I have an NGK powerdex wideband system that cuts out when cranking. It's wired in to a switched power source that stays on when the starter is engaged. The issue I'm having is that when I initially hit the starter, the battery voltage drops JUST below 11 volts, and just momentarily at that. The installation manual that I have says it has to have a power source that is between 11 and 28 volts DC. If battery voltage gets too low, it cuts off. As soon as power is back up above 11vdc, it goes through its power-on cycle. The power-on cycle lasts 20 seconds, and it gives a little countdown on the display. While it's powering up, it also energizes the internal heater.

This really irritates the hell out of me, because no matter where I wire it, as soon as I hit the starter it will die off and then immediately go through the power on cycle. So no matter what, I have no idea what's going on for the first 20 seconds after start up. Now, I understand that the wideband won't give an accurate reading until it reaches 600 something degrees, but the power on cycle DOES that. So it's very hard to tune my "afterstart enrichment", and "warmup enrichment" when I have no clue what's going on until 20 seconds goes by. And believe me, 20 seconds is an eternity when trying to tune for cold startup.

Anyways, my idea is to try and wire in a capacitor in parallel between the power and ground. That should be able to supply the power needed during cranking. Then, I'd wire in a diode to prevent the cap from trying to charge the battery back upon initial draw. Am I on the right track here? And if so, what size capacitor would I need?

 

check your chassis grounds, dont quote me on but dipping below 11v on crank seems low.

 

Isn't it rather normal for the voltage to drop while cranking the engine as pin 3B of the ECU will fall to about 10.5 volts w/key to start as stated in the FSM and this is a best case scenario. Would powering your wideband to a secondary battery creating 12 volts help you get the information you need for tuning purposes?

 

I guess I could... i mean, I do have a spare fully-charged lawnmower battery just chilling out in the garage that I could use. I just figured I could do something a little more permanent than that though. And dipping down to about 10.5 is pretty normal actually. The starter is a series-wound DC motor, and they have some serious starting torque that can take a decent amount of current, especially when CEMF=0. I have an optima red top, and it still drops battery voltage down JUST below 11 volts. That's when the key is FIRST bumped over to start though. After the starter first engages, CEMF builds up enough and the current draw is low enough to allow voltage to go back up in the 12s.

 

you could try something like this

DC 3-35 to 1.2-30V Automatic Buck-boost Converter Voltage Regulator for Solar Power Panel Power Supply

 

I don't think a capacitor will have enough current capacity for the O2 sensor heater. I'd go with the lawnmower battery temporarily.

 

Very true. I was worried about that. The max current draw from the module is 2A though.

I was looking for something like that! I didn't know that companies just sold buck/boost circuits. 2A capacity as well. Can't beat the price either. Thanks!

 

i'd use the battery, or a computer power supply (not sure about the amperage on those @12v)

 

Maybe,Put your wideband to a Switched 12 volts source?
You will always know it is on because it is lit up,so after killing ignition,kill the wideband..
NOTE: You just have to remember to shut it off!(or it will burn the heater out f the sensor).

 

It's due to the massive amperage draw from the starter. It will drop the entire cars voltage because the battery is dropping. It's not possible for a battery putting out sub 11V during cranking to maintain anything higher that that.

You could do something like a Joule thief but honestly it's too much work.
Make a Joule thief.

Your only solution is to use a separate power source. I use a semi dead(enough power to run stuff but not start car) PC680 battery for my car test rig.

//edit. Just saw people already said what I did. I still doubt buckboost/Joule thief stuff will be able to handle the massive current draw. I think it'll still dip with the source, just not as much if joined with a large cap.

 

It says max output of 2A, which is also the max draw of the wideband O2. For less than $10, my feelings really won't be hurt if it burns up

Digi7ech, I was thinking the same thing today actually. I'm not too sure the boost circuit would be able to respond fast enough to account for the input voltage dropping as low as it does. Fortunately, the input voltage to the WB can be as high as 28v, so if I increase the output voltage of the boost circuit to around 20v, maybe the output won't dip below the 11v minimum and kill the wideband.

I'm still considering doing the cap/diode treatment. I'm going to go dig around in my electronics box and see what I can come up with. I'll post results later. If it doesn't work, I'll use the lawnmower battery as a band-aid until I can figure something else out.

 

if the wb is really drawing 2A, the cap will have to be huge to stay charged for a couple of seconds of cranking. the buck/boost converter will work a lot better

 

It's literally a fraction of a second that the batt voltage drops below 11. Only on initial start. An it only draws 2A MAX. I'd assume that's while the heater is energized during the countdown. I'm still looking for a decent sized cap, but I have a feeling I can find one

 

Ding Ding Ding

you need a secondary battery or an external power source. Basically, use a 115V AC --> DC converter to power your wideband and do cold starts in your garage. I can tell you from firsthand experience that these are your only options. IMO, that's too much trouble considering you're not exactly tuning for cold start emissions.

 

I went for broke and wired in a 4700uF capacitor and a large diode like the little MSpaint picture showed.

Works like a champ