drbogg

iTrader: (1)

Hi guys , just another dumb question, a friend of mine has a spare Sequential fire programmable ECU and i was wondering can this be used on a 1.6 miata as i understand the miata use batch firing injectors system, can the 1.6 be converted to Sequential fire or visa versa ??.

Cheers
Dr.

Juffa

Yes. It's a matter of re-wiring the injectors.....or at least thats the case with my FM/Link ECU.

J

DammitBeavis

Sequential injection is actually preferred. You can run bigger injectors and control your injection timing too. I don't know about the earlier ones, but on my '99 I didn't need to rewire my injectors, they were individually addressable from the ECU connector.

Joe Perez

iTrader: (8)

The '90-'92 and non-CA '93 cars (in the US, anyway) have only two wires running from the injector harness to the ECU, the pairing is done within the harness. So to run sequential on one of these cars, all you need to do is open up the injector harness, cut a couple of splices, and run two additional wires from here to the ECU.

On Beavis' car (along with every other '94+ Miata and the CA '93s) the factory ECU already runs in full sequential injection mode at idle and low load.

Braineack

iTrader: (62)

I'm thinking about converting to sequential injection as well as moving away fom wasted spark by upgrading to MSII next winter...

drbogg

iTrader: (1)

sweet sounds fairly easy to do if its just a matter of rewiring the injectors, Yes i see Joe just looking at the injector wiring i can see that there is only a power wire and two signal wires which go to the stock ECU, but if one is not going to use the stock ECU it would not be to much of a job to modify the injector wiring.


Dr.

Saml01

iTrader: (9)

Does the MS2 utilize the MS1's approach to getting the crank inputs?

Braineack

iTrader: (62)

you have to build another little circuit using an optiso, from what I've read.

Joe Perez

iTrader: (8)

Is the MS2 capable of full sequential injection? Serious question. I thought that it was limited to two injector channels just like the MS1, configurable as either two fully parallel banks (ie: rotary) or two channels of bank-sequential (like the '90-'93 Miata).

Logically they are both the same, except that both triggers can be active rising or active falling (whereas the MS1's primary trigger much be active-falling.) In terms of the input hardware, you can use the same input circuits for either. There are several different designs and they all achieve essentially the same thing by different methods.

Saml01

iTrader: (9)

Am I confused, or did I read somewhere that you can buy a daughter board that coverts an MS1 to an MS2?

So you are saying it will continue to utilize the miata specific trigger input mod thats used on the MS1?

Where can I read more about active falling/rising triggers? I have no idea what that means.



As long as I dont have to make another boomslang, I will be up for anything. That was easily the most PITA of the whole project.

Doesnt seem like it.
http://www.megamanual.com/MSFAQ.htm#sequential

Braineack

iTrader: (62)

I know it can do 4 coil outputs, maybe I assumed it can do sequential injection as well. All I know is I still want to try MSII as a project next winter.

Joe Perez

iTrader: (8)

Well, the MS2 CPU itself is technically a daughterboard. Whereas the MS1 CPU is just a big ole' 40 pin DIP, the MS2 CPU is a tiny little surface-mount devices, and it's packaged onto a daughterboard which adapts it to fit the 40 pin DIP socket, along with a stepper IAC controller and a few other little things.

There's some info at the MS2-Extra site about upgrading from MS1 to MS2.

In short, you remove the MS1 CPU, install a jumper on the bottom of the board to bring +12 to pad JS9 (the IAC controller needs +12, even if you aren't using it) and then install the MS2 daughterboard into the CPU socket.

A couple of the pin designations change between MS1 and MS2, so you'll likely need to change a couple of your internal mods. Additionally, if you plan to use the NB stock crank & cam sensors, it'd be advisable to remove your current CAS input mods and build the newer versions described by Abe & Jason. The old ones "should" work, but the NB sensors tend to be more finicky than the CAS.


Ok, here's a quick tutorial. Below is a scope capture I took of the two signals coming out of the CAS. The NB sensor signals are sufficiently similar (in terms of their electrical characteristics) that this will suffice for both:



The upper, green trace is CKP, and the yellow trace is CMP. These signals are shown as measured at the CAS output, assuming externally pullup.

The rising edge is where the voltage goes from 0v to 5v, seen here as the upwards or rising slope (the left side of each plateau). In this case, the leading edge is the rising edge.

The falling edge is the transition from 5v back down to 0, which the trailing edge here.

Rising vs. falling, leading vs. trailing. The former describes the absolute electrical polarity, whereas the latter describes the logical orientation of the signals. If we inverted these traces, then the leading edge would be a falling edge.

OK, now because of the physical design of the MS1, the CPU's hardware interrupt pin is used as the primary trigger. This pin can only "see" falling edges. IOW, the CPU does not notice when the voltage on that pin goes from 0 to 5, only when it goes from 5 to 0.

To complicate matters, the circuits on the MS board can be either inverting or non-inverting. IOW, they can pass along the signal to the CPU exactly as you see it here, or they can flip it over so that 5 becomes 0 and 0 becomes 5. In the usual Miata layout, we wire the CKP input so that the circuit is inverting, and the CMP input so that the circuit is non-inverting.

On MS2, you typically wire both circuits the same, because the CPU is capable of dealing with rising edges or falling edges on both inputs.



Yeah, this is part of my loathing for parallel builds. Too damn much wiring.

You will be able to keep your boomslang as-is. Remember, pretty much every pin on the DB37 that isn't hard-wired to a specific function just goes to a general purpose pad, and from there to your I/O mods. So you have full control inside the unit as to what signal uses what pin. Just make sure that your internal mods, where appropriate, are re-wired to the correct CPU pin, and you're golden.

Braineack

iTrader: (62)

update: can't do sequential injection, only spark. Don't really even see a reason to do sequential as the batch alternating is more than sufficient. But I'd like to really get my COPs away from the wasted spark setup.

y8s

iTrader: (8)

i do love my sequential ign and inj though I doubt it makes much difference above 1500 rpm.

ronniebiggs

This will sound like a NOOB thing to say I know but can sequential Spark be ran without Seq Injection and if so is it worth it?

Where do the 2 extra wires from the cops go to on a 1991 miata? Or should I say which plug/part of the wiring loom?

Joe Perez

iTrader: (8)

Yes.

Unless your coils are overheating (or you're nearing 100% dwell at redline) I kind of doubt it.

Wherever you feel like putting them. No NA or NB ever had fully sequential ignition from the factory, so there's no standard. You can disconnect and hijack a couple of "surplus" wires (such as those going to the AFM, the purge valve, or whatever), or you can just run some new wires through the firewall.

ronniebiggs

Lastly from the schematic in the sticky thread on COPS. I want to be absolutly sure where the 10,000 UF CAP goes. If I put it on the Blue wire (1.6 1991) and take the other pin of the CAP to earth is that definatly right?