open loop to closed loop question
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Burning Brakes
Joined: Sep 2006
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From: Myrtle Beach, South Carolina
open loop to closed loop question
After having the battery disconnected I believe the car runs in an open loop for a period of time before it returns control to the computer and it is then called closed loop...
Well, if that is correct, how long before the computer regains control and is it a function of running time or mileage? I just re-installed my LH and EZK last night and since then I've driven the car twice but not for more than 25 miles total...I'm wondering when I can assume the LH chip is responsible for the fueling.
Well, if that is correct, how long before the computer regains control and is it a function of running time or mileage? I just re-installed my LH and EZK last night and since then I've driven the car twice but not for more than 25 miles total...I'm wondering when I can assume the LH chip is responsible for the fueling.
Drifting
Joined: Nov 2006
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From: Farmington Hills, MI
It will go open or closed loop just as quickly no matter if the battery has been disconnected. Closed loop operation should occur after ~1 minute of the engine running assuming you aren't at WOT. However, the tables it's pulling fuel and spark advance number will take a couple days to "learn".
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Burning Brakes
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From: Myrtle Beach, South Carolina
Or should I start looking for the culprit right away because it's not running right....idle is staying at 1200 rpm's and my air fuel meter is bouncing from 12 to 17 when ever I'm cruising around 3000 rpm's...you can feel a slight surging going on.
I figured it was the O2 sensor but then started second guessing myself thinking the computer wasn't using the custom maps yet...
Am I way off on that line of logic?
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When it's in open loop mode the afr will usually stay pretty steady, usually display a little rich
at startup (12-12.5). Once it goes closed loop, usually after a minute or two, then the brain
will try and balance the system to lambda. So you're going to closed loop when your afr starts
to bounce from 12 to 17. Once you go WOT, then it'll go back to an open loop using the WOT
map. On my car, the narrow band gauge will bounce from stoich to lean, but the wide band display
will stay pretty close to 14.5 when in closed loop.
at startup (12-12.5). Once it goes closed loop, usually after a minute or two, then the brain
will try and balance the system to lambda. So you're going to closed loop when your afr starts
to bounce from 12 to 17. Once you go WOT, then it'll go back to an open loop using the WOT
map. On my car, the narrow band gauge will bounce from stoich to lean, but the wide band display
will stay pretty close to 14.5 when in closed loop.
Thread Starter
Burning Brakes
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From: Myrtle Beach, South Carolina
My AF gauge is fed from a wide band sensor.
At idle it's steady but too high, around 1200 at least. At light throttle it surges so bad it's as if someone is tapping the brakes and the AF is bouncing.
If I put my foot in it it goes rich, around 12 and the surging stops until I stop accelerating.
I haven't tried WOT yet.
At idle it's steady but too high, around 1200 at least. At light throttle it surges so bad it's as if someone is tapping the brakes and the AF is bouncing.
If I put my foot in it it goes rich, around 12 and the surging stops until I stop accelerating.
I haven't tried WOT yet.
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Craig,
With your idle being high and the surge at partial throttle it's not good. On my car that usually
means I have a vacuum leak. What is your manifold pressure at idle? Is it around 16 inches
of vacuum? or less?
When you put your foot in it, it's going into WOT mode, this usually happens at 2/3-3/4 throttle.
In WOT mode you want the AFR to be 12-12.5, so that is working correctly.
With your idle being high and the surge at partial throttle it's not good. On my car that usually
means I have a vacuum leak. What is your manifold pressure at idle? Is it around 16 inches
of vacuum? or less?
When you put your foot in it, it's going into WOT mode, this usually happens at 2/3-3/4 throttle.
In WOT mode you want the AFR to be 12-12.5, so that is working correctly.
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Supercharged
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A high idle is usually because of extra air getting into the intake. At idle, you car should bounce between high 13's and maybe an occasional 16 (in my experience). 12-17 seems too wide. If unmetered air is getting in, that would tend to make the mixture lean - say 17, so the car will richen up the mixture to get it back to stoich (14.7). So I would look for leaks post MAF.
With those big 42# injectors, it may be overcompensating, as most of the custome maps I've ever seen never touch the idle map - which is really based on a 19# injector.
So I think logic would tend to point to some type of leak after the MAF.
Another possibility... slight... is you're making some boost at idle and your BOV is not working right. It should be a quick check.
With those big 42# injectors, it may be overcompensating, as most of the custome maps I've ever seen never touch the idle map - which is really based on a 19# injector.
