PGTMR2
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Joined: Sat Jan 27, 2018 2:34 am

Car engine controls help needed.

Mon Jan 29, 2018 2:40 am

First off Hello, I am new here. Now that that's out of the way...

I would like to use a RPi 3 to control 2 12v vacuum solenoids on my engine. Normally closed vacuum solenoids that opens when they receive 12v... normally from the stock ECU, but some mods happened. The original engine intake had different vacuum solenoid timing. Both the intake and ecu are not stock for this car. The intake is larger and needs different timing for the solenoids, the ecu is from a newer engine and has yet a third set of numbers for the solenoid actuation. It was OBDI is now OBDII with a patch harness :twisted: It functions extremely well, all I'm trying to do is a minor tweak to open the solenoids at the correct rpm for each solenoid. Absolutely no damage can or will occur from this mod, only a minor loss of power will occur at certain rpms when the timing is off. Parts are available on the market, but I want to go this route and add more functions as I go along. There also seems to be an absolute brick wall between electronics people and automotive people. Most searches involving car/automotive, 12v, actuator/solenoid and Pi/arduino lead to carpooters. It's on my list too but secondary. I'm also not impressed with OBDII dash displays, I already do that with my phone when something goes wrong.

I've got an ELM327 Bluetooth on the way specifically for this project. I figure that will be a quick temporary way to get the RPMs for testing while I figure out a safe way to get the high voltage from spark plug no.1 to a GPIO pin. Or I may be able to just splice it off the signal to the ECU/tachometer which is already safe.

I'm going to have to experiment a little with this. The stock solenoids may operate on 5v that would be great and I think should make this a simpler project. But if there's a delay, and or they don't always flip at the correct point I'll have to go with 12v.

So here's what I've got since you're still here. Solenoid number 1 needs to open at 4000 rpms. Solenoid number 2 at 4800 rpms, and they both close at 6800 rpms.

The ECU will have dummy solenoids plugged in to prevent a check engine light, from here on out referred to as a CEL. The CEL will not cause any emissions issues or limp mode so this will not contribute to poor fuel economy or global warming if that is a concern. It passes emissions and has a catalytic convertor as well.

So what is this all about? Well, cars have a peak horsepower and torque number. The system this car came with has the ability to move the peak TQ number a little lower and a little higher, giving it more power over a wider range of rpms. There were 4 variations of this engine. I have parts from 3 of them to make more power by getting more air into the engine for combustion. 25-35% more power than stock, over a wider range.

Draw a rectangle on a piece of paper, now draw an oval inside the rectangle touching the 4 sides. The old intake and heads used to breath through the oval, the new parts, through the rectangle, they have the added area/volume of what's left in the corners, from the throttle all the way to the cylinders.

That was part 1. The other part of this is where the solenoids come in. Helmholz resonance. The long and short of it IS the long and short of it. At lower rpms an engine breaths better through a longer intake and makes more power by keeping air velocity up in a longer tube. As it climbs through the rpms the shorter the intake the better to get a larger volume of air pulled by the pistons. The solenoids operate a metal plate each that open and close a tube at the far end (far from the throttle,) and another tube midway in the intake to connect one bank of intake runners, (tubes feeding the engine air,) to the other set. At low rpms all cylinders draw from the throttle side. 4000 rpms one solenoid flips the valve and the cylinders can draw air from 2 directions, 4800 all the cylinders can pull from 3 directions.

What's this resonance thing about? You have to visualize the air as a spring. Getting pulled in by the engine, splitting into 2 chambers then to the 6 runners (yeah almost forgot 6 cylinder engine,) each taking in air at different times. So there's this pulling of the air right up until the cylinder head valve or valves close. The air traveling at speed suddenly slams to a halt on the back of the valve and compresses like a spring. Then goes back from the runner into the larger intake chamber which if timed right can be used to charge the next cylinder that opens. This is the effect this system takes advantage of. Sort of a micro supercharging the air, the air resonates at different frequencies at different rpms.

