Where does a tune make its power?
07-13-2004, 10:03 AM
#1
Where does a tune make its power? Hi all -
Just researching another basic tuning principle... Whats exactly makes power when tuning? Is it getting a perfect a:f ratio? Is it increasing the timing? Is it something else that Im missing?
I know its very inaccurate, but Ive been tuning on the street with the stock o2 sensors. Ill eventually hit the dyno for a tuning session, but for now, Id like to do the best I can with HPT and a Gtech.
For instance, my car is basically tuned at WOT for ~915 mV on the o2s. If I try and lean it out any more, Ill get some KR. Should I fatten it up just a hair so that I can advance the timing a bit at WOT? Or would I be better off leaving the a:f where it is being as lean as possible without knock.
I guess its always going to be a juggling act trying to get the best of both worlds, and the best bet is to use my g-tech and see how I do both ways.
Thanks for any guidance,
-Tony
Just researching another basic tuning principle... Whats exactly makes power when tuning? Is it getting a perfect a:f ratio? Is it increasing the timing? Is it something else that Im missing?
I know its very inaccurate, but Ive been tuning on the street with the stock o2 sensors. Ill eventually hit the dyno for a tuning session, but for now, Id like to do the best I can with HPT and a Gtech.
For instance, my car is basically tuned at WOT for ~915 mV on the o2s. If I try and lean it out any more, Ill get some KR. Should I fatten it up just a hair so that I can advance the timing a bit at WOT? Or would I be better off leaving the a:f where it is being as lean as possible without knock.
I guess its always going to be a juggling act trying to get the best of both worlds, and the best bet is to use my g-tech and see how I do both ways.
Thanks for any guidance,
-Tony
07-13-2004, 11:12 PM
#4
Originally Posted by Red01Chevy
i would think that the more fuel you can put through the engine the more hp it make
07-13-2004, 11:12 PM
#5
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Your airflow is pretty well fixed by the mechanicals.
Onto that airflow you want to throw the amount of
fuel that maximizes the burn pressure pulse energy.
The peak burn temp / pressure and the width of the
pulse both respond to air/fuel ratio.
The pressure pulse is delivered to the shaft by the
crank torque arm. The amount of delivered torque
depends on the angle and the cylinder pressure.
The integral pressure*sin() over the burn pulse
stroke is what you contribute to the flywheel.
A high fat pulse that peaks at the best-compromise
crank angle is what you want. Spark timing decides
the peak position. Early makes knock, late wastes
pressure that could have been claimed (and burns
valves, etc.).
Shaping the fuel and spark maps so that these are
the best they can be, for every point in the RPM
and cylinder charge / MAP / load space, is the job.
All of this simply optimizes the power extracted from
the engine's air pumping capability. Mechanical and
plumbing modifications aimed at increasing the flow
are what will raise the theoretical maximum; tuning
is getting as close as possible, to it. There is always
a limit and an eventual diminishing return-on-effort
to tuning. Knowing when you've found it, is the trick.
Onto that airflow you want to throw the amount of
fuel that maximizes the burn pressure pulse energy.
The peak burn temp / pressure and the width of the
pulse both respond to air/fuel ratio.
The pressure pulse is delivered to the shaft by the
crank torque arm. The amount of delivered torque
depends on the angle and the cylinder pressure.
The integral pressure*sin() over the burn pulse
stroke is what you contribute to the flywheel.
A high fat pulse that peaks at the best-compromise
crank angle is what you want. Spark timing decides
the peak position. Early makes knock, late wastes
pressure that could have been claimed (and burns
valves, etc.).
Shaping the fuel and spark maps so that these are
the best they can be, for every point in the RPM
and cylinder charge / MAP / load space, is the job.
All of this simply optimizes the power extracted from
the engine's air pumping capability. Mechanical and
plumbing modifications aimed at increasing the flow
are what will raise the theoretical maximum; tuning
is getting as close as possible, to it. There is always
a limit and an eventual diminishing return-on-effort
to tuning. Knowing when you've found it, is the trick.
07-14-2004, 08:07 AM
#6
jimmyblue -
"The integral pressure*sin() over the burn pulse
stroke is what you contribute to the flywheel."
Thanks for watering it down into layman's terms.
But seriously, I kind of figured it would be like balancing a unicycle on a bowlingball. How do I know where the sweet spot is? How do I know if I should pull timing so I can lean it out? Or how do I know if I should fatten it up so I can advance timing. I'm not looking for perfection, but What are some hints to let me know when Im close to optimum?
Thanks,
-Tony
"The integral pressure*sin() over the burn pulse
stroke is what you contribute to the flywheel."
Thanks for watering it down into layman's terms.
But seriously, I kind of figured it would be like balancing a unicycle on a bowlingball. How do I know where the sweet spot is? How do I know if I should pull timing so I can lean it out? Or how do I know if I should fatten it up so I can advance timing. I'm not looking for perfection, but What are some hints to let me know when Im close to optimum?
Thanks,
-Tony