jjcuff1

I have seen many of the post here with Rrob and all his wisdom. I am dialing in my 88 TPI 305 auto with $6E ECM stock with emissions removed. I initially had lean readings with #32b and better but still lean with $6E then switched to southbay Bosch III 19#. Much better but I dialed in an injector constant and small tweak to one cell i the battery voltage vs pw then been tuning the AE/PE and MAF ever since.

I am normally rich at idle sometimes opposite to my expectations after changing the battery PW or inj cont. But always seem lean up top. Some of that is being in PE mode i forget BLM lock out and wondered why always stuck at 131 not say 128. Then I saw a post it takes the last AE read before it locks out into PE mode so hence still lean.

Low-Hi-Slopes and Fuel Bkt
Looking at the data sheets I see there are Low and Hi slope curves and multipliers based on pressure and a fuel value in lbs when it switches. The way I see this is that fuel cutover is just when you look at the low PW tables. and no matter what pressure I played with they were all under 2.5ms so moot point I zero all out from 3.4 down. The curves are moot too since you tune as needed to BLM using the PE/AE and MAf tables. But helps gives insite as to why I might need more fuel in maf3+ and why maf 1-2 seemed lean.

PW vs Battery Voltage.
This one threw me off a little when I recrunched my slopes last night. I used my stock tables from APYM $6E and found I was lean and I normally run in the 12.8-13.8v range. I had my 12.8 as the most critical at 750 it works ok and can tune but at 700 or 800+ I am off. But after reading the data charts again I realize for stock BIII at 39psi my my values slope were all off. then I know I am running low PSI anyway (more down below) so I adjusted the 6-16volts range and all the values decreased with the higher voltages going down more. Like 600 for 12.8 and 400 for 14. And I noticed the fuel pressure multipler for the BII increases as PSI increases? This seem backwards. Why say at 44psi FP would I need to add 6% to the PW? Eitehr way this slope on mine was off so I will adjust and try

Fuel PSI and INJ Constant:
This is really confusing to me. Stock value in the APYM was 20.1 but lets call it 19 in the code. I know 19 is the standard injector and this assumes the 42PSI rate. According to the data chart for BIII that at 42psi I will flow say 10% more then 39psi so it should be 19lbsx1.1= 20.9 constant.

but I have read here that is not the way to look at it. You want to try to stay as close to the 19lb constant, for the 305, 22 for the 350. So then since I will be flowing 21lbs in real world at 42psi and I really will be 10% over the 19 and therefore I should lower the 19 constant by 10% or 17.1. Real world the multipler is 6% so it is 17.86. This means that the ECM will calc late the LV8 and PW based on 17.86 less then 19 lowering the PW demand but because it is flowing more in real world that difference will make it = 19 and therefore all inline with the PW and engine size?

SO which is it? DO you back into the 19 or 22 constant to offset and lower the inj constant for greater psi and flowrates above 19 or 22? Why can you not say have a 24lb flowrate at 44psi real world and type that into the ECM and it will scale the function accordingly?


NOW in my case I know I need to get my fuel pump checked. it works and is brand new but the mech put in cheap or undersized unit and I only get like 36-38psi running at idle no vac port hooked up. I never checked under WOT but I can. So assuming the above logic of fitting the inj constant to a 19. and if I was at 42psi I would lower the # to 17.86. what if I have less presure? at 36psi I am only getting 17.86 real world psi (6% less according to data chart) Is hat the number I can use? (*goes against the logic above if they are same # for more and less psi?)

I currently have found that at 18-19psi inj const my car was super lean like 140lm at idle and above!!! but maybe the voltage charts being off at idle and low pw not zero all effected this.
I have found that running at 16.8-17.1 seem to work well? So what is right direction to head

jjcuff1

Very wordy sorry in a nutshell I am asking/saying.

1: Lo/Hi slope effects the low slop PW table. But in the end zero out the 1.7+ PW anyway and you will tune the fuel with MAF/AE/PE tables

2: Battery Table seemed opposite of logic. With increased pressure, the multipler increased. S0 ay 12.8v nominal say 1000 at 42psi it says I should be at 1060? My pressure might be lower so I will go other way but still I would think at more pressure therefore get more fuel why would you need extra PW ?

3: Big question. I will double check my FP but at idle no vac on I might be at 39-40PSI. according to the chart at 39psi i get 19lb. lets say I am at 40 and I am flowing 20lb or possibly at 38 and flowing 17. how do I set my inj constant for above and below situations?