ULTM8Z

It's always bothered me a little that the ECM ignores 1/2 the engine...

But I had an idea this morning and wanted to see if anyone else has already thought of, rejected, or implemented it...

I'm not an Electrical Engineer (but I know a hot rodder who is and can probably translate this into a real circuit).

Suppose you were running an O2 in each exhaust header collector. And suppose you had both O2's outputting their voltages into a circuit that added them and then took the mathmetical average. That circuit then outputs the average to the ECM which now has visibility on the whole engine.

As it stands, one O2 is essentially "averaging" a bank of 4 cylinders. So why not have the average of two O2 sensors which are "averaging" each bank of four cylinders?

Thoughts?

Orr89RocZ

iTrader: (20)

I guess the idea works but its a batch fire system so you cant tune bank to bank anyway.

If manifold had good air distribution, and injectors matched, then you should have even output mixtures, within reason lol

If one cylinder is way off, ecm will only know it if that cyl is on sensor bank. But you may know something is wrong if its missing or feels/sounds weak. If not it goes on thinking everything is fine. If you average both somehow, then all cylinders get effected trying to make up the difference. I dont know if that is helpful or not. Makes pinning down a missfire or dead cylinder alittle more difficult. I like having 2 bungs and extend the harness to read both banks whenever i want

ULTM8Z

Understood it's batch fire and no individual cylinder tuning.

The car runs really good, don't get me wrong. But there seems to be some variability in the idle quality from one day to another (noticeable enough for someone ****-retentative like me) which I think is a function of which cylinder the "batch" is timed to.

I *believe* the batch injection can only be timed to one cylinder out of 8 once the engine fires up, and that particular cylinder is random on each start up. For example on one start up, the injector batch firing is timed to cylinder #3. However, on the next start up, it's timed to cylinder #8. Is that an incorrect assumption?

If I'm right, I'm thinking this averaging of the O2's may help smooth out some of that variability.

Six_Shooter

iTrader: (2)

Been thought of, (not implemented), decided that it just wasn't worth it, after testing O2 sensors on both banks of a few cars and seeing very little difference from side to side. It seems GM engineers at the time were pretty smart.

The only way dual O2s would be any benefit is if the ECM could fire in bank to bank mode, which it cannot.

ULTM8Z

Except those engineers weren't dealing with the ever-contrary Miniram's idle characteristics!

Dyno Don

iTrader: (7)

Use a SPDT switch and install an 02 in each header.
Then you could switch back and forth.

ULTM8Z

Don, I want to have real-time monitoring by the ECM.

Six_Shooter

iTrader: (2)

If you switch it fast enough...

LOL

Dyno Don

iTrader: (7)

With a '7730 that isn't possible.

ULTM8Z

Ordinarily I would agree. It's my idea that I'm trying to see if I can make it happen.

Six_Shooter

iTrader: (2)

The hardware to make this work would be simple. A simple summing amplifier, then a circuit to reduce the output voltage, even a voltage divider network would do the job. Probably about 5 or 6 components total.

Might have to breadboard this and see how it does.... Maybe just simulate it, would be quicker.

I see it making ZERO difference in the way the engine runs though.

JP86SS

iTrader: (1)

I'd like to see both sides anyway myself.
I'm not sure summing them and average in hardware would be best.
Seeing both sensors on different inputs and doing some averaging in the code would be better (make it selectable left, right, or avg on the control)
I have some split blm with the HSR at low rpm that I can move around using IAC settings. Been problematic for a while but I can make it better with larger IAC openings at idle, but this addition may help to see effects of air, SA, and fuel changes while watching both sides together.
I'm a data junkie so the more info, the better.
Swapping O2 to the other side makes it run differently enough to bother me.
The std O2 uses a differential input IIRC, a second sensor going to a normal analog may not read the same. That should be looked at.
A correction table or offset may be required.
Run it through the same O2 filter routines should work.
Hmmmm......

ULTM8Z

Exactly.

Saar

the issue that comes to mind is what happens when both sensors are reporting opposite voltages?

300mV on one, 600mV on the other?

averaged, they would be 450mV.



i think this kind of situation would actually make control worse, since if the banks are for any reason splitting, the averaged voltage would cause error to appear much less signficant than it is.

ULTM8Z

I could already have a condition worse than that. If the unmonitored side is momentarily running lean while simultaneously the monitored side is running rich, the ECM will lean out the mixture to compensate for what it's seeing. In which case the unmonitored side will get even leaner! And vise vesra of course...

In your scenario, the ECM will (theoretically) split the difference on fuel trim. Neither side is totally "happy", but at I think it would a better-than condition compared to my scenario.

