Intake manifold swap

Swapping intake manifolds on the D14A3 / A4 engines

The following how-to is written as a result of my personal IM (intake manifold) swap, but it might be used as reference for similar engine types as well, i.e. D14Z1, D14Z2, D16Y7 for example. I assume the intake manifolds for these engines all are practically the same. I will now refer to them as the D14A3 IM.

First let’s start with the reason why you should want to swap your intake manifold to D16Z6 (or D16Y8 for that matter). As you can see below the D14A3 IM (left) has very long restrictive runners and almost no plenum (the large tube that connects al 4 runners with each other). This gives us reason one, the airflow and so the performance will increase by swapping manifolds. Reason two is unexpected. I did not make any other major changes to improve the sound but the sound did improve because of the IM swap. The sound turned out much lower and the engine sounded grown up as to say so. One or two sound samples are linked at the bottom of this page. And yes there is reason three: if you like an OBD1 swap so you can get the full potential of 4 injectors, you need to swap the IM in order to support the IACV. Oh, want reason four? It looks much better under the hood! Let’s continue…

Left the old D14A3 IM (with D14A4 gasket) and right the D16Z6 IM.

Shopping lists for the swap (parts I had):
-Intake manifold D16Z6 with TA sensor (Temperature Air).
-Fuel rail D16Z6 with all rubber rings for the injectors and with stock FPR.
-Throttle body from D15B7, D16Z6 just for the throttle cable pulley.
-Intake suitable for an side flow engine (D14A3 model is called downflow).
-Some spare hoses for coolant.
-Fresh coolant.

Parts I wished I had:
-Throttle cable D15B7 or D16Z6, it fits without metal craftmans-ship and is shorter (makes less of a mesh).
-Fuel hose D15B7 or D16Z6. Stock hose fits, but needs adjustment (see pictures).
-IACV from D15B7 or D16Z6.
-Intake manifold gasket. I was very lucky it came of in one piece and could be reused (very dumb).

You do NOT need:
-D16Z6 injectors, they are 240cc and current injectors are 190cc, keep 190cc.
-The D16Z6 throttle body itself. Stock TB is the same bore and is needed for the stock RACV.

The terrible ‘before’ look.

Start with draining some of the coolant. You might reuse it later but we (I and Rene, thanks for the help mate) threw it away and added some new coolant afterwards. Take of the strut bar, air inlet, fuel hose, all vacuum hoses (remember were they go!) and coolant hoses. In my setup all the coolant is short circuited into the block itself. No coolant reaches the intake manifold anymore so no unnecessary warming of the IM. If you do want to keep the coolant lines you have to extend some of them to the RACV (that’s the thing with two hose connectors on the D14A3 TB, see one of the pictures further on). The IACV on the D16Z6 is not important, it will not be connected and therefore it will be closed all the time. I did not knew this back then and so it was closed with a sheet of aluminium. Tip: I did not reuse the IAT sensor (see below) but plugged the wires using a new connector to the TA sensor. Just get a connector suitable for the TA sensor in the D16Z6 IM and plug over the two wires, it does not matter how you plug them. I did it to clean up the engine bay a little more, the TA sensor of the 5th gen Civics is placed low at the back of the IM. The IAT sensor of the 6th gen Civics is placed in full sight. (And to cover it up even better I bought a 5th gen intake tube with no hole in it).

Location of my IAT sensor. Stock inlets do have it else where
Location of TA and IACV on D16Z6 IM.

Maybe some wires have to be cut and extended in order to get them to all the sensors on their new locations but no actual extending of wires was needed for my setup. Beneath is a picture that shows a terrible bolting location. With the D14A3 IM on it you can get to it very easy, just put your tools between runner 2 and 3 and unscrew. Getting the bolt on it after mounting the D16Z6 IM is a hell of a job and even worse when mounting D16Y8 or D15Z6 (and I assume D16Y5). A tip to give you a better chance: remove the unusable IM suppor. It will be too short anyway when using D16Z6 IM. My IM still hangs perfect in the engine bay after a year and a halfof extensive using (over 60.000 km).

Terrible bolt to tighten when a D16Z6 IM is placed. D15B7 IM almost gives the same trouble.

The throttle body of the D14A3 should be reused, but the cable pulley needs to be swapped. Otherwise the throttle cable wants to run down instead of sideways.

