y8s

iTrader: (8)

The adaptronic only needs diode isolation for the cam and crank signals.

I build a circuit to do the O2 simulation. we had the microcontroller hardware built and laying around the office for a different application involving SXGA oleds and the EE guy reprogrammed it to do this simple task. It took a while to narrow down the actual ideal frequency, voltage, and duty cycle, but if you design the circuit to be adjustable initially, it should take less time than it took me. I tried the 555 timer based simulator and it was not accurate enough.

One of the biggest hurdles with simulating the FRONT o2 sensor is trims. since in closed loop the stock ecu expects its fuel adjustments to change the output of the o2 sensor, the o2 sensor (ideally) needs to know about that fuel adjustment. when you remove the stock ECU's fuel control and fake the o2 signal, you're left with a lot of instability.

so... it'll read a miniscule lean on the sensor and add fuel. but since the sensor doesn't change its reading, it'll add more fuel. initially it just walks the Short Term Trim (STT) up to the max, but eventually the stock ECU learns (long term trim--LTT) that it needs more fuel, and the LTT walks up to the max too. once it stays above 15% (I think), it throws a "system too lean" code. similarly, if you miss the mark the other way it throws a too rich code. look up P0171 and P0172 for more information.

My solution basically relies on the narrowband o2 sensors characteristic "dumbness" in that it just swings around a value that roughly means 14.7.

the stock ecu measures how long the signal stays above or below that to estimate the correction (STT and LTT). If you can fire the car up after resetting the ECU power (to clear the LTT), and you have the right o2 signal, it theoretically should never impose any LTT.

Obviously in open loop it doesn't matter that you have a stoich reading. The car doens't check that it stays rich or lean, only that it DOESN'T stay rich or lean for too long.

so if you make the square wave signal generator and have a way to finely adjust the ratio of on to off in 1/2ms increments, you're pretty much set. oddly, the value is not 50%.

Ben

iTrader: (33)

Thanks for the info.
The 96-00 stock PCMs are much dumber compared to the 01+. Hopefully I won't have to deal with simulating o2 signals, but if I do, your data is invaluable.

y8s

iTrader: (8)

all dumbness aside, I think that requirement is part of OBDII for 96-on.

JasonC SBB

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JasonC SBB

Wow good stuff.

Did you bolt on the stock exhaust for the emissions test?

I take it that 3D map you pasted is the AFM signal map?

And your EGR is functioning and controlled by the factory ECU?

Front and rear O2 sensor signals need not by synchronized?
The frequencies need not be that precise?
Do you know what the exact duty cycles need to be?

What did you mean by this:
"double check your airflow ... in your OBDII scanner and make sure they are accurate. airflow should match the FSM"
Under what conditions? Downhill at 55-58 mph with a tailwind in 3rd gear with 20% throttle?

Ben

iTrader: (33)

Pre and post o2 sensors definitely won't be synched.

Matt was right, I really could use that sensor sim.

dgmorr

iTrader: (4)

Do all the NB's have knock sensors? Statements like this confuse me a little and I see it often. Are you referring to all Miatas in general? Did the very early NAs not have knock sensors? Or are you implying using a second knock sensor just for the Adaptronic?

y8s

iTrader: (8)

my homebuilt exhaust with cheap cat.

the 3d map is the AFM map, yes.

EGR is handled by stock ecu, as is all the other stuff that isn't related to going fast.

O2 signals only need to maintain a minimum ratio from front to rear such that the rear is 2-5x the frequency. i guess the gist is that the catalytic converter acts like an oxygen capacitor.

I'd have to measure the duty cycles and get back to you. I want to say it was something like 54.5%, but I'm not sure. it's easy enough to figure out in the car if you just plug it in in place of the front O2 and watch the STT value. just adjust it up and down by a few ms and wait for the line to become steadily near zero.

airflow:
matters most at cruise and idle I think. at idle, it needs to correspond to the values in the FSM functionality test. it gives values in g/min or something. your OBDII scanner should also. I think it has them for a couple RPM points. simply scale the 3D map above so you nail those values and dont exceed, say, 4.75V.

