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Discussion Starter #1
I know I can buy one already made, for a price that vary betwen 50$ and 300$. but this topic is not about this

Iwant to built (myself) an A/F meter for my 200SX ,i'l use a uC and a LCD screen

my problem is that i do not know from were i must read the data, to get the corect A/F ratio

i read about that on the net (research on google) and i saw a project like this based on the readings from the lambda sensor, but because my 200SX has no cat and no lambda sensor, i must found other way to do that.

anyoane can tell me if u know about a similar project, some links from the net

and if u know pls tell me from were A/F meters found on market takes the A/F data

the air i asume that it can be read from the AFM but the fuel?


PS: if u have also some info i want to make a worning sistem based on noking sensor. any info about it will help me alot, how many noks are same to have in a time unit (let's say a second or minute) i thought to track the data from that sensor and if to many noks apear to triger a signal so u can be worned.
 

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Discussion Starter #2 (Edited)
http://www.freescale.com/files/sensors/doc/data_sheet/MPX4250A.pdf
http://www.freescale.com/files/sensors/doc/data_sheet/MPX4250D.pdf
i found this it is about 30$ and it is a presure/boost sensor
with a LCD 5$
and a uC another 5$
and some other cheap part
i can make a Digital Boost meter (i like digital ones - i can make it analog but i do not want)

looking at that sensor do u think it is suitable for this aplication?
he can mesure presures betwen 2.9 and 36.3 psi
the second one reads the boost betwen 0 and 36.3psi

wich one do u think is best the one stating form 0 or the one strting from 3 psi
i think this is more just enough
operation temperature is betwen 0-85'C
i hope air afther intercooler has no more then 85'C
do u know what temperature is there?
if i install the sensor afther intercooler and before ECCS, i'll get the proper redings, or the boost about everyone talk is mesured right at the exist from turbo?



what do u think about this project of making on my own a device wich will display info from the engine. (A/F ratio, boost , number of knoks per second....)
 

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I dont know about all the digital LCD and stuff but I have been thinking about a similar project for a while. Your A/F ratio can be easily told to you by the output voltage of your O2 Sensor in your exaust. In fact, thats how your ECU calculates and compensates for it. They can be found in junk yards for free if you buy something else and make that look like the reason you were there. lol

You can also tell when they go bad by simply ohming them and comparing that to acceptable parameters in you chiltons or whatever manual you use that would be detailed enough to tell the spec ohm of your 02 sensor.

Hope this helps.

EDIT:

Simply take a boost gauge from a car that was turbod in a JY, I know some DSMs have them like the Dodge Shadow, but I dont know for sure of any others. Be sure to check through old turbo mustangs, saabs, DSMs, etc.
 

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Discussion Starter #4
in this topic i do not ask about how LCD uC works (this is my job)
i'm only interested in the sensors that already are on the car

1) finding something at junkyard is not an option (because here i do not find "goodies" in junkyard and if i found they have a price biger then if i buy a new part)

2)from the AFM i'll get a good reading of the air that flows into the engine,
but from were i can take amount of fuel? (i need to take fuel coz later i want to display also the fuel comsumtion)
 

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Discussion Starter #5
anyoane knows were i can found a datasheet for the Ca18DET AFM and 300ZX Z32 AFM?
the only things i know about this sensors is that they output a value betwen 0 and 5V but i do not know each voltage value to wich quantiti of air corespond
 

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ByReaL said:
Iwant to built (myself) an A/F meter for my 200SX ,i'l use a uC and a LCD screen

my problem is that i do not know from were i must read the data, to get the corect A/F ratio

i read about that on the net (research on google) and i saw a project like this based on the readings from the lambda sensor, but because my 200SX has no cat and no lambda sensor, i must found other way to do that.

anyoane can tell me if u know about a similar project, some links from the net

and if u know pls tell me from were A/F meters found on market takes the A/F data

the air i asume that it can be read from the AFM but the fuel?


PS: if u have also some info i want to make a worning sistem based on noking sensor. any info about it will help me alot, how many noks are same to have in a time unit (let's say a second or minute) i thought to track the data from that sensor and if to many noks apear to triger a signal so u can be worned.
There is no sensor which reads A/F with a linear output which comes with a car. The oxygen sensor is used by the computer to set the A/F ratio, but it is not a linear device. This is the output from a typical O2 sensor:




To achieve what you want to do you must install a wide-band O2 sensor. The output is linear. This requires welding a bung into your exhaust system for the sensor.