It's a 2.5l V6 from Mazda that would absolutely trash a 5.0l V8 from the same era. I wish they still made them... with more modern goodies. Anyway I've written a novel. I'm not sure what program I would be looking for. I expect there's more than one way to skin this cat. I do want to get up to controlling ignition coils later with the same Pi.

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davidcoton
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Re: Car engine controls help needed.

Mon Jan 29, 2018 11:49 am

I'm not sure what you actually need help with, but FWIW here's my thoughts:
  1. There is no safe way to "get the high voltage from spark plug no.1 to a GPIO pin." You will have to get the timing from an equivalent low voltage signal. (Or there might be some form or current transformer you could clip round the HT lead.)
  2. The Pi's GPIOs work at 3V3 and are not tolerant of even 5V. So you will need a driver (transistor or opto-isolator) whether you use 5V or 12V solenoids. Assuming the car supply is 12V, I would go with that, rather than running solenoids on the same 5V supply as the Pi.
  3. I don't think you will find a ready-written program, so it's time to get coding. Python would be my first choice, but may not be fast enough. C++ is faster.
  4. Remember that a Pi is not a failsafe automotive device -- you must arrange everything so that it works in a fallback mode if the Pi or its program fails. And make sure that any sudden output changes caused by such failure don't cause damage to your engine.
I'm not an auto-electrician or mechanic, so there may be standard ways round these issues that I'm not aware of.
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PGTMR2
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Re: Car engine controls help needed.

Mon Jan 29, 2018 9:50 pm

Well, automotive ECUs are computers and they safely get the tach signal through resistors, I think 10k ohms or greater. So far as the Pi being reliable for automotive purposes, I was thinking once I got something working and documented, I could make it easily replaceable. But the plan is to have the Pi in a metal case, chassis grounded, to protect it from induced currents, and sealed from moisture with non conductive material, (hot glue, lacquer over the circuit board?) with only heat sinks and plug jacks exposed with a case fan. Hot glue also helps isolate vibration when it comes to wires as well.

So far as the 12v - 5v goes, the work of the solenoid is done by vacuum. So if 5v works it works, and there is some debate over on the car forum as to whether the solenoids are 12v or 5v to begin with since the ECU provides the power to operate them. A lot of relays, automotive included, work like this within a range.

As to damage to the car, engine, or ability to drive, I've already addressed this. It will drive like a normal car does without the system, it will feel a little slower, that is all. Like a Honda with VTEC, but the VTEC doesn't work. Currently the solenoid timing is off and it has enough in it to get to 60 in about 6.0 seconds. I put this engine in the car, I put the ECU it's running on in and drove it as my daily for over a year and a half reliably before a maintenance fail happened. Did fantastic for being 23 years old without a rebuild and hitting 7k rpms all the time. It is currently down for timing belt issues and the weather.

Definitely don't mod your car if you don't understand what you are changing, or other consequences that may arise.

I'm thinking a very simple program whether Python or C++ should do it, I don't expect with 4 processors to really have a delay or a noticeable one. The numbers given in the first post are stock numbers, designed to switch the solenoids at a time when it will have a gentle transition from one to the next. So if I feel a kick when the solenoid flips then I can either enter a higher or lower rpm number into the program to account for the slop. What I can't have is the the spinny wait symbol, or a loading bar when it's supposed to flip the valve open or closed.

So I need direction to a simple program where I can enter the rpm (think clock pulses,) and a GPIO pin turns on at 4k per minute, then for a second pin at 4.8k, then both off at 6.8k. So really it's kind of a noob question that needs answering by the more experienced because of what's involved, instead of a noob with their BVDs wrapped up in an HDMI cable trying to get Retropie to work. :D Maybe some guidance toward appropriate GPIO pins as well since they can have different purposes.

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davidcoton
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Re: Car engine controls help needed.

