How To Smog your Honda Swap

How To Smog your Honda Swap


Emission tests and smog tests are a difficult roadblock for any engine swapper, and today we’ll be showing you how to smog your Honda Swap. This is commonly known as a BAR legal or BAR certified engine swap in California, and the rules (if any) may differ in your state. To find the list of applicable swap and exhaust laws for your area, check out our Am I legal article here.

Hydrocarbons, Emissions tests and CARB stickers, nobody wants to talk about this stuff but if you are planning to swap a Honda and live in a smog regulated state, it’s something you have to plan ahead for. Of course before you plan your legal Honda swap, you will need to remove your old engine.

How To Swap a K series


As we stated above, depending on the area you live in, you may have different laws concerning what you can and can’t do as far as engine transplants are concerned. Always check with your local DMV office before you being to plan for a Honda swap or engine conversion.

Honda Swap Guide – What fits what?


Unfortunately for residents in California and some parts of Arizona, there are several laws in place that severely limit your Honda engine choices. Most of the applicable laws regarding street legal engine swaps generally follow the same guidelines ;

  1. Newer Engine – The donor engine that you are planning to swap into your vehicle must be NEWER than the donor vehicle itself. So you can’t swap that OBD1 B18C into your 1997 Acura Integra and think you will pass smog.
  2. Paperwork – Have all the proper paperwork and receipts for your engine swap, especially if its Japanese and does not have the corresponding VIN number or documentation.
  3. Try to stick to USDM – It’s almost always easier to BAR legalize a Honda swap if the donor engine is a USDM unit. Because the VIN numbers and history behind the car is trackable, your state ref should have an easier time passing you.
  4. Devil in the details – Every single piece of emissions hardware and lines have to be present for you to BAR legalize your Honda Swap. This is the biggest part of learning how to smog your Honda swap.
  5. Live in California? TOO BAD – For some vehicles purchased in California, the new AB2234 emissions law makes it impossible for you to BAR your vehicle unless you also swap in a California engine and catalytic converter.
  6. Match Emissions Equipment – Keep the equipment you are bolting on to pass smog specific to your engine. Try not to mix OBD generations from your engine to your oxygen sensor and catalytic converters.
  7. OBDII conversions – If you need to convert to a newer engine and OBD generation, you will also need to swap electronics and the ECU to match accordingly.
  8. I win ! – Once you read our DIY article on how to smog a Honda swap, you will visit the state ref and pass a visual and emissions test,
    you’ll be given a certification sticker. Place this someplace safe where you can proudly point out when it comes to smog time in a few years.

JDM Engines


Even though USDM engines can be easier to smog, JDM engines can pass just the same with the proper paperwork. The only catch here is that the engine code must match the engine donor you are aiming for. For instance, if you have a JDM B16 and plan on swapping it into a OBDII chassis, plan on a full OBDI conversion, because your state ref will not recognize a OBD0 B16A.

How To Identify a B16


This is a huge reason why the JDM B16 is so popular still to this day, because it can directly relate to the 1994-1997 DOHC Honda Del Sol with the VTEC engine in it.

That does it for our how to smog your Honda Swap DIY guide, if you have any questions or comments please leave them for us below!


  1. So with correct stuff n pass smog n visual I can legally bar a h22a obd1 in a 93 honda civic obd1 Im asking cuz I wana do it thanks any info helps

    • Hi Eddie, thanks for reading.

      Yep! just as long as your H22 OBDI engine is from a 94 or up, you are good to go ! Remember the ECU must also match your engine as well.

      Thanks for commenting and let us know how it turns out!

        • Eddie, as far as your Honda ECU is concerned, you’ve got a ton of options. Take a look at some below :

          P13 – More than likely this is what’s in your car now if you are swapping to a 97 and under engine this ECU is good for smog. You can chip this ECU but your selection is very limited. This ECU is not compatible with Hondata or Uberdata.

          P14 – This is the stock Prelude non vtec 2.3 liter H23 ECU, like the P13 can be chipped but not for standalone.

          P28 – Easily the most common choice, this is what we recommend after you smog your swap. The p28 is chippable and found in the Honda Civic. If you are keeping the intake manifold with IAB butterflies, this ECU will not control it. If you are turboing or adding a power adder to your engine, the P28 also does not have knock control.

          P72 – The Integra ECU can control IAB’s if you are sticking to the stock intake manifold. If you want the stock functionality this is a solid choice.

          P74/P75 – NON VTEC Integra ECU will work for your application, but will not control VTEC or have IAB or knock control.