ULTM8Z

Friend of mine at work is going to generate a circuit for me. At which point I'll wire it up and see what happens!

Two possibilities at that point...



or

Fast355

iTrader: (2)

Time for an 0411 and an EFIConnection 24x reluctor! Might as well add a 4L60E at the same time. Car would have so much better driveability.

ULTM8Z

Can you link me to whatever thread discusses what you're talking about?

The_Punisher454

Of course the 0411 is the ultimate better solution. But I think if you were to spend a little time learning to program a very simple microcontroller like a PIC AVR or Arduino, you could have it read both O2 sensor voltages on the ADC lines (ultra simple) and perform some basic averaging and filtering of both signals.

It would be a really trivial thing to have a rotary switch that would select right, left, combined, or anything else.

you could record the rich/lean min/max swings of one sensor and simply combine those values with those of the other sensor which is the one you will report back to the ECU.
Add an cheap character type LCD (trivial nowdays) and monitor both signals and see the difference in realtime.

With something as simple as an Arduino a non-programmer could pick it up real fast, nothing like trying to learn assembly. Seriously microcontrollers aimed at the entry level hobbiest are getting so easy to program, if you can setup your own XDF or ADX file in TunerPro you could program a microcontroller to do this.

Gumby

how about some back yard trick, 3 position flasher relay, switching back and fourth between the two, ECM can average it out.

devilfish

I like the ide.
Additional I really whant a injector offeset tabel in the 8D code.
So I could read the plugs, or mesuare exhaust temp and adjust accordingly

gp90gta

iTrader: (1)

I really dont think two o2's would correct the problem of side to side rich lean problem seen by the miniram, you would need a correction factor for all cyinders, so that would mean eight o2 to trim all eight injectors. The reason I believe this is because its not all cylinders that are going rich/lean on one side at once. The wide open intake track and short runner cause air from closing valve to bounce back in leaving the closest intake stroke cylinder to be reciveing more air then an adjacent/side that is already in compession stroke, plus add a cam with a lot overlap and it gets much worse.

That said I really can say that my miniram has any idle problems what so ever, could be that fact that my 195 heads have such poor velocity (over sized) in my 350 that its not as prevalent, which does make sence, if I had say a 400 with 195 heads the velocity in the port would be much faster and when the intake valve closes there would be more air to bounce off the valve.

For my setup I just leave it in open loop at idle and worry about pw for best idle, seems to be working just fine for the last four or five years now.

As for full sequential, it's definitely the way I want to go, I wouldn't go as far as doing the 0411 convertion but I have had the chance to work with a couple of MS3's and really feel thats the way I'm going to go, I really fell in love with the software, datalogging and even the hardware used, funny cause on the older MS1 & MS2 I use to steer friends away from them after playing with one years ago, but I would use the 24x reluctor from efi connection.

Fast355

iTrader: (2)

Years ago I wouldn't touch the newer stuff. Now I prefer working with the 0411 and the EE OBD1 LT1.

Finally it doesn't get much more simple than the 2012 and 2014 Titan I have had and tuned. Rescaled the MAF for the 4" tube it is sitting in to make the load scaling accurate, advanced the timing, played with the throttle map until I achieved wide open throttle from zero MPH and got the part-throttle feel I liked, and advanced the intake cams a little more at lower RPMs. Oh and to change the air/fuel ratio, its mostly just set command air/fuel ratio table and let the widebands work. Massive power gains for only a few hours of work. Want more power.....Fill the tank with E85, add a little timing in under load in the low-midrange and lean her out to 0.88 lambda on the E85 map and instantly pickup 15 rwtq and 10 rwhp.

gp90gta

iTrader: (1)

No don't get me wrong, the 0411 is a great ecu, but for me if I was looking to do a full sequential the price of a diy ms3 with the 24x1 reluctor is more within my budget then the efi connection kit. I know I really can't even believe it myself, hearing the words come out of my mouth, there are people right now saying hey didn't I tell you I wanted to do a megasquirt and you steered me away, all I can say is yes that the old ms1 I did years ago can't compare to the new ms3 code.

But again in my opinion even full sequential ignition and injection won't change the problem with the "split blm" problem of the miniram, the only thing I can see helping idle quality would be if we had the ability to change injection phase angle (firing angle of injector), and I'm sure there's a way to adjust it but I really don't know code to see what it is set at and/or if it even is changeable in the $8d.

ULTM8Z

Ok, so I think this is what I'm going to try....

A passive averager circuit... but with two voltages (one from each sensor).

Hopefully it'll split the difference between the two sides of the engine.