Mon Jan 29, 2018 11:27 pm

  1. An ECU may be a computer but a Pi is not an ECU. It is not designed for interfacing with spark plug voltages. Especially not by just using a resistor.
  2. There may be "debate" over whether your solenoids are designed for 5v, 12V, or both. You need to find out from manufacturer's data or by measurement in a known working configuration.
  3. I'm not sure anyone will be able to help with code online without having the same hardware available. Break your code down into sections, get the speed measurement working first, then get the solenoids switching. There's no issue about delays if the program runs continuously -- though obviously the whole system takes time to start when you switch on.
  4. You seem to have that covered. But do make sure that the possible failure modes (any combination of open and shut solenoids) are all safe.
I have two doubts:
  1. Although the code itself is not hard, the overall system is not a beginner's project. You may need to learn to walk before you try to run.
    Read some of the other auto-Pi project threads for an idea of the infrastructure required to run a Pi in a vehicle.
  2. A Pi may not be the most suitable platform for this project. And a general purpose OS like Raspbian is certainly not ideal. Not really something to discuss in detail here, but an Arduino or similar might be a better solution.
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PGTMR2
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Re: Car engine controls help needed.

Tue Jan 30, 2018 1:54 am

Well the ELM327 just arrived and that was pretty quick, I think I ordered it Saturday. I get that Arduino would be better because it is a controller, but I have bigger goals and things I want to add as I go along which will probably require a processor. I also get that there will be time for boot up with a Pi but I usually let my car warm up a little before I get rolling, even if I don't, I shouldn't be ripping on it with throttle until it is warmed up. I'd also like to test out whether it can play a programmed tune that can be heard and I'd like to add manual buttons to the shifter. I'd like to use this to test something as well, I have all 4 engine intakes and I'd like to definitively test some things. Like the benefit of the ECU swap I've done, which I can do by running the car with different VRIS points. VRIS is Mazda's name for the system

So far as safety goes, this will not control the throttle, or the fueling, or the idle, or anything that could cause a surge in RPM. Period. The system already exists in the car from the manufacturer, I am hacking it to tune it, not trying out a crackpot theory that may be dangerous. The valves the solenoids control are like the buttons on a trumpet. They only tune the airflow inside the intake giving it a shorter or longer path. If it fails in any configuration it will drive fine, when they fail they fail closed, due to vacuum loss, and they get shut with spring pressure. They can also be wire tied open, which some noobs to this engine do thinking they will gain power, but they lose power lower in the range and acceleration suffers. Then there's the turbo crowd that completely remove the system since it only has benefits with naturally aspirated engines.

5v - 12v doesn't matter for this. The car has 12v already, the Pi uses 5v, both 5v and 12v will need to be there, I'll wire that up accordingly. I'm thinking an Arduino would be overkill since there already is a Pi for doing the thinking. What about Pmods for interfacing with the 3.3v GPIO pins? I'm open to using Arduinos to directly control the solenoids, BUT, I want a Raspberry Pi in there for future add-ons and controls like distributorless ignition. That may be the better route to go. So far as ECU vs. Pi it makes no difference to me, the original ECU from 94 has an EEprom in it. An ECU is just an underpowered PC wrapped in a metal box, insulated from vibration, moisture, corrosion and stray induction and I can do my best to insulate once I have a finished product.

Okay... so, simple program, quick load up, works every time. C++ or Python.

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Imperf3kt
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Re: Car engine controls help needed.

Tue Jan 30, 2018 3:11 am

Your major concern here should be shutting it down.
The pi needs a graceful shutdown lest you risk corrupting the SD card (potentially write locking it) every time you turn your car off.
55:55:44:44:4C
52:4C:52:42:41

PGTMR2
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Re: Car engine controls help needed.

Tue Jan 30, 2018 4:13 am

Push button shutdown program so it can get a head start before the key is off with a physical momentary switch?

Darkphyer
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Re: Car engine controls help needed.

Tue Jan 30, 2018 6:06 am

i think you might want to use an arduino board to control your solenoids, the code alone is easier and just runs. i'd be willing to bet you could get an rpm reading directly from the motor... you could always add pi later

PGTMR2
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Re: Car engine controls help needed.

