red 2003 VVT test mule Miata NB2 #27

Post by **AndreyB** » Thu Feb 13, 2020 2:21 pm

But even with not eBay coils I have crank signal disappearing if coils are hooked up

Here you can compare second line signal with both coils disconnected VS one coil connected.

puff · Post by **puff** » Thu Feb 13, 2020 2:31 pm

hm. shall I try cranking my oldrusty rover without a coil attached?
do you think it's just affecting the usb connection, or the whole thing?

puff · Post by **puff** » Thu Feb 13, 2020 2:33 pm

one more thing, I've heard that installing a large capacitor across the coil's power lines help (although I don't understand why it should help)

kb1gtt · Post by **kb1gtt** » Thu Feb 13, 2020 2:51 pm

Yeah, it's likely a huge inrush, causing the GND voltage to spike. The huge cap on the supply simply provides allot of HF energy locally, so you don't have that energy on the MCU GND.

Post by **AndreyB** » Fri Feb 14, 2020 4:02 am

After 24 hours of head banging I've noticed that cranking RPM without coils was 480 RPM. 480 RPM is not the right cranking RPM of my car, it should be 240 RPM...

Now I am thinking that there were multiple issues introduced at different points in time - loss of GND during the catastrophic event, bad replacement coil was not helping and on top of that wrongly "refactored" VVT or trigger code has messed up engine cycle

Test mule now starts reliably on MRE 0.3 - if 2019 Xmas firmware is used AND there is a jumper cable between engine block and battery.

Also note how on this picture VVT fronts are inverted comparing with 2019-10-21_rpm_1102_Frankenso_MAX9926_5K_pull_ups.png in first post of this thread.

I will go have some cognac.

Post by **AndreyB** » Thu Mar 26, 2020 4:03 am

NB2 miata has MAF as primary load sensor, but it also has "EGR boost sensor". Could this EGR boost sensor be used as load sensor?

Looks like there is a solenoid between this EGR boost sensor and intake? Not sure.

See also https://forum.miata.net/vb/showthread.php?t=590218

PS: and second question: stock MAF reports +12 analog voltage does it? What would be a good voltage divider value to convert it into 5v signal?

stefanst · Post by **stefanst** » Thu Mar 26, 2020 1:25 pm

The NB2 does have a "boost sensor". NB1 has it as well, as far as I know. I don't remember how the air-side of this sensor is connected though.
If I understand correctly, It is used to ensure that the EGR solenoid is opening correctly and exhaust gas makes it into the intake. The assumption is that when the EGR valve opens we get an increase in MAP. So, in theory, this sensor is a pressure sensor and should cover at least a good part of the operating range of the engine. I do remember somebody who wanted to put an aftermarket ECU in his car, but couldn't use any additional sensors due to class restrictions, planning to use that sensor as an ECU MAP sensor. I don't think we ever had any published result.

Suggestion: Run the engine at different loads and measure the signal. If it's a simple voltage signal, it shouldn't take too long.

scramblr · Post by **scramblr** » Thu Mar 26, 2020 2:33 pm

My undersanding is the same.
I believe the "EGR boost sensors" is ultimately a simple pressure sensor, that most likely limits out at 1 bar (atmosphere).
It should be reading the manifold pressure like any other MAP sensor. It just isn't used as the primary load sensor with the stock controller.

Post by **AndreyB** » Fri Apr 10, 2020 8:37 pm

Latest firmware, Frankenso hardware.
set engine_type 47

Battery coefficient 8.80 looks to match DMM better but maybe it affects MAP calibration negatively? Probably good enough for this test.

Looks like no TPS signal, no idea why but should make no difference for this test?

Cold engine

Logic analyzer shows pretty broken trigger signal while cranking. That's with a jumper cable between VVT solenoid on top of the engine and battery negative terminal in the trunk.

Post by **AndreyB** » Sat Apr 11, 2020 12:29 am

For comparison here is microRusEfi crank line - more or less same signal drama?

Post by **AndreyB** » Sat Apr 11, 2020 4:56 am

Just a recap:

we were suspending "ground issues" for some time. Things are really bad without a jumper cable from VVT valve to battery, and somewhat better with the jumper cable.

I've just added a proper ground strap from OEM body point to non-OEM engine point (OEM engine is hard to reach). I now have three grounds between engine and body - jumper cable, original strap, extra strap.

Can we please look somewhere else now?...

Post by **AndreyB** » Sat Apr 11, 2020 5:58 am

Frankenso uses 4.99K pull-ups and MRE probably uses a 1.5K pull-up

stefanst · Post by **stefanst** » Wed Apr 15, 2020 2:01 am

It may be a voltage issue. NB Miatas have a weird signal-inversion behavior during cranking, especially when cranking more slowly. Cranking drops the voltage and that may cause some funkiness with the sensor. Try a bigger/newer battery? If one is not at hand, run separate power for the sensors (12V wall-wart should do) and use the battery to just crank.

Post by **AndreyB** » Wed Apr 15, 2020 2:36 am

Battery is few months old but I suspect I could have a drain. I am very very close to installing a kill switch next to the battery.