          For more information on chipping ECU’s and Honda ECU’s check here :

          Thanks for commenting and let us know how it turns out!

  2. I have a question. So i have my 92 prelude right now with a H23 non vtec engine. If i swap it to a jdm h22a engine, will I be able to pass B.A.R? Considering that I do everything right with all the swap and everything . The car was bought in California.

    • Hi Henry, thanks for commenting!

      As long as the H22 engine you are swapping in is a OBDI, OBDII or newer than your 92 you are good! Make sure to use the same California catalytic converter that’s found in the JDM Prelude version of your engine!

  3. I have 1992 Honda Civic hatchback / automatic
    I’m thinking to do swap engine but I’m worried about the smog.

    What type of engine I can swap without messing up the smog?

    • Hi Ricky, thanks for reading.

      There’s a lot of swaps that will bolt in and be completely smog legal. Just remember the simple rules :

      1. The engine must be USDM and newer than 1992
      2. The smog equipment from the engine in question must be present
      3. you must use the same ecu as the one from your donor engine

      Thanks for commenting! Sounds like a great project! let us know how it turns out!

  4. I have a 1990 Honda Accord EX with stock motor automatic transmission. I want to know if I can swap a Japanese ingine H23A Vtec engine and do everything right have Ecu, catalytic converter, harness etc. Let’s say I do everything as recommended. Will this engine pass smog check/ BAR?????

    • Hi Sammy, you’ll need the H23 ECU AND all the smog equipment from a 1991+ prelude or USDM vehicle to pass smog and BAR your 90 Accord. This Honda engine swap is fairly popular however, have you seen our CB7 engine swap guide?

  5. I have a em2 and an wanting to swap it with a k20 will that be okay can i pass smog and everything all good with nothing to worry about ?

    • Hi Kevin, thanks for reading.

      In order to pass smog and BAR your EM, you will need modifications to the fuel tank at least. You will also need to transfer over all of your K series smog equipment and use a matching ECU. Sounds like a great swap, let us know how it turns out!

      Thanks for commenting

  6. Hi so I just bout a 97 gsr integra and it has a b18c. I was wondering if I can get the car bar’d I don’t want get the car taken from me so I wanna have everything legit ! If I can’t do it I was thinking of selling the swap and going fully stock

    • Hi Chris, thanks for commenting. Did I read your comment right? You have a GSR with a B18C? You shouldn’t have to BAR your vehicle at all right? Maybe Im confused. please let me know and I can assist

  7. I have a 93 honda civic that has a swapped jdm d15 engine. I need to smog in order to transfer the title to my name but i dont think it will. I bought the car really cheap so i didnt bother asking the owner for a smog. I am thinking of paying under the table just to transfer the title but if i can make the small adjustments to make it pass smog, id rather do that. What parts would i need for the swapped engine to pass a CA emissions test legally? What USDM parts would i need to swap for the JDM components? Intake manifold, headers, catalyctic converter, o2 sensors, map sensor? Any help would be appreciated.

    • Rudy, there’s a long list of things you need, but mostly :

      Intake manifold
      both catalytic converters
      the right 02 sensors ( including new rear )
      breadbox under intake manifold
      PCV and EGR valves

      Sounds like a good project, let us know how it turns out!

    • Hi Peter, thanks for commenting.

      YES! you can totally get your vehicle and engine BAR swapped and legal! All you need is the proper smog equipment AND ECU for the year range of your H22, make sure to stick to the right OBD year range.

      Best of luck to you! Sounds like a great Honda swap! Let us know how it turns out!

      • thanks for the input, reason why i asked because ive been searching and reading oline that jdm engines cannot swap or be BAR in california. can i ask one more should i use my f22a1 catalytic converter and egr valve for this swap?

        • Hi Peter, JDM engines are more than capable of being BAR legal in California. Again you need ALL the USDM emissions equipment, including your EGR valve, catalytic converter and ECU from your USDM engine counterpart.

          Best of luck! Sounds like a cool project!

  8. So to be clear I can’t put a jdm b18c in my 95 civic correct? It states that at most by my understanding a b16 can go in because of the del sol similarity and b18c is from integra so does that b18c not qualify

    • Hi Corey, thanks for commenting.

      Yes you can indeed put a JDM engine into your 95 Civic no problem at all! Just make sure that the emissions equipment is present, and that you use a USDM intake manifold, exhaust manifold, catalytic converter and ECU to make your Honda smog legal! Thanks for commenting!