-2012, 06:16 PM
bazza bazza is offline
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Re: Increasing Compression

Quote:
Originally Posted by icingdeath88 View Post
CP pistons doesn't need a base any more, they have done enough EG33 pistons by now.
Indeed, however you only get sub 10:1 compression pistons for their on file designs.
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  #34  
Old 05-30-2012, 07:11 PM
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Dessertrunner Dessertrunner is offline
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Re: Increasing Compression

baza,
You may not know but I am building a engine dyno so at the end of the day it will be easier for me to shave the head and that way I can play around with different compression ratios.

So guys how much do I need to shave off?

Tony
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1995 - SVX 700,000 K Mine, DMS Struts to lift car 2in. Tyres Wrangler Silent Armor 235/70R16, PBR Radiator. 6 speed with DCCD and R180 rer diff, Heavy duty top strut mounts front and rear. Speedo correction box fitted. New stero (gave up on the old one). Back seat removed and 2 spare tyres fitted for desert driving. ECUTune SC sitting in the box for the next SVX.
1992 - SVX 255 K Wife (Want to stay Married so not allowed to fit SC)
1992 - SVX Pearl with black roof race car roll cauge etc ready to race. Ex Tasman Targa car.
1995 - SVX Green low k mint condiation.
1995 - SVX Rally car, ex Matts car. Now to be used on track.
1992 - SVX red & Black being converted to Mid Engine.
1995 - SVX Red 143,000 bit rough.
Owned 5 others Subaru back to a 1974 1400 GSR.
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  #35  
Old 05-30-2012, 07:20 PM
bazza bazza is offline
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Re: Increasing Compression

Quote:
Originally Posted by Dessertrunner View Post
baza,
You may not know but I am building a engine dyno so at the end of the day it will be easier for me to shave the head and that way I can play around with different compression ratios.

So guys how much do I need to shave off?

Tony
What a top idea. Have you got a thread detailing this build, I'd be very interested
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  #36  
Old 05-30-2012, 07:59 PM
oab_au oab_au is offline
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Re: Increasing Compression

Quote:
Originally Posted by Dessertrunner View Post
baza,
You may not know but I am building a engine dyno so at the end of the day it will be easier for me to shave the head and that way I can play around with different compression ratios.

So guys how much do I need to shave off?

Tony
Tony you need to remove 18.5cc from the clearence volume.
Removing the 0.060" head geaket will only drop it 1.87cc.

Harvey.
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Last edited by oab_au; 05-30-2012 at 11:40 PM. Reason: If I didn't fix the metric/Imperial fault. Tom would.
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  #37  
Old 05-30-2012, 07:59 PM
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Re: Increasing Compression

here,
http://www.subaru-svx.net/forum/showthread.php?t=54640

I have been as "flat out as a lizard drinking" over the last year but plan to get back to it soon. I have worked out soluations in my head.
Tony
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1995 - SVX 700,000 K Mine, DMS Struts to lift car 2in. Tyres Wrangler Silent Armor 235/70R16, PBR Radiator. 6 speed with DCCD and R180 rer diff, Heavy duty top strut mounts front and rear. Speedo correction box fitted. New stero (gave up on the old one). Back seat removed and 2 spare tyres fitted for desert driving. ECUTune SC sitting in the box for the next SVX.
1992 - SVX 255 K Wife (Want to stay Married so not allowed to fit SC)
1992 - SVX Pearl with black roof race car roll cauge etc ready to race. Ex Tasman Targa car.
1995 - SVX Green low k mint condiation.
1995 - SVX Rally car, ex Matts car. Now to be used on track.
1992 - SVX red & Black being converted to Mid Engine.
1995 - SVX Red 143,000 bit rough.
Owned 5 others Subaru back to a 1974 1400 GSR.
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  #38  
Old 06-01-2012, 04:09 PM
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Dessertrunner Dessertrunner is offline
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Re: Increasing Compression

Okay some rough numbers.

