need help with CIRCUIT ECU controlled O2 sensor enhancer

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1

hello i got an interesting project but have no experience in designing a circuit

so basic story is that i got an old volvo that get too much fuel with the new generation fuel, i think its bechause new fuel contanes more oxygen burn cleaner and leave more oxygen in the exhaust witch the O2 sensor pick up and the ECU think its running lean then compensate with more fuel.

anyway how to solve this?

i bought ostrich 2.0

and did the steps in this forum:http://forums.turbobricks.com/showthread.php?t=227153

it turns out that the ECU stay at what is thinks is AFR 14.7 that is 1 volt from the LAMBDA (O2 sensor) no matter what is done in the main fuelmap

so now i can change the fuelmap and the ECU know what to do but get answer from the O2 sensor that say its all wrong!

an O2 enhancer can be used to fix this but then it will change the same value no matter load at the engine, and the engine need more fuel at a higher load to prevent pinging and self destruction.

so my question here:

Can anyone help me to design an citcuit that is controlled by PWM?

Enhancer circuit: http://hydrogengarage.com/DIY/DIYinstructions.html

http://hydrogengarage.com/DIY/O2_sensor_schematic.jpg

this Schematic need to be controlled by PWM and i got only 1 O2 sensor so i only need one side of this circuit

Circuit needs:

-run from car voltage 9 - 17v

-Enhancer for 1 O2 sensor

-to be controlled by PWM

-pot to adjust enhancer value at max dutycycle

-pot to adjust enhancer value at min dutycycle

-linear enhanser value between max and min dutycycle

-pot to adjust dutycycle input bechause my measurements may not be corect

-bechause the ECU vant to keep AFR to 14,7 the voltage from O2 sensor is 1v

so the enhancer need to add or subtract in milivolts, how much volt totaly i dont know

but it could be understood from the chematic of the enhancer

wiring diagram of ECU and other stuff:http://ipdown.net/jetronic.info/tiki-in … 20Diagrams

load signal is found on #8 on ezk(ignition) and #25 (LH2.4)

here is EZK

http://ipdown.net/jetronic.info/tiki-do … 64&display

My measurements:

signal peak to peak with reference voltage at ground: 1,406v

time with at idle: 90 us

time with at trottle (may not be full load): 416us

square wawe PWM 2,404KHZ (this is a bit unstable but around 2,4KHZ

dutycycle can be calculated some how from time with at trottle and 2,4KHZ same with idle

the reason odd measorements is i got only a old ocilyscope and i have no training using it hehe

i got a smal video and picture from measureing but dont know how to add it here

hopefully someone can help

2

To be blunt I believe you are barking up the wrong tree.

1st) What leads you to believe that you ACTUALLY have too much fuel ?

2nd) Slight variations in fuel composition will not cause your engine to

use excessive amounts of fuel. Fuels that are labeled as “oxygenated”

actually have a percentage of ethanol.

3rd) Your engine will always run at 14.7 (stoich) under closed loop conditions.

The fuel map is for open loop conditions (cold engine, wide open throttle)

I hope this helps, it is easy to get caught up with figuring out how to do

something without realizing if it should be done.

-Justin

3

AcidRain:
To be blunt I believe you are barking up the wrong tree.

1st) What leads you to believe that you ACTUALLY have too much fuel ?

This same problem is static on most of the volvos fitted with bosch LH2.4

Amm sensor new engine temp sensor new o2 sensor new no defference.

no exhaustleakage in front of o2 sensor.

if it was leaking injectors the ecu would try to compensate by less fuel and if injectors was leaking it would not help to modify fuel map

when i modifyed the fuel map and drive in fixed open loop its running a lot more nice and uses a lot less fuel

but thats not optimal so i want to change the o2 signal

AcidRain:
2nd) Slight variations in fuel composition will not cause your engine to

use excessive amounts of fuel. Fuels that are labeled as “oxygenated”

actually have a percentage of ethanol.

Here in norway they dont care what the customer wants. One pump one fuel

So who know whats actual there, anyway its not working good at old injection systems

AcidRain:
3rd) Your engine will always run at 14.7 (stoich) under closed loop conditions.

The fuel map is for open loop conditions (cold engine, wide open throttle)

The ecu calculate how much fuel is needed baced on amm. Engine temp. Rpm. Fuel map

Then the O2sensor sends a feedback to the ecu and telling if calculations was correct.

if not the ecu will compensate to make afr perfect and thats when it all go wrong cos there is too much oxygen in the exhaust

Causing ecu to compensate by more fuel.

AcidRain:
I hope this helps, it is easy to get caught up with figuring out how to do

something without realizing if it should be done.

-Justin

thanks for answer

im not looking for help to solve a problem.

im looking for help to design a circuit and tought the whole story would be intetesting.

About the circuit:

Input: change pwm to triangle wawe by opamp, feed it in to another opamp with a pot to the noninvertin terminal to adjust sesebility to pwm load signal. Convert again to dc value by transistor or opamp.

this dc value can be used as reference to the offset of the o2 signal

O2 signal input straight in to opamp

O2 signal output ±500mv offset to the orginal voltage

has to follow the orginal signal but +or- 500mv

Example:

Dutycycle 0% adjusted offset by pot to +100mv

dutycycle 100% adjusted offset by pot to +500mv

dutycycle 50% is linear so it wil add 200mv bechause between adjusted offset 0 -100% is 400mv in the middle 200mv

4

Couldn’t you use an arduino PWM output into a transistor

With a small capacitor before the transistor ?

5

AcidRain:
Couldn’t you use an arduino PWM output into a transistor

With a small capacitor before the transistor ?

Pwm is controlled by the engine load output from the ecu it can not be a fixed value from a pwm source

the circuit need to work like this for testing

adjustable only 100% and 0% the rest linear