Honda B20 Engine Info & Tips

Instead of replacing an Integra’s engine with another B18 (1.8L), several of us have opted for a B20 (2.0L) from the first generation Honda CR-V. These engines tend to be easier to find in good condition, are potentially less expensive, and of course they make more power and torque due to being larger displacement.

We’ve learned a few things along the way, and hope that this will save you some time and frustration:

 

Basic Info

  • USDM B20B: low compression (8.8:1), from ’97-’98 CR-V, has long “giraffe” intake manifold that wont clear the hood of an Integra or Civic, and no knock sensor
  • USDM B20Z2: high compression (9.6:1), from ’99-’01 CR-V, has shorter but more complex intake manifold, and is equipped with a knock sensor
  • JDM B20B w/ PHK pistons: high compression (9.6:1), has the B20B “giraffe” manifold, but is apparently otherwise the same as a USDM B20Z and has a knock sensor
  • JDM B20B w/ P3F pistons: low compression (8.8:1), apparently same as USDM B20B
  • JDM B20B w/ P8R head: rare, medium compression (9.2 or 9.4), possibly P3F pistons, may have larger valves, unique 2-layer head gasket (instead of normal 3), and appears to flow better at high RPM

 

  • The B20 is not “just a bored-out B18”
    • The bore is larger (84mm vs 81mm), but Honda didn’t simply take 3mm out of the cylinder wall thicknesses as so many claim
    • It comes mostly from reducing the coolant passage area / clearance, so the B20 is closer to being a closed deck than the B18 is
    • The weakest point of the cylinder walls appears to be where the cylinders join each other
    • This should be plenty more than strong enough at our power levels, unless the tuning is bad or there are extreme circumstances

 

  • Aside from using different intake & exhaust manifolds, the fitment is the same as other common Honda B-series engines
  • All sensors appear to be compatible with at least OBD-I (’92-’95) and OBD-II (’96-’01) Integras, but probably Civics of that era too
  • OBD-I cars will need to use an OBD-I distributor

 

  • Most B20’s use the same common P75 cylinder head as the B18A/B, but with an 84mm head gasket
  • On JDM motors, the rare P8R head is an option and is believed to flow better at high RPM, and it will change the compression ratio too
  • B20Z2 cams appear to have the same measurements as OBD-II B18B1 cams, but I couldn’t tell if they were timed the same or not
    • OBD-II B18B1 cams have the same lift as OBD-I B18A/B cams, with different timing
  • Low-compression B20B cams may have less lift

 

  • It’s typical to bolt on a B18A/B (aka “LS”) intake manifold, throttle body, fuel rail, and injectors
    • B20 fuel rail doesn’t fit the B18A/B manifold
    • B20 fuel injectors use the OBD-II era connectors and wont fit the pre-1996 wiring harnesses

 

  • B20’s come with terribly restrictive exhaust manifolds; swap this out with an aftermarket header for easy power

 

  • The B20 crank pulley has a larger alternator belt rib than the B18
    • This means more belt movement per crank rotation, effectively over-driving the alternator
    • Use the B18 pulley to reduce the amount of engine power spent on running the alternator

 

Our Dyno Results

The amount of power and torque these engines make are a good fit for Front4 minimum weight rules for Integras, but lighter cars (Civics, CRX) may have to add a substantial amount of weight to be legal. In those cases, a B18A/B may be a better fit.

 

  • B20 Engine 1: 146 whp, 133 ft-lbs
    • 9.6:1 B20, I/H/E, LS intake manifold & throttle body, removed power steering and AC, high flow cat
    • LS ECU, fuel tables tuned, ignition left stock, timed to 16 degrees (standard)
    • AFR around 13.0 to 13.3:1 (0.89 – 0.91 Lambda)
    • Power increases up to 6000 RPM, then drops off
    • May make more power with ignition tuning or aftermarket IM/TB, but this seems pretty reliable as it is
    • Minimum Vehicle Weight (2018 rules): 2372 lbs

 

  • B20 Engine 2: 148 whp, 137 ft-lbs
    • 9.6:1 B20, I/H/E, Skunk2 intake manifold & throttle body, removed power steering and AC, no cat
    • LS ECU, not tuned, timed to 18 degrees (2 degrees advanced)
    • Running very lean at all RPMs (14.0:1 at high RPM)
    • Power increases up to 6000 RPM, then holds steady until rev limit (7000 RPM)
    • More power and reliability expected with fuel tuning
    • Minimum Vehicle Weight (2018 rules): 2423 lbs

 

  • B20 Engine 3: 135 whp, 130 ft-lbs
    • Numbers were likely low due to visible oil smoke while on dyno (appears to be a startup issue that clears after the car runs for a few minutes)
    • 9.6:1 B20, I/H/E, LS intake manifold & throttle body, removed power steering and AC, no cat
    • LS ECU, not tuned, timed to 14-15 degrees (1-2 degrees retarded)
    • Running very lean below 5000 RPM
    • Power increases up to 6000 RPM, then drops off
    • More power and reliability expected with tuning and normal ignition timing
    • Minimum Vehicle Weight (2018 rules): 2253 lbs

 

  • B18B “LS” Comparison: 126 whp, 114 ft-lbs
    • 9.2:1 B18B1, I/H/E, stock everything else, power steering and AC intact
    • More power expected with power steering delete, high-flow or no cat, and tuning

 

ECU & Tuning

  • The B18A/B “LS” OBD-I ECU is typically used, and its stock program can get a B20 running and feeling good, but it will be very lean at points.
    • Typically, it runs lean at full throttle below 5000 RPM, but is reasonable above that point. We’ve seen this in multiple tests and with different cars.
    • You will find yourself at full throttle below 5000 RPM on the race track, so I strongly recommend tuning at least your fuel table to avoid problems and damage.
  • The knock sensor most likely wont be used (depends on your ECU), so I run 91 octane and am conservative when setting or tuning the ignition timing.

 

Oil Pan

  • The B20 oil pan has no baffles!
  • Oil starvation is a concern under high G-force loads with most stock pans, but especially with the B20
  • B18 pans are a little better, but a more baffled pan is what you really want for the track

 

Where to Get a B20

B20B’s and B20Z’s can be found in ’97-’98 and ’99-’01 Honda CR-V’s in most junkyards, often inexpensively if you pull it yourself, but it can be hard to assess their condition before at least pulling the head. A few junkyard tips:

  • Figure out why the car is in the junkyard… You want one that was running good but just got crashed, rather than one that’s in there for mechanical reasons.
  • Pull the spark plugs to get a sense for how well it was running, and to look for any oil / dirt / water in the cylinders or other red flags. A bore scope is useful here.
  • You might want to pull the head to get a real good look at the cylinders before you buy a junkyard engine.
  • Try to determine the vehicle’s mileage. If the instrument cluster is gone, this is sometimes written on the window or noted on junkyard inventory stickers.

 

We’ve also gotten some great condition, strong running, JDM B20’s from H Motors Online. They might cost more than a pull-it-yourself junkyard, but they compression test them and there’s less risk of getting a worn-out engine. I would happily do business with them again!

 

Weston

Front4 Series Co-Director #73 White 1995 Acura Integra

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