Ausmini
It is currently Tue Jul 22, 2025 7:21 pm

Board index » Mini Chat » Mini Chat

All times are UTC + 10 hours




Post new topic Reply to topic  Page 1 of 1
  [ 14 posts ] 
  Print view Previous topic | Next topic 
Author Message
Diesel27
 Post subject: compression test
PostPosted: Sat Jul 26, 2014 7:05 pm 
Offline
848cc
848cc
User avatar

Joined: Sat Sep 21, 2013 9:47 pm
Posts: 324
Location: Melbourne West
just carried out a comp test and only have 120 psi, would have expected more?

_________________
It's easy once you know how.
Top
 Profile  
 
MiniVLT
 Post subject: Re: compression test
PostPosted: Sat Jul 26, 2014 7:42 pm 
Offline
848cc
848cc
User avatar

Joined: Wed Aug 10, 2011 9:01 pm
Posts: 376
Location: Burpengary Brissy Nth
Did you do the test with a warm or cold engine?

_________________
If it's not a Cooper S, the mini was designed to be modified!
Top
 Profile  
 
Morris 1100
 Post subject: Re: compression test
PostPosted: Sat Jul 26, 2014 7:44 pm 
Offline
Causing or creating vexation

Joined: Wed Jul 21, 2004 10:32 pm
Posts: 19124
120 is pretty normal on a stock motor.
Top
 Profile  
 
mini_mad_matt
 Post subject: Re: compression test
PostPosted: Sat Jul 26, 2014 8:45 pm 
Offline
1098cc
1098cc
User avatar

Joined: Tue Aug 05, 2008 8:03 pm
Posts: 1479
Location: Qld, Brisbane
I wouldn't be particularly concerned unless they varied a lot from cylinder to cylinder
Top
 Profile  
 
Monaco
 Post subject: Re: compression test
PostPosted: Sat Jul 26, 2014 9:36 pm 
Offline
998cc
998cc

Joined: Mon Jun 18, 2007 9:00 pm
Posts: 1127
Location: Down South
Depends on the gauge too. It is more the variance across the cylinders that is important. Did you have your foot flat on the accelerator pedal?
Top
 Profile  
 
Scoop
 Post subject: Re: compression test
PostPosted: Sat Jul 26, 2014 9:41 pm 
Offline
998cc
998cc

Joined: Mon Mar 10, 2014 11:38 am
Posts: 1143
Location: Tassie
Monaco wrote:
Depends on the gauge too. It is more the variance across the cylinders that is important. Did you have your foot flat on the accelerator pedal?

How does the accelerator pedal matter?

_________________
1963 Morris 850 Smoke Grey
1963 Morris 850 Shadow Blue
1965 Morris Mini Smooth Van
1966 Morris Mini Van
1969 Morris Mini Deluxe Resto
5/72 Clubman Gt
Top
 Profile  
 
Morris 1100
 Post subject: Re: compression test
PostPosted: Sat Jul 26, 2014 9:48 pm 
Offline
Causing or creating vexation

Joined: Wed Jul 21, 2004 10:32 pm
Posts: 19124
Scoop wrote:
Monaco wrote:
Depends on the gauge too. It is more the variance across the cylinders that is important. Did you have your foot flat on the accelerator pedal?

How does the accelerator pedal matter?

You need to accelerator open to get a proper compression reading.

It is hard to get compression from a vacuum.
Top
 Profile  
 
Convertible Mini
 Post subject: Re: compression test
PostPosted: Sun Jul 27, 2014 6:06 am 
Offline
1275cc
1275cc

Joined: Thu Dec 09, 2004 6:57 am
Posts: 3022
Location: JIMBOOMBA QLD.
You need Air to compress air!