Wed Jan 31, 2018 2:15 am

There is no other direct source for rpms, I know this engine inside and out. Spark tells within a few degrees which direction the crank is facing because it is always adjusting timing. The crank sensor is 3 wire, with a 6 point trigger wheel. Cams spin at half rpm and and have either a half rotation sensor or a 6 square tooth triggerwheel. On top of that, the crank and cam signal go back to the ecu on the same wire and are picked out separately. So when it comes to tapping the signal it's not straightforward.

When it comes to me getting the rpm from the spark plug on #1, please just push the "I believe" button. I can find out the exact ohms I need from the car forum. Or I may get one of these as a shortcut. It's purpose built for converting spark down to 5v. Which I think will work with Arduino. http://trigger-wheels.com/store/content ... coilx.html

I will look into an Arduino as a controller for the solenoids and valves, but I'm going to still want to use the pi to setup the Arduino, to show the operation of the valves, and to, like I said, add on distributorless ignition.

I've been kicking around ideas for going distributorless for years since the single coil that provides the spark and the ignitor suck. It's pretty much something I have to work on every few months or once a year. In fact, an ignitor failure caused my first car to get wrecked. Stalling out mid turn I got hit by a Subaru when I couldn't get out of the way. There were a bunch of fails that happened all at once that led to the accident. 9 years after that accident I bought another one because I missed it, it's been nearly 9 years since then. By the time I bought my second one the automotive forums had come up with a hack fix, which works and is cheaper and readily available everywhere but also could fail. I have that hack installed under the hood as a backup if I need it, but distributorless is the way to go. The biggest problem is heat since the parts are installed under the distributor cap where most cars have them out in the open. The second is issue is rpms, It's a cheap car that physically can run at high rpms all day. It's fun, and it sounds great, and even if you are a hypermiler it runs at 3300 rpm in 5th gear on the freeway at normal speeds. That's probably more than double what the average car runs at. Higher rpms means thousands more sparks even on a short trip. Distributorless could cut the number of sparks per coil to 1/3rd or 1/6th, also eliminates the cap and rotor.

One idea I came up with for this is to put a light, a sensor and a light wheel in the distributor, in place of the rotor and under the cap. Using old parts for the cutting. Keeping the distributor for this system and the cam sensor, but disabling the spark.
This way I don't have to cut anything that is a part of the car, and it can easily go back to stock. But uses a stock ecu, with all the stock adjustments. The wheel would have a hole in it, exposing the sensor to a light as it passes. The ECU is only looking for feedback from the cam position and control over advance/retard of the distributor, which it will still have. With that, the injectors, crank pos. sensor that is all the ECU needs to run allow it to run. Bear with me I'm trying to sort all of this out. Again I am coming to the conclusion that Arduinos would be better, one to control each coil. BUT, I want to tie all of these together and make programming adjustments through a Pi with a simple GUI on a touchscreen. Does that make sense?

For those interested, the car: https://www.youtube.com/watch?v=X_004dMxsps
The intake, (headphone warning at the end!!!): https://www.youtube.com/watch?v=mVcCTana4vw&t=10s

Zebu
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Re: Car engine controls help needed.

Wed Jan 31, 2018 3:00 am

i feel like there might be some confustion here. you don't get the timing signal from the plug side of the coil, even on a stock ignition system thats 10,000+ volts and an aftermarket system can be 45,000 volts

if you need to read when a plug is firing then you do it from the cold side of the coil/driver which swings between ignition voltage (probably somewhere between 12 and 14 volts depending on the health of the alternator) and ground using a voltage divider and then do some maths based on the number of cylinders, number of coils and if its a sequential or wasted spark system.

that's what that converter board is doing ~12v to 5, which is still too high for a pi but can easily be brought down further

im with Darkphyer, arduino is a microcontroller only doing one thing and can attach interrupts to pins going high or low so the accuracy will be way higher and you have no startup/shutdown issues

PGTMR2
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Re: Car engine controls help needed.

