Board Logo
Go To Bottom

Printable Version  
[ Total Views: 901 | Total Replies: 18 | Thread Id: 92009 ]
Author: Subject:  Compression Ratio
Memberjaksc
Officially Full-On Dubber
***


Avatar


Posts: 236
Threads: 49
Registered: January 12th, 2005
Member Is Offline

Location: Central Coast
Theme: UltimaBB Pro Blue ( Default )

posted on August 7th, 2011 at 06:51 AM
Compression Ratio


I'm having a go at screwing together a 1776 for everday use. What compression ratio do i need to run. Doing the measurements it is currently at 9:1. How do i go about raising it or lowering it. Thanks Aaron
MemberPaulc1964au
Custom Title Time!
*****


Avatar


Posts: 1627
Threads: 59
Registered: March 5th, 2010
Member Is Offline

Location: Sydney, NSW
Theme: UltimaBB Pro Blue ( Default )

posted on August 7th, 2011 at 08:05 AM



Am Interested to see if u r happy with the 1776 why have you selected a 1776



Memberhellbugged
A.k.a.: Daimo Pell
23 Windows of Awesome
48's and straight cuts
********


Avatar


Posts: 5080
Threads: 116
Registered: April 17th, 2003
Member Is Offline

Location: Nambucca Valley NSW
Theme: UltimaBB Psyche Blue
Mood: Couldn't care less

posted on August 7th, 2011 at 08:07 AM



was it just a displacment change or other things as well?
Memberjaksc
Officially Full-On Dubber
***


Avatar


Posts: 236
Threads: 49
Registered: January 12th, 2005
Member Is Offline

Location: Central Coast
Theme: UltimaBB Pro Blue ( Default )

posted on August 7th, 2011 at 11:03 AM



Had a 1776 built afew years ago by a reputed vw specialist. Had too much end float movement from when it was built. Had about 1000miles on it. Stripped it down and couldn't find anyone to put it back together. Lots of brand new parts. So having a go myself. just need to be pointed in the right direction. Aaron
Memberhellbugged
A.k.a.: Daimo Pell
23 Windows of Awesome
48's and straight cuts
********


Avatar


Posts: 5080
Threads: 116
Registered: April 17th, 2003
Member Is Offline

Location: Nambucca Valley NSW
Theme: UltimaBB Psyche Blue
Mood: Couldn't care less

posted on August 7th, 2011 at 12:16 PM



So it's stockfish or big cam, heads etc?

Counterweighted balanced?
Memberhellbugged
A.k.a.: Daimo Pell
23 Windows of Awesome
48's and straight cuts
********


Avatar


Posts: 5080
Threads: 116
Registered: April 17th, 2003
Member Is Offline

Location: Nambucca Valley NSW
Theme: UltimaBB Psyche Blue
Mood: Couldn't care less

posted on August 7th, 2011 at 12:17 PM



And how have you worked out the c.r?
Memberjaksc
Officially Full-On Dubber
***


Avatar


Posts: 236
Threads: 49
Registered: January 12th, 2005
Member Is Offline

Location: Central Coast
Theme: UltimaBB Pro Blue ( Default )

posted on August 7th, 2011 at 12:26 PM



Basically stock. Aaron
Memberhellbugged
A.k.a.: Daimo Pell
23 Windows of Awesome
48's and straight cuts
********


Avatar


Posts: 5080
Threads: 116
Registered: April 17th, 2003
Member Is Offline

Location: Nambucca Valley NSW
Theme: UltimaBB Psyche Blue
Mood: Couldn't care less

posted on August 7th, 2011 at 02:06 PM



spacers under the barrels or "flycutting' the heads or combo of both
Memberjaksc
Officially Full-On Dubber
***


Avatar


Posts: 236
Threads: 49
Registered: January 12th, 2005
Member Is Offline

Location: Central Coast
Theme: UltimaBB Pro Blue ( Default )

posted on August 7th, 2011 at 05:13 PM



What compression ratio do i need? Aaron
Memberjaksc
Officially Full-On Dubber
***


Avatar


Posts: 236
Threads: 49
Registered: January 12th, 2005
Member Is Offline

Location: Central Coast
Theme: UltimaBB Pro Blue ( Default )

posted on August 8th, 2011 at 08:22 PM



Anyone with some tech advice on what ratio I should use. What does it depend on.
Super ModeratorBizarre
Super Moderator
The artist formerly known as blue74l
*******

Rank Avatar

Avatar


Posts: 12757
Threads: 732
Registered: August 25th, 2002
Member Is Offline

Location: Abbotsford, Sydney
Theme: UltimaBB Pro Blue ( Default )

posted on August 8th, 2011 at 09:04 PM



low 8's??