Messy isn’t it? You can see the original routing of the throttle cable and placing of the TB.
Throttle cable pulley. 

I closed the IACV, but putting on a stock IACV would have worked as well. The gap would have been be closed when unconnected. D14A3 TB is reused because of the RACV needed with the stock ECU. When actually swapping ECU’s it needs to be changed (see the OBD1 swap).

Closed IACV, D14A3 RACV mounted, TB D14A3 mounted and the TPS and MAP sensors are given.

Put it all back on the engine. See the coolant line running through the IM directly back in the block? 

Don’t switch the TPS plug with the MAP plug.

This is a very populair method to make mistakes.

Looks better doesn’t it?

Connect all the hoses. Fuel return line should give no problem. Maybe some vacuum lines can be nasty and needs extension, but everything is connected at about the same place on the D14A3 IM as on the D16Z6 IM. And behold, a completed IM swap. Do not forget to refill the coolant. The idling will be very bad as long as there are bubbles of air in it. This is because the RACV controls the airflow for idling, warm and cold engine, using the ECT (Engine Coolant Temperature) sensor mounted in the block. It senses a wrong temperature as air bubbles pass it. So it might run strange during start up.

And the beautiful after!!!

Below are some video files (actually more just audio files… produced in a time when it was still legal to hold a phone while driving I must add). Its all really crappy quality, but hey, it is something!

This was the sound after the IM swap.

This setup was never dyno-ed directly since I got quickly to OBD1 swapping. However, having been the witness of many other IM-swap setups being dyno-ed I expect most similar IM-swapped setups to land between 100 and 115 bhp untuned, but with some usual intake filter / header / exhaust mods. With a good tune I have seen most get into the 120 bhp range, but you probably want to have the OBD1 conversion to get there.

Polivias his project

Between the first time this page was launched and now, various other people have accomplished similar IM swaps and this one, from a Greek D14A4 driver named Polivios, is really worth posting. This is accomplished with a very nice aftermarket intake which seems to run very well. Here are the specs, a photo and a certain dyno result (though Polivios and I are certain it scores 4bhp better after a little SAFC). His results are even better than mine after the OBD1 swap, mainly due to his better hardware I figure.

Specs:
-Honda Civic 1.4 EJ9 sedan D14A4
-118bhp@6500rpm
-137Nm@5400rpm
-Simota air Induction Kit
-60 mm intake tube
-Denso iridium power sparks
-5star 9.5 mm ignition cables
-“sport-spec” valve timing adjustment
-Mobil 0W40 engine oil
-Custom cat-back exhaust 50 mm Danelatos
-Dc Sports 4-1 ceramic coated exhaust manifold
-Sebring high flow cat
-3-wire O2 sensor
-JG Edelbrock IM
-APEXi VAFC2

Polivios engine bay
Very nice going!

Dodo Bizar

46 replies on “Intake manifold swap”

Buenas, intenté hacerlo pero el honda al arrancar se revoluciona automáticamente sin acelerar hasta las 7 rpm, o a veces baja a 2500 y está inestable, a qué se puede deber por favor.He puesto la oem de nuevo del d14 y se acelera solo igual. Gracias!!!

Hi man, that can only happen with massive air leaks. Check all gaskets. Intake manifold to cylinder head. Throttle body to intake manifold. And check for all vacuum lines, especially break booster. Hope this helps!

I swapped my IM with this tutorial a few weeks ago and it all went flawless. Then I noticed it was idling higher then usual and found a little crack in one of the vacuum lines so I fixed it. After this fix the car suddenly died on me a few times. When I let off the gas and press the clutch the RPM’s go so low it dies. I can’t really find a pattern in it, however it happens more when the engine is warm then cold. I also can’t find any other vacuum leak..
Do you know what the problem could be?
Thanks in advance!

Groetjes

Great to hear the swap itself went ok. First thing I would consider is whether the coolant is properly bleeded. I have the feeling an air pocket next to the ECT can sometimes get the ECU to handle the IACV or RACV wrong. But there can be more reasons. It can simply be the learning of the proper RACV settings which have to be re-learn (did you disconnect the battery? Then at least the ECU will have relearned that part I guess). But gasket leaks can also harm idle although usually idle is high up with that kind of problems, not low.

I have a question about the IACV. I planned to swap the IM on my D14A4 with a IM from a D15B7. I will also swap the ECU to a P06. Now, do i have to install a IACV or is it possible to do it like you did it and just cover it with a plate?
Thanks for your work!

