TBI location

[dzorde at erggroup.com]

Hi all,

I've now got as far as I'm in the process of deciding how to inject my
supercharged Fiat (4 cyl), and am in need of some experienced help.  For
reference the car will be seeing 30-35psi boost (unless it blows up), the head
is 5 port (ie. 1 inlet so easy to supercharge).

Anyway my dilemma is where to locate the TBI or if I should even use a TBI, here
are the options I have thought up and possibly some of the adv/disadv of these:
1. place TBI on head (similar to current carby setup and blow through TBI), easy
replacement, but fuel needs to be boost referenced and it requires a blowoff
valve to stop seals in s/c blowing when you close the throttle blades at high
revs.
2. place TBI before s/c (suck through setup), may be a problem starting as fuel
would have to go through s/c and intercooler, hence airflow may not be great
enough during cranking to suck the fuel into the engine. Also what happens when
you close the throttle blades at high revs, does the s/c try and suck air in
past its seals ?
3. Just use a plain throttle body before s/c and mount a few injectors in the
manifold pointing into the head (almost port injection). Fuel would not have to
flow through intercooler, etc.  So car may actually start during cranking, but
again fuel needs to be boost referenced.  However, what would happen to the s/c
when you close the throttle at high revs, would it suck air in past its seals
due to the vacuum being generated between the s/c and the throttle blades.

What I'm after is peoples thoughts on which method to use. Thanks in advance for
any help :-)

Dan  dzorde at erggroup.com


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