Wideband short-comings

[We're on Boost]

Decided to see what I could learn by reading about the NGK AFX, also some of the NGK OEM news.
I have a lot of respect for Japanese engineering. They are very attentive to detail, and they are not afraid to study and learn (not just copy) from other peoples designs. They often are able to improve on what they see other people doing.
The europeans I respect too, they seem to appreciate quality. The Germans especially are practically born to be engineers. It doesn't hurt that the europeans have national priorities set at the government level to promote them being on the leading edge of technology. On the other hand they seem to be not too wild about studying other people's ideas. They want to do everything "their own way". So sometimes they leave me scratching my head wondering "why did they do that"? The explanations are usually either not available, or not very compelling.
In the US, we do a lot of cool stuff at the small company level, as in the automotive aftermarket. But at the big OEM's there is a lot of greed and profit milking that has spoiled the day for a long time. Well I don't want to wreck my weekend thinking about that.
NGK AFX - The manual has some interesting points, from the top:
Do not modify the wiring harness
13 foot wiring harness from sensor to control module
Measurement range from 9 to 16 AFR gasoline, 0Volts=9afr, 5Volts=16afr
Free air calibration required. "You cannot reliably calibrate the AFX with the sensor mounted in the exhaust of an engine, even if the engine has been off for several days".
Calibration frequency guidelines -
When new
For every 3000 feet change in altitude - (this sounds like the pressure sensitivity that WB's are known to have)
For mild street engines - once per month of street use
For continuous use with leaded fuel - calibrate once per hour yeah I'm gonna do that!

A feature that I think is cool, there is a calibration knob that you turn when calibrating. They say pay attention to how far you have to turn the knob every time you calibrate. If you don't have to turn the knob very far, or at all, then you could calibrate less frequently. I think with most of the other brands that have a calibration routine you have no idea about this because the calibration is "black box".
"You may use the AFX as a constant AFR monitoring tool, but keep in mind that this will consume the sensor faster. If you are not using the sensor to tune the engine, we generally recommend you take it out".

The reason why us performance tweaks are using widebands is so well stated by them I just have to quote it even though we all know this:
"One way to tune the fuel delivery is to do a lot of track testing. However, because the relationship between AFR measurements and maximum horsepower, best throttle response, engine life, and best fuel economy are well known, it is faster to first tune to specific AFRs and then to use actual track performance for final fuel delivery adjustments."
They do discuss the possibility of excessive electrical noise from the ignition system. I would imagine their 13 foot cable is shielded to reduce this. The sensor cables sold by WBO2.com (in Australia) are also supposedly shielded and WBO2 shows some nice pics of them on their web site. If I were to extend a sensor cable - like on the Innovate LC-1 which has such a short sensor cable, I would buy some of this shielded cable. The AFX manual says not to modify the sensor cable but they don't explain why.
No spec given for response time.

Phew, I need a break.

 

[the_mork]

I'm not sure how reliable this is but I had a guy that I was talking to at the track one day tell me that he switched to using an NGK wideband sensor because once they start failing they just quit working entirely instead of giving false readings that can cause you to hurt your engine.

 

[twdorris]

Decided to see what I could learn by reading about the NGK AFX, also some of the NGK OEM news.

Well, FWIW, many of the "big boys" claim NGK AFX is the way to go as well. I tend to suggest NGK AFX or LC-1 as a result. The LC-1 suggestion is based on my own preference and experience. The NGK AFX suggestion is just based on what I've heard. I've never seen an issue with the AFX come up on our boards...but that may be because so few people (relative to other brands) run them.

Thomas Dorris

 

[We're on Boost]

but that may be because so few people (relative to other brands) run them.

It could be that few people run them because the AFX got a terrible review a couple years ago in Ford Muscle magazine. It was a comparison test that included the LC-1, AEM, and several others. You have to have a subscription to see the whole article on Ford Muscle's website, but there is a reprint of the whole thing on Innovate's web site - probably because the LC-1 won this shootout . In the article they say the AFX came with a Bosch sensor! not an NTK sensor, and the accuracy was terrible. Don't know what to make of that! I just found this article this morning.

