Kit verses PnP; are they really different?
 

I’ve pretty much given up hope on the piggyback solution I’ve been waiting these past three months for. I’m stubborn, too stubborn, but it’s time to move on.

I contacted the good folks at DIY concerning a Megasquirt kit, and Justin came up with this package for my wife’s ’95 w/ BEGI S-2 and Innovate:

MS130-K Megasquirt-I kit with V3.0 PCB
jimstim-k JimStim MegaSquirt Stimulator with Wheel Simulator - Unassembled
MK-PWMIAC PWM idle air control mod kit
MK-Boost Electronic boost control mod kit
MK-Pullup Pullup resistors mod-kit
MK-RelayCtrl Relay control mod-kit (depending upon what all you want to control, you may need more than one of these.)

MSHarness 12' wiring harness
IATwPiggy IAT Sensor
TuneCable 6' DB9 tuning cable
USB-2920 (Only needed if your laptop doesn’t have a true DB9 port)
GM_BoostSol Boost control solenoid
GMBoostPiggy pigtail connector for boost solenoid

I wasn’t sure about the GM solenoid, and it doesn’t seem to be something I’ve seen mentioned here much either, and so I asked a few more questions about it, but I’m not sure I’m adequately prepared to appreciate Justin’s answers. Anyway, and to make sure I hadn’t overlooked anything, I asked, “Will there be any material (or electronic) difference between your MSPnP or the kit you’ve spec’ed for me?”

To which Justin replied, “Yes, Our MSPNP will plug directly into your wiring harness, control your A/c, radiator fans, comes in a nice polished case, and has a couple of extras(Launch control, boost control, etc) already installed for you. Most of those can be done with a kit, but our MSPNP makes this a VERY easy to do.” I wasn’t expecting that answer, and I thought they were the same excepted for assembly, but it seems I might have been mistaken.

I’m not worried about launch control, the polished case, or that the kit requires a bunch of work, but it sounds like controlling the A/C and radiator fans isn’t as easy to do with the kit. And that “Most” word is a problem because it means “not all”. I may be misinterpreting Justin’s answer, but it doesn’t sound like oranges to oranges; it sounds more like oranges to tangerines.

So I asked for a package for the MegasquirtPnP, to which Justin answered:

MSPNP-MM9495 MegaSquirtPNP MM9495 for the 1994-95 Mazda Miata M/T
MSPNP_IAT-S MSPNP IAT Sensor Kit - Steel Bung
GM_BoostSol Boost control solenoid
GMBoostPiggy 6" pigtail connector for boost solenoid

Here are my questions:

Without Herculean efforts, or knowledge of electronics that only Joe Perez possesses, is the kit package spec’ed by Justin the same as the PnP version, or are they inherently different?

Do I need the GM boost control solenoid, or is the wastegate adequate for the <15 psi I anticipate for this setup (GT2554R)?

And what happened to the simulator and some of the other odds and ends?

Lastly, is there anything else I need to order NOW, so I’m not stuck halfway through the installation looking for a part or supplier?

Thanks, everyone. Driving the wife’s turbo equipped car, and keeping it under 5psi vacuum for three solid months, completely and totally sucks.

Hehe. I'm literally chuckling to myself at that JP comment. In all honestly, this stuff isn't rocket science. Knowing electronics helps when you're designing new stuff that hasn't been done before, but you can build and install an MS with only a basic understanding of how to solder and crimp wires.

Apart from the fact that the MSPNP is pre-assembled and the regular MS isn't, the most significant difference between them is that with the MSPNP you just plug it directly into your factory wiring harness, whereas with the regular MS you are either going to need to build an adapter harness (which involves sourcing some male ECU-style connectors) or cut & splice your factory wiring.

In other words, the regular MS has all of its I/O on a generic DB-37 connector, and it's up to you to figure out how to interface that to the car. In my case, I soldered a bunch of wires into the DB-37, and then, with wiring diagrams in hand, cut and spliced the factory wires one by one to attach the DB-37 pigtail to them. It was time consuming, but not particularly difficult. You've got it somewhat easier as your ECU is in a place that's much easier to access then most of ours.

Here's what the adapter harness I'm describing looks like:
http://www.boostedmiata.com/MS/harness/harness009.jpg

And here's what my wiring looks like:
http://www.boostedmiata.com/MS/harness/direct_db37.jpg

It's entirely up to you whether you feel comfortable doing this, or would rather spend the extra few bucks to buy the PNP. If you don't have much experience with doing wiring, I'd suggest that maybe this isn't the place to start learning. If you do decide to go this route, I'd actually advise against buying the 12' harness. Instead, buy the 23" wire bundle and solder the wires to the DB37 that comes with the MS kit. The reason I say this is that a couple of the "standard" wire positions are wrong for the Miata. Specifically, you don't need the shielded IGN wire they use, and you want to have control over exactly where the various IAC and SPR wires go.


