open vs closed loop

[ramcustom]

which loop do you want for better mileage when using HHO? Open or closed on the ecu?

[Alex Tyrrell]

When the ecu is in closed loop it is performing a series calculations to keep the fuel consumption down. When you accelerate hard, or you are missing a sensor the ecu goes into open loop. This means that it does not preform those calculations, instead it lowers the air fuel ratio and the car runs richer. This is for the purpose of better acceleration, or if you are missing a critical sensor; to get the car home without causing damage incurred by running excessively lean. In other words if you are missing a sensor it will run extra rich. To tune with hho you need to higher the afr (run leaner), which is not accomplished in open loop.

[OUScooby]

CL uses single AFR target values the ECU will try and help the car maintain, OL uses a table of different AFR values for varying engine loads vs rpm.

[BackinHHO]

When the ecu is in closed loop it is performing a series calculations to keep the fuel consumption down. When you accelerate hard, or you are missing a sensor the ecu goes into open loop. This means that it does not preform those calculations, instead it lowers the air fuel ratio and the car runs richer. This is for the purpose of better acceleration, or if you are missing a critical sensor; to get the car home without causing damage incurred by running excessively lean. In other words if you are missing a sensor it will run extra rich. To tune with hho you need to higher the afr (run leaner), which is not accomplished in open loop.

I read somewhere (maybe here!) that someone pulled the upstream O2 sensor to force the ECU into open loop mode, basically, turning it off. That allowed them to control AF with a MAP or MAF pot, and not worry about the ECU eventually negating their gains.

[OUScooby]

I read somewhere (maybe here!) that someone pulled the upstream O2 sensor to force the ECU into open loop mode, basically, turning it off. That allowed them to control AF with a MAP or MAF pot, and not worry about the ECU eventually negating their gains.

But you would get better MPG in CL, so why would you force it into OL?

If you want your car to stay in CL (or to switch to OL quicker) it would be safer to do this with a tune and adjusting the CL/OL delay, not by pulling off sensors.

[BackinHHO]

But you would get better MPG in CL, so why would you force it into OL?

If you want your car to stay in CL (or to switch to OL quicker) it would be safer to do this with a tune and adjusting the CL/OL delay, not by pulling off sensors.

It's a good question. The following is from the thread 'Default HHO That Works'

glester
Newbie

Well, I am not getting an 81 percent increase, but I have seen gains of up to 20 percent (tank averages) with my system that I purchased from www.hydrogen-boost.com. I didn't shell out 3500 bucks either : About half that, installed. My system runs open loop which means I have the upstream O2 sensor disconnected. I control the A/F mixture via a 50K ohm pot that is wired into the MAP sensor. I have a 1998 toyota Corolla LE, 4 spd auto, and using Scangauge as a guide, I am seeing upwards of 55 miles per gallon on flat stretches of highway at 55 miles per hour. The HHO system is not on all the time, but is switched on via the combination of both a vacuum switch and a high current relay. The unit will not switch on until the MAP goes above 5.0. I've had this system since October 2008 and am quite satisfied with the performance. Fran Giroux is one of the honest guys in the business who does NOT make outlandish mileage claims. Check out his website. BTW, I am neither a dealer nor a representative of Hydrogen Boost. Hope this helps!

George

[Alex Tyrrell]

When you alter the map sensor signal you change both afr and timing. You need to adjust them independantly.

[ramcustom]

and how do you do that?