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Re: UPDATE, Swapped to carb to rule out ignition.. Holley 4160 - 1850



OK, a wacky idea, but if your O2 readings are even *close*, and the carb
made that much of a difference, and barring the wacky way GM designed these
things to work I'll ask a basic question. What size was the carb, and with
whatever you've done to your TBI, what size do you think it is? If stock
it's around 500-525cfm and even if you've modded it up to 575-600, that
would be still be under most 4bls.

Just a thought.

Kevin R


> Basically convinced my friend to let me try out his carb, i kept the
> computer dist in there, plugged inthe TPS again
>
> went for a spin, zero tuning on the carb and geeez the low end sucked
> compared to the tbi.. but my gawd it hit 4000 rpm and the nearest thing
that
> came to mind was when the millenium falcon hit hyper space, it pegged the
> tach in like .4 nanoseconds and i let off even though it wanted to keep
> going, probably beyond 6500 but I wasnt about to find out... drove around
> for like a half hour and thought the 75 or so horsepower gain on top was
> uhm.. lets just say, Neat :)
>
>
> So, i should have trusted my gut feeling rather than that crappy o2
sensor.
> I didnt get to do any real tuning before it started raining outside today
i
> did crank up the fuel pressure just to see what it would do on the top and
> it seemed to rev up to about 5400 or so which wasa good improvement
>
>
> What really has me here is this whole thing with base pulsewidth.. it
simply
> cannot be right.. theway I understand it is that youd always lower it the
> larger the injector is in relation to the motor using the formula.  Now if
> this were true then the more hp/ci you had the lower your BPW would be
since
> that motor would require larger injectors.    I have found however through
> adjusting BPW that it does nothing to "recurve" the fueling scales at all
> its more like just a cut of fuel across the board.. I might be doing it
> wrong which brings metoanother question.. do you calculate bpw from
> theinjectors static flow rate or at 80% duty cycle?  perhaps not as
> important I guess, but anyways,   using mycurrent bpw calculations it
seems
> to be lean always on the top even if i have100% ve added up in the chip,
my
> WOT AFR has to be well below any real number to even come close to
equaling
> 12.7:1
>
> this is perhaps my greatest dilemma, im about to just put it up at 134 and
> be donewith messing with it.. andjustmake therest of the adjustments in
the
> main fuel and secondary fuel, that promises to be a PITA though...  I dont
> even have a real good idea where to set my fuel pressure. The 65 lb'ers in
> there flow around 90 lbs at 19 psi, according to some ofthe calculations
on
> the net thats good for  300 hp,  perhaps my motor is capable of more..
This
> is another thing i have to decide on. just find a fuel pressure and leave
it
> there and then work on the chip..
>
> I still know squat about this and any advice would be welcome.. it just
> seems like my tbi wont ever pull as hard as that carb did on the top it
was
> literally like a 75 hp difference... but i just cant go carb, the low end
> sucked which I attribute to a weak vacuum signal though the carb guys say
> tuning.. either way i want to make this work with the tbi, its my calling
card
>
> any tips on setting up bpw and injector flow rates etc etc?
>
> Id appreciate it
>
> Pablo
>
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