THATS ALL.
I HEAR IT ALL THE TIME
WHAT IS OPEN/CLOSED LOOP?
THANKS


------------------
Rick
90 Camaro RS 305 TBI
400 small block, Hooker 1 3/4 LTs, Random Tech Cat, Hooker aero chamber cat back on the way!!
TH700-R4 with Trans-Go shift kit (corvette servo here...but not installed yet)
MacEwen Motorsports White Gauge Overlays
14" K&N X-Stream Open Element
GTS Headlight and Taillight covers
5% Limo Tint all around
Classic White Chevy Bowtie sticker on rear window
http://www.geocities.com/esvalenz

Man if my camaro were a rice-rocket all those mods would give me what...easily 50-60 hp!!!

"Just because I've done it, doesn't mean I knew what I was doing!" - Me

 

Closed loop operation is when the computer is monitoring and controlling the variables of your ignition/fuel system. Open loop, the computer is not actively controlling most parameters and is using a set of pre-determined settings to run your engine. This is a BIG oversimplification.

------------------
Mike Metzler (Desert86Roc)
Mike@SpeedworldMotorplex.com
[*] Webmaster: SpeedWorldMotorplex.com[*] Click Here For My Racing Page[*]86 IROC 305 TPI (406 build in progress)
ET's @ 1250 ft[*] 14.28 @ 95.461 mph (uncorrected, NOS, no headers)[*] 15.365 @ 86.785 mph (uncorrected, Headers, no NOS)

 

Another way to look at it:
open loop, the computer ignores input from the sensors and guesses what the engine needs using preset information.

closed loop, the computer uses input from all the sensors to calculate what the engine needs.

This is simplified.


------------------
82 camaro--original steering wheel, brake/gas pedals, seats--everything else modified
82camaro

 

Open loop: The ECM ignores (only) the oxygen sensor input.

Closed loop: The ECM uses the oxygen sensor input in a "closed" feed back loop to control the air fuel mixture ratio.

Tim

 

thanks fellas....one mo thing...how do u tell what loop it is in. idle? thanks again

 

Once again the paper clip comes to the rescue of us loyal GM fans!! Just jumper your ALDL like you're going to pull codes, and start the engine. If the SES light flashes 2.5 times per second or so, you're in open loop. I believe closed loop is 1 flash per second but I could be wrong. Basically if it's flashing differently than 2.5/sec you're closed.

------------------
Base: 89 Iroc-Z LB9 auto 2.73 posi
Exh: 3" Dynomax muffler, 3" Pipe in place of cat
Ign: Accel 300+ wires, cap&rotor
Fuel: Cleaned and flow-matched injectors, afpr, !air pump&diverter valve
Sound: Kicker
Suspension: KYB Shocks, BMR Strut Tower Brace
Misc: TB Bypass, Synthetic Oil, Flexlite Transmission cooler,
free mods, hopefully engine swap and 4th gen seats in the works...

 

Another way to determine open loop operation is to look at the voltage across the port / converter solenoid at idle (is selects whether the air injected goes to the air tubes at the head ports (open loop) or the air tube(s) at the converter(s) (closed loop). If the solenoid is powered, the ECM is in open loop. You may also connect an LED (in series with a 680 ohm resistor) across the solenoid to indicate open loop operation. The solenoid may go inactive at part throttle, while in open loop, but should be active at idle, while in open loop.

Still another way to determine open loop operation is to connect a volt meter to the oxygen sensor output & ground. While in closed loop operation, the voltage will continuously swing from around 100 mv to around 1 volt at a rate of about one cycle per second.

Tim

 

Why the resistor?

 

An LED (Light Emitting Diode) needs to have its current limited to 10 to 20 mA, or so. The typical voltage drop across an LED is 2 volts, so
R = V/I
R = (13 volts - 2 volts)/ 0.016 amperes
R = 687 ohms
Or, for a common 5% resistor value, 680 ohms.

There are LEDs available that have a built in resistor & run directly on 12 volts, however, connecting a non internal current limited LED to 12 volts will toast it.

Tim

 

Think of the loop giving feedback to the computer as an electric circuit loop.

If the loop is open, no current can flow, just like the computer is not "getting feedback" or no flow of information.

If the loop is closed, current can flow, just like the computer is "getting feedback" or a flow of information.

 

Whew, I thought all those replies were people saying I was wrong! Well, I was. Open loop is 5 flashes every two seconds, and closed loop is one flash every two seconds...so fast flash=open, slower flash=closed

my bad

------------------
Base: 89 Iroc-Z LB9 auto 2.73 posi
Exh: 3" Dynomax muffler, 3" Pipe in place of cat
Ign: Accel 300+ wires, cap&rotor
Fuel: Cleaned and flow-matched injectors, afpr, !air pump&diverter valve
Sound: Clarion deck, Kicker speakers and amps
Suspension: KYB Shocks, BMR Strut Tower Brace
Misc: TB Bypass, Synthetic Oil, Flexlite Transmission cooler,
free mods, hopefully engine swap and 4th gen seats in the works...

