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Open loop
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nismotekk Offline
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Post: #1
Open loop
Has anyone tried tricking the ECU to stay in open loop? Usually the reference o2 voltage in open loop is .3v. I will try this once my booster is back in the car.
07-19-2008 05:39 AM
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rpatzer Offline
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Post: #2
RE: Open loop
You don't want open loop. That is when the O2 sensor is cold and NOT working, therefore it reads rich. It is way tooooo rich. I have an AFR meter, and it pegs rich until it goes to closed loop.
07-19-2008 07:13 AM
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nismotekk Offline
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Post: #3
RE: Open loop
rpatzer Wrote:You don't want open loop. That is when the O2 sensor is cold and NOT working, therefore it reads rich. It is way tooooo rich. I have an AFR meter, and it pegs rich until it goes to closed loop.

The reason it is rich in open loop is due to the engine temp, not the o2. The o2 is working, but the ECU will not use the input until it sees a certain coolant temp. In open loop it will get less rich as temp goes up. When you use an EFIE device, you lower the voltage going back to the ECU. So if the voltage was preset at .3 no EFIE would be needed. Although this might throw a light, I am going to try it. I believe its worth a shot, you dont know until you try.
07-19-2008 08:56 AM
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rpatzer Offline
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Post: #4
RE: Open loop
I disagree- when I start out, it is in open loop for about 1-2 minutes or 500 ft, then it goes to closed loop. But the H2O temp still hasn't reached operational temp yet.
But, if you want to do a test, cut the O2 sensor wire and leave it open and see what happens to your mileage. I bet it goes down.
07-19-2008 11:47 AM
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nismotekk Offline
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Post: #5
RE: Open loop
rpatzer Wrote:I disagree- when I start out, it is in open loop for about 1-2 minutes or 500 ft, then it goes to closed loop. But the H2O temp still hasn't reached operational temp yet.
But, if you want to do a test, cut the O2 sensor wire and leave it open and see what happens to your mileage. I bet it goes down.

There is no disagreeing, that is how it works. I never said it had to be at operating temp to go into closed loop. Usually around 170 degrees(coolant temp) the vehicle will go into closed loop. Distance has nothing to do with it. If I wanted to test, I believe it would be smarter to unplug the o2. I had a conversation with my field engineer at work, and he believes that we might get more benefit if it was left in open loop. Like I said its at least worth a shot, this way the ECU can not make adjustments for emissions and if the the vehicle has electronic spark advance these adjustments can not be made either.
07-19-2008 12:49 PM
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rpatzer Offline
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Post: #6
RE: Open loop
nismotekk Wrote:
rpatzer Wrote:I disagree- when I start out, it is in open loop for about 1-2 minutes or 500 ft, then it goes to closed loop. But the H2O temp still hasn't reached operational temp yet.
But, if you want to do a test, cut the O2 sensor wire and leave it open and see what happens to your mileage. I bet it goes down.

I think we basically agree here, but:
There is no disagreeing, that is how it works. I never said it had to be at operating temp to go into closed loop.
(Usually around 170 degrees(coolant temp) the vehicle will go into closed loop.)
No- that was my point. The O2 sensor heats up very fast, 1-2 minutes and w/i 500 ft. Then it goes into closed loop but the rad temp is still cool/cold. Open/closed loop depends upon O2 sensor temp, not water temp. The ECU makes allowances for the water temp while it is heating up.
Distance has nothing to do with it. If I wanted to test, I believe it would be smarter to unplug the o2.
I suggested cutting and leaving it open because that is where you are going to cut it to insert the EFIE.
I had a conversation with my field engineer at work, and he believes that we might get more benefit if it was left in open loop. Like I said its at least worth a shot, this way the ECU can not make adjustments for emissions and if the the vehicle has electronic spark advance these adjustments can not be made either.
(This post was last modified: 07-19-2008 01:06 PM by rpatzer.)
07-19-2008 01:04 PM
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Gary Offline
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Post: #7
RE: Open loop
Oddly enough, you may be right. One of the guys on this forum (4banger Toy pickup, I think) unplugged the o2 sensor and massively increased the mileage, which was allready doing better on the HHO. I'll be trying it on our Toy car after another mileage test, as I just got about 19.3% on a city/highway mix today without electronics.
Nothing to lose but a couple bucks worth of gas. Was doing that anyway!
07-19-2008 02:30 PM
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nismotekk Offline
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Post: #8
RE: Open loop
rpatzer, you are wrong. The ECU is closed loop operation will make adjustments for emissions and fuel economy. It can not effectively do this until the vehicle is at normal operating temp. Although the o2s have heaters, the real task is to get the engine temp up. There is no point in having heated o2s supplying input to the ECU if the ECU is unable to make the adjustments due to a cold engine. If you have a scan tool capable of looking at engine data in real time, look at the what voltage the ECU is seeing from the o2. It should read around .3. Now that is not the voltage from the o2, but a preprogrammed voltage set from the factory for use while the vehicle is in open loop. Now if the ECU was seeing that voltage from the o2 it would see a rich mixture, and then it would shorten injector duration to correct for rich condition. This is why we want to bring down voltage with the EFIE. As the vehicle warms up the mixture will gradually lean out, the ECU makes this adjustment from the coolant temp sensor. Now I cant say for sure that the CTS is the the only input the ECU uses to go into closed loop on all makes and models, but on all the cars I have worked on it has been the primary sensor. The ECU is programmed to start "looking" at the o2s at a certain coolant temp. What kind of A/F ratio sensor do you have?
07-19-2008 02:57 PM
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nismotekk Offline
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Post: #9
RE: Open loop
Gary Wrote:Oddly enough, you may be right. One of the guys on this forum (4banger Toy pickup, I think) unplugged the o2 sensor and massively increased the mileage, which was allready doing better on the HHO. I'll be trying it on our Toy car after another mileage test, as I just got about 19.3% on a city/highway mix today without electronics.
Nothing to lose but a couple bucks worth of gas. Was doing that anyway!

Good job man! I have been rootin' for ya, like you I REALLY want this to work out. Mine is going back in the car tomorrow. I really dont want to modify fuel trim until I see a MPG increase. I will let you know how it goes. My scan tool has a jump drive port so I will be able to post live engine data, Im pretty excited.
07-19-2008 04:42 PM
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Atom Offline
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Post: #10
RE: Open loop
nismotekk Wrote:rpatzer, you are wrong. The ECU is closed loop operation will make adjustments for emissions and fuel economy. It can not effectively do this until the vehicle is at normal operating temp. Although the o2s have heaters, the real task is to get the engine temp up. There is no point in having heated o2s supplying input to the ECU if the ECU is unable to make the adjustments due to a cold engine. If you have a scan tool capable of looking at engine data in real time, look at the what voltage the ECU is seeing from the o2. It should read around .3. Now that is not the voltage from the o2, but a preprogrammed voltage set from the factory for use while the vehicle is in open loop. Now if the ECU was seeing that voltage from the o2 it would see a rich mixture, and then it would shorten injector duration to correct for rich condition. This is why we want to bring down voltage with the EFIE. As the vehicle warms up the mixture will gradually lean out, the ECU makes this adjustment from the coolant temp sensor. Now I cant say for sure that the CTS is the the only input the ECU uses to go into closed loop on all makes and models, but on all the cars I have worked on it has been the primary sensor. The ECU is programmed to start "looking" at the o2s at a certain coolant temp. What kind of A/F ratio sensor do you have?
I am confused but very interested. If the ECU is seeing .3 isn't that a lean signal. please advise
07-19-2008 05:09 PM
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