Wed Jan 31, 2018 4:05 am

12v is not considered high voltage, high voltage is usually anything 400v and above, voltage that can jump a gap. I just took another look just to make sure I knew what I was talking about. The resistor for the tach from the coil in stock configuration is attached to the negative side of the coil. Where it's not the spark directly it can still spike as 4-500v. The design of the coil gives the voltage an easier path through the spark plug, not the tach and ECU but they're basically all tied together with resistance, possibly a diode to send most of the charge through the spark plug. I can do the same thing externally to get a tach signal, that is what I was suggesting. I already am looking for an Arduino solution but I'll still be bringing it back here, and I have to grind out all the details of cans and can'ts of what I'm trying to do. So stay tuned. I do appreciate the interest and help from everyone.

Zebu
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Re: Car engine controls help needed.

Wed Jan 31, 2018 4:53 am

the two sides of the coil are actually separated like in all transformers, the high voltage in the secondary coil is induced by the collapse of the electromagnetic field in the primary coil which is its 12v side.

If you have a CDI ignition or something like an MSD and the low voltage side of the coil is actually getting 400v then you need to find the low voltage signal that is triggering the CDI unit.

an MSD or the like usually has a 12v square wave output to go to the tacho though because otherwise you would burn out the tacho giving it 400 volts.

Ill be keen to see your result. I have a 1985 Alfa Romeo 33 that originally had a fairly similar ignition system to your probe that i upgraded to an MSD and i use the msd tach output to measure from.

PGTMR2
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Re: Car engine controls help needed.

Wed Jan 31, 2018 6:29 am

I see, I didn't expect that sort of a transformer type setup with DC, but I see what you're getting at. The Tach isn't receiving the full charge from the coil it currently is running either way, there is a resistor in the coil in the car, and I'm sure that as of right now the ecu and the tach aren't receiving a dirty signal. The problems usually begin with switching to an aftermarket coil. I still plan on using an o.e. coil or coils or coil pack, ones others have used. The math also makes sense about 10:1 with just the numbers spitballed here.

PiGraham
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Re: Car engine controls help needed.

Wed Jan 31, 2018 7:14 am

PGTMR2 wrote:
Wed Jan 31, 2018 2:15 am
There is no other direct source for rpms, I know this engine inside and out. Spark tells within a few degrees which direction the crank is facing because it is always adjusting timing. The crank sensor is 3 wire, with a 6 point trigger wheel. Cams spin at half rpm and and have either a half rotation sensor or a 6 square tooth triggerwheel. On top of that, the crank and cam signal go back to the ecu on the same wire and are picked out separately. So when it comes to tapping the signal it's not straightforward.
When you say "source for rpms" do you mean accurate timing? You can read accurate RPM from ODBII.

The ECU generates the spark timing and uses camshaft sensor to do that. The ECU controls a coil pack to generate the high voltage pulses for the plugs so you may be able to sample the sensor or the ECU output.
It is possible to sense current in a plug lead. Timing lights often use magntic picuks that clamp around the HT lead and you can arrange any signal voltage level that suits you by winding your own pickup coil. You can possibly use a Hall Effect current sensor, an off the shelf current sensor or the clip from a timing light.

I strongly suggest you do not make any direct condutive connection from the HT to anything.

PiGraham
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Re: Car engine controls help needed.

Wed Jan 31, 2018 7:18 am

BTW if you modify your car you potentially invalidate your insurance, whether or not your mods are implicated in any claim that may be made. All main insurers have clauses in their policies requiring customers to declare any modifications.

jacob.alberty
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Re: Car engine controls help needed.

Wed Jan 31, 2018 1:52 pm

It sounds to me like you're talking about the mazda millenia. That car is common enough and has enough of a following you should just be able to get your ECU flashed to change the set points for the solenoids. That'll be a whole lot more reliable than trying to control those solenoids with anything else.

Also stay away from the high voltage side of things for getting your tach signal. I don't believe your gauge cluster would be on any sort of bus so you should be able to get the tach signal right from the gauge connector. Just look for a pinout for it and tie in to the signal wire for your tachometer.

PiGraham
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Re: Car engine controls help needed.

