[SEL] One for the mathematicians out there :-)

[Pete Alleman]

A compression ratio of 19:1 should produce pressures of about 19 bar.

Pete.


"Jerry Evans" <jerrye at databak.co.za> wrote:

>Hi All,
>    It's Friday afternoon here and this ole brain refuses to work this 
>problem out :-)
>
>         I want to do a compression test on a small aircooled Chinese 
>Diesel engine and need to modify a normal auto tester to do this.
>
>Here are the details that I have:
>         i) Compression ratio is 19:1
>         ii)Bore×stroke [mm] - 86×70
>         ii)Displacement[Lit]  - 0.406
>     iii)Rated power/speed(kW/r/min) 5.7/3000  6.3/3600 (not necessary 
>for the calculation but included for interest sake)
>
>
>         Or, if you prefer it in Imperial Measurements:
>         i) Compression ratio is 19:1
>         ii)Bore X Stroke (ins.) - 3.386" X 2.756" (As Near As Dammit)
>         iii) Displacement[Cub. ins] - 24.77564
>    iv)(Horsepower = 7.6 H.P. at 3000 rpm to 8.4 H.P. at 3600rpm (again, not 
>necessary for the calculation but included for interest sake).
>
>         What I need to know is what the pressure should read on my 
>compression tester (either in Bar, KG per Sq CM or Lbs per Sq. Inch).
>
>         The piston is flat topped but the head has a smallish domed 
>combustion chamber but for these calculations I would think that it is
>O.K. 
>to call it  flat (I realise that this would make the answer greater but
>I 
>only need to be close).
>
>    Alternatively someone may just know what the reading should be and 
>you don't need to do all this maths on a Friday afternoon :-)
>
>       I want to do the tests tomorrow morning so would appreciate any 
>answers in the next 12 hours please. Bear in mind also that I only get
>the 
>SEL Digest version which is due in about the next 1 1/2 hours so if you
>are 
>reading this on the SEL List please copy the mail to me "Off List" at
>the 
>address above. - Old engine list members do not need to do this. (He
>gets 
>pushy now as well !!!)
>
>         Thanks in advance guys.
>
>Keep the revs up (or down)
>Jerry Evans
>Near Johannesburg in Sunny South Africa.
>Etched Brass Engine Plates made to order:
><www.oldengine.org/members/evans/plates/index.htm>  
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-- 
Pete Alleman
pja at ralph.lafayette.la.us
Lafayette, Louisiana USA