Running open loop

[DMC Fanatic]

I remember this being discussed before on dmctalk.com, but I cant find any information here. I'm planning on bypassing the lambda system completely and running open loop all the time. My car seems to run better cold than hot. When hot, the idle becomes eratic and there seems to be a popping noise from the exhaust, however it does not do this when cold. What are the things I have to do to make the car run in open loop. Is it just disconnecting the o2 sensor and adjusting the mixture screw? Any help is appreciated.

Thanks,

Sean

[Bitsyncmaster]

Disconnecting the O2 sensor is one way to run open loop. That will keep your FV at a fixed duty cycle and then you adjust the mixture as normal but you have to do it by guess unless you can read the AFR elsewhere.

[robvanderveer]

I am running open loop for 12 years. The FV was removed by PO.

[Nicholas R]

If you know your O2 sensor is good, while disconnected you can hook a volt meter up to it and read the voltage output. (positive lead to the O2 sensor, negative to ground)

This is all from memory so hopefully someone can verify it but I believe that depending on the air/fuel mixture the O2 sensor will output between 0 and 1 volts. For the optimal fuel ratio you want something like .5v (14.7 x air to fuel); however, if you want the car to have a little more power you can increase it to .7v. This is where mine is currently at and it runs excellent.

this is pretty simple but the relationship looks kind of like this:
http://forums.pelicanparts.com/uploads8/O2+sensor+voltage1150420738.gif

[David T]

The car will run better and get better mileage if you can fix it so it will run well in closed loop. Typically the biggest problem is vacuum leaks. They have a bigger effect on idle quality in closed loop so they will be more noticeable then. Some common sources of leaks include:
the plug over the mixture screw
injector seals
air pipe under mixture unit to idle motor
Also make sure the vacuum advance and the control pressure regulator vacuum lines are properly hooked up and the vacuum and mechanical advance is working.
David Teitelbaum

[DMC Fanatic]

I think I fixed my warm idle issue. It seemed like the wire on the vacuum solenoid behind the fuel distributor was loose. After I cleaned the connection, the car idled like a champ in closed loop with no popping noise or weird idle. :smile: There is still a very slight issue with the warm idle in which it'll fluctuate when the fv buzzes on and off. Is this normal? Ill definitely going to end up replacing the o2 sensor though since its original.

Thank you all for your input so far!

[Bitsyncmaster]

I think I fixed my warm idle issue. It seemed like the wire on the vacuum solenoid behind the fuel distributor was loose. After I cleaned the connection, the car idled like a champ in closed loop with no popping noise or weird idle. :smile: There is still a very slight issue with the warm idle in which it'll fluctuate when the fv buzzes on and off. Is this normal? Ill definitely going to end up replacing the o2 sensor though since its original.

Thank you all for your input so far!

Good you fixed it. It's common that the idle will "hunt" and hard to find what is causing it. Everything need to be adjusted and working perfectly to not have idle hunting. Changing the O2 sensor is the best first thing to do.

[Nicholas R]

I may disagree about the car running better closed loop. I believe my car runs excellent open loop. In addition, I drove round trip from Cincinnati to Orlando, ~2500 miles throughout the trip, about a month ago, and most of the time I got about 23-24mpg in an automatic! And that is with the AC running almost always. My car does have the UK exhaust so I know that does help, but I had my exhaust checked with an exhaust gas analyzer, set the mixture, and never looked back. My O2 sensor is still good and I occasionally attach the volt meter to it just to see if its reading right. So far, always looks good.

Either way to each their own. I wasn't sure what was wrong on my car closed loop, and this proved a very effective solution.

[Manxmann]

My car has recently had a 'new' crate stage II fitted (Delorean EU), at the same time all the sensors/pipes/fuelling/control valves where replaced. This was necessary as the car had a Renault 25 EFI Turbo engine when I first bought her.

The car is currently running closed loop and is ok but hot idle does hunt a little, would running open loop help on a stage II?

