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Old 12-07-2015, 11:42 AM   #1 (permalink)
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Default 3 wire to 2 wire IACV

Ok before you say search and do the 2 wire mod, i dont have a 2 wire option currently.

I just got done with the build and i need to get it tuned. I was doing some research and found this

Quote:
Ok, so I just spent hella time trying to find this info. Every mook on Honda-Tech is saying you can't run a 3 wire IACV with a 2 wire ECU. This is for all mah D16Y7 peoples running Hondata and similar ECUs (OBD2a->OBD1 conversion). And this is how it's done:

"All you need to do for the IACV 3 wire to work with OBD1 ECU is:

On the OBD2 connector put a Jumper on terminals A12 to A14 and these connect to the A9 terminal on the OBD1 side. The third wire is A13 on the OBD2 connector and it goes to A23 on the OBD1 side. "

This is courtesy of an un-named poster. If anyone knows who this person is, lemme know so I can give him proper props like he deserves.
Anyone tried this and if so, does it work.

I really dont wanna have to pull my intake manifold and drill into it.

TIA
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Old 12-08-2015, 10:14 AM   #2 (permalink)
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Per my understanding, the ECU sends alternating signals on A12 and A14 to control to and fro rotation of the valve. Jumping those pins and sending the same signal on both pins might not work. Still can't hurt to try though.
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Old 01-05-2016, 03:14 PM   #3 (permalink)
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I would really like to figure out how the 3 wire IACV valves work. I'm pretty sure mine was getting some kinda feedback/signal from the CVT. I have converted to manual and would really like to be able to trick the 3 wire IACV to work. If anybody else has any info on the function of the 3 wire IACVs it would be greatly appreciated.
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Old 01-05-2016, 05:38 PM   #4 (permalink)
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It has nothing to do with the CVT. The 3 wire IACV, or RotaryACV consists of an electromagnet wrapped around a magnetic shaft. One of the wires carries a steady 12V. The ECU grounds one of the other try wires to rotate the shaft one way and then alternates to the other wire causing the shaft to turn back.

https://www.2carpros.com/articles/ho...ol-valve-works
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Old 01-05-2016, 07:01 PM   #5 (permalink)
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Can you be 100% sure of that? I'm pretty sure one of the wires from the IACV went to the CVT. I'll have to dig up the old harness and check it again. Why 3 wire for autos and 2 wire for manuals then? What keeps a 3 wire IACV from working properly as soon as you loose the CVT? If it has nothing to do with the transmission then why all the issues with converting to a 2 wire IACV when you convert to a manual transmission?
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Old 01-05-2016, 07:25 PM   #6 (permalink)
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1996-2000 DX manual comes with a 3 wire IACV, there is nothing CVT specific about it.

When doing conversions you match the IACV type to the ECU, if your ECU came with a 2 wire, you give it a 2 wire, if it came with a 3 wire, you give it a 3 wire, otherwise the ECU will freak out.

If you can trick an ecu into believing a 3 wire is really a 2 wire that is kinda neat.
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Old 01-05-2016, 07:34 PM   #7 (permalink)
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Ok, maybe it is something d15b 3stage specific, but if you try to run a CVT ECU with it's 3 wire IACV with a manual trans it doesn't work.
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Old 01-06-2016, 02:05 AM   #8 (permalink)
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Of course it doesnt work, you need a manual ECU. Thats like plugging an unmodified ECU from 6 cylinder into a car with a 4 cylinder then thinking it doesnt work because the coolant sensor isnt correct.
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Old 01-06-2016, 08:03 AM   #9 (permalink)
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Quote:
Originally Posted by JoelEspinoza View Post
Of course it doesnt work, you need a manual ECU. Thats like plugging an unmodified ECU from 6 cylinder into a car with a 4 cylinder then thinking it doesnt work because the coolant sensor isnt correct.
Oh, everything works quite well except for getting a nice idle. I'm not too sure you know what you are talking about, because many Honda Ecus will run many similar Honda engines. Back in the OBD0 days we would toss Integra ECUs in Civics for more fuel and revs, worked just fine. Many people use manual transmissions with automatic ecus, might get a CEL, but it works. With this setup you just can't get the IACV to work properly with a manual transmission, but if the IACV doesn't have anything to do with the transmission then what is going on here. I don't see why I can't get this 3 wire IACV to find a nice idle using the CVT ECU.
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Old 01-06-2016, 04:26 PM   #10 (permalink)
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I think you are missing my point, I am not talking about ECUS having slightly different fuel or timing maps, I myself own a b18a1 running on a stock d15b7 ecu and it works great, I am talking about missing electrical components the ECU is looking for and cant find.

It is true I am not familiar with honda CVT transmissions, however I would expect they have a lot more electrical components in one than the simple locking solenoid the obd0 honda automatics had, so it doesnt surprise me that those engines have running issues when those electrical components and the feedback they provide are missing.