Wed Jan 31, 2018 2:04 pm

PGTMR2 wrote:
Wed Jan 31, 2018 2:15 am

When it comes to me getting the rpm from the spark plug on #1, please just push the "I believe" button. I can find out the exact ohms I need from the car forum. Or I may get one of these as a shortcut. It's purpose built for converting spark down to 5v. Which I think will work with Arduino. http://trigger-wheels.com/store/content ... coilx.html
According to the diagram that connects to the ECU side of the coil, not the HT to plug No.1. That will ne a spiky 12V signal. If there is only the single coil it will give you a pulse for each cylinder so divide by number of cylinders.

tech-mech
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Re: Car engine controls help needed.

Wed Jan 31, 2018 9:01 pm

First off I am an FAA A&P and have worked on and studied cars since a preteen.

The '12V' automotive electrical system can swing from a low of around 8V during start to a high of 14.7 or so when the alternator is working.

The in put to the ignition coil could be below 12V when running, but at each spark you can get a 200V or so back spike. The spike from the starter is not only high but has lots of power. There are lots of spikes in the system and you can get RF problems too. Read up on coil charging and collapsing which would include the starter disengaging.

To check spark timing check for a cam sensor which is how the distributor less systems know where they are in the cycle.

Dale

PGTMR2
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Re: Car engine controls help needed.

Thu Feb 01, 2018 12:03 am

I have never hacked into my tach signal before, but I'm a big boy I will figure it out. I can also buy A solution to what I'm trying to do, but I wanted to build something and learn something, so I can build other things. I won't be able to do any of this if all I get is one after another coming to tell me not to hook up directly to my coil, which no matter how you read it, it was never my intention to hook a spark plug wire directly up to my Pi.

The fact that this is for a car has understandably triggered some safety concerns. So from here on out it will be referred to as a flaming death killbot, which will only be operated in Mexico. Hope this helps.

My flaming death killbot needs to flail a morningstar when the wheels hit 4000 rpm. I suppose we'll need a signal for that. So ASSUME it will be squarewave at no more than 3.3v. for the moment. The morningstar has to stop flailing at 6800. Because Flailing at 6801 rpm just looks entirely ridiculous. Using the same wheel rpm signal and assumptions, my flaming death killbot needs to extend it's flame thrower starting at 4800 rpm and extinguish and retract at 6800.

tech-mech
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Re: Car engine controls help needed.

Thu Feb 01, 2018 1:34 am

Please do not take what I said as anything to do with it being a car or to do with general safety. You really need to understand just how harsh the automotive electrical system is to really modify it. Most mechanics lack the electrical understanding not to mention electronic understanding (there is a difference).

I have worked on and modified cars (including electrical systems) since some tine around 1965 or so.

If you are only wanting a speed value and do not care about timing you can trigger off the crankshaft. Any car with an ecm has the sensor. It is possible to do an inductive pickup off a spark plug wire. If you have a distributor less system you can expect a spark near every TDC , one on power and the other exhaust (one coil for every 2 cylinders).

Automotive wiring diagrams can be hard to figure out but keep at it as it is your best source of information on the system. Remember that it is a logical diagram and find where the pars are at look to the parts book.

You might want to read up on control programming to deal with over / under shoot of the values you want.

In a metal shop class the saying was measure twice cut once.

Dale

PGTMR2
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Re: Car engine controls help needed.

Thu Feb 01, 2018 4:28 am

Dale, I'm sure you're a fine mechanic, but I don't need your automotive experience. I have been to automotive school, and worked in the field for a little while. I also was an aviation electrician's mate in the Navy. I have seen harsh environments, 30+ year old aviation electronics and wiring at sea in the Persian Gulf in the hands of hot shot Tom Cruise wannabees, crash landing to a carrier deck multiple times a day. Maintenance and modding/hacking are 2 very different things. Now, while I have more electrician skills than electronics skills, I assure you I know exactly what I am talking about with my car and what I want to do. I make my own harnesses, if I need to, and I always try to make things reversible when possible. Going so far as to buy sacrificial parts for that if I need to cut something original to the car. I know how to read wiring diagrams, where to get them, if I don't already have them. The ignition is a better source than the crank pulley because the crank pulley might have to change for DIS ignition. Cam sensor is subject to change as well.

