[rusEfi] Miata NA 1996, 1.8L stock (#7)

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Miata NA 1996, 1.8L stock (#7)

Post by tomiata »

This is my other Miata that I've had for about 9 years. The body is in rough shape after getting caught in a bad hail storm, but it runs well. It's more of my project car that I can tinker on.


And a picture of the ECU for reference.
_20140827_223441.JPG
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Re: Miata NA 1996, 1.8L stock

Post by AndreyB »

Is it plated/registered/insured? I mean can you drive it?

The connector looks compatible with the 64 pin connector we are using since that empty part is just taking up the space.

http://rusefi.com/wiki/index.php?title=Vehicle:Mazda_Miata_1996
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Re: Miata NA 1996, 1.8L stock

Post by tomiata »

>Is it plated/registered/insured? I mean can you drive it?

Yes to all the above.
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Re: Miata NA 1996, 1.8L stock

Post by tomiata »

IMG_20140827_224709.jpg
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Re: Miata NA 1996, 1.8L stock

Post by AndreyB »

Once you have some board you probably want to check some basic inputs with ignition and injection turned off. For that you would do
disable_injection
disable_ignition
writeconfig
Now let's see if coolant (CLT), throttle (TPS) and MAF gauges are showing something close to reality with key in ON position. Some commands to troubleshoot would be
analoginfo
tempinfo
Next order of business would be to spin the engine with a starter and confirm that you have valid trigger signal coming in.
triggerinfo
should show something like
trigger event counters 36/36/73/73
we want all four values to be not zero, and the ratio should be more or less 1:2
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Re: Miata NA 1996, 1.8L stock

Post by AndreyB »

With this 1996 you have fuel pump control on the board - that means you should hear your fuel pump running for something like 10 or 30 seconds each time you turn ignition on - that's if fuelPumpPin is configured properly :) See
showconfig
and http://rusefi.com/images/Frankenstein/Frankenstein_v011_pinout.jpg

Once you hear your fuel pump you can test your injectors. The commands allows you to specify a delay before the test so you have time to get out of the car and get closer to the injectors. I think you should be able to hear them clicking if you are close enough. Just do not put too much fuel into the cylinders.
fuelbench2 10000 1 2 1200 3
This command would send out a series of 3 on/off squirts out to injector #1, on time: 2ms, off time: 1200ms, after a 10000ms (10 seconds) delay
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Re: Miata NA 1996, 1.8L stock

Post by AndreyB »

[video][/video]

I have no idea what this squealing sound at the end is, but we end up getting it both times on rusEfi. We do not get this sound on stock ECU. What is this sound?
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Re: Miata NA 1996, 1.8L stock

Post by puff »

you should post the start with stock ecu as well. lack of cranking fuel? could it be the starter is still engaged when the revs get high? or the revs are too slow, and it is the belt making this sound at low rpm? or you should also send control signal to the ac unit to disengage while cranking?
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Re: Miata NA 1996, 1.8L stock

Post by kb1gtt »

Is that noise a consistent noise? Does it happen only when the engine is stopping? It's hard to know what it is when not there, but to me my first thought was air pressure. Perhaps the EGR valve is mostly closed and you have some pressure in your exhaust / intake which is making some high pitch noise for a brief period of time after the engine stops. Or perhaps your IAC being closed it causing a bunch of air to be pulled through the throttle body. If you push the long pedal slightly, do you get this same issue? Perhaps we should sniff the IAC on the stock ECU. Have you gotten it to start? If not, perhaps the also points a finger at the IAC being closed. Perhaps it's being starved of O2 during cranking and idle.

To me I think it's an air issue, as it has a very high pitch. Belt squealing tend to have a lower pitch. I see the AC is a separate system from the ECU, it's probably a good idea to disconnect that AC plug just to make sure it's disengaged ad puff suggested.

