Are you planning to do a D14A4 turbo build ord any other d series engine turbo? These info apply for all the SOHC D series Honda engine which can be installed into a Civic (Eg or Ek the differences are very small). To be honest, these info could also be used to convert a B series DOHC to turbo with very small differences.

If you have an EJ9 Civic and wish to go this route, i suggest before starting this lecture, to read my other article where i explain how to convert it to OBD1.

What to expect from a D14A4 Turbo:

An EJ9 turbo has proven to be faster than a b16a2 with bolt-ons. If you ask me an estimate, i would say that mine was at least 160 Wheel horse power at 0.5 bar produced by a GT2871 garrett knockoff. I never dynoed it, as dyno numbers vary a lot from dyno to dyno and are not significant to me. I prefer track times comparisons and speed reached on the straights of the tracks.

What is needed to make a D series engine turbo:

If you have an EK3 (d15z6) you just need an obd2a to obd1 converter and a p28 Ecu (Or a P30 Ecu or an Hondata).

To make a Civic go chuf chuf here’s what is needed:

  •  Tunable ecu: this can’t be skipped or else you will break the car very soon. PLEASE, DO NOT follow the advices of people who say it’s enough to use a RRFPR (Rising rate fuel pressure regulator), because this way you won’t sort the ignition timing and make big holes into the piston or melt ringlands. There are no shortcuts to make a good build, don’t cheap out on ECU!
  • Turbo exhaust manifold: there are a lot of options out there; the cheap stainless steel ones are so thin and not so robust that will crack with very low efforts. I suggest to use the cast ones, as they won’t crack and they will flow ALMOST the same as a shiny tubular manifold and they are also CHEAP.
    These must have a 38mm external wastegate port since you plan to run low pressure (max 0.7 bar of a ebay GT2871 for stock internals, less if it’s bigger but the same if it’s smaller).
  • External Wastegate: If following my advice to buy cast manifolds, these often come with a 38mm dual bolt flange. You want to buy something that has a low pressure spring installed: ideally 0,5 Bar (7 Psi). You can cheap out in these, if you buy the replica ones, I discovered that they leak boost pressure when closed, so the only downside is that they will make the turbo spool a little slower compared to the genuine units. Usually the membrane is good and these offers good reliability but hey, there are a lot of models out there, and the quality check of these china made units is non existent so you also need a bit of luck there..
  • Intercooler: 7 liters front mount would be good. Water to air is ideally better but that would increase the weight of the car and for only 0.5 bar.. Is not a good tradeoff.
  • Aluminium hoses + silicon couplers: i’ve used 63mm (2,5″ inch) tubes. I used from throttlebody to turbo: 1x 45° coupler 63mm internal, 1x straight aluminium 63mm external, 1x 90° coupler 63mm internal, 1 straight aluminium 63mm external, 1x 90° coupler 63mm internal, 1x 180° aluminium 63mm external, 1 straight coupler 63mm internal, IC with 63mm inlet and outlet, 1 straight coupler 63mm internal, 1x 180° aluminium 63mm external, 1x 90° reducer 63mm to turbo charge pipe size. Also a 90 Degree reducer 71mm to 63mm was used to use a cone filter in the intake of the turbo. This is what i used but of course depending from the turbo you have to change the path and the end diameter. You’re free tu put a blow off valve wherever you want in the charge pipe.
  • Blow off valve: I didn’t use any but I suggest you to use one. Use whatever you want just make sure it’s adjustable since using low boost you want it to be soft enough to open  fast on throttle close without too much pressure buildup.
  • Injectors: Cheapest option with good quality price is Honda RDX injectors (which are 410CC high impedance easily available). Those should be good for 250 Hp. To use them you have to buy or fabricate the adapters to the rail (Ktuned sells them) and also the wiring plugs adapter (ebay).
  • Downpipe: Turbocharger exhaust exit has to be connected to the rest of the exhaust, you have no other options: fabricate one from scratches because the ones in the ebay turbo kits needs to be modified and at the end you spend the same as doing it from scratch, so just do it.
  • Exhaust: Fabricating a stainless steel exhaust without any cat converter and at least of 2 Inch internal diameter is suggested and almost required. This would lead to good power as the stock exhaust is soo restrictive that i would never connect a turbo to it. You can put a muffler at the end of it, just make sure it’s big. The bigger exhaust line you use, the better. 3″ would be IDEAL.
  • Clutch upgrade: Stock clutch will start slipping after 2 kilometers believe me. You need a better unit. If using a d14 i suggest you to upgrade to 212 mm Flywheel from d16 (D14 is 202mm) and use the readily available aftermarket clutches for d16, rated at least for your target torque/power. I used XTC stage 3 unit with no springs, soo far it didn’t break but the chatter is real and the fitment was not straight forward. So please, just buy a good known brand.
  • Uprated radiator: This is a must, with turbo you produce a lot of heat and coolant temperature will climb very easy without a good, at least 2 core, big radiator.
  • Oil temperature sensor and gauge: After going turbo, you have to monitor oil temperature because it will climb to 150° very easy without an oil cooler and you don’t want to push it that high. So if you plan to track it, just install an oil cooler. To install the sensor the best place i found was the drain plug of the sump. Just buy an M14x1.5 adapter that has a 1/8 NPT thread in the middle of it.
  • Turbo pressure gauge: This is helpful if not using a live data tunable ecu, since this will allow you to see what’s the turbo pressure at any time.
  • Sandwich plate: this is needed to feed the turbo with oil. You should get one that has at least a 1/8 NPT female exit for the oil feed. If you plan to use oil pressure sensor, you can use another 1/8 NPT female exit. If you plan to use an oil cooler, get one that has 2x 1/8 NPT exits and 2x AN10 male exit.
  • Turbo oil feed and drain: In order for the turbo to work, it needs to have oil going through it. You want to source a line long enough to go from the sandwitch (1/8 NPT fitting) to the turbo. Depending by the turbo decisions, the fittings on the turbo differs and you should research which one to use. For the oil drain, unistall the sump, make an hole through it and weld an AN10 Male bung. I suggest using AN10 lines for the drain, or at least a 5/8″ or 15mm Hose.
  • A Turbocharger: Choosing the correct size turbo needs a bit of study and also sometimes trial and error since reality is a bit different from ideal physics laws.