So I think logic would tend to point to some type of leak after the MAF.
Another possibility... slight... is you're making some boost at idle and your BOV is not working right. It should be a quick check.
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Burning Brakes
Joined: Sep 2006
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From: Myrtle Beach, South Carolina
Ok, I found a vacuum line that I had plugged had lost its plug. It used to go to the valve that works with the air pump, all of which I had removed. I also found the vacuum line from the four way 'T' that leads through the driver side fender wall was loose at the 'T'. It goes to the vacuum reservoir I believe.
After plugging and reconnecting those two I disconnected the sensor lead from my narrow band O2 sensor and connected it to the analog 1 output of the LC-1 unit, it creates a simulated narrow band signal and now the surging is almost gone and the widely fluctuating AF ratio is much more stable.
It still has some hunting going on but it's hard to notice where as before it felt like some gremlin was tapping on the brake pedal.
I plan to replace the narrow band O2 sensor because I've heard people had trouble using the analog output on the LC-1 as the computers O2 feed.
Andrew, I'll look for post MAF leaks for the cause of the high idle although the chip Tim sent is supposed to have a higher than S4 idle...he said it was from a GT or GTS, I don't remember but I don't think the later cars ran with the idle at 1200 to 1400 do they? So leak hunting I will be!
It sounds like a job for the SharkTuner to be able to watch all the parameters and manually select the idle....maybe I'll do that before I start the leak hunting since it's easier to hook that up than see beneath all the stuff crammed in the engine compartment. Man I wish they had made these cars just about 6 inches wider!!!
Thanks guys!
After plugging and reconnecting those two I disconnected the sensor lead from my narrow band O2 sensor and connected it to the analog 1 output of the LC-1 unit, it creates a simulated narrow band signal and now the surging is almost gone and the widely fluctuating AF ratio is much more stable.
It still has some hunting going on but it's hard to notice where as before it felt like some gremlin was tapping on the brake pedal.
I plan to replace the narrow band O2 sensor because I've heard people had trouble using the analog output on the LC-1 as the computers O2 feed.
Andrew, I'll look for post MAF leaks for the cause of the high idle although the chip Tim sent is supposed to have a higher than S4 idle...he said it was from a GT or GTS, I don't remember but I don't think the later cars ran with the idle at 1200 to 1400 do they? So leak hunting I will be!
It sounds like a job for the SharkTuner to be able to watch all the parameters and manually select the idle....maybe I'll do that before I start the leak hunting since it's easier to hook that up than see beneath all the stuff crammed in the engine compartment. Man I wish they had made these cars just about 6 inches wider!!!
Thanks guys!
Supercharged
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Andrew, I'll look for post MAF leaks for the cause of the high idle although the chip Tim sent is supposed to have a higher than S4 idle...he said it was from a GT or GTS, I don't remember but I don't think the later cars ran with the idle at 1200 to 1400 do they? So leak hunting I will be!
Thanks guys!
Thanks guys!
You should go to you local Lowe's or Home Depot and make one of these https://rennlist.com/forums/928-forum/445400-diy-vacuum-intake-leak-tester-for-s3.html. It will save you a lot of time! Really!
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I think I might be pretty familiar with that chipset. 
If so, they have a steady idle at 775 rpms, and there is no surging while cruising. Drives like stock with these maps unless you put your foot into it.....
Jim
If so, they have a steady idle at 775 rpms, and there is no surging while cruising. Drives like stock with these maps unless you put your foot into it.....
Jim
Thread Starter
Burning Brakes
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From: Myrtle Beach, South Carolina
...You should go to you local Lowe's or Home Depot and make one of these https://rennlist.com/forums/showthread.php?t=445400. It will save you a lot of time! Really!
I should have remembered that since I just asked him what it was the other night!
Ok, off to pressurize the intake
Thread Starter
Burning Brakes
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From: Myrtle Beach, South Carolina
Lol! Tim sent me 3 files to load into the SharkTuner, one of them is named "Jim LH 4-19-08 GT"
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From: Cambridge England
Glad to hear you're sorting it out..... to answer your original question - the car stays in open loop while warming up. The water temps from Temp 2 is used to switch the LH into closed loop. The temp at which this happens is around 80dgeC. You will see this clearly when you have your ST connected.
I agree that it is a good idea to use a stock NB O2 sensor rather than use the simmulated NB from LC-1.
I agree that it is a good idea to use a stock NB O2 sensor rather than use the simmulated NB from LC-1.