ty_ty13

iTrader: (42)

i need a definition/explanation of each so i know what they mean.

closed loop
open loop
Speed density


yes i have done a little bit of tunning but mainly after some one has gave me a base to setup and i do the timming and fuel....


Thanks,

Tyler

horist

Closed loop: AFR is kept inline with O2 sensors
Open Loop: AFR doesn't rely on O2 sensors, instead relies on internal tabling to approximate fueling
Speed Density: Calculating the amount of air via vacuum/pressure (MAP sensor) , then using internal tables to determine fueling based on vacuum (no vacuum = 14.7psi = 100% cylinder fill = ~105kpa at sea level, MAP sensor measures, PCM interprets as kilopascals and looks up the fueling requirements based on that)

sprayjunkie

Check out EFITO.com....lots of good tuning info there.

ChrisS@sdpc

Closed Loop - method of controlling fuel in which O2 sensor's provide feedback to the controller indicating perfect, rich, or lean; thus, the ECM (engine control module) can make changes based on the feedback. If lean, add fuel. If rich, pull fuel. Specifically in LSx vehicles, we are talking about narrowband O2 sensors that only report rich/lean versus the stoichiometric A/F ratio (~14.7:1 for gasoline).

Open Loop - there is no provision of feedback from the O2 sensors to alter the A/F ratio; the ECM simply calculates the amount of air entering the engine (see the next definition) and then determines the amount of fuel to add to achieve a given A/F ratio which is generally set in one or more tables

Speed Density - a method of calculating the mass of air entering the engine; preferably using the ideal gas law
Speed Density can be compared to a Mass Airflow sensor (MAF). LSx cars come from the factory with a MAF which is another means of calculating the mass of air entering the engine. LSx MAF's use a 'hot wire' in which the PCM monitors the amount of current necessary to maintain a given temperature. The amount or current required is converted into a mass of air entering the engine.

foff667

iTrader: (2)

Here's a writeup i did a few months back because of all the confusion about what modes a vehicle can enter http://www.hptuners.com/forum/showthread.php?t=8994

jetblast

along with all the good info coming from the experienced tuners in this forum, i also think you could benefit from a book or two. my choice, "how to tune and modify engine management system" by jeff hartman . and get yourself a wideband instrument.

RedHardSupra

iTrader: (1)

MAF vs SD:
http://redhardsupra.blogspot.com/200...on-part-1.html

OL vs CL:
http://redhardsupra.blogspot.com/200...-2-olvscl.html