More tuning questions- 4.3 TBI

[Carl Summers]

Hello,
    My answer is below....has the >>>>>>'s,



-----Original Message-----
From: owner-gmecm at diy-efi.org [mailto:owner-gmecm at diy-efi.org]On Behalf
Of Reid Bishop
Sent: Monday, September 11, 2000 8:40 PM
To: gmecm at diy-efi.org
Subject: More tuning questions- 4.3 TBI


Okay folks- I have read all the Programming 101 stuff, all the tips, and
still don't understand a few things.  Here is what I have gleaned:

1)  When looking to change the VE tables, one should look for the Integrator
values to hover around 128, then read the BLM's at that time.  Now, do low
BLM's mean lean or rich?  What about high BLM's?

>>>128(80hex) means everything is happy. :)  anything below 128 the computer
is leaning the mixture.

2)  Overall, my data captures indicate I have low BLM's (around 114) at low
MAP/RPM combos, and high BLM's (Around 141) at higher MAP/RPM combos,
especially at WOT.  My O2 readings are constantly swinging back and forth
(often wildly), except at WOT, where the O2 is pegged at near max mv.  Is it
normal for highly swinging O2's?  And should I expect it to be pegged out at
WOT, or can I get it back down somewhat?

>>>>> Sounds like you have a mild cam in it....less vacuum at idle so KPA
instead of 40(for a number) is now 50(for a number)... blm's
lower....computer is dumb and thinks more load and injects more fuel....same
thing happens when at part throttle but backwards since VE has
improved....you develop more vacuum that stock and it becomes lean..blm's
rise......O2 voltage should swing once close to a stoich mixture.....this
helps the cat and is a normal anomoly of closed loop algo......O2 voltage is
a whole diff subject at WOT...cannot tune off of O2 voltage(can get close)
but as you prolly have seen you cannot get fast enough data from the 747 so
will have to rely on outside AFR data...

3)  Being at high altitude, I am certain I need more timing.  I rarely see
bumps in the knock counts, and think I need to at least get closer to 'the
edge'.  Agree?

My rule of thumb that has worked for me is 1 degree per 1k feet.


4)  	Does anybody have a chart that relates MAP mV to MAP pressure?  I
haven't seen anything, and want to begin changing the VE tables at the
proper MAP settings relative to my data captures.  This is a 7747, with AKDX
calibration (4.3, 700R4)

5)  Given that I have pretty low BLM's at low RPM (including idle), would
that explain the very rough condition I run into at just off idle and low
MAP?  It's very irritating, and I'm wanting to fix that problem first.


>>>Yes, fix idle first so block learns don't affect "tip in"...... hth's
-Carl


I have a really descriptive Excel chart if anyone wants to take a look... it
graphs MAP, TPS, RPM, O2 mv, Integrator, and BLM together.  It's a bit
confusing to me, but maybe you "Pros" can glean the basics from it.


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