Assuming the engine has 100% VE... you are correct.
What if his magical aluminum head is so fly it allows his engine to have
more than 100% volumetric efficiency? Let's say he is getting 250 psi.
11.5 * 17 * VE = 250
VE = 250/195.5
VE = 127%
That seems awful high for a Naturally Aspirated Motor! My theory?
Compression gauge has probs. Double check your gauge on another motor. My
backup theory if the gauge checks out. Whoever built the engine was a diesel
mechanic and forgot he was working on a gas engine!
CR * 17 * 1 = 250
CR = 250/17
CR = 14.7:1 !! Actually kinda low for a diesel!
Toby
69 Sprite
-----Original Message-----
From owner-spridgets at autox.team.net
[mailto:owner-spridgets@autox.team.net]On Behalf Of frogeye
Sent: Thursday, November 01, 2001 2:56 PM
To: Larry & Sandi Miller; spridgets@autox.team.net
Subject: Re: How Much Compression Is Too Much?
11.5 x 17(or whatever atmospheric pressure is at your locale) =195.5 It does
not compute. Check your gauge.
Dave@Taos Garage Annex in Albuquerque
'59 AH :{) '54 BN1
----- Original Message -----
From "Larry & Sandi Miller" <millerls at ado13.com>
To: <spridgets@autox.team.net>
Sent: Thursday, November 01, 2001 3:16 PM
Subject: How Much Compression Is Too Much?
> Finally got around to doing a compression test on the 1275 Bugeye engine.
I
> used one of the rubber tipped gauges that you just press into the spark
plug
> hole and hold it there while you crank the engine. After two or three
> revolutions I can't hold the gauge in the hole, it just blows out with a
> loud pop. All four cylinders read around 250 lbs and might read higher if
I
> could hold the gauge in. Guess I will go down and buy one of the screw-in
> types and try to get a better reading.
>
> It really puts out a puff of air while cranking with all plugs removed. It
> is strong enough to move your hand when you hold it in front of the plug
> hole.
>
> This seems awful high to me. The guy that built the engine (I purchased as
> is) told me that the CR was 11.5-1.
>
> The engine is supposed to be 50 over with flat top pistons. It also has an
> aluminum head. I have not had the engine apart.
>
> Any thoughts?
>
> Larry Miller
|