Widebands That You Would or Wouldn't Buy

[Fred]

A quick glance reveals a lean tip in spike from stoich to 1.35 and back to stoich 120ms long. I may be able to find more than this, and this is likely over-filtered in hw as well unless I tweaked the component values, which I can't recall right now. This is with an SLC_OEM in an eval kit. I've got another one here with stoich to 1.3 in 20ms, so I think Alan is, as usual, under selling his product. Absolutely excellent IMO. :-) Granted, these figures could be lagging the actual reality, but there's really no way of knowing that.

I also have a piece of log with a brief PLL loss fuel cut, so brief the cut state didn't show up in the log, the time between packet before cut and packet after cut was 13ms, at 2356 RPM meaning maximum of 1 injection skipped with injections happening 4x per cycle in a TBI configuration. The lag from cut to middle of rising edge is 210ms, which is at least in part exhaust flow time from head to sensor about 1.5m away. The lean spot appears to last about the same, 200ms, which given the TBI setup and fuel puddling, could easily be true.

A LOT of assumptions above, but it's certainly pretty snappy to respond, no doubt about that.

Screeny of PLL loss followed by lean period, excuse lack of scales:

[Fred]

I also have a piece of log with a brief PLL loss fuel cut, so brief the cut state didn't show up in the log, the time between packet before cut and packet after cut was 13ms, at 2356 RPM meaning maximum of 1 injection skipped with injections happening 4x per cycle in a TBI configuration.

This was a bit wrong. After being Cut, resync occurs almost immediately, then there's the conservative wait period, then injection resumes.

1303.625 is when it became not OK to schedule outputs.
1342.75 is when it became OK to schedule outputs again.

So roughly one engine cycle/4 injections skipped.

[Hentai]

In the NTK stuff. I am not a fan of the NTK sensors. They have a few issues. The biggest one is that ,while relatively insensitive to temperature changes, they are VERY pressure sensitive. That is, very small changes in exhaust gas back-pressure cause significant measurement changes. The Bosch sensors are the opposite way around. They are relatively insensitive to pressure changes; but, are very temperature sensitive. Since the controllers can regulate sensor temperature, the overall accuracy is better with the Bosch sensors.

The NTK sensors are MUCH easier to control. The L1H1/L2H2 do not even require active temperature control at all; just a constant voltage. So, many controller manufacturers use them, mostly, for this reason. They are NOT more accurate. And, they are MUCH slower to react.

Which controllers do you refer to?

[HelmutVonAutobahn]

Which controllers do you refer to?

It's not the controllers. It's the sensors. The controllers do the best they can. I would not use the NTK sensors without some kind of exhaust gas pressure compensation. And, then, only for steady-state measurements. They are just way too slow to react for any kind of transition measurement.

[Hentai]

Which controllers do you refer to?

It's not the controllers. It's the sensors. The controllers do the best they can. I would not use the NTK sensors without some kind of exhaust gas pressure compensation. And, then, only for steady-state measurements. They are just way too slow to react for any kind of transition measurement.

Which sensors and controllers is this observed on?

[HelmutVonAutobahn]

Which sensors and controllers is this observed on?

IIRC, it was originally observed with the MOTEC & L1H1/L2H2 series NTK sensors. If memory serves, these are the ones that run with a constant heater voltage, instead of a closed loop control.

More recently tested on my AFX Powerdex with the LHA series sensor. The Powerdex does use a closed loop heater control. But, it is not nearly as tight as the ones used for the Bosch sensors. It works with an intermittent pulse; rather than a constant AC signal to measure the Nernst cell impedance.

This is probably because the NTK sensors have a MUCH higher thermal mass than do the Bosch sensors. Also, as I mentioned, the NTK sensors are relatively insensitive to changes in temperature.

The pressure sensitivity is present in both NTK setups. I could run cal gas through the sensor rig and put my finger over the exhaust port, just enough to slightly affect the flow, and the Lambda reading would deflect significantly. This does not happen nearly as much with the Bosch devices.

So, any setup that has a variable exhaust back-pressure at the sensor will be affected.

This is one reason that I don't recommend the NTK sensors. While the Bosch sensors are temperature sensitive, temperature is being regulated. Without some kind of pressure sensor feedback, there is no way to control for the pressure sensitivity of the NTK sensors.

As for response, while most Bosch based controllers have a response time of 80ms-150ms, The NTK based systems usually test at about 250ms-450ms or longer. The Powerdex seems to be one of the fastest of the NTK based widebands.

[toalan]

That is good information about the NTK, I have been trying to get a hold of the NTK datasheets for a long time but never could find anything, so all this NTK info is new to me. I did have an opportunity to test a brand new AFX unit with a brand new NTK sensor with calibration gas, the accuracy was 0.03 lambda too rich with 0.8 lambda calibration gas, I was not very impressed with the accuracy, but perhaps I was supplying too much gas and there was a pressure build up.

I am a bit skeptical of the lack of temperature control of the NTK sensor, even without considering accuracy; the lack of precise temperature control will screw up the response time of the sensor. The response time of a Bosch sensor is limited by diffusion, high temperature means faster diffusion and faster response time. If the temperature is all over the place, then so will be the response time of the sensor.

[Hentai]

so the ngk afx read 11.2X:1 AFR?

[HelmutVonAutobahn]

Even the NSA doesn't have good documentation on the NTK sensors.

If you want to try them with your controller.

1. For the original L1H1/L2H2 use an effective constant heater voltage of 10.5v ( relies on heater element PTC )
2. For the later LHA type sensors, target 85ohms on the Nernst cell and control normally. w/ adjusted PID values for higher thermal mass & latency.
3. Bypass the trim resistor. The values are all over the place w/ different applications. Use free-air calibration.
4. Nominal free-air current for the L1H1/L2H2 is ~5.8ma the LHA is about ~3.8ma
5. The heater takes about 20% more power than the Bosch sensors.
6. Pump-current to O2% transfer function is assumed to be linear.
7. Don't apply pump current until temperature stabilized.

This information was gleaned by scoping factory ECUs. ( and the AFX ). I don't think anyone outside of NGK/NTK knows much more than this.

With that, you should be able to get get a good idea of the different performance characteristics, using the same controller. Should be interesting

[Hentai]

This information was gleaned by scoping factory ECUs. ( and the AFX ). I don't think anyone outside of NGK/NTK knows much more than this.

Considering the AFX is not a NGK made item, and is a ECM CO dervied product I would disagree there
http://www.ecm-co.com/