This may be a stupid question, but the title says it all. How are you guys figuring out what air to fuel ratios you have? I have a cheesy autometer air fuel gauge but it does not spit out a number ratio. It just says dead on rich, three bars green. Is there a fromula to apply that I have overlooked? I also don't see anything in the PFC commander that would give me a AFR number.

Thanks

 

Its the number of green bars at idle x the number of red bars at WOT / duty cycle +rpm at idle - 2.2324355 + 3% to compensate for water temp=AFR


You need a wideband o2 sensor. Search around for FJO, Techedge, etc... They all make nice widebands.

 

Green Bars times Red Bars? Which gauge are you looking at? I have a autometer gauge and I never seen it go red at WOT. I know it is not the best and a bit cheesy.
Also -2.2324355 number, where did this come from?

and why 3% to compensate for water temp?

Sorry, I am a bit of a laymen.

Thanks

 

It was a joke man. I was just ******* with you. You have to buy a wideband o2 sensor setup to get exact AFR. Its gonna set you back at least $400 or so. Check out the FJO and techedge units I mentioned above.

 

Justin your just mean man.

 

Cool. I thought I may need some more equipment. I don't have the cash for a good wideband (or even a cheap wideband) right now.

Thanks for the input.

 

no problem

 

I do this for a living . all you need is a scope tap into the O2 sensor and you are looking for .5v any thing higher is rich any thing lower is lean . if the feed back system is working it will swing up and down past .5v when you step into it , it should go high .8v or so and stay there as long as you are into it , if it dosen't there is a promble
like poor fuel delivery, pump,reg,nozzles,air meter,so on

 

I would hate to be a customer then.....

Your method would result in many a blown rotary if used for tuning or serious monitoring.

 

This way will not produce a number (like 14:1) for a ratio. I have an autometer Air/Fuel gauge that can tell that information. I know I am running rich. I would like to tone it back slowly, but I know I need a better way to monitor the air/fuel ratio. Does anyone have a wideband set up that I can borrow (ya right)???

 

I also use a O-scope to monitor factory o2 sensors. I installed a Honda 4 wire O2 sensor 4-6 inches from the turbo. Is what makes a O2 sensor not reliable is heat. Installed a EGT gauge right after the tubo. With the O-scope reading and the EGT numbers a A/F ratio can be calculated. This is what a WideBand meter does, gets the O2 and EGT numbers ( from a 5 wire O2 ) then makes calculations on these two figures and gives a A/F number for the average Joe to read. We're taking 1000$ and up scopes to read O2 sensors not 100-200$ DVM's.
chuck

 

With all due respect to professional opinions stated above, AFRs are not measured by considering EGTs. EGT is Exhaust Gas Temperature and while it is somewhat related to actual AFR (AIR FUEL RATIOS) it is not necessarily a direct relationship. The determination of AFR is NOT AT ALL dependent on EGTs. For example rich AFRs do not preclude high EGTs.

AFRs are determined by the production of a microvoltage across a specially designed ceramic sensor. That produced voltage is read by a controller and calculated into either a Lambda reading or an AFR.

If you need a better explanation, I would be glad to direct you to some very explicit sites.

 

Yes please post some info on this. There is so much more information for me to learn.
My understanding is EGT plays a big part in tuneing. If one does not get a complete burn of all oxygen your a/f will/can show lean. High EGT numbers. Adjusting timeing, giving the cumbustion chamber more time to complete a burn cycle can richen a/f ratio. Lower EGT numbers. To much burn time in the cumbustion camber will/can show richer a/f ratio so some will lean the fuel mixture to lean there a/f numbers not thinking they should/can try to adjust there timeing also.

I have heard so many blown motor on a dyno with low 11 high 10 a/f ratios with out posting any EGT, air and water temps. One of the other reason why I am thinking EGT plays a big part in a wideband is the placement of the wideband O2 sensor. Read a few post were moving the O2 sensor further away from the motor produces beter a/f reading.

If I read the wirering dia. for the 5 wire O2 sensor from Honda, it show a temp sensor, a/f sensor and was told the ECU makes a correct a/f ratio from these two out puts.
Please correct. Not a professional, learning something new every day.
chuck

 

Try this for some AFR basics
http://techedge.com.au/vehicle/wbo2/wbntk.htm

Check out the section on How the NTK Pump Cell Sensor Works then click on the hotlinks to get real confused.