[DMC5180]

I may disagree about the car running better closed loop. I believe my car runs excellent open loop. In addition, I drove round trip from Cincinnati to Orlando, ~2500 miles throughout the trip, about a month ago, and most of the time I got about 23-24mpg in an automatic! And that is with the AC running almost always. My car does have the UK exhaust so I know that does help, but I had my exhaust checked with an exhaust gas analyzer, set the mixture, and never looked back. My O2 sensor is still good and I occasionally attach the volt meter to it just to see if its reading right. So far, always looks good.

Either way to each their own. I wasn't sure what was wrong on my car closed loop, and this proved a very effective solution.

I did a 1000 mi Rd trip to Detroit in August. Averaged 30.6 going 29.8 returning. Stage I Manual Closed loop.

[Nicholas R]

I did a 1000 mi Rd trip to Detroit in August. Averaged 30.6 going 29.8 returning. Stage I Manual Closed loop.

Don't the manual's typically always get better fuel economy? Especially since 5th gear is underdriven where 3rd on the autos is 1:1. Either way, thats awesome! Thats great mileage on a brand new car let alone a 30yr old one.

I have the original window sticker for my car and it says the car gets 17 miles per gallon.

[Bitsyncmaster]

Don't the manual's typically always get better fuel economy? Especially since 5th gear is underdriven where 3rd on the autos is 1:1. Either way, thats awesome! Thats great mileage on a brand new car let alone a 30yr old one.

I have the original window sticker for my car and it says the car gets 17 miles per gallon.

Not only the gearing loss but the torque converter loss with Autos. Most new small cars will get low 30s for highway MPG. Mostly due to EFI, gearing and a lockout torque converter.

[DMC5180]

Sure manuals are more efficient. But my comparison was to show the 6-7 MPG difference. I would suspect that gap would narrow to 4-5 if you ran Closed loop. Your milage would increase a 1-2 MPG. The Factory Sticker for a manual car was 21 mpg average. 4 MPG difference with your auto at 17 MPG.

Also the mileage I got was with 87 octane E-10 blend.

[Nicholas R]

My car never ran right closed loop. I dont know if it was the Lambda ECU, the o2 sensor, or what. As soon as I went open loop all problems went away, fuel economy went up, the car had way more power, and I've never once had the car hunt.

I'm also running just a tad rich for the increase in power. I'm sure if I backed my AFR back off to the "optimal fuel economy" I'd probably gain at a mile or two per gallon. I'd rather have the little extra power.

[David T]

When you run "open loop" you can adjust the mixture screw for only one point in the air/fuel-RPM curve. That is why you have the Lambda. You adjust the mixture so it is just a little less than what you need and let the Lambda run the frequency valve to add what you need to get to the ideal mixture. Without the Lambda system you are running the basic Jetronic system. The "K" designation tells you it has the Lambda system running "over" the basic Jetronic mechanical system making fine adjustments to get closer to the ideal A/F ratio at all points along the curve. Running rich will eventually kill the catalytic converter and waste gas. You really are not getting all that much more power running rich. In fact, all of the other systems on the motor are set up the ideal mixture. Without modifying the timing and advance you cannot take advantage of the rich fuel mixture.
David Teitelbaum

[Nicholas R]

When you run "open loop" you can adjust the mixture screw for only one point in the air/fuel-RPM curve. That is why you have the Lambda. You adjust the mixture so it is just a little less than what you need and let the Lambda run the frequency valve to add what you need to get to the ideal mixture. Without the Lambda system you are running the basic Jetronic system. The "K" designation tells you it has the Lambda system running "over" the basic Jetronic mechanical system making fine adjustments to get closer to the ideal A/F ratio at all points along the curve. Running rich will eventually kill the catalytic converter and waste gas. You really are not getting all that much more power running rich. In fact, all of the other systems on the motor are set up the ideal mixture. Without modifying the timing and advance you cannot take advantage of the rich fuel mixture.
David Teitelbaum

No need to worry about damaging catalytic converters :)! UK cat-free stainless exhaust.

I'm not saying that I'm running excessively rich. Its just a tiny bit. I know its only my opinion but I remember when we adjusted it and I notice a difference in pickup. (maybe I just want there to be a difference and just imagine it but still). Plus with the fuel economy as high as it is, it's hard to believe I'm wasting that much gas.

