[rusEfi] Hunchback 1991 Miata NA/NB2 rusEfi official racecar #20

[AndreyB]

Need to add a muffler - it's too loud with just a glass pack, need some black zip ties to mount a clock - but we are getting closer

Either http://rusefi.com/forum/viewtopic.php?f=3&t=906#p18363 is not a divider or I am missing something. I took three measurements but I do not get consistent pull-up value, maybe I am doing something wrong?

ignition on, weak battery: vbatt=11.0v, wire connected=4.6v, wire disconnected resistance to GND = 120R. divider formula gives pull-up = 86.25R
ignition on, 50A charger: vbatt=13.0v, wire connected=5.5v, wire disconnected resistance to GND (still) = 120R. divider formula gives pull-up = 88R

car idles, cold engine shows 45 lb/in^2, vbatt=14.2, wire connected=3.2v, wire disconnected resistance to GND = 79.3R, divider formula gives pull-up = 23.07R

I do not get it. I would expect the pull-up to be the same regardless of if car is running or not, since ignition is on?

[stefanst]

The gauge itself has a resistance and that's an inductor- no idea, what it will do. There may be other things going on as well. Hard to tell without bench-testing the gauge.

I'd say you're overthinking it. You have two reasonable looking data points: Voltage at 0 psi and voltage at 45 psi. And that means probably anything between 35 and 50 psi- those gauges are not calibrated. Use those two data points, do a linear interpolation/extrapolation and ignore any and all lack of precision.

[kb1gtt]

The guage in the schematic shows 12V, GND and signal wire. So I'm not sure that's just a resistor. Is there a way to get a sensor in hand? Salvage or new. I wonder what it is exactly.

[stefanst]

The sender is just a resistor, the gauge consists of multiple resistors and electromagnetic components. Some resistors in series with electromagnets, some parallel. One of my '99 Miata gauges - don't remember which one - even has a diode. So no surprise these things are non-linear. Don't bother with trying to figure out electrical behavior, just use it as an estimator.

[AndreyB]

Sorry Miata fans - that's a Lemons car.

[stefanst]

Like a ginger stepchild that only a mother could love. It's the hunchback Miata. Let's name it Notre Dame?
Awesome!

[kb1gtt]

Is the OEM gauge supplying power to the oil pressure sensor? I think not, as I think the gauges have been removed. So the below assumes the Frankenso is providing the pull up. This means you can use 5V pull up instead of 12V pull up.

Assuming the sensor is a variable resistor that varies from 120R at 0 pressure to 79.3R at what ever is idle pressure. Also assuming you are using input 7, you would want to use a 300 ohm resistor for R270. This will limit current such that the resistor sees less than 1/8 watt, and it would provide a voltage that varies from about 1V to 1.4V. See below picture which came from attached xls file.

Sensor_Resistor.PNG (26.37 KiB) Viewed 27314 times

To get this, you would simply wire that signal wire to the input, and install R270.

[AndreyB]

So the below assumes the Frankenso is providing the pull up.

Frankenso not yet connected. I will wait for the second muffler so that I can get to higher RPMs while in the garage and get more data.

[kb1gtt]

I was thinking that the gauges are gone, and originally this didn't go to an ECU, so I understand you are currently using rusEFI as a glorified shift light, and longer term once you know it works, you'll slowly migrate to rusEFI for engine control. For now I was thinking you were going for shift light with optional oil pressure indicator. I guess I must be missing something, I don't fully understand your goals or exactly what you are doing. If you need help figuring out how to make this sensor do something, let me know and I'll see what I can do to help.

[AndreyB]

It was raining most of the day so one of the drivers put it into a wall just a little bit. There will be video later.

[AndreyB]

My race stint yesterday. I am still very afraid of driving RWD, but I am making progress I hope!

[video][/video]

totally uneventful, a tap from behind at

It was a 9/10 race for us considering its a brand new car.