 

Sorry but I am not able to totally comprehend what the Techedge link is trying to teach me. I knew I should have paid more attention in school. Just have to many questions. Gong to try to find someone locally to explain a few things to me.

I do remember seeing the type of AFR meter that has a small pump to extract exhaust gas from the end of the exhaust pipe. It used a small pipe that is inserted in the exhaust. This did produce a AFR. You are right, I believe this type of unit is not heat sensative.

The thing that stands out in my mind is when I witnessed a conversation between two guys at the track about EGT numbers. Car was running poor mid 13s. Question was asked, what is your timing at full boost and your EGT at WOT. Anser was 15deg BTDC at full boost and EGT number at WOT was 1350f. The guy was told to lean the fuel out in five % increments until the EGT numbers where in the 1500f range and the car finnally ran high 12s.
Thanks
chuck

 

This whole thing is got me confused. I know that the O2 sensor measures the gases to determine lean or rich condition and I understand that EGT is not directly proportional to AFR. From reading this it is my understanding that the O2 sensor will give a lower voltage reading for Rich measurments and Higher voltages for lean measurements. This is contrary to what I have always been told....... so which is it??

 

the stock O2 sensor...the higher the number ie .90 is richer than .50. You are correct about the A/F and EGT not being a direct relationship. I believe SCC mag stated this when they were tuning one of their test cars. Timing also plays a part in the EGT readings and in one article, they richened the A/F and got higher EGT reading.

Tim

 

Bottom line is that "lean" conditions (>12.0 AFR) can contribute to detonation. Setting the fuel maps to keep the AFRs reflecting <11.5 AFR during boost is considered good practice. High EGTs (without more information) may be indicative of "too rich" or "too lean" fuel map conditions but may also indicate poorly adjusted timing. All these factors must be considered when tuning.

 

aight I re read the articles on the O2 sensor and now it makes sense must have been tired the first time.

ON the topic of EGT and AFR I was taght a long time ago that if your EGT is high then you don't have enough fuel. I dynoed a sideport, stock turbine , Tuned ECU, with 4-550cc injectors and it dynoed 245 or so. I went back to my tuner/builder and asked why and he said not enough fuel so at his suggestion I installed a larger fuel pump, regulator and a EGT guage. That engine ran super high EGT and no matter how much fuel I added I could never change the EGT more than 20-25 deg.

Later I got a different ECU and the EGT dropped by about 45 deg from the old readings. Recentley I have installed a EGT meter in my current car and with using the test page on the Power FC adjusting timing and fuel I cannot change the EGT more than 20 deg. in any direction. Not sure what all that means but it is something that I am playing with right now.

 

What are you considering super high egts?
Assuming they are really "super high"--you may have a timing problem.

Where is your egt sensor mounted? If it is post turbo and you are rich and not properly timed (for example), you can be still igniting the remaining fuel after it has exited the manifold and gone through the turbo-----> High EGTs normal AFRs.

Lots of analysis is still required

 

Well back then the probe was located in the manifold and I finally got the EGT down to about 840Celcius. In my current car the probe is in the down pipe about 1 1/2inch behind the turbo I have never seen a EGT higher than 720. When it was firs installed pulling through 2nd gear gave a peak of about 680 looking at 02 sensor voltage and things decided to pull some fuel out all across the board. Readjusted cells on the PFC and now it peaks about 720. This seems normal to me and I am not worrying about it too much more until I get a wideband installed but it has just been my experience with my car and others that changing timing and fuel dosen't result in great changes in EGT.
It is my opinion at this point that many things will effect EGT such as spark plug heat range , compression, all around combustion effeciency as well as AFR and ignition timing.

 

My understanding is that Wideband O2 setups read Voltage and Sensor Temperature, NOT Voltage and Exhaust Gas Temp. There are two problems with Narrowband O2 sensors that cause the innaccurate readings; The way the O2 sensor detects the AFR is more innaccurate the richer you get from 14.7:1, and the sensor's output voltage is greatly affected by SENSOR temp. The EUGO Sensor differs in that it uses different technology to read the fuel content, and reads the sensor temp and adjusts the voltage reading accordingly.

Why don't you guys save yourself the trouble and risk of all this and just spend the $340 for a Wideband. Especially if you are useing this on a customers car!