Where to start with MS and a sr20det engine
 

So my buddy may be buying a 240sx with a sr20 enigne, and we would love to megasquirt it (so much cheaper than anything out there, I love MS). So I have no clue where to get started. It lookes like the SR engine has coil over plugs, and a CAS. Also im not sure now the injectors or coils fire, im assumeing similar to the miata engine? Any help to get me started would be really great guys.

Step 1: Purchase the Datsun factory service manual for the 240SX, with wiring diagrams and truth tables.

Step 2: Everything else.

Ok now what exactly should I be looking for? Also, its a '95, not the older datsuns. I think people have MSed the SR motors, I shot DIYautotune a email too.

Yes, I know. The 240sx was first produced '89, after the transition to the Nissan name. It's a joke, like when someone refers to a Porsche 911 as a VW Beetle, or implies that Hustler is a real person.

Basically, you need to know how the injectors and coils are wired, what the trigger signal(s) look like, what the idle control looks like, and so on.

Actually, since this is an SR20 conversion you'll want the FSM from the donor car as well, whatever it was. Which SR20 is this? There are quite a few. Did they transplant the sensors from the KA24 engine onto the new motor?

Lots'o'variables. :D

Sell it and buy a mazda??

alright cool. Its the red top out of the eairly 180sx's

Before going down the standalone road check out Calum ecu's. He only wants $325 for a Realtime version with Consult support. Its instantly programmable via laptop and has onboard Consult (the Nissan factory diagnostic computer) functionality so you can monitor maf voltage, inj duty, speed, rpm, water temp, base timing, tps, and many other parameters using a virtual gauge included with one of the many software packages (nistune, conzult, etc).

Interesting. What plans does he have for the car?

I thought early 180sx's had CA18DET's :giggle:

I would suggest hitting up Zilvia or something.

Almost forgot. KA24DET > SR20DET

well jeez im a miata guy not a 240 guy. Wll the car already has:

Full intercooler piping kit, polished aluminum
XS power FMIC
Koyo Radiator
HKS SSQV blowoff valve
Tubular turbo manifold
full 3 inch exhaust from turbo back to N1 muffler
GReddy oil catchcan
Battery relocation kit to the trunk
Excedy twin plate clutch
OEM SE VLSD Differential
Full cusco strut/coilover suspension

Any 240 guys want to chime in on what to do next? My fiend is looking for like 300 hp, whatever the max is on stock internals. That would problaly need a new turbo and good management, right?

Thanks, that looks sweet. I dont understand how it handles real time tuneing or say if you put on larger injectors how it compinsates.

Stock Turbo? The most we've been able to push out of the stock T-25 was 236 whp @ 15 psi with meth injection. If he wants to make 300whp I'd pick up a Walbro 255 some 550cc injectors and a gt-28. I've had lots of success with both the emanage blue and the ultimate. Id say the blue would be plenty for 300whp but theres a lot more potential with the ultimate. Oh and get some stock in tires :P

Alright, this is the kind of info I need. As for the turbo, the gt-28 is exactly what ive been lookin at, a 2871r should work nicely.

Ill have to take a look at the emanage.

You just hook your laptop up to the usb cable and make the necessary changes when you upgrade to larger injectors or a larger maf. When I upgraded to STi injectors and a Z32 maf on my DET and it took all of 5 minutes to reprogram the ecu.

I've often heard, but not confirmed myself, that you can put the optical trigger wheel disc from a first gen DSM into the SR20DET CAS. Some NA Miata CASs may have discs that fit too. This would make Megasquirting an SR20DET a lot like putting it on a Miata (which also uses a DSM-like ignition). The signal for the coil on plug ignition is not very well documented so the easier route there is to go with a wasted spark ignition and either lift a Miata or 4G63 coil and ignition module, or use direct coil control.

AFAIK, you can put down more than 300whp before the bottom end gives out. I want to say ~350 is still in the safe range but I've never owned one myself. Also, look into AEM F/IC piggyback. It's pretty sweet.

Well DIY autotune emailed me back (and thanks for posting matt)

From the options DIY showed me in the email, it seems it would be pretty easy to just use a trigger wheel on the crank. The whole swaping CAS whels seems iffy, and I dont have a miata one laying around anyway.

