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H23a VTEC & PCB need wideband O2?

 
Old 03-23-2019, 01:10 PM
  #1  
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Default H23a VTEC & PCB need wideband O2?

I honestly tried to avoid posting yet another "help me" post but through all my searching and forum browsing I couldn't find a definitive answer. Here is the quick and dirty
  • 2002 Accord SE w/full 2001 Accord EX 5-speed swap (had parts car so everything is there)
  • OBD2b PDE H23a VTEC
  • PCB manual ECU (also OBD2b)
Keeping everything OBD2b for simplicity and to keep it emissions compliant. So I understand the wiring involved for crank and TDC etc and don't have an issue there.

Questions
  1. Using the PCB will I need to use a wideband O2 to keep it happy as if it were an F20b?
  2. Will IACV need to be converted to 2-wire in conjunction with the change to wideband O2?
  3. Provided 1 and 2 are handled correctly should I expect any lean conditions due to the displacement, C/R and CAM differences between the H23 and F20b?
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Old 03-23-2019, 02:16 PM
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Default Re: H23a VTEC & PCB need wideband O2?

1.)You will need to use whatever O2 sensor the ECU is designed for. Putting a wideband into an ECU that is looking for a narrowband will not work.
2.)I don't see how a 2 wire IACV is related to the oxygen sensor. 2 wire IACVs are for OBD1 setups and the ECU will not recognize it. OBD2 ECUs need a 3 wire.
3.)Uh yes. The F20B ecu cannot adjust for a 15% increase in displacement. I don't know what the max long term fuel trim adjustment is offhand but 15% is a more than what it's capable of. That is a substantial difference in displacement and will cause it to be nearly totally lean across the board.

Speaking from experience, swapping from an F20B to an H23A requires more or less a complete re-tune on an OBD1 setup for reference. Not only is the H23A significantly larger but it also wants more fuel in different places due to the difference in engine geometry. The longer stroke plays a part in not only how much but also where it wants fuel. The fueling table differences between a standard H22 ECU and an H23A are enough to cause issues and lean spots so I know the PCB ecu will be noticeably worse.

You are asking for issues trying to make that setup work. The ECU will make adjustments if it sees a less than ideal fueling condition but you're really stretching it. I have seen someone try to do something similar before and they melted pistons. It "ran fine" but was just "down on power" and before you know it, it was burning oil and had lost compression. The only plausible solution I can think of that includes keeping that ECU is to use injectors at least 10% larger than what the PCB ecu is looking for. They would have to be the same impedance and have nearly identical dead times/offset values for the engine to run correctly though. That would "trick" the ECU into thinking it's preset values were at least close to correct because when it injected X fuel it would really be X+10% and that would reflect in the O2 sensor down the line.

Alternatively you could try to find an OBD2 H22 ECU out of a base 97-01 Prelude. It would still not be ideal but a better alternative than the PCB ecu. There would still be issues with lean spots and it would likely still have an effect on engine longevity and reliability.

You're trying to reinvent the wheel here and you're gonna have problems. There's a reason conversion harnesses and OBD1 ECU tuning exist. This is it. Your argument about emissions goes out the window with what you're trying to do either way. Rich or lean conditions will fail emissions. The PCB ecu is not going to pass emissions on an H23A by a long shot. You could try either of the solutions I wrote about above or just bite the bullet and do it right with a conversion to OBD1 and a tune. Otherwise you're risking a whole host of issues including destroying your shiny new H23A.
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Old 03-23-2019, 03:22 PM
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Default Re: H23a VTEC & PCB need wideband O2?

Thanks for the reply.

[ 1.)You will need to use whatever O2 sensor the ECU is designed for. Putting a wideband into an ECU that is looking for a narrowband will not work
That's logical and makes total sense. I asked specifically about the wideband due to F20BSlug's excellent write up here

2.)I don't see how a 2 wire IACV is related to the oxygen sensor. 2 wire IACVs are for OBD1 setups and the ECU will not recognize it. OBD2 ECUs need a 3 wire.
I also asked that due to the post I linked above. He was running OBD2a but I'm not sure that would have made the difference, this is from his post
IAB Wiring

-You are now equipped with IAB’s, and in order to make these useful, look at the sensor connector on the little black box under the intake manifold. You should find a matching plug for the sensor on the F20B harness. It will have a yel/blk wire and a pnk/blu wire on it I believe. You’ll tap the yel/blk wire into the yel/blk wire (12v power source IGP1) on the ECU harness at pin B1. The other wire you will pin in at B16 on the ECU harness. The grn/red wire that was in B16 before can be de-pinned and taped off as it was a part of that messy primary O2 sensor relay you bypassed. So just de-pin a B harness wire from the hacked F20B harness and solder it to the pnk/blu IAB wire so you can simply insert it into the empty B16 spot on the harness in your car.
I've seen reference to that type of 3 to 2 wire change in some of the B swaps as well, just trying to sort out what will carry over or not.
3.)Uh yes. The F20B ecu cannot adjust for a 15% increase in displacement. I don't know what the max long term fuel trim adjustment is offhand but 15% is a more than what it's capable of. That is a substantial difference in displacement and will cause it to be nearly totally lean across the board.
I was afraid of that. So unless I can find the magic injectors you mentioned I'm just asking for trouble. Sounds like the H23 VTEC maps are pretty critical

Regarding emissions, where I live they don't do any sort of sniffer if you are OBD2 or visual inspection aside from a mirror to make sure the CAT is in place. If they plugin and the ECU is telling them everything is kosher that's all I need to pass. But it's sounding more like I need to keep a PCF on hand for yearly testing and just swap out after to a converted OBD1 unit.
How would you handle the emissions part?
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Old 03-23-2019, 04:23 PM
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Default Re: H23a VTEC & PCB need wideband O2?

Originally Posted by bavarianbl3ss3d View Post
I've seen reference to that type of 3 to 2 wire change in some of the B swaps as well, just trying to sort out what will carry over or not.

IABs are a totally different thing from an IACV. IACV = Idle Air Control Valve. IAB = Intake Air Butterfly. The two are unrelated. IACV is what controls the idle. IABs open the secondary set of runners in the intake manifold. The IABs can be deleted with a spacer for simplicity, wired up or simply hooked to a vacuum source so they will always open under WOT.

I was afraid of that. So unless I can find the magic injectors you mentioned I'm just asking for trouble. Sounds like the H23 VTEC maps are pretty critical

Yes, the correct fuel and timing maps are paramount. Without the correct calibration it doesn't matter if you have a $500 junkyard setup or a $50,000 setup, you will destroy it. Unfortunately there is no USDM equivalent to the H23A VTEC so even aftermarket basemaps from reputable tuners aren't the most reliable. An OBD1 conversion and proper dyno tune is the best way to ensure maximum reliability, power potential and engine longevity.

Regarding emissions, where I live they don't do any sort of sniffer if you are OBD2 or visual inspection aside from a mirror to make sure the CAT is in place. If they plugin and the ECU is telling them everything is kosher that's all I need to pass. But it's sounding more like I need to keep a PCF on hand for yearly testing and just swap out after to a converted OBD1 unit.
How would you handle the emissions part?

I handled it by registering my cars in a county that doesn't do annual inspections.

The PCF ECU will still throw codes because it will be looking for an auto transmission so that may be an issue for you. Swapping back to a stock ECU is a common practice for people who live in states that require inspections though.
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