You can use a 02 sensor /bung housing from an old section of exhaust and put your own ends on. Or buy a new sensor housing to put into whatever pipe you want, new thicker pipe won't burn through too badly either. Think 18mmx1.5 but stand to be corrected... Maybe get a thick block of steel, tap hole 18mm in it,plus big hole for exhaust gas , use as removable spacer between silencer an tailpipe...
Its definitely the case that the PLX and Innovate LM2 type systems use a Bosch sensor. These sell for more now than a few years back. Meanwhile there are Chinese sensors that are a quarter the price. And which work. You need a heater control loop to get it to a stable temperature and a feedback circuit to force the oxygen into the cell. Basically an Arduino and a couple of other parts.. thats what is inside the PLX control box. The two wire sensors just produce a voltage that flips from nothing to full scale around 14.7:1 AFR. A multimeter and a calibration chart would work. But that sets idle only. I drive all the time with the O2 sensor installed amd watch the AFR gauge from time to time, as this means I can watch the effect of jetting at mid throttle as well as flat out and idle. Something its harder to find on a rolling road where mostly you are measuring things while trying to maximise acceleration against the inertia of the rollers for those torque and HP measurements.
I’ve taken the plunge with an AEM X series A/F gauge. I got sick of mulling it over & decided to go for it. My thoughts are to check the idle A/F before hard wiring it so the gauge is at the back while i tweak the mixture screw. Then install it with an extension loom front to back to the O2 sensor. That way i can easily remove it & sell it on if needed.
It's pointless and actually wrong to set your idle mix by AFR. Just set to best idle in time honoured fashion. Sure look and see what results but don't adjust to it. It's use is idle jet sizing if you're trying to get mileage if you have an SVDA distributor and carbs you can drive without the main jet stacks fitted and then sizing your main jet to be as lean as possible but safe. Lean is good for mileage and good for crisp acceleration but too lean is dangerous hence the AFR meter.
Yep it was more checking than adjusting at idle. I have an O2 port for each bank so want to see if they are something like balanced. (TwinICT’s) . I spent quite a while setting up for a decent idle last year when I fitted the engine so don’t want to spoil it. Particularly with it being an auto.
Some like the PLX gauge (and the AEM setup) have an analog output on the computer box, which on my bus is left as a bullet female connector hanging down. It gives out a voltage which is proportional to the AFR for use with EFI, but you can wire a multimeter to it in the engine bay. 14.7 AFR becomes 2.35 volts. For PLX it is defined in a simple equation (AFR-10)/2. The AEM output is different .. it covers a different richer range. What I did in the end was to have a multiway connector under the dash on one end of the extended AFR gauge wiring and another identical one teed off in the engine bay. The display is on a quick release mount under the dash, so I just unplug it from the front and plug it in the engine bay for fiddling. One thing you will find is that the harnesses provided for these gauges are for front engined cars and so just like rev counters you will need 5 to 6 metres of cable. So splicing an extension on the cable or finding matching plugs and sockets and extending with another multicore cable will be needed to reach the dash for the gauge to be useful. I dont think the cable on the AEM unit is fancy, it looks like it is just a lambda sensor cable on one plug, just the heater power and ground cores have to be reasonably thick. PLX is different. The sensor goes to a computer box, what goes to the front is power and serial data for a separate multifunction display. Which I totalled when a 12 volt wire melted across the PLX wiring in an engine bay fire. For some reason PLX feed 7 volts and 3.3 volt power with data down their cable. I now use a 12 volts plus data 3 core cable and my own multifunction display.. If you have maker skills you could take the rs232 or CANBus output from an AEM gauge permanently mounted in the engine bay and make a dashboard display using that data.
But... Any fiddling with fuel/air mix based on O2 content without the engine being under load is completely pointless? What do you do with the AFR meter in the engine bay? Q to Gooders - how will you balance your carbs with AFR. I'm not seeing that as possible.
So the Vintage speed silencer has 2 lambda sensor ports, one for each bank. I toyed with getting a dual lambda gauge set up but the price is crazy. So i have taken a reading at one bank then swapped the sensor to the other bank & vice versa. My manual set up of idle mixture wasn’t far out only 0.5 between readings. All i have done is evened them both up to balance both banks. They are both at 13.1 now & idle is sweet. If i go nearer 14.1 it’s more lumpy so I'm happy at 13.1. Next stage is to install the gauge in the bus so i can check cruise & WOT.
The other reason I am going the AFR way is engine life. The rolling road can break things expensively (more with an inexperienced operator). I've seen two engines that might have lasted 10000m or indefinitely need a rebuild, from the strain. The type4 unit doesn't have massive oil pressure in most rebuilt/well used ones. The rolling road simulates road use, but that's not real world use, I suppose air-cooled have permanent fans its but no guarantee of overheating. From this info am erring toward asm, but more researching to do for me.... I could manage extending cable or attaching voltmeters but not a lot more...
On the other hand with AFR you will perform a lot more wide open throttle test runs trying all kinds of combos of vents and jets just because you can and because a lot of different ones will work, but one will be seat of the pants better for your engine/vehicle. I kind of regret putting mine through that and then ending up where I guessimated in the first place before I got the meter. I don't think it's done the engine any favours. As you say in real life I don't drive it up the revs like that ever but you have to do it just in case you did. Once could kill it if you were too lean at high revs WOT.
Ironic I've spent many hours at work shoving the probe up exhausts for mot, but when I need to do my own car there's no equipment around! Suppose those machines were a bit big to drag about the streets... Not much learned at work, bar exhaust leaks affect figures and putting a wet rag on holes helps that. There is the cb performance supply carb with rich jets then work lean method, and if you have been not far off before using guages......
But I didn't know I was doing it ok. Well I did really...because I'd previously taken it to an RR with AFR - it was a tad rich on the mains. But then I got into trying for a lean idle jet cruise to save fuel. God knows why. I found I can run my bus on tiny idles but that more than a couple of mm of throttle and the idles were over. That's coasting at 30mph, any more throttle and you're on the mains. In a beetle it would be 50-55mph so worth the effort. But with lean idles it basically screwed up everything else no matter what I did and was incapable of running big enough venturis while covering the hole between idles and mains that the lean idle jets caused. All quite interesting actually. With the std 55-57 idles it all works and I can run smaller mains in bigger venturis, have more power and ironically get better mileage...which is where I started before going round in a big circle. I have 4x just about every jet and vent that will fit my carbs.
So A/F gauge installed, just been out for a run & I’m getting 13-14:1 cruise at 40mph+ . 12-13:1 full throttle under load so I’m happy enough with that. Think im pretty rich in idle circuit though as idle & part throttle also on over run im around 11-12:1. Don’t see this as an issue but I might see where i am with 55 idles rather than 57s. Not going to compromise the smooth idle I have at the moment though.
Late answer, use it to display RPM and AFR , for idle setup/ confirmation. Or display battery voltages or MAP or oil pressure. Its all a twist of the selector knob.
But the subject was afr, not battery voltage, MAP or oil pressure and if you set your idle mix by afr it's highly unlikely to be optimum.
