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MPFI Swap
I found this on my drive, and I didn't see anything similar posted here yet. Enjoy!

bladesilver writes "Many DX owners feel left out of the fun that the Si's get to have all day. Bolt-on after bolt-on with limited pay-off, something is wrong with the equation. That something would be the DPFI system.

Luckily, there is light at the end of the tunnel for DX owners. Multi-Point Fuel Injection system can be swapped off an Si onto a DX, for significant gains in horsepower in torque to even the playing field. This is probably the best mod you can make to your DX, starting out. DPFI is basically a glorified carburetor-turned-fuel injection, and was found in the CRX DX, Civic DX, and Civic LX of the 4th gen line. This is evidenced by the fact that the manifold itself is almost identical to the manifold of carbureted civics, and works in the same way: gas goes in up-stream, and whatever cylinder happens to be on the down stroke gets the mixture. Besides that, the DX manifold is the size of a golf-ball and is highly restrictive of airflow. If you have bolt-ons on your DX, you'll be familiar with this by the limited gains they provided, and the fact that unlike your buddy's Si, your DX's intake doesn't seem to make that nice induction noise.

So now to the good news. You can swap an MPFI system into your DX, and for cheaper than a lot of bolt-ons. The gains will be significant, in fact, its said that the chief difference between the DX and the Si when it comes to making power is not the .1L displacement but the increased input due to the MPFI system.

So getting this show on the road, you'll need the following parts:

From an Si:
MPFI Intake Manifold (intact with fuel rail, injectors, throttle body, etc)
Injector Resistor Box
PM6 ECU from Si
Si Distributor
both sides of the Si Distributor plug if possible

From any car:
a few small pins from the ECU side B and C plugs on the wiring harness. If you can just cut a whole plug and disassemble it later, do it, becuase this is a pain.

From the parts store:
Various color wire
A coolant hose with a 180 degree bend, like the one on the Si.
Intake Manifold Gasket
Coolant
Solder
GOOD Electrical tape. 3M 33+ is what I used.
Wire Shrink Wrap
NO BUTT SPLICES, BAD!

First off, you'll need to release the fuel pressure and drain the radiator so you don't spray gas and coolant all over you when you're unhooking the manifold.

Now to get your manifold off. You'll need to get creative with the swivels and stuff with the ratchet to get to some of the bolts on the bottom of the manifold. Remove the manifold support first, it'll afford you some room under there, and remove any vacuum hoses in the way, remembering where they went by labeling them or using your photographic memory. Remove the throttle cable from the gas pedal by using needle nose pliers to squeeze the tabs together and pull it back off the pedal. After you've removed all the bolts and unplugged everything, pull the manifold back and put it to the side. Good riddance.

Next you'll want to mount the injector resistor box on the screw on the driver side shock tower that the harness clip is fastened to. You can remove the bracket that is already there because the injector resistor box has a bracket on it that you can put it on.

Remove your distributor by loosening the 3 bolts that hold it on, just like you were adjusting the timing but by taking all 3 fully out. Then pull it a little, you may have to turn it some to get it out. Replace this with the Si distributor. If the lugs on the distributor seem to be matching up but it won't go in, rotate them 180 degrees. The lugs are offset slightly to prevent you from installing it 180 degrees off, so the only way it will go in is if it is in the right configuration. Now, with the other side of the Si distributor plug you hopefully got, remove the pins from the DX distributor plug (square) by using a precision screwdriver to release the tabs, and pushing the pin out of the back, and put them in the Si plug so that the colours all match the corresponding colours on the other side. You'll be missing 2 wires, blue with a green stripe and blue with a yellow stripe.

Here's where the wiring begins.
Run a blue wire with a green stripe (or something close) from that plug, through the boot in the firewall above the passenger footwell down by the ECU. Do the same with a blue wire with a yellow stripe. Connect these 2 wires to the correct locations on the Si distributor plug. You've just added the wiring for the Crank Angle Sensor which is vital to the synchronistic operation of the MPFI system.

Next, find the green plug that has 3 wires feeding it on the harness that you removed from the ECU. There is only one plug with 3 wires feeding it, so that's it. This is the Throttle Position Sensor. Since the throttle on the DX goes in the opposite direction as the throttle on the Si, you'll need to switch the 2 outer wires of the TPS (not the middle one). Do a pin swap and you're done. Well... not quite. The throttle body on the Si is also up right where the intake enters the manifold, so you'll need to extend the wires about 10 inches. Use SOLDER, electrical tape, and shrink wrap. Don't butt-splice things in your engine or you'll end up paying for it one day when you're driving and your ECU starts throwing codes all over the place.

