Megasquirt Write-up for KA24 series engines.

[sil80drifter]

Can someone describe what exactly constitutes the "engine" harness which we can take out and have completely replaced by our own MS harness? We wouldn't want to cut out important wires thinking we don't need them...Also, I am a bit rusty on this, but does the engine harness control only fuel/spark? What controls thins like the alternator, starter, etc?

I am trying to figure out whether it's worth to just make one's own harness for the MS...Has anyone removed the engine harness completely and made their own relay box? What would be included in such a relay box?

[bige240]

okay...If you throw away the entire engine harness, (every single little bit of wire in the engine bay), You would have to replace the injector, TPS, O2, coolant temp., and distributor wiring. You would also have to tee off the FPR vaccum line to go to the map sensor and add a GM ambient air temp sensor.

The alt and starter are controlled by the ignition... In actuality you could just pull every one of the wires out of the back of the stock ECU and connect them to the relay board or make the pigtail to go to the megasquirt and just leave the rest of the stuff hanging.

You can't make your own relay box, at least I don't think so. You have to buy the relay board, or make your own pig tail

[sil80drifter]

Thanks!Well here is the deal... I think one of the really good reasons for making a new harness is that the one in there right now is between 13-18 years old. It's cracked, rusted, heat cycled, salted, oiled, etc etc etc. And in many cases (such as mine) the many engine pulls have nicked or damaged some wires to the point where they make the engine run poorly on the stock ECU. What you'v described below is SO easy to make! What about the various relays/fuses and etc, are those at all involved with the engine operation? Things like the fuel pump fuse, and etc...I just saw the ending of your post about buying the relay board.

Has anyone got an examples of such a board on the 240? What relays are needed and which can be re-used?

Also, does the tach use the engine harness for signal? I know that once I've connected my SAFC, the RPM's wouldn't work right on the SAFC (but worked fine on the tach), but then, oddly, when I connected the MSD BTM (some wiring on the coil) the SAFC started working great but the tach died. As soon as I unplugged the BTM and replugged the wires on the coil, the tach came to life again and the SAFC started showing rpms poorly like before.

So those are some of my worries about the engine harness...

[bige240]

You are right about just wanting to make a new harness, the stockie is old and messed up, and has some stuff you don't need. It'll also help you trouble shoot, since you know exactly what wires are going where. Just snip off the stock plugs with some wire to spare and splice your wiring onto them. Looking into the megasquirt relay board is something you might want to do, since it makes hooking up the harness 100x easier. The relay board has fuses in it, and also has a signal for the tach and the fuel pump. You just screw your wires into a block that has everything simply labeled for you.

Yes the tach gets its signal from the engine harness, namely the dizzy wiring, but with the relay board you just connect everything up and you run a signal wire to the tach from the relay block, along with a power and a ground.

I'm not sure what relays you'll want to keep, since I went buckwild and tore them all out.

You can also do ABS Megasquirt, if you so choose...The hall sensor is a powerful thing...

[98240kat]

My only real qualms are these. Assembly for one. Although I have quite a bit of expirience in electronics from building computers to electric race cars assembly is still an annoyance and risk. All its takes is one slip with a soldering gun and ur out 256 bucks pretty much depending on what part u happen to score. My other qualm was I believe somewhere on the page it stated the map sensor was only good for 21 lbs of boost, which i plan on running possibly more on occasion. And our course the wiring could be a bit crazy all depends on the person and what have you. My one question is does anyone know if it will work with 98 style KA24de? If so do all the same guides above apply? Also if it was a matter of 1000 dollar difference would u just buy an AEM EMS if you had te money?

[bige240]

You do not have to assemble the board by yourself!!! You can buy boards already built from several places including DIY autotune and Ebay for not much more money.

This ecu will work on ANY fuel injected engine.

You can get a 2bar (26psi) or a 4bar (52psi) map sensor for the Board also and run boost until your engine explodes.

The wiring is very simple and not much different than the wiring you already have in your engine bay.

I could buy just about any standalone out there and I still like the megasquirt. If more 240 guys would buy it, I'm sure someone would make a plug-and-play harness for it just like someone did for the Toyota 4AG series (corolla, mr2) engine.

[FattyMcBaggins]

I am very interested in using this for my KAE-T. I'm not so great with wiring, but I think this would be a really good way to get a handle on it.

[98240kat]

I think Im going to go with the MegaSquirt does anyone know of any diagrams or DIY's for a 95-98 model??

[sil80drifter]

Google it, but I'd doubt it.The guys above are the first ones to do a 240sx DIY as such, and I think they were doign it to show how to us a general kind of distributor setup with MS-I. I've already written tot hem and asked about any differences from that to MS-II, and will post their answer as soon as I get it.

Their write-up above states that "We'll be adding more information on settings, the S14, and the factory ignition module soon!"

So keep your fingers crossed and try to reasearch it on your own for now. Best of luck and don't forget to post any findings!

sil80

[sil80drifter]

Don't I love myself for not reading things properly the first time!The MS-II changes are right there in the explanation!

