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