[Diy_efi] crankcase vacuum control

[Dave Dahlgren]

10 to 15 inches seems to be the average amounts of vac with a SBC.. I would not
use that as a rule for everything though. Like nitrous again a little is good
and a lot just breaks parts. If it were a new combination engine wise I think i
would play with it on the dyno and see where the curve starts to trail off and
stop just before that point. the first rebuild would come early as well to see
how the splash lube parts are holding up as well. This is mostly done on drag
race stuff where the time between rebuilds is short. On an endurance engine you
do need oilers for the pins and a dry sump system as well. This vacuum pump
thing is not as new as everyone would lead you to believe anyway. If you have
ever seen a Cosworth dry sump pump the scavenge stages are roots type rotors and
very large so they have been doing it for decades. The next time we have an old
DF series Cosworth on the dyno i will see if i can sneak a gauge on the
crankcase somewhere and see what it pulls for vacuum for laughs. might have some
idea from that point as to what an DOHC endurance engine can live with. I am
sure they spent a ton of time and money coming up with optimum numbers for their
engines.
Dave Dahlgren
Engine Management Systems

Adam Wade wrote:
> 
> --- Dave Dahlgren <ddahlgren at snet.net> wrote:
> 
> <snip>
> 
> I'm wondering how one would get a ballpark estimate of
> what, if any, positive effect it would have, and what
> would be an optimal amount of vacuum.  Of course trial
> and error is the way to be sure, but can it be roughly
> calculated to give one starting points?
>


_______________________________________________
Diy_efi mailing list
Diy_efi at diy-efi.org
http://www.diy-efi.org/mailman/listinfo/diy_efi