DIY_EFI Digest V4 #436

[Charles Brooks]

Hi Dan, I'm nearly certain that the Float will have to be replaced or modified so id doesn't crush under boost. I'm slowly putting parts together for a twin turbocharged small block Chevy (And I'm selling a complete single turbo system for a SBC to finance the TT project, if anyones interested contact me off list) and one gentleman I ran into showed me a float from a 2bbl Holley that was on his Turbo Ford 2.3, the float looked like someone had stuck a straw in it and sucked REALLY hard :)

You do have to reference the regulator off of boost however, if you run more boost than the pump itself can handle...  The home grown turbo projects I've seen have been on V8's and used a mechanical pump that was modified to accept a manifold pressure reference. The Holley Mech. pumps are easily disassembled for the mods. I'm not sure if you could use a high pressure EFI pump with a low pressure regulator or not. If you do, make sure the regulator is a 3 port (Or more) design that has a bypass for fuel to return to the tank. That way the fuel flow will cool the EFI pump, if you use a "Deadhead" regulator with no bypass the pump will probably overheat and be damaged.

I'll take a look at some of my parts books and see if I can find a regulator that looks like it'll work. How much boost are you thinking of running?

Charles Brooks


---------- Original Message ----------------------------------
From: DIY_EFI-Digest-Owner at efi332.eng.ohio-state.edu (DIY_EFI Digest)
Reply-To: diy_efi at efi332.eng.ohio-state.edu
Date: Wed, 28 Jul 1999 05:00:01 -0400

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Date: Wed, 28 Jul 1999 09:33:29 +0800
From: dzorde at erggroup.com
Subject: Some efi: carby/super charger setup

Hi all,

With the list in digest mode it seems the mail has really slowed down.  Anyway,
I'd appreciate if someone has a solution for this minor inconvenience.  I have
finally managed to get my Fiat 850, with the MR2 supercharger on it, running.
Currently its using the original carby in a blow through configuration (the
setup is crap, but will have to do for the time being).  With the whole carby
being pressurised there is enough fuel pressure in the electric pump to make the
car idle, however I'm sure as the pressure builds up the fuel pump runs out of
steam.  What is the solution?

Do you use a high pressure efi pump with a 0.5bar regulator, vacuum/boost
compensated to the inlet manifold, so the fuel pressure is always 0.5bar above
boost level ?

What about the float.  The carby currently uses a soldered brass float, will it
be strong enough to withstand say 20psi of boost ? Or will I  need to fill it
with something non collapsable ?

What about the needle and seat, will there be any problems here ?

Might sound logical, but I'm a bit out of my depths here and so appreciate any
answers, on list or off list.

Dan  dzorde at erggroup.com