[DeTomaso] efi horse power gain

JDeRyke at aol.com JDeRyke at aol.com
Tue Aug 11 15:59:01 EDT 2009


In a message dated 8/11/09 8:02:16 AM, kirby.schrader at gmail.com writes:

> I have no idea how each cylinder's vacuum pulse can cancel out each 
> other. That
> means one pulse would be negative (vacuum) and the other positive 
> (pressure).....
> 
Correct- the strong pulses going back & forth thru an IR manifold are 
indeed positive and negative, as the pressure wave oscillates between the intake 
valve and the ram-tube top. As one intake opens and starts a negative wave 
downward, the preceding cylinder has just closed and starts a positive wave 
back out. I found the net from combining cylinders is zero. It's so prevalent 
that experts suggest using a fairly long piece of rubber tubing to connect 
a single intake port to a vacuum advance, so the rubber's normal pliability 
will dampen the pulses. Using metal lines is the worst- as I found. My 
vacuum with Webers wouldn't accumulate until I added a check valve like is in the 
power brake booster. But maybe the rules change with EFI- dunno; haven't 
tried it yet. FWIW- J Deryke



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