biff206

Hi, I'm working through my first engine swap. I just finished rebuilding it, and now its ready to go in, so I'm researching the steps involved.

The car is a 1990 Si. The engine is a D16Z6 (not sure which year).

I have the z6 harness and P28. Everything is OEM.

I have a few newbie questions. I tried searching but it was difficult to sift through everything. I tried google too but I'm having trouble finding answers.

1) Will the hoses from the A6 work on the Z6? Or do I need to buy all new ones? Or is it a mixture of both- if so which ones transfer over?

2) Will the alternator on the A6 bolt on to the Z6? I looked on autozone's website, and I noticed that the part numbers are different, but still wondering if its compatible with both engines.

3) Could I please get an explanation of how exactly the rywire harness works? I'm confused.

So, originally I had planned on using the Z6 harness and P28, and I knew I would have to buy some kind of jumper to mate them to the chassis harness on the car. Last night I started in on that research and thats when I found the rywire site.

I see two different harnesses that look like the right ones: First one and second one.

I called them to find out which one I need to buy, and they told me not to use the Z6 harness. So their harness sits between the A6 (OBD-0) harness and OBD-1 distributor? So the OBD-0 harness from the A6 plugs right into the Z6? That doesn't seem right. Is there any modifying that I need to do, or does it literally just plug right in to everything on the Z6? Are there loose plugs left over after plugging in the A6 harness into the Z6 engine? Is there any way I can use the Z6 harness and then buy just the ECU jumper? The harness in the first link looks like its just the ECU jumper- is that one also for the OBD-0 harness? ...Man I'm so lost.

Thank you for any help and advice, much appreciated!

4drEF

Obviously the P28 ECU does not plug into your stock ECU connectors under your dash. That's where you need the conversion harness. You plug their conversion harness into the P28 ECU and then plug the stock plugs that used to go to the 1990 ECU into the other end of the conversion harness. The conversion harness reroutes all the wires from your stock OBD0 ECU plugs to the appropriate pins on the OBD1 ECU.

The main connectors that connect the engine harness to the dash harness (found on the firewall) are not the same on the Z6 engine harness and A6 engine harness. You need use the A6 engine harness that originally came with your car. Most of the connectors will plug right in, but a few will require some modifiation. Off the top of my head, you will need to extend the wires for the ECT. The A6 had this sensor next to the oil filter and the Z6 has it on the thermostat housing. The connectors are completely different. The distributor connector is different as well. The O2 sensor on the A6 is 1 wire and the Z6 has a built in heater element making it a 4 wire connector.

Freemananana

iTrader: (3)

1) Radiator hoses are radiator hoses, if they will fit (the bends are right) then it should be fine. You should be able to just trim the hoses you have to get them to fit.

2) This is easy. Look at the alternator, I don't have photos so I can't say. But if the mounting is the same, they will fit. I know the D15B1 and D16A6 alternators are the same. They have a bolt on the bottom and the belt. That's about it. The alternator will function if it fits.

3) This is also really simple, you are over thinking it. The A6 harness should mate up fine with the Z6 motor. Remember what plugs are what. The thermostat switch for your fans might have to be extended. Same goes for the TPS and maybe the MAP sensor. Depends on where they are on the new motor. Other than that, you can buy jumper harness plugs for the distributor or just make your own. $40 on eBay. The plugs aren't the same, so the OBD1 distributor won't plug into the OBD0 plugs. You can cut the plugs off of your A6 motor harness and put on the plugs from the Z6 motor harness and match the wires. Then it will plug in. You also need a jumper harness for the ECU. The P28 is OBD1 and uses a different plug than the OBD0 PM6 or whatever you have in there before. This can also be had for about $40 on eBay.

If you need more help, I can talk you through anything you don't understand. Just shoot me a PM and I can text/call or PM you more information.

suburban_ninja

When I ordered my rywire I never saw the second option you posted and that kinda scares me lol I ordered the first one but have yet to install it.

suburban_ninja

Never mind I just called and checked. The second one is the same as the first just that the second ones price includes the distributor and vtec harness bundled with the jumper.

biff206

4drEF, Freemananana, you guys are great!! Thank you so much. It makes a lot more sense now. Yes, I tend to over think things. I'm in IT. I get paid to over think things.

Freemananana, I might take you up on your offer for more help via PM. I am ordering the rest of my parts on Monday-ish and will probably be doing the actual swap in a couple weeks.

Suburban, I see what youre talking about. I was actually wondering what the difference was too. I looked closer and I was able to see that theyre basically the same.

The package listed for $189, has a drop down menu "VTEC Solenoid type." Which do I choose? I have the OBD1 ecu (p28). So I choose the second option, gray plug, right? Just double checking. Thanks.

suburban_ninja

Yea should be obd1 distributor. D16z6 and obd1 gray plug vtec harness. That should be the drop down options you pick.

DCRB

to clarify the radiator hoses, swap the upper inlet from the a6 head to the z6 head so you can use the a6 upper radiator hose. the z6 one doesn't quite fit right.

if you keep your a6 alternator you'll need to keep your a6 crank pulley, the obd1 alternators use a 4 rib pulley.

for your car you will need the following:

obd0-obd1 ecu jumper harness, with a pigtail that has the vtec solenoid, vtec oil pressure switch, and the heater wires for the 4 wire o2 sensor that you need to ad. for simplicity you'll also need an obd0-obd1 distributor jumper harness. always loom up wires you ad and use solder for any wires you connect.

rywire can build you an engine harness that has the needed plugs integrated into it, as well as move the fan switch location from the back of the block (a6) to the thermostat housing (z6)

that's pretty much it, if you're using the z6 intake manifold use the throttle body mounted map sensor, you can un plug and remove the stock fire wall mounted one as well as the evap solenoid and charcoal canister. keep it simple.

lastly, you can re use your stock a6 injectors if you don't want to mess with the resistor box, or you can swap in the z6 injectors and obd1 plugs and delete the resistor box. the injectors have no functional difference, they'll spray the same amount of fuel, so up to you.

hope this helps

bprsk8r4272

I'm using the z6 crank pulley with my a6 alt. I just went to the parts place and got a 3 rib belt which woks fine think it was a different length though

halfhilloa

The conversion harness reroutes all the wires from your stock OBD0 ECU plugs to the appropriate pins on the OBD1 ECU.

biff206

DCRB, thanks for the input! That helps out a lot. Do you know about how long it would take them to put together a harness for me?

and bprsk8r4272, halfhilloa, thanks for your input too.