Using the MS-II PCBv3 ECU

Build the ECU up to trigger from the Hall/Optical Input (all of our MS230-C units are by default configured this way). The only change is to enable the IGBT High Current Ignition Coil Driver Circuit to directly drive the coil. Remove the jumper from JS10 to IGN (if exists) Jumper IGBTIN to JS10 Jumper IGBTOUT to IGN (This will enable the VB921 Ignition Coil Driver)

That's it!

Well, at least the guys from DIYAutotune are really nice. Matt responded to my email almost immediately and was the one who pointed out that there are very few differences between the two boards in terms of set-up, so hey! I'm an idiot but at least it's all settled now.

Let's hope they come out with something for the 95+ 240s soon.

In the mean time I am selling my SAFC II, VAFC II (Honda phase, don't ask), SOHC VTEC Head and MSD BTM, so I can buy the MS! Whoo!

sil80

[WDRacing]

Just need to know what wires go where on the MSII, the rest we can help figure out. Hell, I could probably hook up a wiring diagram and I've never even seen a MSII. The existing wires are easy enough to tap into, and a harness is even easier.

But don't count on me for this writeup...but one of you other guys could head that up.

WD

[98240kat]

Well if I choose to go with the MS I am going to use their harness and rewire the engine, I figure that will be the easiest way to do it really. Im still unsure though I may still wind up with an AEM EMS if i can't find to much on the MS. Id rather just plug and play really but ill give MS a shot if they can give me more info soon. So as you said fingers crossed. Ill post some pics up of the car as soon as I wash it

[The_Chosen_One]

come on guys theirs a ****load of information already on this forum.

Look at my write up I did a yr ago.

Even though its for a CA and FORD EDIS it still should explain EVERYTHING for you.

zerothread/164446

Heres a wiring diagram I made for my harness as you can see the color changes







So pretty much remove the ecu and the plug that goes with it. Leave the lower harness and transmission as that controls your speedo, reverse lights, alternator, starter etc etc. All that will connect to the main body harness.

As for the RELAY board, thats really only meant for older cars that arent as advanced as ours. The 240sx has its own relays so you tap into them which in reality is only 2 wires 1 for the fuel pump relay and 1 for the Ignition switch.

98240KAT I could probably help you in the future as I live in South Florida as well. Pembrooke Pines is like 30mins south of me.

[98240kat]

Wow thats actually awesome to know man. Im pretty new to Pembroke we should get togeather some time and hit a car meet or something. Plus itd be great to have someone else to work on my car with. Let me know.

[180sx]

There is quite a fe ka's out there with megasquirt. And its better to rip out old ecu and harness and just run new clean wires all together. Old harness has useless crap. But yah people still prefer to buy easy tap ins or tuned ecu. ALot just wanna plug and play, or punch in or load in a few settings.Tuning standalone requires time and knoweledge and a few blown engines or money to pay someone to tune it right. Othrwise you'll never see full use out of it.What support does Megasquirt provide for knock sensor that comes oem on ka24de?

[The_Chosen_One]

There is quite a fe ka's out there with megasquirt. And its better to rip out old ecu and harness and just run new clean wires all together. Old harness has useless crap. But yah people still prefer to buy easy tap ins or tuned ecu. ALot just wanna plug and play, or punch in or load in a few settings.Tuning standalone requires time and knoweledge and a few blown engines or money to pay someone to tune it right. Othrwise you'll never see full use out of it.What support does Megasquirt provide for knock sensor that comes oem on ka24de?

Just wire up the knock sensor, input your parameters and off you go. Plus knock sensors are crap useless little buggers.

[sil80drifter]

Where would examples of these "many" KAs be found? I've googled my *** off and didn't find much info... I am asking because this directly pertains to my situation and I would like to communicate set up and install questions with others.

I am in the process of talking to DIYAutotune and starting my own MS-II conversion soon, sans the EDIS stuff, as it makes me uncomfortable and seems moot with the stock dizzy able to be utilized just as well.

I will be doing a detailed write up and hopefully this will be the start of the KA24E MS period, where people see just how easy it is to standalone their KA-Es themselves. Someone should do one for the KA24DE.

You got me fired up, WD, I don't have much time lately to write up things I do, but this seems like a great contribution to a board which has given so much to me in terms of knowledge and experience.

I'll be making a separate thread soon.

sil80

[The_Chosen_One]

have you tried other forums, such as http://www.msefi.com, http://www.sfldrifters.com, HybridZ.com too name a few.

As for doing a write up if ya want sure, but not really necessary their are 2 write ups.

1 is for a KA with ITB and the other is for the CA18DET. Even though the CA18DET write up isnt KA specific its the same concept the Ford EDIS-4 doesnt care what more as long as its a 4 cylinder and that you have the crank trigger positioned correctly, so using the write for the CA is exactly the same for the KA.

zerothread/164446

[WDRacing]

Any additional writeup is a good idea. Especially if it includes tuning!!!

[The_Chosen_One]

well if you want a write up on tuning megasquirt II here ya go.

http://www.megamanual.com/ms2/tune.htm

http://www.megamanual.com/v22manual/mtune.htm

[WDRacing]

The Lambda chart is sweet. I always have to look at the specific lamda for each...now I have a cheater. Plus, you simply see what lamda is for 14.7 and 12.5 then use those two numbers as a cross reference.