3,318 Litre
6 Cyclinder
97 mm Bore
7.3928 Area of piston

Target compression Final Volume Difference MM to Shave
Current 10 55
11 50 5 0.680
12 46 9 1.247
13 43 13 1.726
14 40 16 2.137
15 37 18 2.493


I think there maybe mistakes so if so please yell.
Tony
__________________
1995 - SVX 700,000 K Mine, DMS Struts to lift car 2in. Tyres Wrangler Silent Armor 235/70R16, PBR Radiator. 6 speed with DCCD and R180 rer diff, Heavy duty top strut mounts front and rear. Speedo correction box fitted. New stero (gave up on the old one). Back seat removed and 2 spare tyres fitted for desert driving. ECUTune SC sitting in the box for the next SVX.
1992 - SVX 255 K Wife (Want to stay Married so not allowed to fit SC)
1992 - SVX Pearl with black roof race car roll cauge etc ready to race. Ex Tasman Targa car.
1995 - SVX Green low k mint condiation.
1995 - SVX Rally car, ex Matts car. Now to be used on track.
1992 - SVX red & Black being converted to Mid Engine.
1995 - SVX Red 143,000 bit rough.
Owned 5 others Subaru back to a 1974 1400 GSR.
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  #39  
Old 06-02-2012, 12:41 AM
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Dessertrunner Dessertrunner is offline
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Re: Increasing Compression

Here is some more info,


It might make more sense in the JPG.
Spoke to the guys with the cam pullies and they allow plus & minus 12degree adjustment. According to my calcs if you were to run 15:1 the left bank would need 7.8 degree of adjustment.

Okay were am I at.

Shave heads is the only way to go because I have a lot of heads and I can experment with different compression ratio with little effort. I can just put them in my cnc mill and plan them off. The pullies will enable adjustments simply.

Have a great day all.
Tony
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1995 - SVX 700,000 K Mine, DMS Struts to lift car 2in. Tyres Wrangler Silent Armor 235/70R16, PBR Radiator. 6 speed with DCCD and R180 rer diff, Heavy duty top strut mounts front and rear. Speedo correction box fitted. New stero (gave up on the old one). Back seat removed and 2 spare tyres fitted for desert driving. ECUTune SC sitting in the box for the next SVX.
1992 - SVX 255 K Wife (Want to stay Married so not allowed to fit SC)
1992 - SVX Pearl with black roof race car roll cauge etc ready to race. Ex Tasman Targa car.
1995 - SVX Green low k mint condiation.
1995 - SVX Rally car, ex Matts car. Now to be used on track.
1992 - SVX red & Black being converted to Mid Engine.
1995 - SVX Red 143,000 bit rough.
Owned 5 others Subaru back to a 1974 1400 GSR.

Last edited by Dessertrunner; 06-02-2012 at 12:54 AM.
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  #40  
Old 06-02-2012, 12:55 AM
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Dessertrunner Dessertrunner is offline
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Re: Increasing Compression

detail of calcs
Attached Images
File Type: jpg Shaved head calcs.jpg (183.7 KB, 185 views)
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1995 - SVX 700,000 K Mine, DMS Struts to lift car 2in. Tyres Wrangler Silent Armor 235/70R16, PBR Radiator. 6 speed with DCCD and R180 rer diff, Heavy duty top strut mounts front and rear. Speedo correction box fitted. New stero (gave up on the old one). Back seat removed and 2 spare tyres fitted for desert driving. ECUTune SC sitting in the box for the next SVX.
1992 - SVX 255 K Wife (Want to stay Married so not allowed to fit SC)
1992 - SVX Pearl with black roof race car roll cauge etc ready to race. Ex Tasman Targa car.
1995 - SVX Green low k mint condiation.
1995 - SVX Rally car, ex Matts car. Now to be used on track.
1992 - SVX red & Black being converted to Mid Engine.
1995 - SVX Red 143,000 bit rough.
Owned 5 others Subaru back to a 1974 1400 GSR.
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  #41  
Old 06-02-2012, 07:54 PM
oab_au oab_au is offline
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Re: Increasing Compression

Quote:
Originally Posted by Dessertrunner View Post
Okay some rough numbers.

