Any electrical engineer? Circuit design help

[Zrun]

Can anyone help me draw a schematic for the circuit board?

 

Description:

There are 3 inputs to the board and 1 output.

Input 1: 12 V (Power)

Input 2: 0-5V (selector signal)

Input 3: Oxygen sensor signal

 

Output: Connected to input 3 if input 2 is less than a threshold. This threshold must be adjustable using a potentiometer or something.

If input 2 is above threshold, output normal O2 sensor signal.

 

See if anyone can guess what's this for.

[Thumbs]

Seems like an O2 simulator to prevent CEL on a stock ECU. Most likely doomed to failure.

[Zrun]

Kindly tell me why so that I will not waste my time exploring this possibility.

 

I heard about this from some MR2 owners who used this to maintain slight lean when boost is introduced, thus causing ECU to enrich rather than cut fuel when AF is at 12:1

 

That is not o2 simulator, but a signal "clamp".

 

Thanks.

[Thumbs]

Same difference. You're trying to fool the ECU with a false O2 reading.

 

This is unwise for a number of reasons. Just one example: in the event of a rich misfire your AFR is going to read lean. So what happens? You add more fuel and the problem gets aggravated.

[Zrun]

This is to solve problem of partial throttle (closed loop) boost condition.

 

The activation signal is only turned on when boost goes above a threshold. So, during normal driving, stock O2 signal is used.

 

The partial throttle boost problem is that the boost increases, while the ECU work against the e-manage map to enrich the intake charge to return it back to 14:1 from 12:1.

Edited March 22, 2005 by Zrun

[Thumbs]

>>The partial throttle boost problem is that the boost increases, while the ECU work against the e-manage map to enrich the intake charge to return it back to 14:1 from 12:1. <<

 

Don't you mean enlean? Numbers going lower than 14.7 are richer while those going higher than 14.7 are lean.

 

Anyway, I wish you luck in your endeavor. There're a few reasons why most sensible people go for full standalone if they wish to tune fuel, ignition and compensation maps.

[Zrun]

Thanks for pointing out the problem.

 

I've modified my sentence, hope that clarifies it.

>>The partial throttle boost problem is that while boost increases, the ECU work against (e-manage map which is trying to enrich the intake charge) to return it back to 14:7 from 12:1. <<

 

Full standalone is indeed better than other methods. But saying that standalone is the only way to do it is not true, much less saying people who does not use standalone is ignorant. There are many success stories with non-standalone solution, maybe for low boost (6-12psi) application, but they do work very well.

Edited March 24, 2005 by Zrun

[Thumbs]

>>Full standalone is indeed better than other methods. But saying that standalone is the only way to do it is not true, much less saying people who does not use standalone is ignorant. There are many success stories with non-standalone solution, maybe for low boost (6-12psi) application, but they do work very well<<

 

Whoa, whoa.. hold on to your horses. I didn't say "standalone is the only way to do it", nor "people who does not use standalone is ignorant". Don't put words in my mouth, thanks very much.

 

What I did say is that what you're trying to accomplish can be done easily on a standalone and would be a better investment of your time and money. The reason is that a standalone has much better control over engine management and would already include features like acceleration enrichment for clamp/sensitivity/decay. In any case, any factory ECU worth a damn is certainly not going to give you stoich or lean mixtures when you're on boost.

[Zrun]

>> Just one example: in the event of a rich misfire your AFR is going to read lean. So what happens? You add more fuel and the problem gets aggravated.

 

Any tuning that's worth a damn will not be in rich misfire situation during boost.

[Normal_aspirated]

dun mind asking, mine ride O2 sensor hv 4 wires, and u mentioned here only three? So the 4th wire is the output? Or, issit the three wires u r refering to at the input socket at the stock ECU?

Edited March 24, 2005 by Normal_aspirated

[Zrun]

>> dun mind asking, mine ride O2 sensor hv 4 wires, and u mentioned here only three? Confused So the 4th wire is the output? Or, issit the three wires u r refering to at the input socket at the stock ECU? Wave

 

4 wires.. there's power, ground, signal and heater.

