Can someone explain open and closed loop!!
12-20-2002, 09:09 PM
#1
Intermediate
Thread Starter
Join Date: Dec 2002
Location: Riverside, CA
Posts: 41
Likes: 0
Received 0 Likes
on
0 Posts
Can someone explain open and closed loop!!
I'm fuel injected challenged and I'm wondering if someone has a few minutes to teach me the ropes on open loop or close loop... thanks <img src="graemlins/c.gif" border="0" alt="[ouch]" />
12-20-2002, 09:29 PM
#2
Racer
Join Date: Sep 2002
Location: Victoria, BC, Canada
Posts: 313
Likes: 0
Received 0 Likes
on
0 Posts
I'll try it this way since my background is in electronics.
Say you have a slow speed motor you want to rotate to to a certain place. Well, you just tell it to go for a certain amount of time, and it should get there rigtht? Wrong. Inertia, mechanical resistance, and all sorts of other things can prevent it from getting to where you want it to go. With open loop, there's no way of knowing if the motor got to the place you wanted it to because you don't have a sensor telling you where it got too. What closed loop does is employs a sensor that's on the output shaft of the motor, for instance, that tells you where you've actually got to.
With the 951, you've control electronics that tell things what to do, but not much in the way of feedback to tell the computer what it has actually accomplished...it only knows what it tried to do, and not what it actually did.
Someone else will have to fill you in on the details of the 951 systems, as I don't know them too well yet. This basically explains the difference between open and closed loop.
Hope it helps!
<img src="graemlins/beerchug.gif" border="0" alt="[cheers]" />
Say you have a slow speed motor you want to rotate to to a certain place. Well, you just tell it to go for a certain amount of time, and it should get there rigtht? Wrong. Inertia, mechanical resistance, and all sorts of other things can prevent it from getting to where you want it to go. With open loop, there's no way of knowing if the motor got to the place you wanted it to because you don't have a sensor telling you where it got too. What closed loop does is employs a sensor that's on the output shaft of the motor, for instance, that tells you where you've actually got to.
With the 951, you've control electronics that tell things what to do, but not much in the way of feedback to tell the computer what it has actually accomplished...it only knows what it tried to do, and not what it actually did.
Someone else will have to fill you in on the details of the 951 systems, as I don't know them too well yet. This basically explains the difference between open and closed loop.
Hope it helps!
<img src="graemlins/beerchug.gif" border="0" alt="[cheers]" />
12-20-2002, 09:41 PM
#3
Intermediate
Thread Starter
Join Date: Dec 2002
Location: Riverside, CA
Posts: 41
Likes: 0
Received 0 Likes
on
0 Posts
Thanks guardsred!!!! so Im assuming the 02 sensor gets dissabled when the car reaches a certain rpm's or speed....god this is why is why I try to learn as much as I can about whatever I do...frustrates me not to know!!! <img src="graemlins/cussing.gif" border="0" alt="[grrrrrrr]" />
12-20-2002, 10:06 PM
#4
Racer
Join Date: Jul 2002
Location: Modesto, CA
Posts: 271
Likes: 0
Received 0 Likes
on
0 Posts
[quote]Originally posted by Raul951:
<strong>Thanks guardsred!!!! so Im assuming the 02 sensor gets dissabled when the car reaches a certain rpm's or speed....god this is why is why I try to learn as much as I can about whatever I do...frustrates me not to know!!! <img src="graemlins/cussing.gif" border="0" alt="[grrrrrrr]" /> </strong><hr></blockquote>
open loop ='s fuel via the ecu maps only
closed loop ='s ecu monitors the O2 feedback and adjusts the fuel properly
At times when the car is in open loop, its because the O2 sensor doesn't respond quickly enough (WOT for instance) and/or a narrow-band O2 sensor is really only accurate at close to stoich.
Easy enough?
-Matt
<strong>Thanks guardsred!!!! so Im assuming the 02 sensor gets dissabled when the car reaches a certain rpm's or speed....god this is why is why I try to learn as much as I can about whatever I do...frustrates me not to know!!! <img src="graemlins/cussing.gif" border="0" alt="[grrrrrrr]" /> </strong><hr></blockquote>
open loop ='s fuel via the ecu maps only
closed loop ='s ecu monitors the O2 feedback and adjusts the fuel properly
At times when the car is in open loop, its because the O2 sensor doesn't respond quickly enough (WOT for instance) and/or a narrow-band O2 sensor is really only accurate at close to stoich.
Easy enough?
-Matt
12-20-2002, 11:03 PM
#5
Intermediate
Thread Starter
Join Date: Dec 2002
Location: Riverside, CA
Posts: 41
Likes: 0
Received 0 Likes
on
0 Posts
O.K!! so when does the go from closed to open? I have bad exhaust smells at hard acceleration and I'm trying to diagnose the problem while learning more about the system...thanks for that explanation mledbetter... 
12-20-2002, 11:14 PM
#6
Racer
Join Date: Jul 2002
Location: Modesto, CA
Posts: 271
Likes: 0
Received 0 Likes
on
0 Posts
[quote]Originally posted by Raul951:
<strong>O.K!! so when does the go from closed to open? I have bad exhaust smells at hard acceleration and I'm trying to diagnose the problem while learning more about the system...thanks for that explanation mledbetter... </strong><hr></blockquote>
Only my family calls me Mledbetter, you can call me Matt.
All cars are the same... its programmed in the ecu. Normally, greater than xx% throttle or above xxxx rpm's will kick it to the maps, cold-starts, etc as well. closed loop is really only used for cruising and very light throttle.
If you get one of those cheap A/F meters, you can see the lights swing back and forth as it adjusts the fuel. rich, lean, rich, lean, etc. Then when you stomp it, it should stop fluctuating and will most likely go rich, dropping a notch or 2 as you get close to redline.
What type of smells? Does it smell like fuel? If you have the stock chips and its running excessively rich, its not going to be the O2 sensor as its out of the loop at WOT. Fuel injectors and/or regulator are possiblities.
-Matt
<strong>O.K!! so when does the go from closed to open? I have bad exhaust smells at hard acceleration and I'm trying to diagnose the problem while learning more about the system...thanks for that explanation mledbetter...
</strong><hr></blockquote>Only my family calls me Mledbetter, you can call me Matt.
All cars are the same... its programmed in the ecu. Normally, greater than xx% throttle or above xxxx rpm's will kick it to the maps, cold-starts, etc as well. closed loop is really only used for cruising and very light throttle.
If you get one of those cheap A/F meters, you can see the lights swing back and forth as it adjusts the fuel. rich, lean, rich, lean, etc. Then when you stomp it, it should stop fluctuating and will most likely go rich, dropping a notch or 2 as you get close to redline.
What type of smells? Does it smell like fuel? If you have the stock chips and its running excessively rich, its not going to be the O2 sensor as its out of the loop at WOT. Fuel injectors and/or regulator are possiblities.
-Matt
12-22-2002, 01:01 AM
#7
Intermediate
Thread Starter
Join Date: Dec 2002
Location: Riverside, CA
Posts: 41
Likes: 0
Received 0 Likes
on
0 Posts
Matt...I'm getting rotten egg smell only when I punch it. My manifold has a nasty repair job and has cracked again, by the way, is it hard to istall an a/f meter? I've been wondering what gages I should add below the radio and am considering this one....THANKS!!