Rigol has started to pay for itself: VVT PWM noise is very visible on this not running engine with pretty much discharged battery. Now I need to plug battery charger extension cord in and give it a couple of hours.

At the moment VVT uses FSIO aux PWM generation and that thing does not turn itself off with stopped engine. VVT will be unplugged for now.

Post by **AndreyB** » Wed Apr 15, 2020 4:50 pm

Some composite logs gathered so far

Post by **AndreyB** » Wed Apr 15, 2020 6:06 pm

Super long adapter harness may be adding enough inductance to be a problem.

Adding a shortish (2') alligator clip from Frankenso ground to intake reduces spike from VVT turn on/off by an order of magnitude. (down to ~0.5v peak-to-peak)

To be continued.

Post by **AndreyB** » Mon Apr 20, 2020 6:32 pm

Things have improved from "nearly impossible to start" into "starting is reliably poor", only 8 out of 21 attempts were successful

Two things have helped:
1) Both crank and cam sensors of this NB2 should be considered VR for software decoding and we shall rely only on rising fronts. Still Hall-style hardware decoding with pull-up resistors.
2) my tune was not using idle solenoid due to a configuration mistake. this is now improved under https://github.com/rusefi/rusefi/issues/1332

Still look for better starting obviously. Tune, sensor and composite logs attached.

Post by **AndreyB** » Tue Apr 21, 2020 3:42 am

As an experiment we've switched to CAM sensor only. With attached tune I can start every time! Minor improvements to idle air were made.

So it looks like crank+vvt trigger decoding is part of my starting issue.

Crazy Striker · Post by **Crazy Striker** » Wed Apr 22, 2020 1:42 pm

For referencing purposes so that nothng get lost, here is the MAF transfer tab for 94+ miata. I'll run it but just to monitor flow, nothing more.

Cheers

Gwendal

Post by **AndreyB** » Mon Apr 27, 2020 12:59 am

the way rusEfi was handing NB2 special symmetrical crank was one of the reasons of unreliable cranking experience on this car. https://github.com/rusefi/rusefi/issues/1278 code change has addressed this issue.

Post by **AndreyB** » Mon Apr 27, 2020 3:04 am

Crazy Striker wrote: ↑
Wed Apr 22, 2020 1:42 pm
For referencing purposes so that nothng get lost, here is the MAF transfer tab for 94+ miata. I'll run it but just to monitor flow, nothing more.

Thank you, this is now part of NB2 default tune.

Post by **AndreyB** » Sat May 02, 2020 4:36 pm

A very quick run with speed density fuel and MAF recording

Post by **AndreyB** » Sat May 02, 2020 5:56 pm

Crazy Striker wrote: ↑
Wed Apr 22, 2020 1:42 pm
For referencing purposes so that nothng get lost, here is the MAF transfer tab for 94+ miata.

Is https://forum.miata.net/vb/showthread.php?t=486064 the source of this data? This looks like NA miata.
NA and NB MAF sensors seem to be different at least in terms of IAT sensor internal vs external. No idea if same transfer function or not.

Post by **AndreyB** » Sat May 02, 2020 9:16 pm

Just double-checked that OEM ECU has 1K between pins 4X "MAF" and 4O "Sensor GND" yet the MAF function we find on the internet does not produce reasonable readings for rusEFI Frankenso with a 1K pull-down.

As a work-around I took a known 0280218004 MAF sensor - that one needs both +5v and +12v supply but at least output is voltage without any pull-down magic. And the car is running!

Next step would be to guesstimate Miata NB MAF based on 0280218004 data. One of the logs show 0280218004 voltage in "oil pressure" column while running on MAP, the other one shows running on 0280218004.

Post by **AndreyB** » Mon May 04, 2020 12:29 am

Another day and fresh drama to chase!

TunerStudio via TTL disconnects on engine start, with two different HW setups:
1) MRE72+MRE+Bluetooth HC-06 @ 38K
2) Frankenso+Prolific USB-to-Serial, hard-wired, at 115K

Frankenso log & comms log attached.

Post by **AndreyB** » Mon May 11, 2020 11:19 pm

Digital multi-meter shows 1K pull-down on MAF signal line inside OEM ECU and a 5.5K resistance to +5v? Shipping OEM 279721-1201 PCB to @mck1117 for him to do some poking.

Post by **AndreyB** » Sun May 17, 2020 10:08 pm

Looking at this schematics I was hoping to see either 2O or 2M wires but not both in my harness? My car has both wires on the "2" ECU plug. I was really hoping 2O would be a pin available for rusEFI purposes

Post by **AndreyB** » Mon May 18, 2020 12:31 am

I have a very beautiful test mule!

Took it on a very lean field trip. MAF sensor was driving, MAP was just riding along, WBO was... concurned.

Post by **AndreyB** » Tue May 19, 2020 12:41 am

Emil says a bypass hose would be needed to use OEM pressure sensor to run the engine.

Post by **AndreyB** » Tue May 19, 2020 5:36 pm

Ha, there is a crazy idea to actually drive that EGR solenoid since we have outputs! That would be low side pin 3D.

rusefi.com

[rusEfi] red 2003 VVT test mule Miata NB2 #27

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