first of all I,m a diesel truck tech by profession but computers are everywhere so I'm learning! I have a Auto x-ray I use at work for gas pick ups maybe some info I get may help my 96 Z-28.
Ihear a lot of talk about widebands what is it? I think it's a very detailed O2 reading? what do they cost? and if I can use it how does it help? thanks for any info!

also is there a set # on where knock retard is too much? I have long tubes and lt-4 k.m. and have seen up to 8 degrees retard.

 

You want "0" knock retard.... once the PCM pulls timing, it tends to overshoot, then puts the timing back in slowly. My experience indicates it isn't unusual to see some knock retard on lifting throttle shifts, but that's about it.

Stock O2 sensors are "narrow-band". They are intended to be extremely accurate at 14.7:1 A/F ratio, because this is what is generally targeted at low/moderate/part throttle. It gives the lowest combined level of the pollutants CO, unburned HC and NOx. Also delivers decent fuel mileage. When you increase the load substantially, and approach wide open throttle (WOT) you generally need a richer mixture to make max power/torque. Generally in the range of 12.8-13.2:1... but varies with each unique engine setup.

When the A/F ratio deviates on the rich side from 14.7:1 by more than 0.1 A/F units, the stock, narrow band sensors are no longer accurate. The curve of sensor millivolts (mV) vs. lambda (A/F ratio as a function of stoichiometry) is so flat that a very large change in A/F ratio will make a very small change in O2 sensor mV output. And, because the sensor output in the "rich" range is highly dependant on sensor operating temperature, a change in operating temperature can cause a larger change in O2 sensor mV that a major change in A/F ratio.

So.... we need an O2 sensor that is accurate at richer A/F ratios. That's where a "wide-band" sensor comes in. These are O2 sensors that cover a wider range of A/F ratios.... typically from an extremely lean 20:1 to an overly rich 10:1. Using a wide-band sensor, it is easier to spot problems with A/F ratio at the rich conditions needed for max power/torque. And then to use the wide-band sensor to "tune".

If you are running a factory computer (PCM), you must use a narrow-band sensor (0-1000mV output) to allow the PCM to control A/F ratio in closed loop at low/moderrate loads. So, in that case, a wide-band sensor becomes an "add on" sensor connected only to an A/F ratio meter specifically designed to accept the 0-5V signal from a wide-band sensor.

Until recently, wide-band sensors were $300 and more, and required another $500-1,000 of electronics to indicate the A/F ratio. Couple that with a much shorter "life" than a factory narrow band sensor, and the wide band was pretty much limited to a "tuning" function. Some aftermarket computers, like Accel/DFI, FAST, or MoTeC allow you to run wide-band sensors as part of the normal A/F ratio control scheme, allowing "closed loop" (computer alters A/F calculations based on feedback from O2 sensor) control at WOT.

Recently, the cost of the sensors has dropped, and the electronics have become more reasonable. I believe the LM1 A/F ratio meter, with sensor is about $350. And there is a "kit" meter available for even less, using one of the pseudo-wide band sensors from one of the lean-burn Japanese engines.

 

wow thanks for the great reply! but I still have a couple of questions. do most dyno shops have or use wideband o2s or before I go is this something I should ask?
and about my knock retard mine does it while acclerating. no roller rockers yet! just long tubes and bolt ons. my computer has be reprogrammed by Ion and I have a new LT-1 knock sensor and new LT-4 knock module after the program.

 

Most shops will have a wide-band O2 sensor. They may charge you extra for using it on the dyno pull. I would ask before you go.

 

Where can we get wideband O2 sensors the stick into the exhaust pipe at the end.

I need something for the shop that I can tune cars with, and that I dont have to drill and tap hole into the exhaust on someone else's car.

The dyno that I went to had a O2 sensor that looked like a metal rod, that just clamped into the end of my exhaust pipe. This would be good for what I need.

Thanks,

D Moss

 

I don't think a sensor in the tailpipe would be very accurate, and it would take on heck of a long time to heat up. The bungs needed for an O2 sensor cost a few bucks and take a few minutes to weld in place.

The LM-1 works great, I was using it last night. Bought mine at www.kennedysdynotune.com

Rich Krause

 

I've been using the Innovate tailpipe clamp with the LM-1 recently and it seems to work pretty well.
It's much easier than requiring that every car have a bung welded into the exhaust that I'm going to tune.

 

Dan: how long does it take to warm up? Do you see ~14.7 when it goes into clsed loop?

Rich

 

Does the tailpipe clamp clamp into the end of the tailpipe, or do you have to drill into the pipe up by the engine and clamp it into the drilled hole?

Thanks

D Moss

 

Rich:
I'm seeing anywhere from ~14.5-15:1 in closed loop.
Only thing I can't seem to get is an accurate a/f ratio at idle. I was working on a car the other night that I set to idle in pe mode and couldn't get a decent afr. Not sure if it has something to do with the amount of backpressure at the tailpipe at idle or something?
Warm up time is probably 20-30 seconds, not sure exactly. All I know is it's quick enough for me.

D Moss:
It just calmps right on. Really easy.

 

I think that's what I'm looking for.

I may be putting in an order soon. Are there any drawbacks to this unit?

D Moss

 

I haven't found any drawbacks yet.
Then again I've only used it twice, and neither time has been on either of my cars.

 

We use a clip on wideband at our shop when doing dyno tuning. It works very well, the only problem I've found so far is that sometimes you have to make sure it's on there really good, or it sometimes gets knocked off when you hit the gas.

 

The clamp goes right on the exit of the exhaust. No drilling needed. There is a screw that holds the clamp in place.

 

On the cars we have done, it takes the unit about 10 seconds to warm up the heater. If you are talking about the narrowband sensor in the car, it varies between vehicles.