Howcome the MS cant fire the stock SR coil on plugs? I mean it works on the miata fine, is it just the the SR fires the coild in a weird way?

Crank wheel FTW! (they are indeed full of awesomeness)

I'm sure it can. I interpreted that post as meaning simply that the SR20's ignition coils are not well documented in the aftermarket as compared to Miata and Toyota coils. If you have access to the factory wiring diagram for the engine donor, then it will be fairly simple to reverse-engineer the triggering scheme. Heck, if the engine is currently in running condition you can figure it out with nothing more than a voltmeter and a wire cutter.

One thing to bear in mind is that with a crank trigger only, you must run wasted spark. This has not been a problem for those of us using Toyota coils, and will probably not be an issue on the Nissan coils either. Just a tidbit of info to remember.

http://www.sr510.com/tech/sr20det_eccs.gif

you have to copy and paste the URL into the browser.

Does that help at all?

It looks like the ignitor packs have 5 inputs, 4 outputs going to the coil packs, then each coil has 1 wire to go to a common ground, and 1 wire going to a coil relay.

So each coil have 3 wires, and the ignitor has 5 inputs and 4 outputs.

Well, that's tremendously simple, actually.

The coils each have a +12 input (through the coil relay, into pin 2), a ground connection (from pin 1) and a trigger connection (from pin 3). It looks to me that the coil triggers are active-low, judging by the orientation of the transistor symbol in the igniter pack.

The igniter is slightly confusing in that picture. Those symbols appear to be PNP transistors, yet they are wired in an open collector, common emitter configuration with the emitters all tied to ground. I'd expect to see NPN transistors in such a configuration. I think the symbol is wrong, and these are NPNs, meaning that the ECU will emit a +5 trigger into the igniter, and then the igniter will provide a closure to ground for the coil primary.


It looks to me as though the ECU is driving the ECCS main relay with a closure to ground on pin 4. When the ECCS relay activates, it turns on the coils relay.

The ignition relay makes no sense at all- it would be on all the time (even when the key is off) if it's wired as per that drawing.

There is a variable-speed fuel pump in that diagram which is controlled by the ECU. Did that get transplanted into the car as well?

Here's a useful link: http://www.xspeed.com.au/manuals/SR2...e%20colors.doc

And another: http://www.silviansw.com/manuals.php


edit: I found a diagram that does not suck in an S14 manual, which I believe confirms my assessment of the ingiter / coils configuration. It truly is a very simple circuit. The igniter just provides a closure to ground for one side of the coil primary, which has the other side tied to +12. So it is almost 100% certainly a set of NPNs wired open-collector, with +5 trigger inputs from the ECU. Exactly the same as the 1.6 Miata, just twice as many of them. Google is truly our friend:

http://img26.picoodle.com/img/img26/...sm_aff98ef.gif


Oh, and here's a version of the same overall diagram you posted that sucks much less: http://jimwolftechnology.com/wolfpdf...20DET_EURO.PDF

You rock joe. One other thing, I did see the ignitor in the engine bay, it looks exactly like a miata one.

So for building the MS, using this link http://www.diyautotune.com/tech_arti...s_overview.htm

I should:

use the directions for the Distributor Based Ignition on a Megasquirt-I V3.0 Board

or

use the directions for the Direct Coil Control Distributorless Ignition on a Megasquirt-I V3.0 Board



I mean if the COPS work just like a 1.6 miata would, I dont need to add the VB921 circuits that are in the 2ed link, right?



Finally will I need to do any more mods to the bord for the tach input or the such?

Interesting, I've never seen that link... Anyway, do neither of those.

If you wind up using a crankwheel (which I hugely recommend), then you'll build the VR input circuit as per the normal MS build directions, but wire two coil outputs exactly as per "Option 1: Spark Output to factory Miata ignitors" in this link: http://www.diyautotune.com/tech_arti...azda_miata.htm You'll have two trigger outs from the MS, and you'll pair the igniter's trigger inputs to those- coils 1 & 4 on the MS SparkA, 2 & 3 on SparkB. Actually, not exactly exactly, I suggest you use 330 ohm resistors instead of 1k.

