Is this still the stock ECU? IIRC pre 86 ECU's really couldn't manage the motor in real time.
Running open loop
Burning Brakes
Joined: Feb 2000
Posts: 1,247
Likes: 2
From: Parker, Colorado, USofA
Originally Posted by TPI BOY
Do any of you run open loop, if so whats the advantage
or disadvantage
or disadvantage
My car only goes open loop at WFO and when cold. Other folks have managed to keep the system in closed loop when at full throttle. It's nice if you can, but not particularly necessary.
The question is: Why CAN'T the car go closed loop? A common situation is an O2 sensor that can't get an accurate read. (too cold, too far from the cylinder bank, only reading from one cylinder.) I had to go to a heated O2 sensor in the header collector to get my car to go into closed loop.
You WANT closed loop control.
Pro
Joined: Jul 2002
Posts: 703
Likes: 0
From: Milwaukee Wi
i am running CL now. it was OK last year until i swapped in a larger cam 226/230 @ .05 and cranked up FP to 17.5 lbs on my TBI with 80 lbs injectors. now it appears i cannot get idle stable as i feel the ECU cannot control the BPW in order to hit the 14.7/1 in CL. if i can run richer at idle say 13.7/1 car may run better and same with A/F at cruise again say 13.7/1. from what i hear the CL is to keep cat convert functional for most part. not sure what GM commanded for A/F in pre emmision vehicles but i suspect it may have been richer than 14.7. also i have no heat to TB's and manifold so unless they are heat soaked when i hit CL car does not run as well. the richer mix OL seems to help drivability. when CL kicks in at first drive of morning drivability suffers. so i will try the OL operation for a while and see how it goes. my BLMS are pretty good(124-128) and a bit rich on purpose.
Burning Brakes
Joined: Feb 2000
Posts: 1,247
Likes: 2
From: Parker, Colorado, USofA
Originally Posted by Rohn
i am running CL now. it was OK last year until i swapped in a larger cam 226/230 @ .05 and cranked up FP to 17.5 lbs on my TBI with 80 lbs injectors. now it appears i cannot get idle stable as i feel the ECU cannot control the BPW in order to hit the 14.7/1 in CL. if i can run richer at idle say 13.7/1 car may run better and same with A/F at cruise again say 13.7/1. from what i hear the CL is to keep cat convert functional for most part. not sure what GM commanded for A/F in pre emmision vehicles but i suspect it may have been richer than 14.7. also i have no heat to TB's and manifold so unless they are heat soaked when i hit CL car does not run as well. the richer mix OL seems to help drivability. when CL kicks in at first drive of morning drivability suffers. so i will try the OL operation for a while and see how it goes. my BLMS are pretty good(124-128) and a bit rich on purpose.
Pro
Joined: Jul 2002
Posts: 703
Likes: 0
From: Milwaukee Wi
the rest of the story..... 
previous crossfire vette. 350 cid, xram, 2.0 TB's, 454 injectors, edel rpm aluminum 64 cc heads, crame 2040 cam 210/216 @.05, crane roller rockers, ceramic hedman 1 5/8 headers, dual exhaust/crossover, hooker aero chambers, 7747. Innovative WB.
CHANGES COMPLETED 10/13/2004:
7.4L TB on Holley TBI manifold(Projection), Summit AC with K & N, Aeromotive FP reg, Comp Cams 224/230 @.05 114 LSA, Innovative input of tps/rpm data
previous crossfire vette. 350 cid, xram, 2.0 TB's, 454 injectors, edel rpm aluminum 64 cc heads, crame 2040 cam 210/216 @.05, crane roller rockers, ceramic hedman 1 5/8 headers, dual exhaust/crossover, hooker aero chambers, 7747. Innovative WB.
CHANGES COMPLETED 10/13/2004:
7.4L TB on Holley TBI manifold(Projection), Summit AC with K & N, Aeromotive FP reg, Comp Cams 224/230 @.05 114 LSA, Innovative input of tps/rpm data
Burning Brakes
Joined: May 1999
Posts: 760
Likes: 1
From: Greenwich, CT
TBI isn't my area, but there is a fair amount of info on updated controls here:
http://www.thirdgen.org/techbb2/show...hreadid=270266
And quite a bit of interest in TBI big-blocks here:
http://www.454ss.com/cgi-bin/2004for...l?board=Engine
Someplace in that truck tech section Ken C (Half Ton Rat) posted a program hack that
indexed TBI inj pw to manifold pressure - which he seemed to think helped CL. That
work goes back a year or two, dig around and see if you can locate it.
HTH
http://www.thirdgen.org/techbb2/show...hreadid=270266
And quite a bit of interest in TBI big-blocks here:
http://www.454ss.com/cgi-bin/2004for...l?board=Engine
Someplace in that truck tech section Ken C (Half Ton Rat) posted a program hack that
indexed TBI inj pw to manifold pressure - which he seemed to think helped CL. That
work goes back a year or two, dig around and see if you can locate it.
HTH
Pro
Joined: Jul 2002
Posts: 703
Likes: 0
From: Milwaukee Wi
7747 for now. will read thru that thread. BPW index to manifold pressure? i have a 114 LSA. i think i have adequate manifold pressure at idle but did not check with vac gauge after install of new cam. i wanna say old cam was 16-17 when i did check. My issue is my BPW may be too small at idle and am going asynch or shutting off injectors. that is why going open loop as soon as car out of shop.
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