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Article 1 - Technical History of the JDM ZC & U.S. D16A1 Engine(s)
Author _ Katman | Created_ September 2004 | Last Update_ October 2004

This ever so popular 1.6 DOHC engine was introduced in late 1983, when Honda of Japan debuted the E-AT civic & E-AS crx. This motor was tagged "ZC" and was found in the higher end AT/AS models. Why Japan dubbed this engine the "ZC" still haunts me (and others) to this day. The US wouldn't see this same 1.6 DOHC engine until 1986, when Acura first opened their doors with the debut of the 'Integra' line up. This first generation US Integra would contain this 1.6 DOHC engine, and become known as the "D16A1". Of course, the US is wack in many aspects when it comes to the auto industry and we never received any 84-87 civic/crx's that came equipped with this same engine, hence the reason for hybriding!!! In Europe, their version of the ZC/D16A1 engine was known as the D16A8 or D16A9 engine, and came in the same AT civic/AS crx models (lucky them!). To add to the chaos, there was also a JDM SOHC ZC engine that came about in 1987, known to the US as the D16A6 engine (but that's another story).

All U.S. 86-89 integra's (RS, LS, GS) all have the same initial D16A1 engine design. Only slight engine changes were made between the 86-87 and 88-89 Integra models. The biggest difference between the two is wiring/ecu/& ignition. Remember I mentioned Vacuum Advance Ignition earlier? Well among Integra's, only the 86-87 Integra's use this Vacuum Advance Ignition system (just like the the 86-87 Civic/CRX Si models do). This is a big reason why 86-87 D16A1's electronics & wiring are compatible (plug n play) with 86-87 Si's. Whereas 88-89 D16A1's electronics are not -- you cannot carry over & use (plug n play) the OBD-0 ecu/wiring/ignition system that 88-89 Integra's have into an 86-87 Si. It's just not compatible. But, you technically can convert an Si to OBD-0, but it's an enormous pain in the ass and I don't suggest doing it unless you're the adventurous type and love playing with wiring.

Normally, the browtop ZC & D16A1 engines are a dead ringer for having Vacuum Advance Igntion (VAI) systems, which were pre OBD-0 engines; blacktop's being OBD-0. So, when purchasing a motor for your 84-87 civ/crx (especially for an Si model), a rule of thumb would be to look for a browntop ZC/ D16A1 engine if you don't want to run into ignition & wiring incompatibilities. Of course, it is possible to convert an OBD-0 blacktop ZC/D16A1 to a VAI system by simply removing the OBD-0 components and replacing them with VAI components. Doing this will allow you to take advantage of an updated and slightly more powerful ZC/D16A1 engine.

There are 3 continental versions of this 1.6 DOHC engine:
  • ZC (JDM)
  • D16A1 (US)
  • D16A/9 (EDM)
I'm not too keen on the history of the Euro D16A8/9 engine (I'm learning!), I assume it ran along the same timeline as the JDM ZC. On a side note, in the U.K., there's an automotive company known as Rover which had a line of coupes that went by the name of 416GTI, which used Honda's D16A8/9 engine. Visually, it looks identical to a ZC engine, but what makes it different from the Honda version is the unique valve cover it has seen here:
click here for images of the 4-bolt browntop D16A1 & ZC engines Rover Coupe 416 GTI engine (pics stolen from an ebay ad)
Pretty weird eh? Kinda reminiscent of a an 84-87 Si's SOHC valve cover! I'm not sure how long the Rover coupe lifespan series lasted.

Rover had other coupe models that shared Honda SOHC D-series engines as well. A fella by the screen name of Ben_K on the D-series.org forum has kind enough to share some detailed info on the Rover SOHC & DOHC coupes. Here's what he told me:

The first generation of this 1.6L DOHC engine (JDM/US/EDM) all had a 4-bolt brown colored valve cover, which overtime has been nicknamed "browntop" by Honda enthusiasts. The browntop ran for about 3 years in Japan and 2 years in the US and ?? in Europe.
click here for images of the 4-bolt browntop D16A1 & ZC engines Browntop valve cover(s) ZC & D16A8/9
click here for images of the 4-bolt browntop D16A1 & ZC engines Browntop valve cover U.S. D16A1

Browntop ZC/D16A1 engine specs:

