Date:         Sat, 18 Sep 2010 17:18:56 -0700
Reply-To:     Scott Daniel - Turbovans <scottdaniel@TURBOVANS.COM>
Sender:       Vanagon Mailing List <vanagon@gerry.vanagon.com>
From:         Scott Daniel - Turbovans <scottdaniel@TURBOVANS.COM>
Subject:      Re: actual numerical readings off Compression test?
Comments: To: Don Hanson <dhanson928@gmail.com>
Content-Type: text/plain; charset="iso-8859-1"

re
And what kind of PSI are people commonly getting from compression tests on various motors? 

the spec for an ABA is 145 to 189 psi with a wear limit of 109 psi.

so expect possibly more than that ..
my WAG is you have around 170 psi in most cylinders...wildly guestimating for your higer CR but also it's not a fresh very new engine.  

about CR ..
I'd only worry about if it pings or not.
got it  though ..that you might not be able to hear it back there with your muffler etc.

just lug the snot out of it once ..
give it a lot of throttle at say only 1,800 rpm in a high-ish gear ..
that'll make it ping. 
then tweak back on timing until it's very hard to make it ping, if it'll act that way. 

and no timing light at all ?
there are  many good uses for a timing light besides just checking timing , it's silly not to have  a basic inductive one. 

have you ever read early smoggy carbed Rabbits will run better if the cam is retarded a bit ? 
  ----- Original Message ----- 
  From: Don Hanson 
  To: Scott Daniel - Turbovans 
  Cc: vanagon@GERRY.VANAGON.COM 
  Sent: Saturday, September 18, 2010 4:50 PM
  Subject: actual numerical readings off Compression test?


    Here's one..

  how does a fellow or a gal determine the compression ratio of a motor?  I've been thinking to take a reading with my compression tester,  then divide that by the barometric pressure.  Is that correct?  And what kind of PSI are people commonly getting from compression tests on various motors?  Does anyone have any actual numbers scrawled in the back pages of their Bently books?

    This is in aid of trying to determine the CR of my "new" inline four 'Franken-mouse' motor..with 1.8liter head on top of a 2.0 liter block and a pretty stout headgasket from a specialty tuning shop..  I am not so sure I will hear it if it is detonating, way back there and with my magnaflow exhaust system kinda buzzy.  If my ECU gets "knocking" signals from the sensor and adjusts the spark back always, I will probably need more octane.  If I know the number I can decide without really guessing too much.

    Don Hanson