Bently_Coop

When you call rywire they will give you a time frame.

suburban_ninja

I got mine fast. I'm assuming they sell so many now they have some ore built before ordering. Unless you were buying a complete harness or maybe a tuck kit. But my obd0 to obd1 kit came in like 5 business days or so, so just the ship time really.

biff206

ah ok good to know. When DCRB mentioned relocation of the fan switch I was thinking that they would have to custom make the harness.

Suburban, do you have any issues passing emissions? Sounds like you have the same setup that I'll have- P28, A6 harness w/ rywire conversion kit, OBD1 distributor?

suburban_ninja

Well first of all I'm still in the process of my build it isn't together yet. And secondly I've never had a emissions test.... Ever. Lol guess we don't have them in Tennessee. And yea the fan switch part I'm not sure on that I didn't have them make one for me haven't got that far in yet. But just the distributor vtec and jumper was all I got. Oh and the 4 wire o2

DCRB

nope. honestly you can do it yourself, you can extend the wires off the obd1 fan switch and add two male bullet connectors to plug into the stock fan switch wires.

even though it's directed to Suburban, emissions will depend on where you live. here in Portland they only care about noise, smoke and if you have a cat or not. if you're not smoking and you have a cat they shove a sniffer up the exhaust and if you're within specs it's "x amount of dollars please!" and if not they give you a list with why you didn't highlighted and what you can do. no engine checks nothing like that. our cars are old enough we only have to do the sniffer test.

biff206

ok sounds like the same kind of emissions here in WA. I think I should be good to go.

Freemananana

iTrader: (3)

Makes me love my very Republican Florida. These old people keep us from getting emission checks.

biff206

ha! Yeah I'm jealous, emissions are a pain in the ***.

I thought of another question. I have a 4-2-1 header, I'm guessing none of my oem exhaust piping will lineup or fit, right? I'm already planning on driving it to a muffler shop afterwards to get a new muffler, but its a risky drive because I have to pass by several cop stations. It will be pretty loud if its just open header. Any advice to get me to the shop without getting a ticket? Maybe just the cat bolted on will be ok, if it even fits?

Freemananana

iTrader: (3)

Well, my 4-1 header on my B series WOULD have fit my stock piping, but the flange was rotated. The header isn't really that hard to swap, may be worth running your stock set up till you get there, and undo the 8 exhaust header bolts and the 2 that hold it to the cat. That, or do what I would do, drive it open header but leave your old cat back on and if a cop pulls you over, explain you are going to the muffler shop right now to get it fixed. They usually will just give you a verbal warning at worst. Or maybe follow you that way. Do you have noise laws there? If not, they really shouldn't pull you over. Just be safe, get there, get it fixed and get away clean.

DCRB

if it's an ebay style header the stock cat will bolt up, i ran a stock cat bolted to an ebay header on mine, the fit will be kind of tight due to it being a 2.5" collector flange bolting to a 2" flange but you can make it work. a good alternative would be to buy a cheap ebay test pipe and have your muffler shop chop it up and install your cat in it

biff206

I was reading an article that said I need to replace the backup switch on the A6 transmission with the Z6 backup switch. Is this the part they are referring to? How important is this? Is it only for the reverse light, or does it serve another purpose? I'll be using the A6 harness, coupled with the rywire adapter harness, shouldn't I still be able to use the A6 backup switch?

Also, this is my injector resistor box for the A6, right?


I picked up some miscellaneous parts today- starter, alternator, battery, spark plugs, o2. I'm getting excited, can't wait to drive it with the new engine. Thanks for all the help so far guys!

Freemananana

iTrader: (3)

That is the injector resister box. And for the back up light, I would just use any plug to make the new harness connect to the back up lights. They are on the transmission by the way. If you are using the A6 trans, don't worry at all.

biff206

got my rywire harness in the mail today! Just a few more parts to get and then I'll get started on it. Cant wait!

So I've been reading up on the break-in process. I know its a controversial topic, but I was wondering if I could get a little advice on something. I think I have the basics down. I plan on picking up two gauges- 1-oil pressure, and 1-air\fuel. Would you recommend another, or should I be ok with those two? I just want to make sure everything is running how it should when I fire it up for the first time. This is just for daily driving, not racing. Everything I used to rebuild the z6 is oem.

Freemananana

iTrader: (3)

No, I wouldn't buy either. If it is an AFR gauge, stock narrowband, it's useless. You shouldn't need to worry about the oil pressure. Just check your oil regularly for a couple weeks. It's OEM, it's not built or boosted or anything out of the ordinary. Just take it easy, drive through the RPM range and make sure everything is working. If the temps go up, check for your fans. Simple things like that. Take it slow and easy and it should be fine.

As far as a break in procedure for the oil, definitely run the motor pretty hard and then change the oil immediately. Something to do with piston rings and the cylinder walls shaving off pieces. Someone else can give you a definite answer on the break in procedure for a rebuilt motor. Just change the oil plenty.