9 is a tad high for a stockish motor - but what would I know

It all depends on the cam, heads, valve size, deck height and a whole heap of experience.

Did you cc the heads??




Futue te ipsum!!!
MemberOllie
A.k.a.: Ollie Clarke
Insano Dub Head
Yeah Buddy
****


Avatar


Posts: 840
Threads: 122
Registered: October 5th, 2009
Member Is Offline

Location: Sydney
Theme: UltimaBB Streamlined2
Mood: Hungry for another 676cc

posted on August 9th, 2011 at 11:31 AM



Go 14.5:1 and you'll just love it :)

I lie.

As all above have mentioned, A good strong engine is the sum of it's parts, rather than one standout performance enhancement.

IMO a stockish 1776 would benefit from somewhere between 8 and 8.5:1 compression. It should give it that extra zap without causing too much stress to the engine.

That said, I could be so far wrong It's not funny!

Ollie




Follow the Photo Fun:
http://forums.aussieveedubbers.com/viewtopic.php?tid=95238 

- '70 1500 Beetle (The Clean One)
- '76 1300 Beetle (The In-between One)
- '69 1500 Beetle (The Mean One)
MemberBiX
Veteran Volks Folk
*****


Avatar


Posts: 2499
Threads: 154
Registered: September 2nd, 2002
Member Is Offline

Location: Brisbane
Theme: UltimaBB Pro Blue ( Default )

posted on August 9th, 2011 at 01:43 PM



My old 1776 with stock bottom end, mild port and polish and W100 cam had about 8.5/9 ish.

But in the end, that was selected by the engine builder based on the engine combo.




I have no sympathy for my car, only the wallet that pays for it!
Go hard or go home!!!!
Memberjaksc
Officially Full-On Dubber
***


Avatar


Posts: 236
Threads: 49
Registered: January 12th, 2005
Member Is Offline

Location: Central Coast
Theme: UltimaBB Pro Blue ( Default )

posted on August 9th, 2011 at 06:09 PM



I worked out the ratio by
cyl volume + head volume + deck height volume
_______________________________________
head volume + deck volume
Stroke = 69mm
I am getting confused. Am i going to to much trouble. Just bolt the barrels down and forget about it. Thanks Aaron
Super ModeratorBizarre
Super Moderator
The artist formerly known as blue74l
*******

Rank Avatar

Avatar


Posts: 12757
Threads: 732
Registered: August 25th, 2002
Member Is Offline

Location: Abbotsford, Sydney
Theme: UltimaBB Pro Blue ( Default )

posted on August 9th, 2011 at 08:40 PM



check your answer against this calculator

http://www.aircooled.net/gnrlsite/resource/specgeninfo/calcs.htm 

We are just saying 9 is on the high side
You could put a small spacer under the barrels or open the heads up a bit
The spacer mucks you deck height up and that mucks "squish" up

You could whack it all together and see what happens - you might just have to run 98 octane to keep pinging at bay




Futue te ipsum!!!
MemberGracey
Wolfsburg Wizard
***


Avatar


Posts: 511
Threads: 17
Registered: February 6th, 2003
Member Is Offline

Location: Beaudesert, Qld
Theme: UltimaBB Pro Blue
Mood: Itchy

posted on August 9th, 2011 at 09:14 PM



Impossible to say without knowing what cam you've got.
Memberjaksc
Officially Full-On Dubber
***


Avatar


Posts: 236
Threads: 49
Registered: January 12th, 2005
Member Is Offline

Location: Central Coast
Theme: UltimaBB Pro Blue ( Default )

posted on August 10th, 2011 at 07:01 PM



Bizarre, I used the calculator and came up with a figure of 8:1 ratio. I think I am going to go with just bolting everything up as is. There was a lot more involved to this topic than I thought. Thanks for the help guys. Aaron
MemberRISKY4LIFE
Officially Full-On Dubber
***


Avatar


Posts: 308
Threads: 5
Registered: July 4th, 2010
Member Is Offline

Theme: UltimaBB Pro Blue ( Default )

posted on August 10th, 2011 at 07:26 PM



i think that you could run upto 8.5 for every day use if it was built right
but im no engine builder!
Super ModeratorBizarre
Super Moderator
The artist formerly known as blue74l
*******

Rank Avatar

Avatar


Posts: 12757
Threads: 732
Registered: August 25th, 2002
Member Is Offline

Location: Abbotsford, Sydney
Theme: UltimaBB Pro Blue ( Default )

posted on August 10th, 2011 at 09:08 PM



jus go for it and see what happens

Only way to learn :tu:




Futue te ipsum!!!


  Go To Top


Powered by GaiaBB, © 2011 The GaiaBB Group
(C) 2001-2024 Aussieveedubbers

[ Queries: 40 ] [ PHP: 2.6% - SQL: 97.4% ]