Now for the injector wiring. This is easier than everybody says it is, just take your time and make sure you're using the right wires. When in doubt, check again. When you think you've got it right, double check it one more time. That being said: you should have some wires connected to each of the injectors. The red wires are all grounds that go to the Injector Resistor Box, and should be connected to a square plug on one end. This plugs right into the box. That was easy. Now you need to run the wiring to the other side of the injectors, and supply power to the injector resistor box. Starting out, connect the yellow wire with the black stripe from the injector resistor box to the large yellow wire with the black stripe that used to feed the main injector of the DPFI system. Next, the injectors. Connect the brown wire from Injector #1 to the yellow wire that went to the secondary DPFI injector.
Connect the blue wire from injector #3 to the red wire that went to the primary injector.
Connect the Red wire from injector #2 through the firewall, and leave it by the ECU
Connect the Yellow wire from injector #4 and through the firewall the same as you did with #2.

Now the final step in the wiring is to connect the correct wires to ECU. You should have 3 wires that you put through the firewall: a blue with a green stripe, a blue with a yellow stripe, a red wire, and a yellow wire.

First, remove the pin from C1 and plug it into the open position at B10
Then do the same with C2, moving it to B12
This may be a pain to remove the pins, but have patience. It takes something very small like a tiny precision screwdriver to release the pins, and you need to poke around in there and look inside with a flashlight to figure out where the release is at. Once you've finally figured it out and you've moved the pins, you've made room for the crank angle sensor wires (the 2 blue ones). Connect the blue/green wire to pin C1, and the blue/yellow one to pin C2.

2 wires left, the red one and the yellow one. There are wires coming from pins A3 and A7 (the bigger plug) on the ECU, but they no longer feed anything under the MPFI system. Cut them and try not to think about it too much. Now connect the red wire to pin A3, and the yellow wire to pin A7. This completes the wiring. Don't put your ECU back yet until your car starts, you'll want it out anyway to be able to easily check for codes.

Now that you've double checked every connection, triple check them, make sure everything is clean, no wires are exposed, and no tape is hanging. Now get the MPFI manifold, slide on the new gasket, (make sure any previous remaining gasket that is stuck to your MPFI manifold has been removed), and slide the manifold on. Don't connect any wires yet, first screw on the manifold tightly, tightening the bolts just like a header, tightening the inside bolts first, and alternating moving out. Reconnect all the vacuum hoses to their correct locations, at this step it helps to have the vacuum diagram available off the bottom of an Si hood, or an Si to look at. Use the 180 degree bend coolant hose in place of the old coolant hose. Connect the throttle cable. Plug in all the sensors as follows: The white plug fed by red/yellow and green/white wires goes to the air temperature sensor on the driver's side of the manifold. The green plug with 3 leads goes to the throttle position sensor on the throttle body. The green plug fed by black/yellow and blue/yellow wires goes to the EACV on the back of the manifold. There is a plug fed by black/yellow and orange wires. This plug just hangs there because you won't need it anymore.

Now double check everything once again. Refill the radiator, make sure the line to the fuel rail is extra tight, make sure you remembered to connect your cold air intake back to the throttle body, cross your fingers, and turn the key. If all is right, your car might take a little bit to realize that you did a brain transplant, and you may have to adjust the timing and retard it some to get it to start, but once its going, you'll be good. Take it for a spin, watching for the check engine light. In the off chance that you get one, check the little light on the ECU for codes to see what the problem is. But you took your time, and did it right, so you shouldn't have to worry about this. So enjoy what you've been missing out on for so long."

xxPaulCPxx adds

To really open up the DX engine, i would also suggest swapping in the Si Camshaft. I found that after I did that, everything really came together. Just a note, with the Si camshaft, your timing will be about 1/2 a tooth off on the timing belt, which is just at the far end of how far you can adjust the timing. I found that to get the correct timing (and pass Cali emissions) I had to adjust it a tooth retarded then advance timing about all the way... or maybe it was the other way around. Just keep in mind to look hard at the timing!

To the above, I add this for MPFI Auto Tranny

If you are doing the MPFI swap to an automatic tranny DX, then you need a couple more parts:
- 88-91 Civic EX Automatic tranny ECU
- Tranny to throttle cable from the Auto EX or from an auto 86-89 Integra, as well as the adjustment brace on the TB and the cable pulley.
You will need to remove the battery and its support to get to the cable on the tranny.