Or perhaps the noise is an outburst of excitement as the engine knows what's to come :)
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Re: Miata NA 1996, 1.8L stock

Post by AndreyB »

The Miata Facebook group is confident that this is the A/C compressor which is constantly engaged, it then builds too much pressure and locks, thus locking the belt. Trying to figure out how to have A/C compressor constantly off.
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Re: Miata NA 1996, 1.8L stock

Post by AndreyB »

[video][/video]
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Re: Miata NA 1996, 1.8L stock

Post by puff »

that wasn't you!
have you checked what it does to keep running at idle? logic analyzer to see ignition timing and injection duration on the stock ecu? it's a bit frustrating. if it takes that effort to start a working engine previously equipped with a properly working ecu, i wonder what issues will face a person when converting from clear carb to efi.
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Re: Miata NA 1996, 1.8L stock

Post by AndreyB »

Timing map was in fact not activated on this video, there will be a new one with hopefully better timing. Idle solenoid duty cycle we will start by just trying to guess it and then switch to automatic idle adjustment.
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Re: Miata NA 1996, 1.8L stock (#7)

Post by AndreyB »

Now with timing map, still this horrible sound comes & goes

[video][/video]
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Re: Miata NA 1996, 1.8L stock (#7)

Post by tomiata »

After a few rounds of trial and error and speculation, I got a good tip from here:
http://forum.miata.net/vb/showthread.php?p=7158314#post7158314
And isolated the problem to the clutch, disabled the clutch safety interlock and I can start without scaring the neighborhood.

Now I can get a decent start on rusefi with no "horrible" sounds. For added flair I put the frankenstein in a box....:-)
IMG_20141002_204826.jpg
IMG_20141002_204826.jpg (580.05 KiB) Viewed 21596 times
... and got lots of help from russian and kb1gtt. Thanks!
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Re: Miata NA 1996, 1.8L stock (#7)

Post by kb1gtt »

Now I need to figure out a way to claim the trough out bearing is making the noise from air pressure some how. That way I can keep my original claims about the problem :) I guess you wouldn't have the problem in a vacuum. Also keep in mind if you start it with that bearing problem, the neighbors will probably stop by and see what you hare killing in you garage. This could be some free advertisement :)

Good to hear you have the problem isolated. I guess it's time to play with fuel trims and such.
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Re: Miata NA 1996, 1.8L stock (#7)

Post by tomiata »

I'm trying to get it to idle now. And I'm comparing the stock ECU IAC line to what the Frankenstein does.

Looking at it on an oscilloscope at idle while running on the stock ecu I see pulses about 12v at the peak, about 4ms wide, about 4v p-p, offset by 8v from ground. When I hook up the Frankenstein I hear a semi-loud buzz coming from the IAC. I can adjust the IAC pulse width "set_idle_pwm 200" and it cuts down the noise, but still buzzes.

Here is what the Frankenstein IAC signal looks like with just the keyswitch on, not running.
IMG_20141006_203216.jpg
IMG_20141006_203216.jpg (378.24 KiB) Viewed 21560 times
Looks like the solenoid coil is causing a huge spike when switching on, about 48vdc, ouch. Maybe the drive circuit needs clamp on it?
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Re: Miata NA 1996, 1.8L stock (#7)

Post by AndreyB »

There is something about clamping in the VNS14NV04 datasheet but Jared should comment. Injectors are also solenoids so they might show something similar, but injectors are usually running at lower frequency.

Image

How does the car react to IAC pwm changes? Can you post the second picture so that we can compare OEM with Frankenstein?

I believe Mazda IAC frequency is about 160Hz, that's a 6.25ms period.
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Re: Miata NA 1996, 1.8L stock (#7)

Post by jfive »

Thats easy unplug it. :roll:
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Re: Miata NA 1996, 1.8L stock (#7)

Post by kb1gtt »

For IAC you probably want a sluggish reaction, so you probably want the subbing diode instead of the clamping topology. Do you have a large-ish diode? If so can you install it across the IAC line at the ECU? Here is a crappy wiki I put together to help explain the difference from a snubbing diode topology vs a clamping MOSFET topology https://code.google.com/p/daecu/wiki/Injector_driver_theory If you install the snubbing diode, it will prevent the clamping from happening, and will create a more sluggish reaction from the IAC. This sluggish reaction will likely remove most of the noise.
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Re: Miata NA 1996, 1.8L stock (#7)

Post by tomiata »

I can try a diode across it. Like a 1N400x, say 100v or more?

