Alternatively you can hook up your tach wire to the negative terminal of the COIL on the coilpack (not the tan wire). I'm using the leading pack for this at the moment as I have not mounted my trailing coilpack permanently yet. This at least applies for a 1st gen RX7.

 

yeah, that's if you want to run fuel only...

 

awesome how to onthe MS2

 

I meant the tach wire going to the dash. That is how i am running my stock tacho without any extra MS outputs. When you hit the rev limiter the tacho goes crazy :P

I think Ben ran an extra output to run his stock tach from the MS, and still when you hit the rev limit, the output there stopped and tach bounced.. so it looks like wiring the stock tacho direct to the coil (between the coil and ignitor) is suitable.

 

yup, thats what happened paul. I ended up with the tacho going bananas on limiter whether it was from MS or from the coilpack. I also noticed that the stock tacho in my dash (rx2) was more accurate when getting signal from the coilpack that from the MS.

 

1st off great job on the write up!

im on my second MS build and i have a couple questions, maybe you guys can help. first off does the .33 uf capacitor have to be a tant? i dont believe the cap i have is tantalum (sp?). the first ms i built was for an rx7 and seems to work well. but the second one is for a 1jz engine, so i was going to build the following circuit instead of the rx7 specific vr circuit.



the difference is as follows.

300 ohm resistor from vr sensor input to ground
.1 uf cap between pin 8 and ground
39k resistor instead of 82k resistor

could someone give me some insight into what those three components would change. i believe i might have to play with the 39 k resistor to get it to work with the 1jz vr sensors.. but i cant remember.. its been a while since my last ms build. any help/direction would be great.. and please dont hate me because of the 1zj thing.

 

Excellent guide for sure. It would also be helpful to add the wiring pinouts to the wiring diagram in your guide for the bosch-style IAC (or BAC if using the stock Mazda unit) and perhaps another diagram with pinouts for those who might choose the GM-style 4-wire IAC.

 

Does anybody know if i can use a VR circuit like that on my autronic SMC?

 

hey guys
im in the process of modding my board to the duel setup and had a few questions on the resistors?.
On the write up posted earlyer ago on that link. the list says to use a 82K resistor does it have to be stressed on the number? cause i was only able to find a 100k ohm resistor 1/4 .can i use that or is that too much for this setup?

And aslo the part where it also says to use a 18K resistor ,i couldnt find one of those too and was only able to find a 22K what kind of differances would i see if i was to use those? more noise prone or the unit not working at all??

i too am not to clear on the ( 0.33 uF cap Tantalum type-polarised) on digikey.com i was seeing a shopping list of the 0.33 uF caps but nothing of it being polarised or i think i must not be understanding what the site is trying to show me.
Or do you have the part number off the uF cap that you had used for this .

thanks in advanced

 

Sorry for not replying sooner, I feel like I let you down not sharing this because I know and have gotten so much help from the board.


The 18k coming from the VR sensor is just a current limiter. We are interested in the voltage waveform from the VR sensor. OK an example on the low end of the RPM's the VR output voltage will be weak, say 5V @ 200rpm (when cranking)

I=V/R = 5v/18k some small current. (just say 280uA peak which could be wrong anyway)

the voltage drop across the 18k resistor will be a ratio of the input resistance of the LM1815N and the resistance across the resistor. Output resistance of the VR sensor will come in but lets not go there.

Just say the input resistance of the LM1815N is 100k. Then we are loosing VR1 = R1/R1+R2 * V = roughly 0.7V, leaving over 4.3v which is shitloads to trigger the VR input.

At high rpm the generated voltage is higher and thats where the input resistor is needed to stop burning out the LM1815, the calculations for that are in the LM1815N datasheet but these values are fine regardless.



Regarding the RC timing I don't use the fixed output pulse duration, so I don't need that capacitor or resistor. Talking the R and C connected to LM1815N Pin 14. I can't remember how to put it in zero crossing mode I will check.

EDIT with answer:


Regarding the 0.33uF Tant, the part probably doesn't need to be polarised but a tantulum is, and is a good part to use here. So don't worry about it, just check if the part you buy has a +ve/-ve leg, or if it is non-polarised and then can go in any way.


I have my car relatively noise free so I can give some help

#1 Have awesome ECU grounds, mine are heavy wires straight to battery -ve
#2 Put both pots completely couterclockwise. Then Adjust Hysteresis VR pot (closest to V3.0 board heatsink) clockwise until you loose cranking rpm or get monkey business happening at cranking, then go back counter clockwise a little bit.

#3 Enable all the noise filters in the ecu software
#4 Use resistive spark plugs such as BUR6EQ series. NOT B9EGV's
#5 Use quad core shielded microphone cable for VR sensor wires.
#6 Route VR sensor wires completely away from anything high current or high voltage, this includes starter motor, alternator, ignition coils etc. My VR sensor wire goes down to front bottom of engine under pulley, across past waterpump, back up to top of join between upper and lower intake manifold, across firewall and then into the cabin.

 

#3 Enable all the noise filters in the ecu software

#5 Use quad core shielded microphone cable for VR sensor wires.

for number #3 where do i go for that im not to sure where that is located can you post a pathing/?

on number #5 where can i acquire a quad core? i was only able to use microphone cable will that be suitable?

 

also to reduce noise from high current/voltage, if you have to cross or go near other main wires (ign wires, alt, batt) cross them at 90deg's and don't run the wires parallel to other wires if possible. make sure to twist any a/c wires (cas) together (a.k.a. twisted pairs) at least two twists per inch (this is how car manufactures do it).

 

I don't know if you've found it yet but surely digikey, mouser or farnel would sell it.

 

... and only ground one end of a shield, preferably the ECU end. Jobro, nice concise writeup!

 

I may be missing something, but wouldnt pin 10 (gated output), have a cleaner, easier to use output signal than pin 12 (reference pulse out) with a pull-up? The way I'm interpreting the data sheet for the LM1815, pin 10 is supposed to be used with the zero crossing (and otherwise as well).

From what i've read, MS2e 2.x has been using interrupts for sensing when a pin goes high. What is the voltage the MS2 needs to see to cause an interrupt? Are the interrupts only triggered off of the rising edge, or by any change of state?

 

Depends on what you set. You can set it to rising edge or falling edge.

With the noise filter it triggers on both, but only sets the second-trigger bit if the width of the pulse is large enough.

I'll be releasing that code soon (after I've done some more testing on my car).

Ken

 

Hey Guys,
Can you post the cap. and resist. values for the 2nd VR circuit components(i.e., 1/4W, 50V, Ceramic, etc.)?
I'm trying to gather the parts from a local source(L.A.) and they're picky about specs.
Much appreciated.

-turb'd