When you only swap IM and stay with P3X/P3Y ECU you need to put the plate.
When also using P06 ECU you need IACV there.

In my case the plate was only temporarily there between the IM and OBD1 projects.

i have a complete y8 Im with throttle body and sensors
do i need to change anything on it so it will work with my d14a3 engine
and do i need a y8 throttle cable?

It will work. Keep the old injectors of the D14A3 if you are not going to tune it. The Y8 throttle cable sits much better in place. You can reroute the D14A3 throttle cable probably, but it might require too much bending due to the long length.

hello again i just got a d series skunk2 intake manifold and a 66mm alpha throttle body do you think it will fit good ?

and would i need a y8 iacv and y8 throttle cable with bracket?
also do i need a y8 gasket for the skunk2 pro dseries intake on my d14

As you are only doing the intake manifold swap (are you?) you have to stick with the 3-wire RACV for now. It depends which Y8 IACV you got. If you got Y8 3-wire it will work in the same way and will work, the 2-wire will not work on stock ECU. If I am correctly informed, it depends whether you got the manifold from an manual or automatic model what IACV you got. I do not know which gasket is best to use, depends on the final setup that will work for you I guess. Get the one that comes with the throttle body is my best advice (but it can be wrong, check yourself how your gasket routes MAP and IACV holes).

i had a y8 manifold but i traded it for brand new skunk2 pro dseries manifold. I’m only doing the manifold swap for now
so the only thing i have to buy is a y8 iacv with the 3 pin and a y8 throttle cable?

See my other reply, but as far as I can tell the Y8 auto IACV is what you already got, no difference. And the Y8 manual has the 2-wire version if I am correct.

also do i need any other sensors for the throttle body or any other ones from a y8 or will my d14 sensors fit

The TB self may be a problem as for the IACV mounting, but other than that most sensors fit. Only the intake air temperature sensor is really different. The 6th gen Civics have it before the TB, the 5th gen after. Connectors are different, functioning is same and can be swapped out for each other. Although to prevent heat soak issues with the sensor I always prefer the 6th gen version.

Hey man, since I have no experience with the Y8 automatic its a bit of a guess. But I’d say from what I see on the internet, don’t bother. The 3-wire IACV probably is exactly the same for all of them. The 3-wire sits on the throttle body anyhow if I am correct. So, if you only swap out the manifold, you probably have to stick with the old throttle body.

I use the Skunk2 manifold with a 70 mm throttle body (which was way overkill btw). It did fit… barely… I had to remove a tiny bit of bracket somewhere on the firewall.

Im gonna swap the IM and swap the engine loom for a ek3 one , ecu and a remap
I should use the 240cc injectors or the 190

Hello! I have a D15Z6 head with the I’M also ordered a d16А8 I’M and injectors. Should I consider the D15 swap with the d16A8 I’M and will it work without going for OBD1 or it would fit nice and easy without that much work? I have a D14Z2 civic ej9!

I am afraid the D16A8 IM will not fit if its the DOHC head engine, the bolt pattern is different on the inlet side of the DOHC engines compared to the SOHC engines (exhaust side does match between DOHC and SOHC though). First time I was trying to do the IM swap in 2004 or 2005 I tried the D16A9 IM (we have those a lot here, the D16A8 I have never seen up close), but it was not even close to fitment. So just go for the D15Z6 IM I’d recommend.

OBD1 swap should be plug and play with a OBD2b to OBD1 conversion harness. D14Z1/2 is much much easier compared to the D14A3/4.

I just completed this swap thanks to you! I almost plug the coolant hose under the intake manifold to the pcv breather but luckily I caught before tighten all the bolts lol ?. I also couldn’t get nut on the bottom middle bolt and lost it but she’ll hold up until I get a new one! Thanks a lot guys!

Yeah the bottom middle bolt is a though one. But it can be tightened using normal ratched and extension bits… not the best designed bolt location though.

what did you do with the little module that goes to the charcoal canister? It connects to the old D14 manifold and goes to the charcoal canister? I did the IM swap a few days ago and this article really helped me. The car does not start yet but will shortly.