 

to add another useful info tidbit--
when the SES light is flashing once every two seconds you can also use this to monitor your air fuel ratio. for example
if the SES light stays on for most of the two seconds your O2 sensor is "seeing" a rich condition and likewise if the SES is off for most off the cycle you are lean.
this is called field service mode and you dont want to drive around with your paper clip in the ALDL all the time because it prevents the computer from doing other things. but it is a cool way to tune your AF ratio.


------------------
88 WS6 T/A 305 TPI--
K&N,Air foil,hypertech chip, thermostat+fanswitch
free mods, dynomax exh, urethane motor+trans mounts,
SSM frame con, Bilsteins
very trick homemade ramair, Accel 300+ ignition system.
http://www.geocities.com/transam617

 

Forgive me if I'm wrong but aren't you NOT suppose to start the engine while the paperclip is in the ALDL? I though you start the engine then put the paperclip in :/

 

So, what's the ALDL look like, where is it, does it have anything to do with the coil or the ignition?
I ask, because, I, think I need a paperclip stuck somewhere on my
89 Camaro
RS
5,0
rusted out
piece of junk
that won't start.

Hey! I, need some help here! Check out Muehlbauer's post, this board, and, get me back on the road again...

 

the aldl is like a harness. basically, its in the car, under the steering wheel, above....the brake pedal....but closer to the driver seat. its black and has i think 8 or 10 holes in it. maybe this will help.
__________
|_|_|_|_|_|
|_|_|_|_|_|

like that. putting a paper clip in it will not start your car however. good luck though.


------------------
Rick
90 Camaro RS 305 TBI
400 small block, Hooker 1 3/4 LTs, Random Tech Cat, Hooker aero chamber cat back on the way!!
TH700-R4 with Trans-Go shift kit (corvette servo here...but not installed yet)
MacEwen Motorsports White Gauge Overlays
14" K&N X-Stream Open Element
GTS Headlight and Taillight covers
5% Limo Tint all around
Classic White Chevy Bowtie sticker on rear window
http://www.geocities.com/esvalenz

Man if my camaro were a rice-rocket all those mods would give me what...easily 50-60 hp!!!

"Just because I've done it, doesn't mean I knew what I was doing!" - Me

 

Cool things to do with the ALDL A & B terminals...


With the car off you get the codes. (duh)

With the car running you get the O2 sensor status (open loop and fuel mixture {Light on indicates a rich condition, light out is lean. It should be equal unless your peggin the throttle})

Placing a 3.9k ohm resistor in there forces the computer into limp-home mode and it will not go closed loop

Placing a 10k ohm resistor in there forces the ECM to go into special mode and it forces the ECM into closed loop operation, ignoring all run timers fixing the idle speed at 1,000 rpm with a fixed IAC position. The only practical purpose of this is to test drivability probs of the unstable idle type.

 

BB, is there something in that 'harness' that has to do with the ignition, as far as, getting electricity to the coil goes? You see, my only problem now (I think) is getting electricity to the coil. Once I accomplish charging the coil I think my car will get along just fine.
On top of the coil there are two contraptions that interlock with each other and fit down into slots. Both of these contraptions, one is black the other is white, have two wires running into them, two white wires and two red-to-pink wires.
On the white side of the contraptions the red wire is a thicker guage than is the red wire on the black side.
My thinking is like this: the thicker guage red wire has to do with electricity that flows into the coil and ends up coming out at the end of the plug in the cylinder. The thinner guage red wire I am supposing has to do with something about the ignition and/or maybe the spark advance.
I have bared a part of each of these 'red' wires and applied a hot wire to them each, though separately - nothing happened. What if I jumped across the two so that there would be no separation?
The paperclip idea made me think like this, but, I have no idea what it is I am dealing with.
If there is a harness not enclosed in the culling but under the steering column, that I can access, through which the ignition sources run, then I could plug a switch controlled hot wire in there and maybe get electricity to the coil.
Is there such a harness? What color would the wire(s) be? Is this something that might get me back behind the wheel, and off the bus?

 

wow...i dont know where to start...or where to end. ya know. what i would do is....
a) check for voltage on those wires, with and without the key ON. not started.
b) follow the wires back...see where they go.
harder than it sounds
c) talk with Tim Burgess, the moderator of this forum, he knows his stuff.
good luck. sorry i could not be of more assisstance. (spelling??)

 

The connections to the coil are as follows:

Harness connector on coil:
Thick pink wire: Power source from the ignition switch.

White wire: Signal to the tachometer.

Distributor connector on coil:
Thin pink wire: Power source to the distributor module.

White wire: Signal from the distributor module that switches the coil on and off (from ground to open circuit).

There should be approximately 13 volts at the thick pink wire to ground, with the ignition switch in the on position, and, if a test light is put across the coil (white & pink wires), it should flash when the engine is cranked.

Tim