It sounds like your best bet might be to remove the IACV, plug the hole, and provide enough vacuum leak to let the car idle when warm. If you want a manually variable idle you could simply run a vacuum line into the cabin and attach an adjustable fish tank airline regulator to it that you can open to increase the idle.
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Old 01-06-2016, 07:00 PM   #11 (permalink)
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Then you were missing my point. Here is my earlier post:
Quote:
Originally Posted by liquidoblivion View Post
I would really like to figure out how the 3 wire IACV valves work. I'm pretty sure mine was getting some kinda feedback/signal from the CVT. I have converted to manual and would really like to be able to trick the 3 wire IACV to work. If anybody else has any info on the function of the 3 wire IACVs it would be greatly appreciated.
So you're agreeing with me. That's what I'm trying to say, there has to be some kinda feedback from the CVT to mess up the idle. I like your idea to fake the idle, but if I could figure out how to fake the CVT feedback to control the idle with a switch or pot I would dig it a lot more.
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Old 01-08-2016, 04:24 AM   #12 (permalink)
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What I am saying: That person isnt walking very well because their arms were just ripped off so their brain is having a hard time figuring out what is going on.

What you are saying: The arms must directly control the legs because otherwise they should walk just fine without arms.
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Old 01-08-2016, 06:03 AM   #13 (permalink)
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What are you talking about? Can we please just talk cars here? When I built the harness for this swap I could have sworn one of the legs of the IACV went to the CVT. All 3 legs have pins on the ECU. Seems this would support that the CVT does provide a feedback to the IACV and ECU. I thought this is what you were saying and would be in agreement with me. This would make sense due to the fact of everything working perfectly except for a poor or no idle, it will idle hunt. I'm not saying the CVT controls the IACV totally. Just that it does seem to have a feedback loop that can make changes to the idle. I feel like if I can fake this feedback I might could get a steady idle with this setup.
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Old 01-08-2016, 07:19 AM   #14 (permalink)
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Quote:
Originally Posted by liquidoblivion View Post
What are you talking about? Can we please just talk cars here? When I built the harness for this swap I could have sworn one of the legs of the IACV went to the CVT. All 3 legs have pins on the ECU. Seems this would support that the CVT does provide a feedback to the IACV and ECU. I thought this is what you were saying and would be in agreement with me. This would make sense due to the fact of everything working perfectly except for a poor or no idle, it will idle hunt. I'm not saying the CVT controls the IACV totally. Just that it does seem to have a feedback loop that can make changes to the idle. I feel like if I can fake this feedback I might could get a steady idle with this setup.


Is your CEL on?


should have made your own thread ,your question has nothing to do with what the OP is...

Last edited by robgoof; 01-08-2016 at 07:22 AM. Reason: :)
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Old 01-08-2016, 07:33 AM   #15 (permalink)
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Wow, I couldn't have made that analogy any clearer, I am sorry it flew so far over your head. The brain is the ECU, the arms are the CVT, the legs are the engine.

You think the CVT was controlling the idle because you removed it and now the idle does not work properly. I am saying you ripped out the CVT and the ECU is confused as hell because it is missing a major part of its programing equation, so it is causing a poor idle, and likely other running issues you don't even know about yet, due to its confusion.

Does it make sense now? Or is it still too complicated?

Let me reiterate: 3 wire IACVs came on cars WITHOUT CVT transmissions, without automatics even. You are VERY likely barking up the wrong tree.

Most everyone here thinks I jerry rig stuff way to far, but what you are attempting to do is way below even my insanely low standards of what acceptable jerry rigging is.

Either get the right ECU for a manual, figure out how to convert your ECU into a manual ECU, or get a different ECU and tune it for your engine after supplying both your Vtec solenoids with 12v at the correct RPMs.
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Old 02-04-2016, 09:40 AM   #16 (permalink)
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Quote:
Originally Posted by JoelEspinoza View Post
What I am saying: That person isnt walking very well because their arms were just ripped off so their brain is having a hard time figuring out what is going on.

What you are saying: The arms must directly control the legs because otherwise they should walk just fine without arms.
I laughed so hard on this one.

And you're right. The CVT has nothing to do with the 3-wire IACV. Every manual D14 and D16Y7 engine here in Europe runs on the 3-wire one. So do the auto versions of the engines that come with a 2-wire IACV in manual.
It's just controlled in a different way by the ECU.

@liquidoblivion:
If the engine isn't idling properly with that CVT ECU then you should either clean your IACV or it's plain and simply ECU-related. Are you sure the ECU requires a 3-wire IACV? If so, then it's freaking out because of the missing A/T controls. I think I remember there being more than just one thread on this.

By the way, the third wire (yel/blk) is for ignition voltage and goes to some junction connector where it gets that voltage from the PGMFI main relay.. I assume the ECU might be getting its power from the same junction connector.

Last edited by Blues; 02-04-2016 at 09:49 AM.
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