Lambda...Gasoline...Propane...Methanol...Ethanol.......Diesel0.70...........10.3.........11.0.........4.5...........6.3...........10.2 0.75...........11.0.........11.8.........4.9...........6.8...........10.9 0.80...........11.8.........12.5.........5.2...........7.2...........11.6 0.85...........12.5.........13.3.........5.5...........7.7...........12.3 0.90...........13.2.........14.1.........5.8...........8.1...........13.1 0.95...........14.0.........14.9.........6.1...........8.6...........13.8 1.00...........14.7.........15.7.........6.5...........9.0...........14.5 1.05...........15.4.........16.5.........6.8...........9.5...........15.2

Very good tuning writeups. MSII gets better everytime I look into it. By the time I get the motor swap half done, the MSII won't have any bugs and probably a few new options.

WD

[The_Chosen_One]

if you wanna get extra fancy you can mess with Flex Fuel.

http://www.megamanual.com/flexfuel.htm

At the moment its the only aftermarket EMS that allows you to use Flex Fuel technology. The way it works is that you use a sensor from any of the flex fuel cars and what it does is sense the frequency change from Gasoline to E85 even straight up Alcohol. What this does is megasquirt will adjust your maps accordingly when it senses the new fuel. So you dont have to constantly tune if you switch fuels.

As for bugs I havent noticed any, only problem I had was a fuel richness problem which was my own stupid fault.

Overall I'm REALLY REALLY happy with my setup.

[WDRacing]

I doubt I'd be able to trust a sensor to control my mapping. I'd just have two set maps, one for ethonal and one for 91 pump. Most people just use a seperate injection kit anyway. More of a detonation suppresent then a fuel source.

WD

[sil80drifter]

It's on its way!I am as excited as a very excited person who's got a special reason to be excited.

I figured when I make a separate thread, I could open it up with my progress on removing the old harness and prepping the rest up for MSing, and then go into the detail of wiring it up and seeing if it blows up when I try to crank it.

I am SO happy I won't have the damn MAFS anymore... ugh, how I hate that wire that goes to it, it's never in a good place and always in the way.Also, that really thick wire that combined injectors and distributor that always rubs the valve cover, I'll figure out just how to make it nice and concealed and NOT RUBBING.

On the other hand I am concered about passing emissions without an air pump... Not baswed on visual, but on the smog results alone...has anyone passed them before while turbo and w/out air pump? I would think yes, but just wondering...

sil80

[WDRacing]

I can get you to pass emissions easy, shoot me an email. [email protected]

[The_Chosen_One]

when you start wiring do yourself a favor and buy this kit. I made my first megasquirt harness from scratch, when I did my customers I purchased this kit from DIYAutotune and probably took 1/3 of the time to do the wiring than my first one. Eventually I'm gonna redo my harness using this kit as it makes it easier since the wires say what it is.

http://www.diyautotune.com/cat...e502f

[sil80drifter]

I'm going to be using the relay board/box, so I've purchased this:

http://www.diyautotune.com/cat...e502f

AND this:

http://www.diyautotune.com/cat...e502f





sil80
Modified by sil80drifter at 3:38 PM 3/22/2007

[The_Chosen_One]

why did you waste money?

[sil80drifter]

I chose a very simple, reliable, and easy to track path of wiring up the MS.

I like the relay board a lot, it will make it a snap to trace down any issues, and wiring to it is also very simple. Yes I could try to utilize the old fuses and relays, but WHY? To me it's worth to have a simple solution, and if I spent an extra $100 on it, it's ok. The total coat of the MS with all the stuff is still $620 total for me, and that's under my $700 budget. I know I will be buying some connectors and etc, but again, simplicity and ease of use are important to me.

Similar to why you chose the pre-made harness instead of making your own again, I chose to buy the MS assembled and ready to go. I am comfortable with soldering, but it's just not worth my time, especially having to worry about tracking down solder issues with the Stimulator, when I could be spending that time tuning/driving/f-in my ex. Yes, someone could spend $250 less and 20-30 more hours DIYing the whole thing, instead of buying complete components.

But to me 20 hours are worth more than $250. I make more at work , and I def don't need solder practice.

sil80
Modified by sil80drifter at 6:43 AM 3/23/2007

[The_Chosen_One]

I understand your point on having everything ready, but adding the relay board isnt gonna make things easier, your gonna spend more work because your gonna have to redo the things that are already their. The main purpose of the relay board was for people who dont have them in the first place, more older cars. I understand your point on simplicity but the regular harness cant get any simpler its practically MS to whatever sensor and if you follow my guide I took all the guessing work out of it.

Also the only relay you have to tap into is the Fuel Pump, which is taken care of when you splice into a Black/Pink wire thats on a 8pin brown connector near the battery. Than you give power to MS via the ignition switch on the steering wheel.

With the relay board you do the same work as if you did the regular harness but with a few steps more like wiring it to the fuel pump.

If the OEM setup is too old just replace the relays.