It seems as though WickedESI, Gilee_8, and I have had spark problems using the MSnS code with the MSI ECU on a V3 board sharing the crank sensor with the stock computer. The engine will run ok with just fuel, but hook up spark control and the engine bucks like crazy at 2500+ RPM. The RPM will drop out, spike, and generally freak out when the engine bucks. This seems to happen whether you have internal coil drivers (VB921) or external coil drivers (4G63 transistor). A noisy tach signal (likely related to the stock ECU and unsheilded stock wiring) is probably to blame. More sheilding, different grounding, capacitors, and other fixes don't seem to help. So what is a person to do?

1. Unhook the "TACHSELECT" to "XG1" jumper
2. Unhook the "OPTOOUT" to "TSEL" jumper
3. Build the VR sensor input circuit on the board per the standard V3 assembly instructions (if it is not already installed)
4. Jumper "TACHSELECT" to "VRIN"
5. Jumper "TSEL" to "VROUTINV"
6. Turn the R52 potentiometer (middle of the board) counterclockwise until it clicks (minimum hysteresis)
7. Turn the R56 potentiometer (bottom of the board) counterclockwise until it clicks (setting crossover point at zero)
8. Turn the R56 potentiometer clockwise 8 1/2 turns clockwise (setting crossover point well above zero)

All of this tricks the VR sensor input circuit into reading the stock hall type crank sensor. No software changes are necessary versus using the hall/opto sensor input circuit. The engine should start and the RPM shown on the MS should be accurate and stable. If the engine won't start at all, you should first try to turn R56 counterclock wise a turn. If turning it counterclockwise a couple more turns doesn't do help, you better check out your circuit. If the RPM doesn't read right, but the engine starts, you probably hooked up "TSEL" to "VROUT" instead of "VROUTINV". That makes the RPM display jump in between a normal RPM and twice that number. If you did all of this right, you should not see any tach spikes or drop outs at any RPM or load point. At least for me, I tested 500 to 7500 RPM and 20 inHG vacuum to 15 psi boost. No hiccups, no nothing! Hopefully this works for others.

Corbin

'95 ESI-T
Now with more power and fewer leaks



Gimme fuel...Gimme fire...Gimme that which I desire

Sup Corbin.. Thanks for the update!

So bascially we switching over to use VR instead of Hall circuit?

But don't we have to tune with those two potentiometer resistor? From your description, it's more like we just leave R52 alone forever, and just set R56 so it will read the signal? I thought we have to tune both potentiometer to get the correct cross over?

Also I thought VR is not what we wanted for our 420A MS setup?

I don't really get what you mean by "this tricks the VR sensor input circuit into reading the stock hall type crank sensor".
Do you mean, to MS and software, it still think it's reading from hall circuit , but actually we using the VR circuit?

And last question. Just out of curiousity. why using the VR will solved the RPM SPIKE problem? do I have to remove the CPS completely from the ECU still even with this VR setup inorder to have no RPM SPIKE? or can I leave it as it? (shared signal)

Sorry for all those questions, but I am kinda lost on what you did, did helped to solve the problem. But then I don't like to do something until I know what is going on and why it works. Thanks!

Thanks alot! This is definitely a GREAT news to all of us!

You are the man Corbin. Thank You!

good to hear you got your to work. Nate tried this about a year ago and still had noise.

Terry

I am sure that the noise is still there, but now it does not interrupt proper reading of the RPM. So, the coil drivers and injector drivers can do what they are supposed to. Here is my explanation of it:



All the VR input circuit cares about is when the signal crosses the cross-over point you set with R56. For the VR sensor, that is set to zero. As the VR sensors magnet passes over a steel tooth of the crankshaft, the output will smoothly swing from negative to positive. The hall sensor output is the same general shape waveform. It is just shifted up by a couple volts and changes sharply from 0 volts to 5 volts as it passes over a notch in the crankshaft. Since all the VR input circuit cares about is when the signal crosses the cross-over point, the number of cycles per time (to calculate RPM) is the same. Because of this, noise and spikes are meaningless. It doesn't matter how high the output goes, as long as it hits the cross-over point at the right time. The R52 potentiometer sets the hysteresis. As I see it, that adds an additional constraint. Not only does the signal have to cross the cross-over point, but it has to hit a certain amplitude before it is registered. That allows the circuit to ignore noisy outputs that dance around the cross-over point. This is my simplified understanding. Nate can correct me on whatever I got wrong.

Corbin

'95 ESI-T
Now with more power and fewer leaks



Gimme fuel...Gimme fire...Gimme that which I desire

intresting, Bookmarking.

Any EE's have the tools necessary to test this out?

I did this a while ago, and I was never able to completely get rid of those false triggers (see the pic with the 1 little noise spike going above the trigger level)

I've got some ideas on how to get a nice, stable, clean signal but I haven't tried them yet. Most of the ideas include things already tried like more sheilding, a better 8 volt power supply, or maybe some kind of LC filter on the input. An inductor might work, or the correctly sized capacitor. The thing about the capacitor is that if you put one in there that is too small it won't be able to smooth out the noise. Too big and the square wave signal gets all rounded off.

Interesting.... the concept behind this VR instead of Hall make sense to me!

Thanks Corbin!

I will definitely try it out.

great visual and explanation Corbin, that's the only way to get the message across to non-EE knuckleheads like me

LOL.. I am EE and CS background. how come I don't know the different of VR and Hall until I see the graph? lol... me dumb!

your a EE?:scratch Fix this problem!

