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Re: Two barrel TBI must have a flaw, I give up.



I dun read tuning tips and dun red programmin' one oh one ten hundereded
millyan times, it still leaves alot of unanswered questions, theres no
mention of base pulse width, or the internal calculations the ecm makes when
you make a change to BPW. Ive also read archives a million times, and even
ahve downloaded both (diy and gmecm) and searched through them using word
for things like BPW, and PLECAN (yes i do value your knowledge)  and ANY
hint of ANY problem at high rpm and how to solve it.. yet, nothing
absolutely nothin be happenin ta help me run themz high rpms that thar carb
dun ran
I know all about your car grumpy, and its a sweet example of how its done.
I either am too inexperienced to know what signs mean what or two barrel tbi
has this flaw.. if im not mistaken, Crossfire has some small deflectors
directly under the TB that would probably eliminate the puddling problem as
I have hypothesized.

I cant tell you how many times Ive gone over the WOT tuning part of your
article and emulated the same process.. I can get it running AWESOME up till
about 4400... or so rpm.. after that, nothing.. To make it go fast I need to
shift at like 58-- but its just screaming and doing nothing for the last
1500 rpm or so

Im not sure if youve done more tuning.. perhaps more educated tuning, you
obviously have been around this much longer than I have.. but im on summer
break and only work weekends so i have all day every day to mess with this,
i think ive eclipsed your mark of 400 chips trying to get it right. If you
want to give me a hint as to what is wrong Id appreciate it, but Id think
that with all ive done i surely could have gotten on the same continent fuel
wise as the carb yet the carb pulled soooooooooooo much stronger.. when i
say 75 hp gain i LITERALLY MEAN like 75 hp, this is while holding the
ignition side constant, I do really like how the tbi pulls on the low end
though, it smokes the carb 0-4000.

If you wanna give me a hand here Bruce, Id appreciate it, but if not that is
cool too


Pablo






At 07:10 PM 5/31/00 -0400, you wrote:
>Dun run 13s with a cross fire (84 Firebird) (admittedly lots more tuning,
>experimenting then ya'll did).   Shifted at 5,500 to 5,800 rpm (cause it was
>to last long term).  Dun splained it in tuning docs., and various postings
>Grumpy
>
>
>> I dont know exactly, but I think it has to do with fuel flow and puddling
>at
>> the bottom of the manifold
>>
>> I just did a s--tload of testing and was as methodical as pablo gets..
>> issuming I was going lean I started off with 20 psi, and just increased
>the
>> pressure in like 3 psi increments.. there was a point where it had gotten
>> slightly better at the top, my test was in first gear starting at 3500 rpm
>> the drop in power occured always at the same rpm but at differening
>severity
>> somewhere slightly above 30 psi yeilded the least severe drop (very very
>> mild improvement if at all) but severe nonetheless (did not pull past 5000
>> much).. as i increased pressure from there i was greeted with diminishing
>> returns.. there was NO possible way I was going lean, my BPW was set at
>134,
>> and I was at around 90% ve wot at high rpm, 65 lb injectors (yellow/brown)
>> as i increased the pressure still further. the problem became worse. It
>was
>> very very bad the higher it went. I believe the same problem a carburetor
>> has at high rpm, the TBI has, only worse since the fuel is injected at a
>> higher pressure, that is the fuel hits the bottom of the manifold and
>turns
>> into little streams.
>> This is all just hypothesis though, I have no other way to explain my
>total
>> lack of high rpm horsepower
>>         Perhaps a much lower pressure would remedy the situation.. i dont
>> know.. the only problem is that a lower pressure would also yield less
>fuel,
>> at 19 psi these injectors would only support 300 hp
>>
>> Unless anyone here has had any good luck with two barrel tbi setups at the
>> high rpm end of the spectrum and can tell me anything ground breaking I
>> think this battle is lost.
>>
>>
>> Pablo
>>
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