Advice on O2 sensor/gauge

M

mg_john

Well-known member
Ok, you tech guys have convinced me that I need to add an O2 sensor/gauge to the ole Spridget HPLP. I am pretty sure I was on the rich side at the SIC and the Prodfest with high EGTS but no problems with the engine.

I have looked at some afr gauge/sensor kits online but am unsure which one to choose.

I talked to someone at Autometer about their 4379 kit. The website says that the Bosch O2 sensor with the kit is specially calibrated for the gauge. I asked the Autometer person if a regular Bosch O2 sensor would work as a replacement. He said no, it had to be a Autometer sensor.

Is this the case with all sensor/gauge kits?

Any sugestions on a good kit for the Spridget?

Some high tech help would be appreciated by this liberal arts major!

Thanks,

John
 
they all use a similar bosch lsu 4.2 wideband sensor, but connectors may be proprietary / different. when I had my dyno, I had good luck with PLX widebands (but I dumped it right into a logger, no guage).

I can get a "deal" on AEM UGEGO packages (and probably autometer too), they all seem to be a touch under $200. replacement sensors are $50-80 (and I would plan on keeping a spare).

I did not have luck with the innovate widebands - they have a separate free air calibration & always seemed to lose the cal during a session (or on a dyno pull). You then have to pull the sensor, let it sit in clean air, and they press a cal button. No fun.

Kendall
 
The main normal options are Innovate LC1 and one of their gauges for about $200. I have been having issues with my LC-1 not reading all the time or giving flashing errors. I have to power cycle it and free air calibrate it sometimes to get it to work. They say to list it warm up before running the engine where everyone else says not to let the O2 sensor to run with out the engine running.

http://www.innovatemotorsports.com/products/lc1.php

PLX. They offer a gauges too.
http://www.plxdevices.com/product_info. ... EMOSMAFRV2

Another option is by 14point7.com that is used by some megasquirt people. They also offer gauges.
http://www.14point7.com/

Most of these wideband that use a Bosch 17014 LSU 4.2 Oxygen Sensor. You can get it from Amazon.com for $52 or from Advanced Auto for about $60.
 
mg_john":3dhjx75n said:
Ok, you tech guys have convinced me that I need to add an O2 sensor/gauge to the ole Spridget HPLP. I am pretty sure I was on the rich side at the SIC and the Prodfest with high EGTS but no problems with the engine.
Click to expand...

I'm confused. You think you were rich but your EGTs were high? That's backwards to me. Too much fuel quenches the explosion and lowers the EGT. Rich does no harm to the motor except it robs you of power. It's when it's lean that bad shit can happen. I always aimed for 1350-1400F on my EGTs. Please clarify for us.

Now, as for the AFR meter, I too have an Autometer (I don't know which one....I'll look it up when I'm at the shop tomorrow) in my LPHP 1275 and it works fine. I was told by them that the stock Bosch sensor would work.

Dayle
 
John,
I have 2 of the PLX units and the have worked great for several years.
They also have a output to record on a DL1 data system should you acquire one for your car.
Bob C
#31 HP
 
Dayle and others:

I told you guys I am a liberal arts major so here is my reasoning for the rich/high egt scenario. Too much fuel for complete combustion gets dumped into the exhaust system where it burns and shows high egts. Mine were 1500. My egt probes are about 1.5 inches downstream from the header mating surface.

Thanks for all your help. It looks like I can replace a sensor with a standard Bosch unit so I will probably go with the autometer 4379 - about $190 plus shipping.

John
 
The "external combustion" you're thinking about won't happen 1.5" from the port. At the collector, yes, not at the port. You'll have the real answer when you get AFR data. That's the trouble with EGTs alone, they really don't tell you much.
 
Where do you mount the O2 sensor on a spridget? I too am adding one, was looking at the pipe off the connector that dumps into the tunnel pipe - and am thinking Iwill have to use exhaust sealant on both ends of this pipe to make sure I don't have ambient air leakage making for false readings -
 
I agree with Dayle that you probably weren't running too rich. The high reading is more likely because you have the senseors too close to the head. I don't know where you got 1.5 inches from but I believe that they tell you to mount them further away. Mine are about 4" and I get 1400 degrees on the EGT's. I've never seen 1500 and I would agree that is too high, and if you saw that at 4" out I would be concerned. What does your tailpipe look like?
 
