Welcome! Please use the navigational links to explore our website.
PartsASAP LogoCompany Logo (800) 853-2651

Shop Now

   Allis Chalmers Case Farmall IH Ford 8N,9N,2N Ford
   Ferguson John Deere Massey Ferguson Minn. Moline Oliver

Attention Forum Users: On the 28th of December 2023 at 9:00am Central Time, we will be taking the forums down for maintenance while we prepare the new forums for your use. Please click here for more information.

Massey Harris & Massey Ferguson Tractors Discussion Forum
:

Compression ration to PSI Formula

Welcome Guest, Log in or Register
Author 
George in Mi

11-20-2003 16:36:43




Report to Moderator

Anybody know, offhand, what the conversion for compression ration to PSI is? Had it somewhere, but can't find it. Hope that's clear, I mean the PSI corresponding to numbers in the ration. That is, in a 7:1 ration, how many pounds for each of the numbers in the seven.

Thanks

George




[Log in to Reply]   [No Email]
Jerry/MT

11-20-2003 18:23:15




Report to Moderator
 Re: Compression ration to PSI Formula in reply to George in Mi, 11-20-2003 16:36:43  
As I recall, the equation is p2/p1 = (v1/v2)exp1.4, where v1/v2 is the compression ratio, 1.4 is the specific heat ratio for air at 59 oF and p2/p1 is the pressure ratio assuming and isentropic compression. For a compression ratio of 7.0, p2/p1 =12.245 and at p1=14.7 psia, p2= 224.1 psia. You won't see this on your compression guage, though. Remember the valves are not closed for the full compression stroke and there are pressure losses in the induction system (air cleaner, carb, intake manifold, and intake valve.) Hope this helps.

[Log in to Reply]  [No Email]
Gavin M

11-21-2003 02:35:29




Report to Moderator
 Re: Re: Compression ration to PSI Formula in reply to Jerry/MT, 11-20-2003 18:23:15  
Sounds about right. Also assumes ideal gas behavior, which is reasonable for air, totally wrong for the fuel. At an A/F ratio of say 10:1 there is about a 9% volumetric (ideal gas) concentration of fuel, which will bias the compression test result lower unless the carb is off the engine. There is some dependancy of Cp/Cv on temperature. The "Compression Ratio" is not that at all, it is a measure of volume ratio, not pressure. As such the pressure losses (volumetric efficiency) will affect the amount of cylinder filling, as Jerry/MT said.

[Log in to Reply]  [No Email]
[Options]  [Printer Friendly]  [Posting Help]  [Return to Forum]   [Log in to Reply]

Hop to:


TRACTOR PARTS TRACTOR MANUALS
We sell tractor parts!  We have the parts you need to repair your tractor - the right parts. Our low prices and years of research make us your best choice when you need parts. Shop Online Today. [ About Us ]

Home  |  Forums


Copyright © 1997-2023 Yesterday's Tractor Co.

All Rights Reserved. Reproduction of any part of this website, including design and content, without written permission is strictly prohibited. Trade Marks and Trade Names contained and used in this Website are those of others, and are used in this Website in a descriptive sense to refer to the products of others. Use of this Web site constitutes acceptance of our User Agreement and Privacy Policy

TRADEMARK DISCLAIMER: Tradenames and Trademarks referred to within Yesterday's Tractor Co. products and within the Yesterday's Tractor Co. websites are the property of their respective trademark holders. None of these trademark holders are affiliated with Yesterday's Tractor Co., our products, or our website nor are we sponsored by them. John Deere and its logos are the registered trademarks of the John Deere Corporation. Agco, Agco Allis, White, Massey Ferguson and their logos are the registered trademarks of AGCO Corporation. Case, Case-IH, Farmall, International Harvester, New Holland and their logos are registered trademarks of CNH Global N.V.

Yesterday's Tractors - Antique Tractor Headquarters

Website Accessibility Policy