From my experience, these are the turbo that i recommend for a D14A4 Turbo build:

  1.  If you like low rpm spool sacrifying top end power then the TD04L from Iveco Daily 2.8 Turbo diesel is the turbo for you. OEM Code: 49377-07000.
    Why these?
    Because in Italy it’s commonly installed in 1.4 Tjet Fiat engines and these are proved to be reliable and produce good power. These needs custom flanges to be made but are smaller than t28 or t3 which make them compact nice units. Expect them to spool at 2800 Rpm up and produce good power up to 7500 Rpm. Of course you should limit them at 0,5 bar.
  2. The one i used: GT28 family turbo. You can pick a double ball bearing from garrett and expect a fast spoolup and big power. Since for me it was a budget build, i picked up an ebay knockoff GT2871 50 trim ar 64/60 which I sent to test and balance in a specialized shop in order for it to not granade into my engine. Expect the knockoff unit to spool up at 3500 Rpm, full boost at 3800 Rpm and very good power until redline. You can feel it doesn’t choke on itself and would definitely push a lot more. I used this because i calculated its efficiency at 0.5 bar with an equivalent compressor map and it was in the good spot. Since IATs were low enough, I think i just got the right size.
  3. T3/t04e trim 55 ar 50/63 definitely too big for a 1.4 but would be more suited to a DOHC b18 or b16.. Never tested on a SOHC so i don’t really suggest it.
  4. TB03 garrett family turbo. These are the one i wanted to test. In Italy it’s easy to source TB0367 from Fiat coupè 16V, TB0385 from Lancia Delta Integrale 16V , TB0361 Ford Sierra Cosworth 2wd, TB0384 Ford Sierra Cosworth 4wd, TB0338 Delta integrale 8V. In my opinion these are very suited for 1.4 and 1.6 SOHC Honda engines but sadly i haven’t tested any of them.

After everything is sourced, take your time and install it.

Please use good bolts and make sure to use locking washers at the turbo because it happened to me to get loose. Stay away from stainless steel bolts and use an HIGH grade steel bolts. Somebody uses copper nuts or wire locked nuts.. You could just get a set of Wedge lock washers and call it done.

About ecu tuning:

Once everything is connected, you need a map for your D14A4 Turbo. Or at least a base map to start with. In >this< article I’m sharing the basemap I successfully used, ofc it needed to be tweaked accordingly. I can provide one for every D series engine and it will be very close but further tuning is required to sort the fuel map. You need an AFR wideband gauge to do so, it’s the only true way to tune the fueling. I usually tune ignition maps conservatively so you won’t get any sign of detonations but.. I suggest you to take to a tuner if you don’t have enough knowledge to write a map and understand what’s going on. I will try to make articles about tuning but usually it takes a lot of experience to be made so, at the beginning, don’t be afraid to ask for help.

Stay tuned.