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a few questions about ecu's, tuning, and the lot.

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  • a few questions about ecu's, tuning, and the lot.

    current setup:
    - chassis - 90 Rs
    - engine/trans - 98 9.2 cr, jdm, p8r head, b20b/LS 5spd
    - mods on engine - 3in dia. air intake, gen1 skunk IM, 64mm tb, 2-piece 4-2-1 header with 2.5 exhaust pipe, no cat, 24in glaspak, and dual tip 3ax muffler tip.
    - ecu/wiring/and electrical components - pr4/obdo all stock.

    im wanting to do a full obd1 conversion using my modified obd1 p06 ecu thats chipped/socketed, already.
    a local shop wants 20 to reburn a tune, but ive heard issues being had with their tunes, considered sending the ecu to Xenocron also.

    ive been told that an obd1 p75 is better to run a b20b rather than a p28, be it stock or not.

    ive also been trying to figure out what the differences between the orthia and stepwagon regarding their hp,/torque stats

    the Orthia's hp/torque stats are 145/136
    while the stepwagon is 125/136 (there abouts).
    since they both list the p8r head b20b as the engine,
    i assume the only difference is in ecu's correct?

    i hope this post isnt as random as i think it is,
    thanks in advance for any help

  • #2
    Those two hp/tq ratings sound like the variance listed between the P8R spec and P75 spec models of similar generation. Are you sure the stepwagon came with the P8R? Maybe they used both types of head and the rating you found was with a P75 head?

    You really want to use an ecu mapped for the B20. The LS ECU will run the engine fine in closed loop but in open loop it will run it lean. I was seeing AFRs in the 16-17:1 in open loop while using a P75 on my B20. It just doesn't deliver enough fuel for the B20 until it's compensating using the 02 sensor.

    Comment


    • #3
      Originally posted by rollinmyda View Post
      Those two hp/tq ratings sound like the variance listed between the P8R spec and P75 spec models of similar generation. Are you sure the stepwagon came with the P8R? Maybe they used both types of head and the rating you found was with a P75 head?

      You really want to use an ecu mapped for the B20. The LS ECU will run the engine fine in closed loop but in open loop it will run it lean. I was seeing AFRs in the 16-17:1 in open loop while using a P75 on my B20. It just doesn't deliver enough fuel for the B20 until it's compensating using the 02 sensor.
      the numbers i listed were cited from b20vtec.com in their faq section, which they acquired directly from the japan honda website.
      here is web address of the faq im referencing.

      http://www.b20vtec.com/forums/thread...vtec-FAQ-Guide

      i found a statement on a different forum. saying the first digit of the serial number on a jdm b20b is either a 3 or a 5.
      the 3 = low cr
      the 5 = high cr.
      the jdm b20b in my da waz originally imported HmMotors which they confirmed mine to be the 9.2 cr b20b.

      "You really want to use an ecu mapped for the B20"
      - agree, i want to source a 98 jdm orthia ecu, and the oem distributor, for it and do a obd0-obd2_ conversion.

      instead of using a p75 or p28 be it stock or it having modified fuel/air maps and ignition timing tables originally designed to run a smaller displacement, lower compression, as well as it being a lower rated engine. in power output.

      . The LS ECU -
      (the pr4, or the p74, p75, ecus,?)

      will run the engine fine

      in "closed loop"

      closed loop is when the ecu isnt actively reading real time sensor data and making real time adjustments to afrs right?

      but in
      "open loop"

      open loop is when the ecu is actively reading the o2 to adjust the afrs, right?

      andit will run it lean. I was seeing AFRs in the 16-17:1 in open loop while using a P75 on my B20. It just doesn't deliver enough fuel for the B20 until it's compensating using the 02 sensor.

      so is the fuel delivery issue a fuel hardware issue, or is it a tune issue?

      reason i opt for a p75 is that id like to run a knock sensor and the p28 wont recognize it, regardless of tune

      right now im runnibg that b20b
      off a stock obd0-pr4,
      one rear mounted and malfunctioning single wire o2 sensor,with a frayed sensor wire,
      the dash cel light always turns on so i just flip the key backwRd in the ignition and flash the ecu, the red light blinks code for o2, why i say its malfunctioning thst is.
      and the
      the stock obd0 1.8l distributor,
      with ngk r heat range 7 spark plugs, and
      93 octane pump gas, lol
      Last edited by jtkc; 05 Nov 2015, 15:27:28. Reason: typos

      Comment


      • #4
        Open loop is when the ECU is using a "pre-established" fuel/timing map to run the engine. It isn't using information gathered from the O2 sensor to make fuel corrections. An ECU will be in open loop until the engine is at operating temp then it switches to closed loop. If you're throwing a CEL for the O2 sensor it will also stay in open loop though because it is either not getting signal voltage from the 02 sensor or the voltage is out of spec.