I'm not here for mights and may bes about my car. I've gotten nearly 0 PI help aside from 3.3v to the GPIO pins (which I already knew when I came in here,) and go get an Arduino, I think there was a read a book in there as well :D

Listen, I've ordered an Arduino and that is the route I'm going with for these solenoids.

PiGraham
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Re: Car engine controls help needed.

Thu Feb 01, 2018 9:18 am

PGTMR2 wrote:
Thu Feb 01, 2018 4:28 am
The ignition is a better source than the crank pulley because the crank pulley might have to change for DIS ignition. Cam sensor is subject to change as well.

Ignition timing is also variable. Crankshaft is the ultimate reference - where the pistons are in the cycle.
What is most relevant to controlling vacuum from RPM? It probably doesn't matter. You aren't going to be timing vacuum solenoids that fast. You can get RPM from any of these sources

PiGraham
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Re: Car engine controls help needed.

Thu Feb 01, 2018 9:42 am

PGTMR2 wrote:
Thu Feb 01, 2018 4:28 am

I'm not here for mights and may bes about my car. I've gotten nearly 0 PI help aside from 3.3v to the GPIO pins (which I already knew when I came in here,) and go get an Arduino, I think there was a read a book in there as well :D

Listen, I've ordered an Arduino and that is the route I'm going with for these solenoids.
People can only go by what you write, and you did seem to suggest it:
PGTMR2 wrote:
Mon Jan 29, 2018 2:40 am

I've got an ELM327 Bluetooth on the way specifically for this project. I figure that will be a quick temporary way to get the RPMs for testing while I figure out a safe way to get the high voltage from spark plug no.1 to a GPIO pin. Or I may be able to just splice it off the signal to the ECU/tachometer which is already safe.
When you probably meant the LT side of the coil or the ECU controlling the coil, not the plugs at all.

It can be hard to judge a poster's meaning and competence, we can't read minds. So it's best to caution what seem to be stupid ideas to avoid damage.

You are obviously set on reading RPM from ignition timing, but you mention "plug No.1" without saying why. Do you need any angular position info at all and if so, what precision and why?

From what you have posted it doesn't seem to matter. You need only open valves at particular RPMs.

Someone mentioned hacking the ECU to change the solenoid RPM switch thresholds. Have you considered that? It seems a much better option if it can be done.

PGTMR2
Posts: 23
Joined: Sat Jan 27, 2018 2:34 am

Re: Car engine controls help needed.

Fri Feb 02, 2018 12:32 am

Let it go. Your quote of me has what I meant in there. Which is "a safe way to get voltage from spark plug no.1 to a GPIO pin." That won't happen. I miss understood the exact way the ignition coil worked before. The part about how internally it was a transformer. I understand now how it works, fully and the difference it would make.

The part you didn't highlight after also shows I understood I could get the signal from another point. Which is all I've spent the last few days talking about. No that particular ECU isn't hackable or tunable. This, from the people that hacked the earlier ECUs. The old ECUs were easy, the newer ones are proprietary and secure.

At this point you're not helping, you're just selectively reading my words to be critical.

I'll get this done with an Arduino.

PiGraham
Posts: 3678
Joined: Fri Jun 07, 2013 12:37 pm
Location: Waterlooville

Re: Car engine controls help needed.

Fri Feb 02, 2018 8:32 am

PGTMR2 wrote:
Fri Feb 02, 2018 12:32 am
Let it go. Your quote of me has what I meant in there. Which is "a safe way to get voltage from spark plug no.1 to a GPIO pin." That won't happen. I miss understood the exact way the ignition coil worked before. The part about how internally it was a transformer. I understand now how it works, fully and the difference it would make.
Then you have had some help, despite your bad attitude. Naybe you should give more thought to other posts. Many have gifted you helpful comments in this topic.

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