Live monitor both front 02s

[team-zr1]

Many times people want to monitor the AFR but want something compact, a standalone meter.
In doing research on AFR meters I found that these meters only monitored 1 02 and were not very accurate.

I decided if I had such a meter what else would I want it to include so I designed a dual 02 AFR meter.
It attaches to 2 02s output wires and via a slider switch will report via 20 LEDs using 3 colors to 1 of the 02s, slide switch to position 2 and see other 02's values or slide to position 3 and it averages both 02s output and displays that on the LED bar.
Also made sure outpput of 02s were clean and any noise was weeded out so LEDs report accurate values.

Here is what it looks like :

http://teamzr1.com/project/afrmeter.jpg

This way the user can check to see if both front 02s are reporting the same, if one has gotten lazy or 1 head leaner/richer then the other and have the meter average both sides and report the AFR average.

Size of PCB is 2 1/8 X 3 inches.

[MKOTZE]

Originally posted by team-zr1
Many times people want to monitor the AFR but want something compact, a standalone meter.
In doing research on AFR meters I found that these meters only monitored 1 02 and were not very accurate.

I decided if I had such a meter what else would I want it to include so I designed a dual 02 AFR meter.
It attaches to 2 02s output wires and via a slider switch will report via 20 LEDs using 3 colors to 1 of the 02s, slide switch to position 2 and see other 02's values or slide to position 3 and it averages both 02s output and displays that on the LED bar.
Also made sure outpput of 02s were clean and any noise was weeded out so LEDs report accurate values.

Here is what it looks like :

http://teamzr1.com/project/afrmeter.jpg

This way the user can check to see if both front 02s are reporting the same, if one has gotten lazy or 1 head leaner/richer then the other and have the meter average both sides and report the AFR average.

Size of PCB is 2 1/8 X 3 inches. Hello Team-ZR1, Thanks for the information.:chevy: MKOTZE

[fatherlarry]

Great info, Team ZR1! I'm very interested in this.
I thought you guys might find this interesting also.:smoke:
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Tuning Via EGT
There seems to be a lot of mystery and misinformation about using exhaust gas temperatures to tune engines. Claims by many EGT gauge manufacturers about it being the best way to tune an engine must be qualified. The BEST way to tune an engine is on the dyno- PERIOD. What EGT is good for is a reference for where the engine made maximum torque at wide open throttle. Once removed from the dyno, a similar air/fuel ratio can be established a later date by dialing in the mixture to achieve the target EGT. It is really the AFR that is important, not the EGT. Most engines will make maximum power at an AFR of between 11.8 and 13 to 1 however, the EGT may vary from 1250F to 1800F and is dependent on many factors.

It should be mentioned that the target EGT is valid only on the same engine configuration as was used on the dyno. If you change the ignition timing, cams, pistons, headers etc., the optimum EGT may also change. Raising the compression ratio with no other changes will drop the EGT at the same AFR. Retarding the ignition timing will generally raise the EGT at the same AFR. One engine might make best power at 1350 degrees while a very similar engine might be happier at 1500. You can't guess at this or you are simply wasting your money on the instrumentation. Wankel engines have higher EGTs than comparable piston engines due to their lower thermal efficiencies. 1800F is not uncommon here.

Some gauge manufacturers say you should tune to achieve maximum or peak EGT for maximum performance. This is incorrect. Peak EGT generally occurs at an AFR of around 14.7- 15.0 to 1 on gasoline. This is far too lean for maximum power and is dangerous under continuous WOT conditions. Many people think that the leaner you go, the higher the EGT gets. This is also incorrect. Peak EGT occurs at stoichiometry- about 15 to 1 for our purposes. If you go richer than 15 to 1, EGT will drop and if you go leaner than 15 to 1 EGT will ALSO drop. It is VERY important to know which side of peak EGT you are on before making adjustments. It is safe to say that peak power will occur at an EGT somewhat colder than peak EGT.

You can sometimes feel a lean of peak condition as the mixture is hard to ignite and power will be down a bit as well. Once the AFR gets close to 17 to 1 at WOT, generally the engine will start to lean misfire. Most tuners always recommend to begin jetting or programming from a known very rich initial setting and carefully leaning until torque falls off slightly, then going back richer to the point of max torque. Note the EGT at this setting. Be aware that altitude, barometric pressure and ambient air temperature may affect this optimal temperature to some degree.

Are EGT gauges better than AFR meters? Conventional narrow band oxygen sensors and digital LED meters are not the best devices to measure AFR in the richer ranges but they certainly warn of a too lean condition immediately and obviously, without translation by the driver and they are affordable. Meters combined with wide band sensors are laboratory quality usually, highly accurate and useful but very expensive and sometimes bulky. EGT gauges have the limitations above and are generally priced between the other two. I would suggest that the two types are complimentary. EGT gauges have the advantage of working long term with leaded fuel which will clog oxygen sensors. EGT gauges are widely used to set mixture on engines used for steady state high power applications where operation has been carefully documented such as in aircraft. The choice would depend on the application. Both are better if you can afford them.

[team-zr1]

Originally posted by MKOTZE
Hello Team-ZR1, Thanks for the information.:chevy: MKOTZE

Your welcome!

Was a real task to do all the research, design, finding parts, I even tried to burn my own 2 layer PCB but too much of a hassle and then had to find a vendor to build small amount of boards, not cheap.

I had looked around at the AFR meters that are being sold and found them to be cheapo designs and not very accurate so if forced me to design a better circuit.
I made a prototype and tested if using my '99 and then had some PCBs made and I will stuff and solder them sp those noy good with a soldering iron can get one pre-made.

This at least will average both front 02s and give the driver a better idea what the AFR is since both sides never really equal and thus if they only monitor 1 02 they never know it the other one is getting lazy as they get older and see a more accurate AFR value with the average of both 02s.

[team-zr1]

Originally posted by fatherlarry
Great info, Team ZR1! I'm very interested in this.
I thought you guys might find this interesting also.:smoke:
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Thanks, I spent about 4 months on research, design and testing the protype.
I did this because I was surprised rhat most people do not even own a PCM scanner and are always guessing what the AFR is and since I do PCM tuning I find there is a need for people to have some standalone device that monitors the o2s before the cats.

Funny when we had points and carbs people thought nothing about owning a timing light or dwell meter but with ECM or PCM based Corvettes use no test tools at all.