So, we have the Innovate MTX. How the heck do you know when the thing has to be recalibrated?!

Last weekend it seemed like our A/F readings were wonky, and I found myself wondering if the gauge was malfunctioning . . .
 
dellenwood":f48lgs6e said:
So, we have the Innovate MTX. How the heck do you know when the thing has to be recalibrated?!

Last weekend it seemed like our A/F readings were wonky, and I found myself wondering if the gauge was malfunctioning . . .
Click to expand...

I have the Inovative LC-1 with their DB gauge. Originally I did the calibirate test with the Bosch free of the exhaust pipe. Now when I start the motor sometimes the gauge reads 7.1 IIRC & I push the little red push reset button & the thing comes to it's sences & works well. It does change while flashing it's gauge numbers while on track. I have also been told by someone with their own personal Dyno & Inovative AF in many customer cars that the Inovative reads .4 to .6 leaner than reality. Meaning that if the deal is reading 14.1 (best normal to LEAN) reality is the AF IS 13.5 ish which is ideal ratio.
 
David Dewhurst":rhswfc47 said:
I have also been told by someone with their own personal Dyno & Inovative AF in many customer cars that the Inovative reads .4 to .6 richer than reality. Meaning that if the deal is reading 14.1 (best normal to LEAN) reality is the AF IS 13.5 ish which is ideal ratio.
Click to expand...

It is was reading 14.1 and really 13.5 that means Innovative reads leans not rich. If it is really reading rich it would read 13 when the AFR is really 13.5. Just wanted to check what your were trying to state. Lower number is richer. I have also heard Innovate reads a little rich also which is on the "safe side" which may be why they are this way. When dyno tuning we use the AFR as a starting point but make adjustments based on the dyno numbers. Then any changes after that at the track are to get it back to the AFR we were reading during the best dyno tune. Same with EGTs.

Anyone ever used a 4 or 5 Exhaust Gas Analyzer when doing dyno tuning?

Now should we also talk about an O2 per cylinder and doing EFI trimming per cylinder?
 
mg_john":12gd9w7s said:
Dayle and others:

I told you guys I am a liberal arts major so here is my reasoning for the rich/high egt scenario. Too much fuel for complete combustion gets dumped into the exhaust system where it burns and shows high egts. Mine were 1500. My egt probes are about 1.5 inches downstream from the header mating surface.

Thanks for all your help. It looks like I can replace a sensor with a standard Bosch unit so I will probably go with the autometer 4379 - about $190 plus shipping.

John
Click to expand...

John I've seen this firshand, Mike Barefiled had this problem with his LP 1275 Midget several years ago and was using a way richer needle than I, and others were running. He asked me to go to the chassis dyno with him, and I did with my LP 1275 carbs in hand, sure as hell his EGTs were off the chart lean, but his AFR was way rich, I put my carbs on his car with leaner needles, and everything worked great, EGT and AFR wise, so the I duplicated my needle and jet settings on his car, and 100% cured his problem, so not theory, but actual dyno testing.

I also saw a similar issue on another car with overly rich condition, no EGT to give me feedback in that, but it was internal distributor issue, causing the timing to be way retarded, and on chassis dyno the header would turn almost transparent red in a single dyno run, and AFR was off the chart rich, I'm 100% positive had that car had EGT gauges on it, we would saw the same thing we saw on Mike's car.

As weird as it sounds, this condition does exist and I saw it before, it has gotten me to conclusion that EGTs are great for fine tuning , but can give you false readings if the fuel mixture is out to lunch. On my vintage MGB I have both EGTs and O2, and when things are right I see close to 1300 on EGTs and about 12.5 on O2, I like having both on our type cars, with our dual carbs, because if all is right I can use the EGT to separate the two carbs, and the O2 to give me the overall picture.
 
We are going to take the car to a dyno, hope that the A/F reading from the dyno is accurate, and calibrate our A/F gauge against the dyno. If our guage is wrong, at least we will know how far off it is.
 
Nothing can replace a full throttle ignition cut. We do 2 pulls on the dyno then look at all the plugs. You have to know from the plugs and ignition timing that your mixture is in the window or you are wasting time.
 
With the O2 sensor you have to make sure there are no leaks in the exhaust system including the exhaust manifold gasket. Air intrusion will cause all kinds of weird readings. I have not had any issues with my Innovate LC-1. My experience has been if I can get the engine to run the readings will be in the range of a wideband O2 sensor.
 
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