_________________
DID I MENTION THAT I AM THE BEST SUPPLIER FOR MINI ELECTRICAL PARTS AND REPAIRS?
"Let us remove your "SHORTS"
Top
 Profile  
 
Scoop
 Post subject: Re: compression test
PostPosted: Sun Jul 27, 2014 10:07 am 
Offline
998cc
998cc

Joined: Mon Mar 10, 2014 11:38 am
Posts: 1143
Location: Tassie
So your saying no air enters the engine if you dont have the accelerator open. Or just not enough for the compression test.

_________________
1963 Morris 850 Smoke Grey
1963 Morris 850 Shadow Blue
1965 Morris Mini Smooth Van
1966 Morris Mini Van
1969 Morris Mini Deluxe Resto
5/72 Clubman Gt
Top
 Profile  
 
Irish Yobbo
 Post subject: Re: compression test
PostPosted: Sun Jul 27, 2014 11:47 am 
Offline
1098cc
1098cc
User avatar

Joined: Mon Apr 06, 2009 9:02 am
Posts: 1233
Location: Sandy Bay, Tasmania
Scoop wrote:
So your saying no air enters the engine if you dont have the accelerator open. Or just not enough for the compression test.


The butterfly is almost closed to restrict air down to idle speed, so less air.

For an accurate reading you will want a strong battery and a foot on the accelerator. You're supposed to do it with a warm engine too.

If you get a low reading, put some oil in the cylinder and try again. If the compression jumps up dramatically, your rings are worn.

I would say that 120 is a little on the low side, but it's not reconditioning territory yet.. A new modern engine (which has a good starting system and higher compression ratio) will read about 200psi, my mini reads ~145psi (998 with no mods).
Top
 Profile  
 
Diesel27
 Post subject: Re: compression test
PostPosted: Sun Jul 27, 2014 12:34 pm 
Offline
848cc
848cc
User avatar

Joined: Sat Sep 21, 2013 9:47 pm
Posts: 324
Location: Melbourne West
cheers Irish that is what I wanted to hear.
120 compared with 145,

_________________
It's easy once you know how.
Top
 Profile  
 
smac
 Post subject: Re: compression test
PostPosted: Sun Jul 27, 2014 5:08 pm 
Offline
1098cc
1098cc
User avatar

Joined: Fri Aug 26, 2005 1:03 pm
Posts: 1540
Location: Napier, NZ
Diesel27 wrote:
cheers Irish that is what I wanted to hear.
120 compared with 145,

Which could just be the difference between two gauges.

_________________
http://www.mini-hb.co.nz
Top
 Profile  
 
Morris 1100
 Post subject: Re: compression test
PostPosted: Sun Jul 27, 2014 5:23 pm 
Offline
Causing or creating vexation

Joined: Wed Jul 21, 2004 10:32 pm
Posts: 19124
smac wrote:
Diesel27 wrote:
cheers Irish that is what I wanted to hear.
120 compared with 145,

Which could just be the difference between two gauges.

Could almost be the difference between brands of head gaskets. :lol:
Top
 Profile  
 
MiniBob
 Post subject: Re: compression test
PostPosted: Fri Aug 01, 2014 1:03 pm 
Offline
998cc
998cc
User avatar

Joined: Wed Mar 02, 2005 2:05 pm
Posts: 1084
Location: Manly NSW
Compression is also reliant on good valve seal / adjustment.
If there is a bit of carbon present or the tappets need doing then the figure will be lower.

_________________
'98 Mpi Sportspack + 7 port alloy head
Top
 Profile  
 
Display posts from previous:  Sort by  
Post new topic Reply to topic  Page 1 of 1
  [ 14 posts ] 

Board index » Mini Chat » Mini Chat

All times are UTC + 10 hours


Who is online

Users browsing this forum: cjm_007 and 66 guests

You cannot post new topics in this forum
You cannot reply to topics in this forum
You cannot edit your posts in this forum
You cannot delete your posts in this forum
You cannot post attachments in this forum

Jump to:  

© 2016 Ausmini. All garage work involves equal measures of enthusiasm, ingenuity and a fair degree of irresponsibility.