holley 4d_ efi changes??

[Bill the arcstarter]

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


______________________________________________________
Get Your Private, Free Email at http://www.hotmail.com