They did some cool things in this test. For one thing they measured "Latency". The quickest WB was the LC-1. It was the only one less than 100 milliseconds. I like this comment they made about latency: "Response time is critical because it's possible to have accurate data, but, due to high latency/delay, the data is essentially in the wrong column of your fuel map." Latency of some of the other units ranged all the way up to 500 ms. However I don't see where they described the conditions under which they measured latency. I know the delay will vary depending on what the afr is, for one thing.

http://www.innovatemotorsports.com/resources/FM_WB_Shootout.pdf

 

[We're on Boost]

The other thing I found this morning is the Innovate paper called "Direct Digital" which explains how their controller works. The way they control the pump cell is completely different than how other people do it. The bottom line is much faster response. They show a graph of their response time vs AFRs from 12 to 20. The slowest response shown is at afr 12 and it is only 10ms! The chart doesn't go below afr 12, I suppose response keeps getting progressively slower as afr goes down from there. They show their blue curve flat-lining at 12 afr which is confusing. Guess I'll have to call.

They make some comments relative to OEM usage of widebands, like this one: "Due to the slow response time of PID systems, even the most sophisticated modern vehicles must go "open-loop" for up to 500ms after major throttle transitions". They go on to describe how OEMs could improve their emissions and mpg performance by using the Innovate style controllers which would enable "full time closed loop operation". From other reading I found it sounds like the OEMs using widebands currently are basically using them to implement "lean burn" (leaner than stoic) at light loads, they still go open loop I think at higher loads and during transitions.
The above comments about OEM usage and response time answered a lot of the questions that I was looking for answers on. But the next thing in the Innovate paper was something I didn't expect and wasn't even looking for. They say "Direct Digital technology is fast enough to enable a single sensor to detect individual-cylinder lambda as the "slugs" of exhaust pass the sensor. This allows the ECU to vary each injector's duty cycle, and precisely manage each cylinder." Now that is pretty amazing if it is true.

http://www.innovatemotorsports.com/resources/AN19_1.2.pdf

 

[romeen]

We're on Boost, you may find this an interesting read.

http://secure.telematica.gr/images/web/plxdevices/download/PLX_Critical_Response_Technology.pdf

Apparently, PLX uses the PID technology that Innovate criticizes. PLX doesn't give any actual numbers with regards to response time which might imply that the numbers aren't as good as the LC-1.

Having said that, I can say that my PLX unit seems to work very well and reacts instantly to the slightest of throttle inputs. From my own personal observations it doesn't seem to bounce around as much as the AEM unit. I have never seen the LC-1 in action.

 

[We're on Boost]

We're on Boost, you may find this an interesting read.

Thanks! They are the only people I've seen with a discussion about requiring free-air calibration vs not requiring it. They say it's not required with their stuff.

They talk about the very small changes in voltage and current that have to be measured accurately in order for these devices to work properly. A few months ago I won a lottery that got me into a 3 day class in Instrumentation Engineering taught by Pat Walter. He worked at Sandia Labs from 1965 to 1995. I call him "one of the guys who won the cold war". After the cold war he helped design the fuse that detonates our "bunker buster" bombs. This fuse has to be smart enough to let the bomb penetrate dirt and concrete without blowing up, then it is supposed to blow up when it finds itself inside a room, within a very short time window, before going into the dirt again. Then he led a team that did the failure analysis on that Boeing 737 "convertible" that flipped its lid over Hawaii a few years ago. ANYWAY, one of the things I came away with from that course is that it's amazing any of these sensors work at all, not to mention being accurate or reliable or anything that you would want in a day to day device like a car. We have come a long way with technology that's for sure. And when I asked Pat if he knew anything about oxygen sensors like we use in cars he said, "Not a thing". So here I am.

Gary