The wire that you cut at B16 (white/red) is used for the Shift lock solenoid. If your wire harness has this, you will need to open up the center console around the shifter to get to that solenoid. You will have to tie the solenoid into its fully retracted position.
NOTE: If you do not do this, you will not be able to shift out of park!
 

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anyone live in eastern pa and willing to give me a hand with this over labor day weekend so i dont fuck it up, will throw you some cash and i would like to do it saturday.
 

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i am thinking about doing this but it seems a little too complex for me. i am just a newbie. i guess there is only one way to find out...

well the only thing i cannot do now is solder the wires, i have no access to soldering iron.
 

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its rather easy to solder wires together, and a soldering iron is not too expensive, and also a general tool which you can use for years to come. Its a good investment, and you can practice on an old piece of wire and get the hang of it after a few tries. If you need specific guidance, google has the answers.
 

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that is true. i would just hate to not get it 100% and encounter something very shortly after doing the swap. don't want my daily driver giving me problems and then i can't get somewhere.

time will tell if i decide to try this out. maybe i just gotta man up.
 

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Hopefully gonna be trying this next month sometime. The other site says if you have the harness from the si completely intact you can skip a lot of the wiring by splicing in the two wires you added the ecu and the dx injector wiring into the si harness. Can anyone explain this better? Possibly with pictures? Lol. I know the si harness I acquired has the plug for the resistor so that would save me some time.
 

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I still need an Si harness for the 4 injector harness ends..right?
Sorry..all this reading has got my mind working in 30 different directions lol.
I've got a stock DX DPFI

I just picked up an MPFI intake manifold (no support bracket doh!)
it has all sensors/hoses/fuel rail/injectors.
I also got the resistor box, the distributor and a pm6 ecu.

Should I just cut off a few connectors from a junkyard MPFI harness (along with the resistor plug) and wire it up from there?

The resistor box I got unfortunately has been hacked into..but I have a soldering iron so I could hardwire, but I would still need injector harness ends off an Si (or MPFI) harness correct?
And I should cut off a harness at the ecu (with a few inches of wire) so i could have the extra pins?

Sorry just wanna get it all figured out before I dive into it...this is my daily driver. lol

I'm also seeing I need an Si throttle cable..correct or can i just reroute the DX cable?
 

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xxpaulcpxx said:
If you are doing the MPFI swap to an automatic tranny DX, then you need a couple more parts:
- 88-91 Civic EX Automatic tranny ECU
- Tranny to throttle cable from the Auto EX or from an auto 86-89 Integra, as well as the adjustment brace on the TB and the cable pulley.
You will need to remove the battery and its support to get to the cable on the tranny.

The wire that you cut at B16 (white/red) is used for the Shift lock solenoid. If your wire harness has this, you will need to open up the center console around the shifter to get to that solenoid. You will have to tie the solenoid into its fully retracted position.
NOTE: If you do not do this, you will not be able to shift out of park!
Weird.I thought you use a pm6 ecu on autos also. :?
 

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CRX DX said:
Weird.I thought you use a pm6 ecu on autos also. :?
If you're doing an MPFI swap on an auto, you'll need the PS9 ECU.
It shouldn't be weird though.
The ECU tells the car when to shift.
If you converted from auto to manual, you wouldn't keep and use an ECU from an automatic with your 5spd swap.
 

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Baker said:
The ECU tells the car when to shift.
Actually that's not accurate; the big difference is the auto ECU's output for the lock-up control solenoid, which locks the torque converter. In an auto CRX, the transmission itself determines shift points based on input shaft RPM and throttle position (as conveyed by that extra cable that goes from the throttle body to the front of the trans).

The PS9 is an obvious choice because it's already designed for an OBD-0 automatic D16A6, but you can also use a chipped PR4. It is possible to use a standard M/T PM6 too, you just have to have another method to lock the converter.

More and more I recommend grabbing the parts you need from a 92-95 Civic Dx/Lx, as the parts are a little newer, you don't have to mess with an ugly resistor box, the ECU (P06) is widely available for either transmission, and it's better matched for an MPFI D15. It does mean an OBD-1 conversion though.
 

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Baker said:
If you converted from auto to manual, you wouldn't keep and use an ECU from an automatic with your 5spd swap.
Also you can keep the auto ecu on a 5sp swap you will throw a code but this can be remedied in by a tuning program or by doing some simple soldering, more info is on pgmfi.org
 
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