If you are able to procure a 4/1 CAS, then you'll be able to do full sequential ignition and you'll have to build this circuit: http://www.msextra.com/manuals/Ignit...ual.htm#5Vpull Actually, I don't like that circuit as it's drawn- we'll come up with something a tad different for you perhaps.

ok I think I understand what ill do now.

Get the 36-1 wheel

use the settings for a 4 cylinder engine that DIYautotune provides in my link above.

Mod the MS like a miata, using joes link

tap into the sr wireing harness similar to the miata

then all it would take is finding the right dewll times for the coils and im good to go!


Then I just need to work on values for the water temp sensor, id use a GM IAT sensor, OH


Joe, does it look like the SR fired the injectors like the miata? Thus no mods specifically need to be done to the MS for fuel.


And one more thing, where do you get a VE sensor at??

Sounds like a plan. If you have access to an oscilloscope it might be worth probing the lines between the ECU and the igniter just to double-check that they're 5v and not 12v, but I'm betting very strongly on 5v- it's a much more common standard on Japanese motors.
Yeah, pretty much all injectors, even factory lo-z injectors, are triggered the same way. Put a solid +12 on one end, and switch them to ground through the ECU. You should use an ohmmeter to verify that they're hi-z (10 ohms or more) vs. lo-z (typically 1-4 ohms) before finalizing the MS build.
Damn near any Ford. I'm using one from a '95 Escort 1.9, but you can also get 'em off T-birds, Tauruses, etc. Electrically they're all the same, but they differ greatly in physical packaging.

Alright! and Joe,

Using this diagram http://www.scribd.com/word/full/1033...u6ienji9k9adum

I will have to tie together pins 101+103, 110+112, 1+8, 2+9, correct? those would be what I would then connect the fuel and spark outputs to from the MS

Also, do I have to worry about pin 105?

And how would I tackle the MS ground connections?

So I could just take out the whole ecu, and have MS run spark, fuel, fans, idle air control, and be good?

Or should I just leave the stock ecu, and run it piggyback style, just with the wires for the injectors and coils disconnected from the ecu? Or would this cause the ECU to freak out?

I'm afraid that link is no workee for me.

http://www.scribd.com/word/full/1033...u6ienji9k9adum

or

www.sr510.com/tech/SR20DET%20ECU%20S.doc

Hmm. That Wolf document does not agree with the two documents I'm looking at- the image I posted, and the PDF of the "Sylvia S14 Europe Spec ECU Wiring, SR20DET" document. This is why we need an actual factory wiring diagram specifically from your donor engine.

Ok, assuming that the two documents I refer to are correct (which I don't know to be true) and that the new motor has the same firing order as a Miata, then 101+103 would be one injector channel, 110+112 would be the other injector channel.

1+12 at the ECU would get you 5+1 at the igniter, and this would be coils 1 & 4, to SparkA of the MS. 2+11 at the ECU gets you 4+2 at the igniter, for coils 2 & 3 to Spark B of the MS.

Pin 105 in the Wolf document indicates fuel pump speed. Frankly, I have no idea how the fuel pump in your car is wired, the different documents I come across differ in this regard. If it's got the variable-speed pump system, you'll need to bypass that and wire the pump to simply switch on when commanded by the MS. That'll be a relay. If your fuel pump is the more conventional style which is simply on or off, then you can just connect the existing fuel pump relay to the MS.
By connecting them to ground.



There are so many uncertainties here that you're probably going to end up doing some trial and error research with a multimeter and a flashlight. Again, I cannot stress enough the importance of finding the correct and actual documentation for whetever combination of engine harness and ECU harness your particular car has.

Sounds good, he should be getting the car soon, then I can take the ECU and fine exactly what connections are what, and ill update the thread.

JOE, here is the exact wireing diagram:

http://jimwolftechnology.com/wolfpdf...%20DIAGRAM.pdf

and here is a english pin out diagram http://www.plxdevices.com/ECUDatabas...0DET_91_95.pdf

By that wireing diagram, just beacuse each coil has its own ecu pin, that doesent mean it cant be used in a wasted spark mode, just tie the wires together right?