[Jeffu]

I have been following this thread trying to educate myself on an open loop system. To the best of my knowledge I have an open loop system in my car. My question is this...is an open loop system the best for a turbo set up, is closed loop or does it matter??
Here is what I have:

I am the 2nd owner of the car. The original owner put a BAE turbo system on the car shortly after he purchased it in '81.
The car does not have an oxygen sensor hooked up.
The car is not running a CAT.
FV is still hooked up ( I am assuming running a constant normal duty cycle?).
The car runs very rich at idle. I have hooked the motor up to a gas analyzer and we have dialed the AF mixture in as best we can.

I have heard people tell me that a turbo system needs to run a little richer than a normal set up. I am just not sure if I should be running my set up through the lamba or not? Any input would be gratefully appreciated!
Thanks!

[David T]

I am not sure about the single turbo kit but on the Island kit you can run in closed loop with an O2 sensor. You do not have to run richer bit on some cars it is done to try to cool the intake mixture slightly more. If you have a cat you should be running closed loop.
David Teitelbaum

[Farrar]

The "K" designation tells you it has the Lambda system running "over" the basic Jetronic mechanical system making fine adjustments to get closer to the ideal A/F ratio at all points along the curve.

Negative. The K stands for kontinuierlich, which is German for "continuous," a word used by Bosch to differentiate CIS from its predecessors. (Reference: Bosch Fuel Injection Systems, ISBN 1-55788-365-3.)

Farrar

[jerzybondov]

My car has recently had a 'new' crate stage II fitted (Delorean EU), at the same time all the sensors/pipes/fuelling/control valves where replaced. This was necessary as the car had a Renault 25 EFI Turbo engine when I first bought her.

The car is currently running closed loop and is ok but hot idle does hunt a little, would running open loop help on a stage II?

Simon - post on the DCUK forum about this. My suspicion is that it would help but Nick T will give you a definitive answer!

[David T]

You are correct Farrar. Technically our system is called K-Jetronic (Continuous Injection System or CIS) with Lambda Control or shortened to K-Lambda. One step up off of the basic K-Jetronic or K-Basic. I am getting this out of Bosch Fuel Injection & Engine Management by Probst in 5.2. As long as we are on this topic I always wondered how adaptable it would be to try to "improve" the engine systems by moving upwards to KE-Jetronic or Motronic. Probably more expensive and harder to do than Mega-Squirt or something like it. Aftermarket systems are more "open" and easier to program. BTW looking at the table on page 13 Bosch fuel injection systems sold in the US it says only 2,000 were sold to be used on Deloreans. Hunting is "normal" on the Delorean when everything is working as it should. As they say in the world of Lotus, "They ALL do that Sir"! By integrating all of the various systems on the motor together you could get the engine to behave better and eliminate the hunting. IMHO a better project than trying to go backwards and use a c-rb.
David Teitelbaum

[Bitsyncmaster]

Most of the hunting problems are caused by the lambda system changing the mixture and the idle ECU tries to adjust the resulting RPM changes and gets into over compensating.

When I added my wideband system all that hunting caused by the OEM lambda stopped. But if I were doing it all over again, I would just try a heated narrow band sensor. I think that is the major reason the OEM lambda system causes hunting. When it makes the mixture richer that cools off the O2 sensor which further indicates to the lambda ECU the mixture is to lean.

The wideband system uses a more complex heated O2 sensor.

[Farrar]

I am getting this out of Bosch Fuel Injection & Engine Management by Probst in 5.2. As long as we are on this topic I always wondered how adaptable it would be to try to "improve" the engine systems by moving upwards to KE-Jetronic or Motronic.

Great book! I read it frequently. After I first read it, I wondered the same thing about KE-Jetronic/Motronic. I think Motronic was perhaps more widely used in the U.S. and therefore parts would be easier to source, at least in theory. However, I never got around to seeing if either KE-Jetronic or Motronic* could be adapted to our engines. Folks would probably see it as an incremental upgrade as opposed to a giant leap forward in EFI.

Farrar

--
*or Larrytronic, or Curlytronic...

[mluder]

I'm not sure if this is the right place for thi...

