Spreadsheet Tool for Calculating Compression, etc.
#1104430
10/31/11 01:24 AM
10/31/11 01:24 AM
|
Joined: Dec 2010
Posts: 392
Mississippi
lahatte
OP
enthusiast
|
OP
enthusiast
Joined: Dec 2010
Posts: 392
Mississippi
|
I had posted this (see attachement) in another thread, but I thought people might find it useful. It gives you compression ratios, both static and dynamic (based on intake opening angle), and some other useful info. If you find it useful, great, If you find it to be crap, well, let me know. 
Last edited by lahatte; 11/02/11 03:33 AM.
|
|
|
Re: Spreadsheet Tool for Calculating Compression, etc.
[Re: lahatte]
#1104431
10/31/11 11:44 AM
10/31/11 11:44 AM
|
Joined: Oct 2007
Posts: 4,206
New York
polyspheric
master
|
master
Joined: Oct 2007
Posts: 4,206
New York
|
Very nice work, thanks.
If you will permit, an observation?
1.4 is a bit optimistic for the heat expansion ratio. It's always going to be slightly lower depending on heat lost from the chamber and cylinder walls which as you can imagine varies quite a bit with water temp, exposed area, material, etc.
Boffin Emeritus
|
|
|
Re: Spreadsheet Tool for Calculating Compression, etc.
[Re: mr_340]
#1104435
11/01/11 07:53 AM
11/01/11 07:53 AM
|
Joined: Nov 2003
Posts: 3,428
Dandridge TN
Dabee
master
|
master
Joined: Nov 2003
Posts: 3,428
Dandridge TN
|
Quote:
I couldn't download it for some reason. If the 1.4 number is the ratio of specific heats (as in the Otto cycle efficiency), then I remember my combustion engines professor at UT telling us sometimes using 1.3 is a better number to use. I think the 1.4 number is for pure air instead of the air/fuel mixture. 
My Norton software says the file is corrupt. 
|
|
|
Re: Spreadsheet Tool for Calculating Compression, etc.
[Re: lahatte]
#1104436
11/01/11 04:51 PM
11/01/11 04:51 PM
|
Joined: Jan 2003
Posts: 16,925
NC
440Jim
I Live Here
|
I Live Here
Joined: Jan 2003
Posts: 16,925
NC
|
Quote:
...dynamic (based on intake opening angle
Thanks for sharing.
The spreadsheet needs intake valve closing for dynamic calc.
What cam event should we use? 0.050", 0.020", actual lash (ex/0.022") ?
|
|
|
Re: Spreadsheet Tool for Calculating Compression, etc.
[Re: 440Jim]
#1104438
11/01/11 08:07 PM
11/01/11 08:07 PM
|
Joined: Feb 2005
Posts: 4,314
Prospect, PA
BSB67
master
|
master
Joined: Feb 2005
Posts: 4,314
Prospect, PA
|
Quote:
Quote:
...dynamic (based on intake opening angle
Thanks for sharing.
The spreadsheet needs intake valve closing for dynamic calc.
What cam event should we use? 0.050", 0.020", actual lash (ex/0.022") ?
Although I cannot open the attachment, I struggle with this same question on all of the Dynamic CR formulae that I've looked at as they are not clear. Is it actual seat timing?, or at 0.004" or 0.005" or 0.006" like hydraulic advertised?, or 0.050" @ the lifter?, or valve?
I measure and record all of these (and more) at the lifter, the valve, and at different lash settings. The few times I've plugged the values in to some DCR formulae, I question the results relative to the rule of thumb on what is acceptable for pump gas.
|
|
|
Re: Spreadsheet Tool for Calculating Compression, etc.
[Re: 440Jim]
#1104440
11/01/11 08:34 PM
11/01/11 08:34 PM
|
Joined: Dec 2010
Posts: 392
Mississippi
lahatte
OP
enthusiast
|
OP
enthusiast
Joined: Dec 2010
Posts: 392
Mississippi
|
Regarding the intake valve closing, it is based on the number specified by the manufacturer as the ABDC closing, as in this example... http://www.compcams.com/Company/CC/cam-specs/Details.aspx?csid=708&sb=2Because compression can't truely begin until the intake valve is closed, I assume the number should refer to the actual degrees where the valve shuts, or very close to it. A cam spec expert might want to chime in on the intended meaning of that number in the specifications.
Last edited by lahatte; 11/01/11 08:41 PM.
|
|
|
Re: Spreadsheet Tool for Calculating Compression, etc.
[Re: lahatte]
#1104441
11/01/11 08:55 PM
11/01/11 08:55 PM
|
Joined: Jul 2005
Posts: 512
Illinois
Mopar_Ray
mopar
|
mopar
Joined: Jul 2005
Posts: 512
Illinois
|
Quote:
Strange the attachment is just an Excel 2003 file that was zipped so I could attach it. I'll try again here...
Try just attaching the excel file...don't zip it and it it will probably work.
|
|
|
Re: Spreadsheet Tool for Calculating Compression, etc.
[Re: lahatte]
#1104442
11/01/11 09:08 PM
11/01/11 09:08 PM
|
Joined: Feb 2005
Posts: 4,314
Prospect, PA
BSB67
master
|
master
Joined: Feb 2005
Posts: 4,314
Prospect, PA
|
Quote:
Regarding the intake valve closing, it is based on the number specified by the manufacturer as the ABDC closing, as in this example...
http://www.compcams.com/Company/CC/cam-specs/Details.aspx?csid=708&sb=2
Because compression can't truely begin until the intake valve is closed, I assume the number should refer to the actual degrees where the valve shuts, or very close to it. A cam spec expert might want to chime in on the intended meaning of that number in the specifications.
i.e. 0.006" measured at the lifter.
|
|
|
|
|
