Need help building a bypass circuit

[despat]

I'll try to briefly explain what I have done and what I want to add (help needed).

In my latest car project, I have an HHO generator that's adding Hydrogen to the Air/Fuel mixture. The idea is to reduce the consumption of fuel by replacing some of it with an alternate energy source (Hydrogen gas). However, just adding Hydrogen alone does not help until the ECU programmed to lean the engine (provide less gas to the engine). Here is where the EFIE (intrument that intecepts the Signal from the oxygen sensor to the ecu) and reduces the voltage (signal) that the ECU recieves; so in a way we fool the Car's Computer (ECU) into thinking that there is too much Oxygen in the exhaust and thus reduce the consumption of fuel. The problem is my car has a turbocharger installed and the EFIE is only good until I boost (happens only if I press down more then usual to engage the turbocharger). For normal intown driving, I the EFIE will help to save gas but when car is boosting (say on the highway or when I suddenly need to accelerate) it needs all the fuel it can get (must run rich) so I don't want the EFIE intercepting the signal from O2 sensor to ecu. At boost, I want to bypass the EFIE.
So here is what I have currently installed: I have a relay setup to connect to an EFIE in the NORMALLY CLOSED circuit (30 and 87) on the relay so when I start the car the efie gets power and controls the fuel. However, when I boost the ground part (pin 85) of the relays COIL get a negative trigger from the BOOST GUAGE (EBOOST2) so that 30 and 87a are connected to a led that signals I am boosting and the EFIE is not working.


Problem is that I don't want the EFIE to turn off. Reason being is whenever the EFIE is powered, there is a 5 minute delay before it becomes active. This delay allows the car to warm up (as the car normally runs richer on cold start to allow for quicker warming up esp in winter). What I would really like is that the EFIE stays powered on, but the O2 sensor signal is bypasses it instead. The EFIE has two connection points for the O2 sensor signal ; one wire coming from the O2 sensor and and another going out to the ECU (carrying the altered voltage to fool the ECU). Now these voltages are very small. We're talking 350Mv to 290Mv.

WHAT I WOULD LIKE :
I would rather have a transistor or relay (or whatever is suitable) that could be connect in such a way that it would be triggered to shunt the actual O2 signal from the sensor directly to the ECU (bypassing the EFIE). But this must happen only when the coil on the relay is energized.

Any ideas would be greatly apprciated. This may be a simple 2 relay problem, but I'm not sure a relay can be used in this application. I am a beginner in electronics and would really appreciate help from more experienced people on this forum.

 

[chuckey]

the EFIE is what you are going to put in?. It would seem that your relay solution is OK, but you need to think what is actually going to switch it on, the vacuum level (boost pressure?). Also the current law between the the O2 sensor and the fuel used. Does the ECU just adjust the fuel to keep the O2 down to 1%, or does this change across the fuel useage, i.e. at low speed the O2 is .5% and at full throttle the O2 is 5% (very lean mixture). The levels you mention ~300 mV are small enough NOT to be able to drive relays but are big enough so that with an op-amp they can drive relays, have special shaped input/output functions etc.
Frank

 

[despat]

the EFIE is what you are going to put in?. It would seem that your relay solution is OK, but you need to think what is actually going to switch it on, the vacuum level (boost pressure?). Also the current law between the the O2 sensor and the fuel used. Does the ECU just adjust the fuel to keep the O2 down to 1%, or does this change across the fuel useage, i.e. at low speed the O2 is .5% and at full throttle the O2 is 5% (very lean mixture). The levels you mention ~300 mV are small enough NOT to be able to drive relays but are big enough so that with an op-amp they can drive relays, have special shaped input/output functions etc.
Frank

The EFIE is currently running but it's running all the time (when I start the engine). That's good for vacuum levels below 0 (minus = no boost) but if I boost (+vac level) it's not good as the engine runs too lean for turbo. I need to take the EFIE out of the equation at boost time. The EBoost2 guage can be set to provide a negative trigger to a wire (provide ground) between a certain min and max boost range. I'll set it at 1 to 6psi (my max boost). It' a humble Honda oddy 2.2 cylinder van so I'm not drag racing. Just want the extra power to improve drivability. So when boost psi is 1, the coil on the relay will trigger the efie to shut off and a light will glow (telling me it's boosting). Now if there is another Op-amp that you mentioned that could be connected (instead of the bulb) to the 12volt signal from the relay to transfer the O2 sensor signal directly to the ECU, then this way I don't have to turn the EFIE off. If you know of a better way that could transfer a 250mV - 350mV signal through it to the ecu, please let me know?

see attached file


Thanks