Issues: oil got a bit low after 6 hours, we've added a quart and switched to 20-50 instead of smth-30 Saturday night. That's a cheaply refreshed engine.

We got pulled off track for fuel leak - looks like fuel cap seal was jammed mid thread and did not seal. Added some tank ventilation also.

Gearbox does not like to up-shift into 3rd, downshifting into 3rd is fine. Good news 2nd could be avoided on this track but we will have to look into this! That's it for technical issues and that's great.

We've started with everyone driving for 30 minutes just to make sure everyone gets a chance to drive so lost a lot of time there, also made a slow checkup mid race - so we are like 55th overall and 25th on class - that's mid-pack both ways.

Fastest driver did 1-50 and I was making constant 2-02 because still very conservative with RWD. The other miata guys their fastest guy did a 1-39 so there is room for me to go.





start of race
[video][/video]

fastest driver
[video][/video]

[AndreyB]

Difference between me and @?
I've used a full SD card for data logging at the race a week ago. Only a few files are not zero size.

Day #2 I was trying to record oil pressure data but well... I've failed - no files from second day.

[stefanst]

Not sure if this matters, but your MAT and CLT show the same pattern on the noise. The short term variations on both move in lock-step. Interestingly, the vbatt moves opposite to that.

Also with a 90hp car, you need to COMMIT to the throttle. There's waaaaay too much throttle-feathering going on.

Last but not least, what's up with the MAP signal?
Edit: Looks like the MAP is just a capacitor charging. No actual signal.

[AndreyB]

No MAP sensor on this car, it's probably a floating wire. Real Time Clock is pretty doable and it's kind of on the list - once RTC is here it would be possible to say who was driving. We are four drivers with huge variation in experience.

As for the noise, turns out only Dodge Neon settings have ExpAverage enabled for slow sensors, both race cars were running with this disabled. I will probably change the default from slowAdcAlpha = 1 to slowAdcAlpha = 0.33333 which is a random value which worked OK on the Neon. Thank you for noticing!

[AndreyB]

Next time I decide to part out a car, somebody please stop me! Too much effort!

On a brighter note, I've fixed the turn signals on the this green race car: that would be the 3rd wire I should not have cut in my harness stripping career

[AndreyB]

Considering to use Toyota MAP 89420-02010 just because I have three of them - 1993-1997 Toyota Corolla and Geo Prizm models.

yellow - 5v
brown - ground
lt green/red - signal

decoding formula TBA
3.94 In Hg drop = 13.34237 Kpa = 0.3-0.5v = ~0.4v drop
7.88 In Hg = 0.7-0.9v

19.69 In Hg drop = 66.677993 Kpa = 1.9-2.1v = ~2v drop

[Thommm]

Trust me, MAP eill make your life so much easier ;p. I'm running a €6 MAP and the car has never run better on the AFM. Are you going to mount it in the engine bay or near the ecu?

[AndreyB]

[video][/video]

No MAP sensor, no AFR sensor yet. Pretty random cranking fuel and fuel map values, requires a little bit of throttle to start, but it starts!

I had to change the trigger shape definition just a little to get it started, also I've warmed up the engine with stock ECU as part of the troubleshooting. Well, one step a time - next time I promise to have the idle solenoid flyback diode and not warm with stock ECU.

Update: turned out I've managed to start the car on two cylinders! No wonder it was starting & running so poorly!

[Maxi]

How I see this...

1.PNG (1.23 MiB) Viewed 26974 times

2.PNG (863.6 KiB) Viewed 26974 times

[AndreyB]

Wow, that's some effort with the poster on the wall

@ to be honest your irony is lost on me, would you please care to elaborate?

[Maxi]

Wow, that's some effort with the poster on the wall

@ to be honest your irony is lost on me, would you please care to elaborate?

Do not worry - it is lost for all who have not seen this movie. )) Аnd it is very difficult to explain.