As to boost control... The wastegate can isn't suitable for 12PSI all by itself, but EBC isn't the only answer. I have to admit that even though I bought the GM solenoid and wired the MS for it, I'm still using my old manual boost controller. Although EBC is pretty cool, my MBC works just fine and I can't motivate myself to make the switch. So you'll have to rely upon the council of others as to setting up and tuning EBC.


A/C is extremely easy, and doesn't even involve the MS: The Great A/C FAQ - Miata Turbo Forum - Home of the turbo Mazda Miata.


As to Jason's use of the word "most", I'd interpret that as "all". The only function that the MSPNP has built in that isn't well documented in the general literature is A/C, and as I said above, that's easy. Functionally, the MSPNP is pretty much 100% identical to a standard MS1, as that's what it has inside. Anything they've done you can do, it's just a matter of wiring and circuit-building. Know that some of these functions do involve placing transistors and other components into the proto area (where there are no labels) and doing your own point-to-point wiring on the main circuit board. It's all pretty well documented and isn't hard to do if you know how to read a schematic, but if you don't then you'll likely find it challenging the first time.

yeah, i wish my ECU was behind the seat, I could only wire in my EMB for 3 minutes at time before I had to let the blood leave my head. Personally running the wires without a direct plug in harness isn't that bad, but looking back I would get a PNP. But you'll be thinking, "Oh they said it isn't that bad to wire it in", and you'll get the DIY squirt and install it. At which time you wish you had just bought the PNP. So just get the PNP

Thanks Joe. After three months waiting, and my patience just about past run out, I think PnP is the way to go. Any thoughts on whether there's anything else I should pick up with the PnP or is Jason's package everything I need? Sensors, switches, simulators; anything?

And thanks to you too Mazda/Nissan. Yeah, I'm thinking you've pretty much summed up what would be going through my head if I didn't buy the PnP version first.

I went MSPNP for my 96 mainly because I suck with electronics. I got the MSPNP, plugged it in, hooked up the IAT, fired up the car, and started tuning. Simple as that.

Building a megasquirt is a really fun project and saves a lot of money versus the pnp. If I can do it i truly believe anyone can.

You don't need a stim with the MSPNP because you assume that it works. The stim is just to test the ECU before you ask it to run your motor.

Installing the PnP is retardedly easy. Like, 20 minutes, 15 of which is removing your passenger seat and running a vacuum line.

lmao at joes sig hahahahahahaha!! To the OP, I have one of Braineacks MS's that he makes and really, there isnt much of a difference at all aside from the harness thing that Joe mentioned. He basically sets it up like a pnp so you really should be able to just plug it in and drive. You WILL have to tune it though to fit your needs as is the same with the pnp and any ecu

I think everyone should build a MS at least once. It really gives you a good background into the nuts and bolts of the thing. I think the time I spent doing it was totally worth it.

However, if I was building another car, id get the PNP.

No, if you go with the PnP, then the list you posted pretty much covers it. The IAT sensor and bung are a necessity. The EBC solenoid and pigtail are optional. You can use EBC, or you can use an MBC if you have one.

The PnP comes pretty much ready to rock-n-roll.

Two things which are peripherally related and which I didn't see you mention are injectors and a wideband O2 system. These aren't really MS-specific (you'd want them with any good ECU) so do you already have plans in this regard?

Joe, I have an Innovate LC-1 installed and working very well. I'll also look for a used set of injectors for rebuilding; something along the lines of one of these (thanks Sam):

89-92 Mazda RX-7 NA 440cc - Blue Top #195500-5740
89-91 RX-7 NA 460cc - Red Top #195500-2010

Either one should put me in the 225 hp capacity range at 75% or 80% duty cycle. The turbo's a GT2554 so I don't believe I need anything larger.

Corky's already installed an IAT bung on the post IC hard pipe, though it's aimed squarely at my wife's AC lines. Hmmmm; was Corky trying to tell me something???. The boss refuses to give up her AC, though removing it would certainly simplify my summer cooling worries.

So the plan is to plug in the unit, tune it for the stock injectors to both learn, and while I'm sourcing larger injectors, clutch, etc., and to then move on to bigger injectors and up boost to the efficiency of the little 54.

Go with the 550's. I have the RX7 460's because I got them for a reasonable price. Otherwise, I would have gone for the 550's to give myself a little more headroom.

I was thinking of the smaller injectors because the GT2554 really isn't very efficient much beyond 225 HP, and the smaller injectors should give me more precise control within the range I'm most likely to be operating. Bigger injectors would give me more headroom, but they'd probably be beyond the capacity of the turbo.

Of course this is all theory since I've no experience with any of this, and it's possible that the 550's have both more capacity and are more precise. I just don't know, and so I doubt I'd turn down a nice set of 550's if I stumbled across them.

Just a noob here, but I believe I read somewhere that a duty cycle above 80 or 85% is bad for some reason. Or I'm remebering that wrong. Help me out here, oh wise and experienced ones.

I think it's because that's where the injectors are maxed out, though some folks get more out of them; either by increasing fuel line pressure (thereby flowing the same at a lower cycle) or by not worrying that they might overheat (because they exceed the 85% value for only a short time).