        Closed loop is when the ECU looks for the signal voltage from the O2 sensor and varies injector duration based on the O2 voltage "switching". Since the O2 is constantly telling the ECU whether the AFR is rich (below 14.7:1) or lean (above 14.7:1) the ecu is able to quickly make fuel corrections and keep the AFR as close to 14.7:1 as possible in real time.

        The issue with running a B20 on a PR4 or P75 ECU isn't its performance while cruising around in closed loop. The integra ECU will do a good job keeping the engine running optimally in that condition. But in open loop the map is just too conservative for the extra displacement of the B20 and the injector duration is too short causing a lean condition. It is 100% an ECU map issue though because the B18 and B20 injectors have the same flow capabilities. So to answer your question it isn't a "fuel hardware issue" but an "ECU mapping issue."

        Why is it that you want to convert to OBD2? Is your reason simply to be able to use the original ECU for the engine? I honestly wouldn't advise that. Not that it can't be done, but to put it simply it's a lot of effort just to run on a more restrictive EMS. If I were in your position I would suggest converting to OBD1 and either have a basemap for a B20 burned on a chipped ECU or even more ideally, get it dyno tuned. Either way OBD1 is the OBD genre that you can benefit the most from.

        In my civic (97 so OBD2A) I left it running the OBD2 ECU just long enough to pass BAR and then converted to OBD1 and am running a chipped PR4 with a B20 basemap. I also have a P8R B20B and the chipped ECU is running it much better than the original P75. I have a wideband AFR gauge so I'm not speculating, I'm basing that off the AFRs and driveability in open loop. It would get so lean that it would misfire and bog with the P75. That's no longer an issue with the chipped ECU. AFRs are damn near perfect. I got my chip installed/burned by phearable and I'm happy with it for what it is. Still want to get it on the dyno eventually...

        Comment


        • #5
          ah so i had it back word, about closed open loop. understand now. thank you.

          yeah the that connects to the o2 then runs to the ecu in the cabin needs replaced someone cut the connector off it, is it fairly straightforward to unpin that wire from the ecu plug and repin another one?

          i definitely plan on obd1 conversion, including a 4wire o2 (i think i saw a wide band 4wire o2 for 85 somewhere? does that sound right?
          id like to run the obd1 LS distributor also opposed to the obdo distributor also.

          unless im totally not understanding how the distributor, the ecu and the engine, interact
          i still think it would be a slight benefit to run the distributor that is matched for the engine. unless the distributor simply just reacts to what the ecu tells it to do, if that makes senze

          id like to understand more about the relationship between the engine tbe distributor and ecu, and how they function together, etc. i think im missing something.

          i have an obd1 po6 thats socketed and chipped, it also looks like it has had vtec capability installed on it as well. along with the 4pin hondata datalogging plug. that i plan on having a basemap created for it, then once i get enough money saved up get a full tune on it, and upgrade to an s100 hondata unit,

          idk the average expected mpg of a b20b or the mileage when driving it aggressively, but it seems to get around 20/gallon if i drive it aggressively and 25 ish if i drive it normal.

          my b20b doesn't seem to like 3000-3800 rpm. it seems have timing hiccups stutter etc but smoothes out and runs awesome @4000 and beyond

          Comment


          • #6
            Our ECUs look for a narrowband signal voltage from the O2 sensor. They won't recognize a wideband O2s voltage range on the signal wire. If you want it to work correctly you'll need the correct type of original O2 sensor, a wideband setup that also outputs a simulated narrowband output that the ECU can read, or an OE O2 sensor feeding the ECU information and add a bung for a wideband and just run it independently with no connection to the ECU.

            If you convert to a different OBD variant, you will have to convert some components to match (injectors,distributor, etc.) the ECU you're using. It isn't really that your engine will perform more efficiently with them, it's simply that it either won't work without the correct component or won't work even close to ideally. I'm not very familiar with converting from OBD0 to OBD1 so I couldn't tell you exactly what is needed but the information is readily available if you search this site or google.

            I have monitered my MPGs pretty closely since completing my B20 swap and if I drive aggresively I get roughly 25 MPG out of a tank. If I drive conservatively and mainly highway miles I average about 30 MPGs but I've gotten as high as 32 MPGs on a long road trip with very little in town driving. I'm guessing you would really see a benefit from installing a working O2 sensor, both in performance and fuel economy. Open loop is not the ideal long term solution in this case, especially since it's running on a fuel map for a smaller displacement engine. Have you done a tune up on your ignition system? Cap, rotor, plugs, wires?

            Comment


            • #7
              Originally posted by rollinmyda View Post
              Our ECUs look for a narrowband signal voltage from the O2 sensor. They won't recognize a wideband O2s voltage range on the signal wire.

              - ah ok.

