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

[olbap <olbap@mail.mia.bellsouth.net>]

That carb is a 600 cfm unit I believe.. not much difference i dont think

see my latest email

Pablo


M 5/31/00 -0400, you wrote:
>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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