ECMlink Why lock in open loop?

[enriquez2000]

I have my car tuned with traditional closed and open loop active.. my buddy that tunes my honda says he always locks cars in open loop.

Ia there any real benefit to this on my dsm?

 

[blktalon3]

I run mine in open all the time. It's seems a tad smoother and if my wbo2 sensor goes out when I'm driving around( which it has before, a few times) my car will still run good until I replace it.

 

[AdR]

If your tune is perfect, open loop is fine but you will tend to use slightly more fuel this way. The whole point of closed loop is to keep stoichiometry to 14.7-15.2 for the best, most efficient burn while on low rpm, part throttle scenarios. If you take it off, you usually have to go a little richer to compensate the fact that there won't be a nanny continuosly monitoring your fuel trims. If you have big injectors controlling trims tends to aggravate itself as they don't like low fuel, low rpm scenarios.

 

[bling5tatus]

Locking in open loop allows you to run leaner than stoich if you so choose and completely tune all aspects of your motor's output. You can definitely make your car get BETTER cruising MPG with full open loop than targeting stoich in closed loop.

 

[Kapok6]

Open loop here.

 

[dustyboner]

When tuning with hondata, you have to disable closed loop when your tuning the car. After tuning, closed loop is re-enabled.

heres why:

It is best to disable closed loop operation while tuning. Otherwise what commonly occurs is that the ECU will alter the mixture using the long term adjustment while the car is idling between dyno runs, which means that the mixture is not repeatable between dyno runs.

If changes are made to the engine which alter the amount of fuel that is delivered (bigger injectors, increased fuel pressure or altering the air temperature sensor voltage) the ECU will compensate the best it can using the long term adjustment. Under high load when the ECU stops running in closed loop the long term adjustment is not used so increasing fuel delivery via these means in not recommended unless the ECU is recalibrated or closed loop disabled.

At part load it is best if the ECU is tuned so that the mixture is close to stoichiometric. This reduces the amount of time the ECU will take to use the short term adjustment to alter the mixture to get the oxygen sensor voltage to swing past 0.6V, and keeps the long term adjustment from the zero position.​

 

[Black95TSIawd]

Luckily for us, our closed loop trims do not affect the wide open throttle fueling. (with stock ecu and dsmlink) You'd have to be a perfectionist to get the fuel map perfect. I see no reason to turn off closed loop these days. (You had to in the past to free up a port to log from.)

 

[turboglenn]

onfull stand alone systems (and some others) I like to lock in open loop while tuning the cruising and low boost areas, this way you can get the AFR"s as close to "stoich" as possible without the ECU being a band aid and correcting it to the desired AFR for you... this makes tuning the normal "closed loop" areas a lot easier, which helps tune out any stumbles from areas where the ECU may have to correct in a large amount one direction (richening up) then hitting a cell where it needs to lean out a bunch causing a buck in the otherwise smooth cruise.

As also mentioned above, it's great if you lose the 02 sensor while driving because the mixtures will be damn near perfect already. Also mentioned above, on ECU's where you cannot set the voltage you want the closed loop to operate around, it will allow you to run leaner or richer than what the ECU is wanting to run (on most stand alone systems you can set the "02 sensor stoich voltage' at both cruise and idle), so locking in open loop is again simply a tool to make tuning those areas easier. I know I've got mine right when I can re-enable closed loop and when I watch the correction factor and see adjustments of no more than3-5% in either direction.

just the other day my AEM sensor died (which it's 0-5v signal is what I use to control my closed loop operation, and since the tune was done so precisely without closed loop, there was no notable difference in drivability or fuel economy for the few days it took me to get and install a new sensor)