              - our ecu's, meaning the obd0 or obd1 series ecu?
              obdo pr4 (1 signal wire o2 )
              obd1 pr4, p74,p75, p28 etc. (4 wire o2)


              If you want it to work correctly you'll need the correct type of original O2 sensor,

              - for immediate fix, i am going to just buy a 1wire o2 sensor


              a wideband setup that also outputs a simulated narrowband output that the ECU can read, or an OE O2 sensor feeding the ECU information and add a bung for a wideband and just run it independently with no connection to the ECU.

              If you convert to a different OBD variant, you will have to convert some components to match (injectors,distributor, etc.)

              yes i know, about obd0-1 conversion.
              the first da i had i had replace the entire engine harness (it was hacked to death) , then modified the new harness for obd1.
              extend ect fan switch 8in. also had to delete the fuel injector resistor box to use the RDX injectors (obd2) i had.
              the distributor from obd0-1 is simple if you spend 20-30 bucks they sell jumper plugs, ive found wiring diagrams that tell you what every wire coming out of each obd series distributor isfor and what to connect to what depending on what your needs are.


              - obd0 injectors are peak n hold (or low impedance, resistor box required. its the silver finned box on drivers side corner mounted on firewall)
              - obd1 and obd2 injectors are satured (high impedance no resistor box required )
              *obd0 and obd1 injector clips are the same.


              the ECU you're using. It isn't really that your engine will perform more efficiently with them, it's simply that it either won't work without the correct component or won't work even close to ideally. I'm not very familiar with converting from OBD0 to OBD1 so I couldn't tell you exactly what is needed but the information is readily available if you search this site or google.

              I have monitered my MPGs pretty closely since completing my B20 swap and if I drive aggresively I get roughly 25 MPG out of a tank. If I drive conservatively and mainly highway miles I average about 30 MPGs but I've gotten as high as 32 MPGs on a long road trip with very little in town driving. I'm guessing you would really see a benefit from installing a working O2 sensor, both in performance and fuel economy. Open loop is not the ideal long term solution in this case, especially since it's running on a fuel map for a smaller displacement engine.

              - the IAT sensor is bad as well, i just remembered.

              Have you done a tune up on your ignition system? Cap, rotor, plugs, wires?
              yes, its the first thing i do upon purchasing used vehicle. plugs, wires, cap, rotor, distributor itself, all replaced,

              Comment


              • #8
                By our ECUs I mean B series ECUs. Almost all Hondas use a narrowband O2 sensor. There are a few oddballs (civic hx I believe) that use a factory wideband 02 sensor but it doesn't really matter to us with B series engines. The only way you'll benefit from running a wideband is if you're using an aftermarket engine management system like hondata, Neptune, AEM, etc. that can recognize the different voltage of a wideband. I think by replacing the 02 sensor or repairing the damaged wiring you'll be in better shape. The only reason I installed my MTX-L is to monitor my AFR while playing with different ECUs.

                Sounds like you have done your research on converting to OBD1. You shouldn't have any issues there.

                How do you know your IAT is bad? If you know it's faulty I'd replace that asap as well.

                Comment


                • #9
                  ok, thanks, i never knew all this info about o2 sensors, etc. really good info.

                  i accidentally found out the IAT could be faulty, when ihad to troubleshoot a drivability issue, ended up having to disconnect and inspect, and clean off all sensor plugs and the connectors on the sensors, check wiring etc.
                  when i reinstalled and was connecting everything back together, and started it up, all was great except the CEL light lit up and stayed lit after i started the engine, but the idle sounded way better, stable, solid, didnt hiccup or stumble or anything.
                  and so i took it for a quick test drive and noticed the throttle response and decel was noticeably crisper, quicker etc. so i knew i had forgotten to reconnect something. so got back shut it off popped hood, started looking and i saw that id forgotten to reconnect the IAT plug, so did that, started back up, and idle was funky again, etc. so while it waz running i reached over unplugged the IAT and bam, idle quickly stabilized sounded healhier,, etc but cel light immediately lit up after i disconnected the iat soo. that's how im guessing the IAT is faulty also.

                  yeah, i kinda stumbled into what i thought waz a simple small project DA, yeah not so much, lol. all due to lack of knowledge about modified engines, and project cars and what to look for, and what to ask etc. when buying one.
                  so i had to do a bunch of reading, researching, etc. year and a half and 2500 dollars in parts, later lol. my friend offered to trade me with it still not running, so i did and now got this one.
                  Last edited by jtkc; 06 Nov 2015, 22:15:31. Reason: adding info

                  Comment


                  • #10
                    Right on. I would get that IAT sensor replaced soon then!

                    Comment


                    • #11
                      would it be ok to run with it unplugged? since it doesn't function properly anyway.
                      what can it end up damaging if its not replaced?

                      Comment


                      • #12
                        The ECU uses the IAT sensor for fuel trim and ignition timing corrections afaik. Although your car will run without it, I would get it replaced ASAP, even if you replace it with a used one. They rarely go bad.

                        Comment


                        • #13
                          id speculate that the o2 and the IAT have been bad since i became owner of it back in February,

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