3,318 Litre
6 Cyclinder
97 mm Bore
7.3928 Area of piston

Target compression Final Volume Difference MM to Shave
Current 10 55
11 50 5 0.680
12 46 9 1.247
13 43 13 1.726
14 40 16 2.137
15 37 18 2.493


I think there maybe mistakes so if so please yell.
Tony
Tony yes there is a problem with those numbers. You are assuming that the combustion chamber is a cylinder, so that each 0.5mm shaved will result in a reduction of 3.7cc, but the chamber is not round, it is a flat sided oval, so the cut of 0.5mm of the chamber, won’t yield 3.7cc, it will be a lot less.
You would need to cc the chamber to see what volume that shaved 0.5mm would be.

Harvey.
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Tell it like it is!

95 Lsi. Bordeaux Pearl, Aust. RHD.149,000Kls Subaru BBS wheels.
97 Liberty GX Auto sedan. 320,000Kls.
04 Liberty 30R Auto Premium. 92.000kls.
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  #42  
Old 06-02-2012, 08:21 PM
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Dessertrunner Dessertrunner is offline
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Re: Increasing Compression

Good point Harvey you are right.

Do you agree with the basic Logic on timing adjustment or did I get that wrong.
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1995 - SVX 700,000 K Mine, DMS Struts to lift car 2in. Tyres Wrangler Silent Armor 235/70R16, PBR Radiator. 6 speed with DCCD and R180 rer diff, Heavy duty top strut mounts front and rear. Speedo correction box fitted. New stero (gave up on the old one). Back seat removed and 2 spare tyres fitted for desert driving. ECUTune SC sitting in the box for the next SVX.
1992 - SVX 255 K Wife (Want to stay Married so not allowed to fit SC)
1992 - SVX Pearl with black roof race car roll cauge etc ready to race. Ex Tasman Targa car.
1995 - SVX Green low k mint condiation.
1995 - SVX Rally car, ex Matts car. Now to be used on track.
1992 - SVX red & Black being converted to Mid Engine.
1995 - SVX Red 143,000 bit rough.
Owned 5 others Subaru back to a 1974 1400 GSR.
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  #43  
Old 06-02-2012, 09:05 PM
oab_au oab_au is offline
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Re: Increasing Compression

Quote:
Originally Posted by Dessertrunner View Post
Good point Harvey you are right.

Do you agree with the basic Logic on timing adjustment or did I get that wrong.
Yes that is the way the timing will change. Looking at the timing belt, if it is all set to the marks, and the heads are moved in towards the crank, the adjuster will pull the belt slack down, rotating both pulleys anticlockwise, the right will move twice as far.

Harvey.
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One Arm Bloke.
Tell it like it is!

95 Lsi. Bordeaux Pearl, Aust. RHD.149,000Kls Subaru BBS wheels.
97 Liberty GX Auto sedan. 320,000Kls.
04 Liberty 30R Auto Premium. 92.000kls.
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  #44  
Old 06-19-2012, 08:57 PM
dynomatt dynomatt is offline
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Re: Increasing Compression

Admittedly it has direct injection, which allows a higher compression ratio, but the latest Subaru BRZ/Toyota 86 has a boxer Subaru engine with 12.5:1 compression. Might be a target for you Tony? Or are you already past 12.5?

Matt
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  #45  
Old 06-19-2012, 09:55 PM
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Dessertrunner Dessertrunner is offline
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Re: Increasing Compression

I want to go higher Matt, good pice of info. You got to wonder if they can get away then would E85 or direction injection be more likly to be able to go higher compression.
Tony
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1995 - SVX 700,000 K Mine, DMS Struts to lift car 2in. Tyres Wrangler Silent Armor 235/70R16, PBR Radiator. 6 speed with DCCD and R180 rer diff, Heavy duty top strut mounts front and rear. Speedo correction box fitted. New stero (gave up on the old one). Back seat removed and 2 spare tyres fitted for desert driving. ECUTune SC sitting in the box for the next SVX.
1992 - SVX 255 K Wife (Want to stay Married so not allowed to fit SC)
1992 - SVX Pearl with black roof race car roll cauge etc ready to race. Ex Tasman Targa car.
1995 - SVX Green low k mint condiation.
1995 - SVX Rally car, ex Matts car. Now to be used on track.
1992 - SVX red & Black being converted to Mid Engine.
1995 - SVX Red 143,000 bit rough.
Owned 5 others Subaru back to a 1974 1400 GSR.
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