holley 4d_ efi changes??

[andy quaas]

OK, you're all partially wrong.  The 2D system is a microprocessor
unit that is tuned with a few pots.  The 4D system is uP controlled
also.  It is tuned with a few pots, also.  It is closed-loop only and
has an IAC.  The 4Di is the exact same as the 4D except you program it
with a laptop (very powerful ECU).  The analog systems are still
available.  The 4D/Di kits share nothing with the 2D or the analog
systems.  NOTHING.  You can buy a closed-loop kit for the analog
systems.  I had a 4Di on my truck.  I would have to recommend it to
anyone who wants EFI, but can't afford to burn chips and pay for port
EFI.

Andy Q


---Bill the arcstarter <arcstarter at hotmail.com> wrote:
>
> It was written: (re: ProJection kits)
> 
> >has the holley 4d_ system throttle body changed at all since its 
> inception?
> 
> I haven't seen one but it looks like the old analog unit has been 
> discontinued and replaced with a low-end digital unit.  This would
be a 
> 2d system I think.  It still contains the 5-6 pots on the front for 
> hacking up the fuel tables...
> 
> The 2d system is $620 from Jegs.
> 
> I think only the 4di system allows laptop-type remote adjustment of
the 
> specifics.  (4di is $1242 from Jegs-open loop - no learning)
> 
> There is some sort of closed-loop O2 kit you can get for $100.  But I 
> have a hard time seeing how this thing would know if the engine is 
> warmed up yet, etc.  Other than that I *think* it connects in between 
> the injectors and the ECU.  I think is "massages" the injector pulse 
> widths.
> 
> Someone else on diy_efi said this thing runs at a fixed frequency and 
> variable duty cycle, if that matters...
> 
> One problem I've had researching these ProJection systems is FINDING 
> good tech information..  Yea I called Holley but they weren't keen on 
> chatting.  I bought the stupid installation video for $15 just to see 
> what I could learn (was worth it).
> 
> So is anyone using one of these things?
> 
> I'm thinking I can do just as well with a GM TBI, a PIC and some 
> solder... :)  Anyone care to help?
> 
> 
> >PS just read in hotrod dec/98 has one article w/ the 4di answering a 
> few of
> >my q's, the digital systems TPS is far more sensitive than the
analog's
> >TPS.....so even thought the guy w/ this system upgraded to the 
> Again - just guessing here but I'd have a hard time believing they
use 
> two different TPS sensors, one on the old analog and one on the new 
> digital.  Perhaps the author meant that the new *system* worked
better 
> than the old one? 
> 
> Comments always invited.
> -Bill
> 
> 
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