Oh man...

I hooked everything up to put the MegaSquirt in complete standalone mode. Made it so I don't use the stock ECU for anything other than the alternator voltage regulator. I ran a 5v output from the MegaSquirt to the crank sensor's power, ran the signal and ground to the MegaSquirt in a shielded pair, and I still get f#@!ing random tach spikes!

Is it hopeless? Is your setup w/ spark still working for you with no spikes corbin? I thought it would be a lot of work to try your method with ner saying it didn't help him, so I thought what I did would be flawless, but I was wrong.

I just dumped $3k and 4 months (on top of what I already had) into the motor, people who've done the same know the anxious feeling you get wanting to drive it.

I'm starting to think it could be a software issue. I never had this problem with 024S9 and earlier. Perhaps the 420a decoder code needs to be reworked. I need to learn assembly language...

im sorry, This might be a moment of amnesia, or the alcohol from last nites BBQ. Does the Neons crank turn in the same direction as ours? yes ... right?

Are you running fuel only right now ner? Still using the spikey crank signal?

I have a strong belief that the issue lies in the board construction. The problem is not there if you run fuel only. When adding spark it surfaces. Now if you swap out the v3.0 to the older 2.2 the issue goes away even with spark control.

Terry

If I run fuel only I can still see the tach spikes in the datalog, so can gilee.

Sup guys.
I kidna did what Wicked did. but not the entire ECU, just only completely disconnected the CPS from the ECU, use shielded signal, ground and 5V to MS. no use.

And yes... we get RPM SPIKES even with or without SPARK. basically EVEN if MS is not used to control FUEL, if I just hook up my computer to MS, I still see the RPM SPIKES.

So the TRUE problem is lay on the RPM SPIKE PROBLEM. nothing to do with SPARK or FUEL. just that SPARK will be ALOT more noticable.
Just last nite... I was having a bit fun, and BOOSTING at like 10-14PSI.
And at one point, my car is like hesitated, or bug a bit when I try to accelerate at like 3000RPM. I look back, at that time, my RPM just SPIKE ALOT MORE then usual, which made my fuel completely screwed at that point. SO I FEEL it. but for ignition, even a small difference, we will feel the bug.

I will go and try what Corbin did. I believe that is the ONLY LAST HOPE we can have Wicked. and I will give it a shot..

And yes Wicked, I know how you feel. I spent like $4K on the motor then ever since I cannot run my car faster then 80mph or boost more then 2 sec coz the fuel just totally messed up.
Now I got Megasquirt, and I constantaly getting RPM SPIKE (even thou I just boosted to 14PSI for like 10 sec and up to like 140mph+ lol... SO FUN MAN! haahaa AND GOING UP HILL and EGT don't even go higher then 1520F. SWEET DUDE.

.... good luck guys.
I will post when I did something and let you know the result!
Gil

Hey gilee, I'm in the process of trying some custom mods to the board right now.

It's DEFINATELY a board (or it COULD be a code) problem, most likely the 5v voltage is unstable that drives the opto circuit.

No luck again today...

Note: I have 5v from the MS to the crank sensor, and the signal and ground from the crank sensor going just to the MS.

First the idea I tried was running the opto-out to the vrin, then the vrout (not the inverse one) to the tsel. When cranking the lights seemed to flash off instead of on, and one led would stay on after trying to crank. I think (it was inversed) I should have ran it through the vrout-inv. This would be like one noise reduction step above corbin's idea.

Since that didn't work, I decided to just try corbin's idea and only go through the vr circuit.

Well I got a clean signal, and cranking rpm was steady, but when it start running it sounded AWFUL, as if timing was waay off. Since we have a wasted spark setup is there even a way to check ignition timing?

I set the hystersis adjustment to 0, and first tried corbin's recommended 8-1/2 turns (w/o the injector/ign fuses in place) and cranking rpm was pretty wild, between 100-300. Well I have the crank sensor powered on 5v and the signal not on the stock ecu's circuit, so I assume this would change things. I assume the lower voltage would mean a lower crossover point, I turned the adjustment down and anywhere between 7 and 3 total clockwise turns it would have a dead steady crank rpm. It just seems ign timing is way off...

This is so hard to try to figure out without an expensive o-scope.

I guess the next thing I will try is changing everything back, then sending the signal from the opto-out to the vrin then vrout-inv to tsel and maybe the timing will be right then.

Let me know if you experienced the same thing gilee.

...MegaSquirtnSuck

I figured it out... I'm gonna make a new thread for it, because the application is different than corbin's (his is piggybacked with the stock ecu, we're running standalone), and yes it matters.

Glad that you got it working Joel! Hopefully Gil will find a similar solution. Just as an update. I'm still running without any noticeable spikes. With spark control, I was comfortable enough to bring the boost up to 15 psi. The tach moves real quick in 2nd gear now. I bounced off the 8k rev limiter a couple times, so that works. I feel like my tuning is conservative, so I still have work to do.

Corbin

'95 ESI-T
Now with more power and fewer leaks



Gimme fuel...Gimme fire...Gimme that which I desire

Guess I am the only one left with this RPM SPIKE.
good to hear you both got it resolved. lately I don't have much time to donate to the MS project, School started, and work is kinda tight. so I will definitely try them out later on.

Thanks guys!