JasonC SBB

airflow:
But at what load is that test? Neutral? Basically it's a double check of your AFM 3D map function?

How many spare outputs does the Adap have? (not counting what you use for boost control and VVT).

O2 sim duty cycles:
So the rear duty cycle doesn't matter?
Do you know if those generic ebay rear O2 sims would work on any obd2 car? Or do you think the some ECUs are smarter than others?

y8s

iTrader: (8)

no load, free revving. that's the only test they show.

rear duty cycle doesn't matter. it has to live with varying levels of cat performance and that's pretty inconsistent.

spare on/off outputs? lots.

3 total PWM capable outputs.

using sequential spark eliminates one of those for IGN4.

the generic rear o2 sim will work as long as the frequency ratio is within the range OBDII requires. I think front o2 must be 3-5x rear o2 speed.

JasonC SBB

3 PWM total, so they'll be used up by VVT, boost, and AFM-mimic?

TravisR

iTrader: (9)

Thats probably what people with the 01+ would use them for.

y8s

iTrader: (8)

yup. of course you could ditch the AFM one for water injection after you pass your emissions test

TravisR

iTrader: (9)

What about leaving the MAF inline and powered and running a separate wire for the MAP? Does the computer get angry when the MAF is maxed out?

JasonC SBB

Problem is if you want to let the factory run EGR for fuel economy, you need a proper MAF signal.

Travis you wrote before about simply opening the EGR valve when RPM is 3000-5000 and MAp is 50-90 kPa or some such. How well does that work? When EGR opens or closes, doesn't that create a step change in VE?

TravisR

iTrader: (9)

It shouldn't dramatically effect VE from a fuel standpoint because the gas that enters from EGR is mostly inert. There should be a nominal decrease in air un-burnt air coming in because the pressure gradient would be slightly reduced from the extra flow comming in from the EGR. This would be compensated already by your right foot with a higher TPS setting and a higher MAP setting.

If there was a difference that wasn't within the noise of the WBO2 the closed loop fuel or adaptive mode would take care of it for you anyways.

As far as the method described, it works ok. No one has really done testing on it, but if I remember my engine dynamics the EGR should be accompanied with much higher spark advance. No one probably did that part so they may have not seen a major difference.

y8s

iTrader: (8)

remember a long time ago you generated me the airflow map to start with?

it's just slightly non-planar.

that is to say that 300 RPM / 40kPa is not much different than 3000/100kPa or 1500/200kPa

I bet you could make a simple estimation of it that follows only one axis and obdii wouldn't care. especially since above a certain load it goes open loop anyway.

so basically you feed the ECU a 2D map with the X-axis as MAP and the Y-axis as MAF. I'm not sure what that line would look like though. probably 1.3 V at 20kPa to 4.25V at 100kPa and above.

JasonC SBB

Bad choice of words on my part - I should've said the injector PW's will suddenly drop for a given MAP/RPM combo when the EGR valve opens, because the exhaust gas will displace fresh air.

So if you open the EGR at say 3000 RPM, your map in theory should have a certain inj PW (and timing) at 2999 RPM, and a different PW (and timing) at 3001 RPM (you get the picture).

The other option is to gradually open the EGR valve from 2500 to 3000 RPM (e.g. 0% duty at 2500 and 100% at 3000). That way there's no step.

JasonC SBB

I do.

I think you typo'ed but perhaps the voltage is very close to a linear funciton of MAP x RPM. (with clipping at 100 kPa)

Now are you suggesting that you offload the MAF-mimic to a simple uC circuit just like you did your O2-mimic?

JasonC SBB

Years ago whasisname found out it maxed at 250 whp, and IIRC it CEL'ed.