Large displacement engines & fuel economy

[George M. Dailey]

At 01:44 PM 1/24/97 -0500, you wrote:
>Here's an idea/thought I've been kicking around for awhile and wanted to 
>see what others thought about it:

>
>I don't know how frequently the Cadillac system cuts out cylinders, or how
>many it cuts out in a given firing sequence, but couldn't this idea be
>applied to a large displacement port-fuel injected motor?  In other words,
>to conserve fuel, cut out a cylinder in every firing sequence (but make
>the cut-out cylinder a different one each time so no cylinder gets cut out
>twice in a row). 
>

You still have the parastic loss of the dead cylinder still compressing the
air within it.  If you could stop the inlet and exhaust valves from opening,
you could dramatically reduce the dead cylinder resistance. Some early
caddys did just this. The system is remembered as junk. The Modulated
Displacement Engine they called it. It did meet the objective of having good
steady state fuel economy. 


>I don't know what kind of effect this would have on RPM stability, or 
>engine smoothness (hopefully not too bad), but is this a feasible 
>alternative so that you can have your cake and eat it, too?  You get all 
>of the advantages of extra ci at WOT, and you don't have the gas guzzling 
>at part throttle.
>
>Obviously, this is something that we can only do via a custom programmed 
>EFI system (like EFI332), but would it work?
>
>Comments?
>
>-Jody
>-- 
>http://www.token.net/~jshapiro/z28/

The best power/effiency setup would be a medium compression (9-1), medium
displacement (3L), engine with a low boost (<8lbs/in2) intercooled
turbocharger and an overdrive tranny. The higher compression ratio would
give you good economy under (no to low) boost. Medium displacement would
keep rotating mass at a minimum but not cause a power lag on the bottom end.
The low boost intercooled turbo would provide the high torque. The tranny
would be geared low for the first and second gears for performance.  The
overdrive would provide steady state economy.

Boost and high comp go together like Cryps and Bloods. This will require low
intercooled boost and water injection to controol detonation. 

My home built car will have a power trane that meets all of these specs.
This is very doable and proven to work.

GMD