 

The above is indeed messing with input signal to ECU only. Maybe it is better to peg it at 0.45V(stoich) instead of 0.35V(lean), but this is just a minor tuning factor for boosted application. Allowing closed loop boosting to be more expected.

Edited March 24, 2005 by Zrun

[Zrun]

>> Whoa, whoa.. hold on to your horses. I didn't say "standalone is the only way to do it", nor "people who does not use standalone is ignorant". Don't put words in my mouth, thanks very much.

 

It is obviously insinuated that non-standalone method is for insensible people who will mostly end up wasting time and money. Thanks very much.

 

There are many issues with full standalone, even if it is robust, and chances are, you will waste more time trying to get it to recognize the input signals that you have.

My stance is that there are cheaper, easier, faster solutions that will work very well for different situations. If someone spend all that money on a standalone for a 6psi system, I'd not laugh at their decision, but encourage them to go higher boost with better tuning.

 

The cheapest standalone that I know of is power fc, which cost maybe 1k USD, and they still do not have it configured for my car. I've checked with them, they say my best chance is to get one for a car similar to mine, Toyota MR2, and then hardwire all connections. With that, why go through all these trouble because I only want to boost to 8psi?

 

I used to think that without standalone, the car can never be tuned properly. It is true to a certain extent, but non-standalone car can still be driven, the output potential is near to standalone.

It is like saying BOV does not work because it opens during non-boosted and idling situations. You can spend money on getting the super sequential BOV that stays closed during out of boost, but it does not mean that regular BOV does not work.

Another analogy is waste gate vs boost controller. Waste gate leaks before full psi is reached, but it is used nonetheless.

Edited March 24, 2005 by Zrun

[Thumbs]

>>Any tuning that's worth a damn will not be in rich misfire situation during boost. <<

 

Really? And how do you ensure that does not happen?

[Thumbs]

>>It is obviously insinuated that non-standalone method is for insensible people who will mostly end up wasting time and money. Thanks very much. <<

 

Whatever.... if it's so "obvious" to you... maybe you should ask yourself... why aren't you working on your car instead of asking an electrical engineer to help you with the circuit? Doesn't that prove my point? When this "problem" does not exist at all with a standalone.

 

>>There are many issues with full standalone, even if it is robust, and chances are, you will waste more time trying to get it to recognize the input signals that you have. <<

 

Not true. There are number of very good EMS out there which make use of the stock sensors.

 

If you only want to raise boost, just buy a boost controller and a fuel controller. If you want control over open loop fueling, go piggyback or a reflash. If budget allows, go full standalone.

 

>>I used to think that without standalone, the car can never be tuned properly. It is true to a certain extent, but non-standalone car can still be driven, the output potential is near to standalone. <<

 

Depends on the ECU or your "non-standalone" solution. The problem is when heavily modified cars are no longer within any semblance of factory spec, you can't expect the factory ECU or piggyback or reflash to control everything. Simple thing like higher RPM rev limit for upgraded valvetrain is going to be a challenge for stock-ish EMS.

[Normal_aspirated]

Thansk.

 

The above is indeed messing with input signal to ECU only. Maybe it is better to peg it at 0.45V(stoich) instead of 0.35V(lean), but this is just a minor tuning factor for boosted application. Allowing closed loop boosting to be more expected.

 

Yes, i believe oso. Japs cars cut cost by using narrow band O2 sensors which is less accurate. I hv tapped the O2 signal to a Air/Fuel ratio (0 to 1VDC)meter, the reading is very erratic, jumping up and down like mad. How is it possible to get steady readings at 0.45VDC? This is mad, i think.

 

Wide-band ones better but very expensive. Ever see tuners use narrow band ones?

[Thumbs]

The reading is "very erratic, jumping up and down like mad" is because the narrow-band sensor is supposed to work that way.

 

Seems like there's quite a lot of confusion about how a narrow-band O2 sensor is supposed to work. May i suggest the following link:

 

http://www.picotech.com/auto/lambda_sensor.html

[Normal_aspirated]

Hi Thumbs,

dun mind asking, r u a professional automotive engineer or juz a car enthusiast like me.

[Thumbs]

Hi...

 

Does it have to be mutually exclusive?