General Miata Chat A place to talk about anything Miata

Compression ratio questions

Thread Tools
 
Search this Thread
 
Old 11-18-2007 | 03:30 PM
  #1  
brgracer's Avatar
Thread Starter
Senior Member
iTrader: (14)
 
Joined: Nov 2004
Posts: 1,275
Total Cats: 1
From: Ambler, PA
Question Compression ratio questions

Since I am not an engine builder, just wanted to make sure that my calculations are not completely off as I am toying with some ideas.

1) Since shaving the head increases compression (according to Randy from solomiata 10 thousands shave = approximately a 0.25 compression ratio bump), then I assume that either slightly taller pistons (whether from increased compression height pistons or piston coatings) would also bump compression accordingly? But is the effect of a 10 thousands inch head shave = 10 thousands inch increase in compression height assuming all other things are equal?

2) Again, assuming that you have enough clearance to keep the pistons clear of the valves, is the only other major consideration of increased compression dealing with the additional heat and corresponding increased likelihood of detonation or are there other issues? (Assuming that the increased compression is with taller pistons, not a head shave which I know can affect timing.)

3) Within reason, if you can control the heat/detonation, higher compression should produce more power and earlier spool with all other things being equal?
Old 11-18-2007 | 07:39 PM
  #2  
jif's Avatar
jif
Junior Member
 
Joined: Mar 2007
Posts: 49
Total Cats: 0
From: Auckland, NZ
Default

not sure about more power, but everything else in #3 looks right.

BTW - dynamic compression:
http://lh5.google.com/jifjif/R0DLrOA...tcompRatio.jpg
Old 11-18-2007 | 08:29 PM
  #3  
Rafa's Avatar
Elite Member
iTrader: (22)
 
Joined: Dec 2006
Posts: 3,224
Total Cats: 3
From: Sunny Spanish speaking Non US Caribbean
Default

Originally Posted by jif
not sure about more power, but everything else in #3 looks right.

BTW - dynamic compression:
http://lh5.google.com/jifjif/R0DLrOA...tcompRatio.jpg
This is the message from your link: "Google
Error


Forbidden
Your client does not have permission to get URL /1.1 from this server."
Old 11-18-2007 | 08:38 PM
  #4  
y8s's Avatar
y8s
DEI liberal femininity
iTrader: (8)
 
Joined: Jun 2005
Posts: 19,338
Total Cats: 574
From: Fake Virginia
Default

Old 11-19-2007 | 04:31 AM
  #5  
jif's Avatar
jif
Junior Member
 
Joined: Mar 2007
Posts: 49
Total Cats: 0
From: Auckland, NZ
Default

nice wk y8s ... graph courtesy of Randy @ solomiata.com naturally ...

googling "boostcompratio" gets some interesting results too ...

Last edited by jif; 11-19-2007 at 04:33 AM. Reason: attribution
Old 11-19-2007 | 10:01 AM
  #6  
brgracer's Avatar
Thread Starter
Senior Member
iTrader: (14)
 
Joined: Nov 2004
Posts: 1,275
Total Cats: 1
From: Ambler, PA
Default

Thanks y8s, I saw that chart. Again, just making sure that heat is the major consideration. So you either run less boost or cool the charge really well a la e-cool/pc-pro (haha)?
Old 11-19-2007 | 10:49 AM
  #7  
y8s's Avatar
y8s
DEI liberal femininity
iTrader: (8)
 
Joined: Jun 2005
Posts: 19,338
Total Cats: 574
From: Fake Virginia
Default

detonation will occur at any temperature given enough compression (dynamic or otherwise). though usually only in labs. like in a variable compression engine used for determining a fuel's octane rating.
Related Topics
Thread
Thread Starter
Forum
Replies
Last Post
Full_Tilt_Boogie
Build Threads
84
04-12-2021 05:21 PM
bigmackloud
Miata parts for sale/trade
19
01-08-2021 12:24 PM
Quinn
Cars for sale/trade
6
10-23-2016 08:58 AM
JesseTheNoob
DIY Turbo Discussion
15
09-30-2015 03:44 PM
zephyrusaurai
Meet and Greet
2
09-28-2015 11:59 PM




All times are GMT -4. The time now is 06:24 AM.