I tried a few values for the pwm setting, like default or lower, but didn't seem to be closer to stay up at idle. I'll try again after knocking down that spike.
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Re: Miata NA 1996, 1.8L stock (#7)

Post by kb1gtt »

The reverse voltage is not very important. You want a strong forward peak current and after that the more amps continuous it can handle the better. The typical 1N400X are probably good enough, but keep an eye on heat. They can get hot.

If you decrease your duty cycle (increasing the frequency) you'll probably notice the noise gets less and less. As well you'll probably notice the ripple gets smoother.
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Re: Miata NA 1996, 1.8L stock (#7)

Post by tomiata »

I put a 1N4002 across the IAC coil (to +12v), and now the pulses are clean. The loud buzz sound is gone, but now there is a new sound while cranking or while running, sounds more like a hum at about 150Hz. I guess it's coming from the IAC. If I adjust the pwm setting down to 200, that hum goes away.

I tried starting after warming up on the stock ECU, and I could not get it to idle with pwm values of 100 or 200. If it set it up to 400, the hum comes back. And it sounds wrong.

This drive signal is very different from what the stock ECU does. Here is a picture of that.
IMG_20141004_113036.jpg
IMG_20141004_113036.jpg (117.59 KiB) Viewed 21670 times
Scale is 5v per div, at 2ms per div, 0 is at the center line, so it's about 12v peak. Seems like we need to get this closer what the stock ecu does?
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Re: Miata NA 1996, 1.8L stock (#7)

Post by kb1gtt »

Is there a picture of diode subbed IAC wave forms?
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Re: Miata NA 1996, 1.8L stock (#7)

Post by AndreyB »

Just to confirm:
stock ECU idling IMG_20141004_113036.jpg
rusEfi without diode, igniton on IMG_20141006_203216.jpg
Is that right? This case we need rusEfi with diode picture just to have the full set.
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Re: Miata NA 1996, 1.8L stock (#7)

Post by tomiata »

Ok, here is shot of the IAC drive after putting a diode between the line & +12v. Clean lines at 0 and about 12v.
IMG_20141007_210243.jpg
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Re: Miata NA 1996, 1.8L stock (#7)

Post by AndreyB »

How hard would it be to reach the connector on the actual IAC? I am curious how the OEM IAC would look like with IAC disconnected and some 10k resistor pulling the IAC line to +12. Jared please approve this test :)

This would tell us if the orm ECU outputs plain 0/12v PWM or more like 8/12v PWM
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Re: Miata NA 1996, 1.8L stock (#7)

Post by kb1gtt »

Can you measure the DC ohms of the IAC. Done by disconnecting it's connector and measuring with a DMM the ohms across the IAC directly.

Do you have a way to measure the Henri's of the IAC? Some times a DMM can make such a measurement. If not we can get a good idea via adding resistance as @russian has noted. We can start high and work our way down. I think that something more like 1k instead of 10k is what we need. However start with 10k if you got it and work your way down. We should see the raising and falling edges to round out and look much more like the OEM wave forms.
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Re: Miata NA 1996, 1.8L stock (#7)

Post by tomiata »

I didn't a chance to work on it yesterday, but here are measurements I did today. I don't have a way to measure inductance of the coil that I know of.

IAC coil R=12.1 ohms

Stock ECU IAC drive line shows:
.6 v with IAC unplugged, keyswitch on, same with engine running

about 2v with IAC plugged in, engine off, keyswitch on, voltage dropping slowly
.78A current on dmm with engine off, keyswitch on.

9.2v average on dmm with engine idling
.35A current on dmm with engine idling
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Re: Miata NA 1996, 1.8L stock (#7)

Post by kb1gtt »

So 12 ohms at about 12V-8V = 4V drop from OEM, which means the current is limited to about 4V/12ohms = .3A. So to ball park the same current, you should use a series 12/.3333 = 36 ohms. Then the power it has to dissipate would be less than 4 watts. That's kind of crappy. Do you have a resistor that's about 36 ohms and multi watts?

I suspect on the OEM and MS PNP they limit the current by limiting the bias current in the driving transistor. AKA only allow the transistor to pass .3 amps. We can't do that very well with this MOSFET, so a series resistor should do the job.
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