Bosch sells a wide-band O2 sensor. The output voltage vs. A/F is here.

Lew
 

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Discussion Starter #7 (Edited)
thanks for the info.

i thought that if i read the o2 sensor (i do not care it is linear or not as long i know the variation) and the amount of fuel injected in the car
i can find out a very precise A/F ratio and in same time the fuel value will help me to display the amount of fule consumed by the car

and about that wide band sensor, that table stop around A/F =10
and i have a tuned chip for my engine and the lowest A/F value on the map was 8.9 so i need something that is able to read even a A/F=6 value or lower

anyway anyoanes know how can i get the amount of fuel that flows into the engine?

i already started to work on this project , i chosed a LCD
and i can disply on it 8 values

what do u think it is importnat to know about the car

i thought to the next ones:

boost
A/F ratio
knocks - i do not knowe if anyoane thought to dysplay this data
rpm
speed
instant fuel consumtion
medium fuel consumtion
a temperature i do not know wich yet


what data do u think it is better to be known?
what data u wish do be displayed?

PS: i alredy start to work on this the display part is almost finished, i also have 8 analog input lines waiting to be conected to sensors

untill now the cost are estimated at around 60$ (the will incrase but i think the ywill not be biger then 100$)
 

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ByReaL said:
i thought that if i read the o2 sensor (i do not care it is linear or not as long i know the variation) and the amount of fuel injected in the car
i can find out a very precise A/F ratio and in same time the fuel value will help me to display the amount of fule consumed by the car
Did you look at the response of the stock O2 sensor? The voltage is constant with A/F on the rich side, and varys very slowly on the lean side. Any calculations will be erroneous. You don't need to measure the fuel flow, the O2 sensor varys with A/F ratio. What will you use the fuel flow for?
ByReaL said:
and about that wide band sensor, that table stop around A/F =10
and i have a tuned chip for my engine and the lowest A/F value on the map was 8.9 so i need something that is able to read even a A/F=6 value or lower
Why. An engine barely runs at A/F ratios lower than 9 it is so rich.

Lew
 

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Discussion Starter #9
tthe fuel flow will be also needed to get the amount of fuel consumed in 100km or the miles per galon value,
as i know the 200SX S13 does not tell u how much fuel the engine "eat" to travel 100km so i thought it will be a nice data to dysplay

if the ECU can read the O2 sensor values then this means i can read them also (if i know how)

i know that 8.9 (as A/F ratio) is very low but that was the lowes value on that map

go to :
http://electronik.lx.ro/RomAnalyser.exe
http://electronik.lx.ro/s13manual.bin

and u will see the highest AF ratio on a stock ca18det is grater then 16 and the lower value is lowest then 9

i hope the links are corect i just uploaded the files there


anyway lets ask otherwise, if i'll buy an afthermarket A/F gauge from were he will take the data? (the info wich it disply)
 

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wait, are you planning on selling these things? because if you are, im sure someone would buy one (hint hint)
 

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Discussion Starter #11 (Edited)
KaRdoN said:
wait, are you planning on selling these things? because if you are, im sure someone would buy one (hint hint)
the whole plan, pictures, source code... will be posted and available on the net for free

i'll take money only from someone who wants this device phisicaly built by me, and if he wants me to instal the device on his car

i want to make it for the CA18DET engine non cat, then the z32 afm option will be aded (and if i succed to do all that and are positive ffedbacks on it, i'll do versions for SR20DET and other engines)

i thought to this as a smal project, but since i noticed the price (a price that i canot aford) for the gauges, if i already have all the 8 analog inputs the lcd will be a shame to not take all the advantage from it

soon i'll post on the net the simulation part for the display
then i'll add the boost sensor
and the other inputs as soon as i figure how to read data from them

corect url (sorry)
http://electronik.3x.ro/ROMAnalyser.exe
http://electronik.3x.ro/s13manual.bin

http://electronik.3x.ro u can find here some pictures with my car and my friend 200SX(i succeded to convince him to buy one)
 

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Discussion Starter #13
anyoane knows the part number.. or some info about the detonation (knock) sensor present on the CA18DET?
 
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