I am having trouble getting the car through emisions (hydrocarbons way high) so I can register it. I have read many of the threads here and managed to adjust my fuel mixture so that the dwell signal reads around 35 degrees with the typical fluctuation. This got me better on my second test but still too high to pass. Sometimes, the dwell signal will shoot really high, 75 degrees, and then swing back down again. I'm not sure what's causing the occasional skyrocket - my guess is a vacuum leak (hopefully at a gasket and not a hole in the engine).

Here's my question... If I were to disconnect the lambda sensor and then adjust my mixture really lean, will I be able to get the emmisions to pass.

Any other tricks on how I could pass so I can get it registered?

Don't get me wrong, I want to fix it appropriately but for now I need to get it registered, then I can work out the real problem.

Thanks.

[Bitsyncmaster]

Here's my question... If I were to disconnect the lambda sensor and then adjust my mixture really lean, will I be able to get the emmisions to pass.Thanks.

You may get it to pass going open loop but if you adjust it to lean it may fail another emission test.

You should not see that dwell shoot up to 75. Unplug and plug in the connector on the lambda ECU and the O2 sensor. You may just have a bad connection.

[Manxmann]

Simon - post on the DCUK forum about this. My suspicion is that it would help but Nick T will give you a definitive answer!

Yes will do, not too worried just thought I'd ask as the subject had been raised, Interestingly I've just had Julian's new stainless lines fitted and this has improved matters no end, no figure!

[Jeffu]

I'm not sure if this is the right place for thi...


Here's my question... If I were to disconnect the lambda sensor and then adjust my mixture really lean, will I be able to get the emmisions to pass.

Any other tricks on how I could pass so I can get it registered?

Don't get me wrong, I want to fix it appropriately but for now I need to get it registered, then I can work out the real problem.

Thanks.

I was in the same boat back in July.

My car is running open loop, has a turbo and no CAT

The rules over here are as follows: Fail emissions 1st time you get a 30 day extension to make repairs and re-test. Fail a 2nd time you can obtain a waiver for a 365 day extension only after you can produce receipts totaling a min of $300 in repairs. If you are unable to pass after your 1 year extension your car WILL NOT be allowed to be registered in the State and therefore it would be deemed illegal to drive on any public road.

I did everything under the sun to try and dial in a leaner mixture with a gas analyzer. But we could never get it good enough to pass. After consulting with a few muffler shops about adding a CAT no one would guarantee adding a CAT would aid me in passing the smog test. Plus, once I drove it away from the shop I was on my own w/no warranty after spending $350 to add a non-monitored CAT.

I tried calling the Air Quality Board here in ID to plead my case but they would not make any exception for me even when I explained my car is driven less than 2k miles a year.

I finally resorted to doing this: I drained the fuel out of the tank, filled the tank up with 3 gallons of 85% octane fuel, and added 1 gal of denatured alcohol. Immediately drove to the test station and passed. Once done, I immediately diluted the mixture by filling the tank with 94% premium fuel.

Here are the results of my 1st failed test:

2500 RPM Standard
CO% ≤ 1.20 My Test Result 2.80

Idle test≤ 1.20 My Test Result 2.18

Here are the results of my 2nd test:

2500 RPM Standard
CO% ≤ 1.20 My Test Result 1.20

Idle test ≤ 1.20 My Test Result.28 !!!

Like you I still plan on addressing the issue of an over rich condition, I just was not willing to do it with a car the State told me I could not drive and was forced to park.

[mluder]

You may get it to pass going open loop but if you adjust it to lean it may fail another emission test.

You should not see that dwell shoot up to 75. Unplug and plug in the connector on the lambda ECU and the O2 sensor. You may just have a bad connection.

I'll try re-setting the connections. I replaced the Lambda ECU with a new one recently and I cleaned the connections at that time but I'll check again.

I have not examined the lambda sensor but visually it looks really clean so my guess is it's newish. I also have not tested the sensor connections to make sure it's functioning correctly.

I have been running with Seafoam fuel injection cleaner pretty regularly trying to aleviate dirty injectors. Can the continued use of additives create unburnt hydrocarbons? I would think it's the other way around.

I have also pulled half of the sparks and they don't have soot on them...

I'm spitballing here because I'm not really a car guy... Trying to learn.