[AndreyB]

It's actually good

[video][/video]

[AndreyB]

Are you going to mount it in the engine bay or near the ecu?

Why are people mounting MAP sensors near the ECU? I guess it's easier to run one hose than make power source and mount the sensor, but that just does not seem right to me.

[AndreyB]

Turns out I've managed to start the car on two cylinders couple of days ago! No wonder it was starting & running soooooo poorly

Wired MAP & EGO today - added two extra pins into the ECU connector, also installed the fly-back diode today.

MAP: Frankenso analog #6 pin 3R, W56 top <> W45 bottom jumper, not OEM
EGO: Frankenso analog #7 pin 3J, W48 top <>W48 bottom jumper, not OEM - that's the blue wire




Will shoot some cold engine start video tomorrow - today it took me 15 minutes to find the magic parameters which would reliably start the car on two cylinders, but there is not much value in this now.

[Thommm]

Mounting it near the ecu vs in the engine bay is a chicken and egg story. By placing it in the ecu you are minimizing electrical interference and vibrations, but you are inducing a couple of milliseconds of delay in th signal (due to air having to propagate through the hose). By placing it in the engine bay you minimize the delay, but you are adding electrical interference, because you need a far longer wire, which most of the time isn't even shielded! You are also adding a lot of vibrations to a very sensitive sensor, the membrane inside will probably (unless MEMS) vibrate slightly due to the engine vibrations, also adding noise on the signal. So both ways have their merits, there is not a definitive one size fits all.

[puff]

do you really think leaving the map sensor that way is a good idea? i thought those who place map sensors close (or even inside) the ecu - they're just using pcb mount versions of those sensors, without the casing. I guess it would be much better to first consult the datasheet for those sensors. they have some curves for pressure vs temperature (not to mention condensed water), they are required to be placed in some certain orientation in space (you shouldn't do that upside down or at some random angle - probably because of the same condensate). i'm not sure about vibration levels if you mount it ontop the engine or to the chassis.

[kb1gtt]

Getting data for proper use of the OEM sensors that are often found under the hood is something to consider. While a hand pump can often work reasonably well, not knowing it's capacitance and exact electrical interface requirements can be a bit of a bugger. However it can probably be made to work well enough, but it could also be a key source of problems. So yeah, chicken and egg thing. I don't think there is any 100% correct method. I would tend to suggest what ever method has the most detail in a datasheet. These pressure sensors get skewed for many reasons, some are a bit less obvious.

[AndreyB]

Interesting, I've learned something today!

i'm not sure about vibration levels if you mount it ontop the engine or to the chassis.

this toyota sensor is on a firewall in OEM location, some cars do mount these right on the intake manifold like my 2003 dodge neon.

[AndreyB]

[video][/video]

[AndreyB]

I am reproducing the misfire, have three log files - it's always towards the end. Spike in AFR and dip in RPMs, so the misfire is definitely visible on the logs at least.

trigger statistics shows a low number of synchronization losses - but that number is way lower then the number of misfires, it was probably 20-3o misfires over 30 minutes of testing:

Code: Select all

2016-06-25 21_37: EngineState: trigger#1 event counters up=30062/down=30062
2016-06-25 21_37: EngineState: trigger#2 event counters up=60100/down=60101
2016-06-25 21_37: EngineState: expected cycle events 4/8/0
2016-06-25 21_37: EngineState: trigger type=3/need2ndChannel=Yes
2016-06-25 21_37: EngineState: expected duty #0=0.29/#1=0.38
2016-06-25 21_37: EngineState: synchronizationNeeded=Yes/isError=No/total errors=8 ord_err=1/total revolutions=15020/self=No
2016-06-25 21_37: EngineState: gap from 0.89 to 1.94

MAP calibration is off - cunning of MAF here anyway

Tune & logs - https://svn.code.sf.net/p/rusefi/code/trunk/misc/logs/1991_miata_hunchback/20160625_misfire.zip