Hi.
I recently swap an intake manifold. D14A3 engine with D16Z6 intake manifold. There is one problem. On full throttle running too lean mixture from 2-3k rpm, I would even say detonation. At idle, give it to the floor – everything is ok. The mixture is clearly lean, all candles are white.
What did I do:
1. Replacing the fuel pump with a new one
2. Replacing the fuel filter
3. Filled injector cleaner, cleaned the injectors manually
4. Changed the fuel regulator
5. Cleaned the throttle body
6. Changed the ecu from D14A4
7. New candles
8. I tried high-voltage wires and ignition coils from another Civic
9. New o2 sensor
10. Tried another map sensor
None of the above gave any result. I must say right away that idle is normal, the rev does not float, there are no air leaks from the outside. There is one regularity – if the intake tract is blocked with something, narrowing the incoming air flow, then drives without failures by 90 hp, as before with the vertical manifold. Please, help me!

Hey man,

Too lean can simply mean your setup has an excellent volumetric efficiency, doing all that maintenance stuff will make it very slightly leaner rather even. Only real thing you can do is ECU tune it. As a back-up you may consider higher fuel pressure or slightly bigger injectors, though the 240 cc may be an overshoot already. Please check with a wideband lambda what the current AFR does and see how much you have to correct.

Hello! I swapped my D14Z2 I’M with D16Y8 IM and all went good. Now we have a problem… We connected every sensor properly every thing was nice and clean but my idling is going from 1krpm to 2.5krpm every time when she gets warm and it is acting like a bad IACV… Any suggestions?

Hey 🙂

I recently did a D16Z6 manifold swap onto my D14Z2 and all seems to be good, except I’m struggling with a few bits.

1. My EVAP can/charcoal canister isn’t wired up to the manifold as I can’t find anywhere to wire it to. There’s an empty space on the end of the manifold (opposite side to the throttle body) where some research suggests the D16’s EVAP purge solenoid should’ve been, along with a blocked off hose to the (very thin) vacuum line just below. How have you connected yours up?

2. I’ve a hose with a valve/plastic piece on the end of it hanging down loosely. It looks like it comes from the engine block just under the manifold, and I’ve been told its the PCV valve/crankcase breather. Does this need to recirculate back into the manifold? If so, how do I connect this one up too?

Cheers! 🙂

Hey man,

1) See the picture above with ‘Location of TA and IACV on D16Z6 IM’ beneath it? There is a small pipe to the left of the area that I labelled with ‘TA sensor’. There a connected the vacuum line for EVAP. EVAP solenoid is mounted to the firewall I believe btw.

2) For the PVC breather you should connect it (eventually) to the larger pipe on the front of the plenum. Its actually two parts, first a line from the front of the plenum to somewhere between the runners. There the plastic piece (one way valve) connects into the hose to the plenum. Again, from the top of my head, but that should do it.

Hi,
I did the swap on my EJ9 D14A3, IM is from D16Z6 (exact one you have) BUT I forgot to change the TB and thus kept the IACV on it. I’ve re-wired the 3 pin connector to 2 pin one using your guide, but when idling, I’m at around 1500RPM and it constantly dips down 200, gets back up, dips and again. It doesn’t occur when on higher RPMs which suggest there is something wrong with the xACV. My question is, can the stock D14A3 ECU work with IACV, or do I need to swap the TB to old one (or buy a new ECU and rewire everything)?

Wow sorry for my late reply, kinda spaced out: but here is the deal:

Stock ECU D14A3, keep the old TB with the old RACv and the 3-wire system. Only do the 2-wire IACV swap when you do the full OBD1 ECU swap.

Basically, you got yourself in much more work then needed…

hello, i’ve had this issue with a d14a4 and a d16y7 as well. i used the same d15z6 manifold on both (p much a y8 manifold but with the egr shit stuck to it), and never found a place to put the charcoal canister line into. the d14 i managed to improvise but had issues with idle at times, and now on the d16y7 i just straight up didnt hook up the line. i dont want to cut the hardline, what could i do? would it be fine if i just made a hole into the silicone from the cold air intake and stick it in there? cheers.

Actually not even sure how I connected my cannisters. I know I have one car with a throttle body with the canister line I believe, the other had a nipple for it on the IM. I may get back to this.

A problem with the coldair may be the lack of vacuum, its always pretty equal to atmospheric except on WOT and high rev. Not sure whats needed to do it right.

Hello

I have a d14a4 and I would like to upgrade the IM but unfortunately I can’t find a d16z6 anywhere in Hungary, my question is can I get the same upgrade with a d15z6 IM? Thanks in advance

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