A guy at work has made a meter to check of the car is running lean rich or just right. He uses an oxygen sensor somehow. Unfortunatly he is off for a few days and I want to make one and adjust my carbs for an upcoming autocross. Anyone here know how to make one?

Pick up a cheap 1 wire O2 sensor from the auto parts store. While you're there, grab an air fuel gauge. just make sure the meter has a one wire input and that the meter gets grounded well to make a good connection.

The 2 wire O2 works faster cause one of those wires helps pre-warm it, as O2 sensors work best when warm.

That's about it. I copied this from a forum on HybridZ.org ........

" well your main concern when tuning an engine is to keep the all the cylinders running aproximately the same ratio and at about 12.8:1 for max power up to about 14.7:1 for low emmissions and good mileage,

so whats the advantage/disadvantages

a fuel air meter uses a o2 sensor, if you place it in the header collector it gives an AVERAGE of all the cylinders on that cylinder head,If theres an (X) installed close to the dual collectors reversion pulses can occasionally even give data from the other side of the engine, so in theory and in practice you can have two cylinders run lean and two rich and the AVERAGE tends to look RICH to the O2 sensor as it SEES unburnt fuel, if you place it in the individual primary header tubes you either need eight O2 sensors (VERY EXPENSIVE, and keeping the wires from burning or grounding outs a TOTAL P.I.T.A......IF you don,t succeed you destroy the O2 sensor and need to replace it.) or you need to be constantly swapping very hot and fragile O2 sensors and bung plugs constantly, but with the IR thermometer you can almost instantly see which cylinders are running hotter or cooler and adjust the jets or look for vacuum leaks, or other CAUSED for the TEMP DIFFERANCE, ETC, far faster too get all the cylinders running at approximately the same temp, indicating the same fuel air ratio, youll be amazed at how close the temp follows the fuel/air ratio, and you can confirm it with plug condition and the other test equipment. run any cylinder too lean and detonation can break rings or melt pistons, run it too rich and you can wash the oil off the cylinder walls and ruin rings/scuff pistons, you need to know whats going on in EACH CYLINDER not the AVERAGE of all cylinders.

SO, if your going to install a decent wide band fuel air ratio meter on your car thats fine, its going to be an asset to your tunning skills, if you install the indicator/gauge inside the car and weld in a couple extra bungs in the collectors for tunning and wide band O2 sensors which are a big help, but you will quickly find that its a P.I.T.A. to use it for tune ups on all your buddies cars with the welding collector bungs and installing plugs and O2 sensors while the IR thermometer route is fast and very simple and you can confirm with oplug reading the condition of the engine.

YEAH! theres meters that you can stick in a tail pipe, but they read THE AVERAGE, not the individual cylinders ,

think about AVERAGEs

AS my old physics proffesor once said,

IF, I pour molten lead in your front slacks pockets and pack your butt in solid with DRY ICE,.... ON AVERAGE your comfortable "

Also see these.... Great info as well....

http://www.racetep.com/halmeter.html

http://www.scirocco.org/tech/misc/afgauge/af.html

http://www.redline.lt/magazine/spec-features/article/article/17/1/

Dave.

Thanks that is great info. i like you analogy of average as well.

IF, I pour molten lead in your front slacks pockets and pack your butt in solid with DRY ICE,.... ON AVERAGE your comfortable

One of the main reasons I think the California biennial smog check is such a joke. Sniffer in the tailpipe, 15 and 25 mph. Basically first second gear in any transmission at speeds you'll never drive for any length of time to matter. Plus those speeds would be achieved at different RPM depending on the gearing of the car tested. Ludicrous. End of mini-rant. Back to topic: That's why I bought one of those meters that you can stick in the tailpipe. So I can check the average readings before a smog check. But I doubt the adjustments that put it in range to pass the test result in anything close to a 'performance' tune.

Seems like a good compromise would be to have a wideband on the first and last three cylinders, because you're not going to do any significant amount of adjustment in mixture between cylinders that share the same carburetor (unless your valves are way out of whack). Even the FI systems commonly used (280Z/ZX and Z31 ECCS) aren't tunable to the individual cylinder, because they're batch fire.

So, unless you're running some fancy EMS, going with 6 oxygen sensors is overkill. Go with the number of carbs, or the number of batches (if practical, and the batches fire on the same header, like post-recall wiring for the Z31).

Don't go buy a stock 1-wire unit, though, because they're not spectacularly useful - the voltage slope between very rich and very lean is not very great. A wideband has a much larger voltage slope, which is much easier to read, though they are a lot more expensive.

Anyone else have any photos or preferences oft what tool/guage and sensor to use for AFR tuning on SUs? I'm kind of waiting for the DLG-1 to hit shelves for a dual setup on a single guage.

I have just installed an O2 sensor (2 wire) in each of the exhaust pipes back near the fuel cell with a gauge for each, a dual EGT gauge with TCs in the #2 and #5 header pipes, and an electronic fuel pressure gauge (no gas in the cockpit and getting those isolators to burp is a royal PITA).

 

So I can see EGTs, fuel pressure and O2 readings at a glance, in addition to the engine oil temp & pressure, water temp, voltage, RPM and tranny oil temp.

 

This is overkill on a street or even AX car but is cheap insurance for a track only car. Perhaps the best of all these is the fuel pressure gauge.

 

Weld bungs into all 6 header pipes, tune and then run. Put sensor in and out of the 6 on different runs and see if there is any difference.

I was hoping one in each 'bank' would be sufficient. My header is a 6-2-1, so I have cylinders 1-3 and 4-6 collected separately before the firewall. Other than spark plug adjustment, what could be done to even out a cylinder that is running slightly leaner than the other two, other than richening up the mix for all 3, or degrading spark to that hole?

EGT gauges would be fun. My hope are to avoid a lot of aftermarket gauge pods though. Unless there are decent looking ones out there.

4 John

 

http://www.aircraft-spruce.com/catalog/inpages/sixegtet206pb.php

 

I also use the IR thermo gun to fine-tune the mix after getting it close with the FSM method. I aim at the head near the spark plugs since that seems to give more consistent results than aiming at the stock exhaust manifold (that might work better with headers). I take three or four measurements at each plug and average them since the readings aren't exact (the IR gun needs a minute to get itself together after a reading, or the previous reading throws it off). Interesting to watch the readings change when you adjust the mix.

My question is, is there a way to use the IR gun or EGT meter to get the best mix for racing or everyday driving? Do racers tune that way or are the EGT's just a warning system to prevent losing an engine? Obviously you can't use an IR gun while driving.

In FSX, flight simulator, you have to set the mix depending on altitude (or use automix). The manual says to adjust mix for highest EGT and then bring it down 50 deg.(F). It's a video game, though. If you have EGT's would you use them like that?

It's an issue for me since the non-stock head assembly needs more gas at upper mid-range and top end (I guess it's pulling in more air), improved since having the needles modded.

Also, if the temp gauge is in the middle, about 180F, while driving, wouldn't that mean that there's no need to worry about cylinder head temps due to overall AF ratio, if they're all about the same?

water temp, oil pressure, O2 sensors and EGTs are just indicators or if you like trip wires so the engine can be shut off hopefully before too much damage has occurred.