I just added headers to my mostly stock 305 TBI. When I first tested the car It felt pretty good, but in short order it seemed like I lost a LOT of torque below 3,000 rpm.
Could the computer have made any adjustmets
that could cause this??(really basic and dumb I know) I have access to a scan tool and was going to check rich /lean function
with that.
My o2 sensor is relatively new and came out and went back in ok if that means anything.
I just want to rule computer out as a cause.
Sure appreciate the help. thanks....bob

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91 camaro RS L03 convert,
t-5, ultimate TBI mods,TBI spacer,SLP 1 5/8 headers,
3"cat back, 3.42 torsen posi,alston SFC's,Global West LCA relocation brackets

 

Mostly stock?.
With an EFI car some degree of balance needs maintained.
**too much** exhuast can be worse then the stock setup.
Without getting too complicated:
There is a time when both the in and ex valves are open. Depending on exhuast brack pressure, there will be some bleeding or diluting of the inciming air, it's called self EGRing. Reduce this, and the engine can make more HP if there is enough fuel, if not enough fuel, then HP suffers.
At low throttle opening the O2 sensor can balance things, but at mid to WOT the ecm is just using the programmed info., and no corrections are made to compensat for the difference of EGR
Just the short and sweet of a long story

 

Grumpy, I read your comment several times but i wonder if you are saying that the O2 sensor "balanced things" at low rpm and that my be why I notice a loss of torque after a short time. Do I have that right? A number of people have told me to get an AFPR and increase the pressure to get more fuel.
If ya got the time and patience, let me know if I got this right.thanks......bob

------------------
91 camaro RS L03 convert,
t-5, ultimate TBI mods,TBI spacer,SLP 1 5/8 headers,
3"cat back, 3.42 torsen posi,alston SFC's,Global West LCA relocation brackets

 

At low throttle openings (when warm closed loop), the O2 sensor and ecm forces things to a 14.7:1 AFR. With the lessening of backpress, then there is less EGR so the engine has the potential to make more HP, but it will need more fuel and the timing probably changed.
Your to the stage of needing to tune things, a stopwatch and doing some chipping.
An AFPR is part of that process

 

Grumpy, thanks for clearing that up.
Gotta start planning my next step. thanks....bob

------------------
91 camaro RS L03 convert,
t-5, ultimate TBI mods,TBI spacer,SLP 1 5/8 headers,
3"cat back, 3.42 torsen posi,alston SFC's,Global West LCA relocation brackets

 

Grumpy, I bumped timing up and felt and timed little difference.But I made the TBI adjustible per pablo's article and increased fuel pressure a bit. Big difference!!!
I am gonna check it out with a scan tool this weekend and dial it in as much as I can.
thanks for your help.I appreaciate it...bob

------------------
91 camaro RS L03 convert,
t-5, ultimate TBI mods,TBI spacer,SLP 1 5/8 headers,
3"cat back, 3.42 torsen posi,alston SFC's,Global West LCA relocation brackets