  • The program fuel injected (PGMFi) JDM ZC was rated @ 135ps / US D16A1 was rated @ 113hp.
    There was a dual-carbureted version of the JDM ZC engine which wasn't performance minded, rated at about 108ps. There's also discrepencies in the Honda performance scene as to why the JDM ZC puts out more power than the US D16A1. Japan's "PS" horsepower rating sytsem seems to be a bit overated imo, but the biggest differences lie within the ECU programming & camshaft profiles between the JDM & US browntop engine, but its hard to believe there's almost a 22hp difference between the two types from just an ecu & camshaft change!
  • The compression ratio is rated @ 9.3 for both ZC & D16A1 engines due to the flat top pistons.
  • Both share a square toilet bowl shaped intake manifold design.
  • Both shared the same ignition system which was known as a "vacuum advance" and used an external coil:
    click here to see differences of D16A1 & ZC intake manifoldsVaccum Advance Distributor
  • Nicknames of this JDM ZC version included: "JDM browntop" "browntop ZC", "1st gen ZC"
  • Nicknames of the US 86-87 D16A1: "US browntop", "browntop D16A1", "1st gen D16A1"
Then, sometime in 1987-88, Honda made a few updates to the browntop engine...

Changes made to the US D16A1 engine in 1988-89:

  • The valve cover color was changed to black and became known as the "blacktop" [retained 4-bolt valve cover style]:
    click here to see differences of D16A1 & ZC intake manifoldsBlacktop D16A1 Valve Cover
  • The pistons were upgraded from a flat top to domed piston increasing the compression ratio from 9.3 to 9.5.1:
    click here to see differences of D16A1 & ZC intake manifoldsBlacktop Pistons
  • The connecting rods were slightly lightened up.
  • The ignition system was upgraded to the more widely known "OBD-0" wiring/ecu/and internal coil ignition system.
  • The intake manifold design changed to a better flowing design:
    click here to see differences of D16A1 & ZC intake manifoldsUS 88-89 D16A1 I/M
  • With the update to OBD-0 ecu/ignition system and higher compression pistons, the 88-89 D16A1 gained 5hp making a total of 118hp.
  • Nicknames of the 88-89 D16A1 included: "US blacktop", "blacktop D16A1", and "2nd gen D16A1"
  • 1989 would be the last year Honda would produce the 1.6 DOHC D16A1 engine in America.

Changes made to the JDM ZC engine in 1988-91 and 92-95 ZC:

  • Overall, received the same changes as the blacktop D16A1, but with a slight twist ...
  • The head, block, & tranny design were revamped to accommodate the newer 88-91 EF civic/crx & 92-95 EG engine compartment & chassis.
    [The US would never see this version of the ZC engine, only from used engine importers]
  • The slight head & valve cover redesign changed to a black 8-bolt valve cover dubbed "blacktop" as well:
    click here to see differences of D16A1 & ZC intake manifoldsJDM blacktop ZC [8-bolt] Valve Cover
  • Received the same exact domed pistons & slightly lighter connecting rods as the blacktop D16A1.
  • The intake manifold design changed to a more smoother and better flowing design, different than the US blacktop:
    click here to see differences of D16A1 & ZC intake manifoldsJDM 89-91 ZC I/M
    click here to see differences of D16A1 & ZC intake manifoldsJDM 92-95 ZC I/M
  • Also received the OBD-0 wiring/ecu/and ignition system update.
    The 92-95 ZC was upgraded to OBD-1 wiring/ecu/and ignition type.
  • Nicknames of the 89-91 JDM blacktop included: "2nd gen ZC" / "blacktop ZC" / "JDM blacktop"
  • Nicknames of the 92-95 JDM blacktop included: "OBD-1 ZC" / "hydro ZC" / "3rd gen ZC"
    This OBD-1 ZC engine was only found in the JDM EG-5 model.
    Only minor changes were made to the OBD-1 ZC - mostly the change to OBD-1 and a hydraulic transmission.
    The overall look of the engine remains the same as the 2nd gen ZC. The intake manifold has light cosmetic changes as seen above.
  • 92-95 would be the last year(s) Honda of Japan would produce the 1.6 DOHC ZC engine -- R.I.P. DOHC ZC!!

The information in this article applies to:

  • JDM/Euro 1st generation Integra, 1st generation CRX, and 3rd generation Civic
  • US 1st generation Integra, 1st generation CRX, and 3rd generation Civic
  • US D16A1