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D16y8 to D16y7 Downgrade Issues...

Discussion in 'HYBRID -> EG-EK / DC' started by NHBsi, Mar 30, 2007.

  1. NHBsi

    NHBsi New Member

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    Looking for someone to check my notes on upcoming swap. I got my hands on an EK for cheap: 96 EX Coupe A/T with a toasted D16y8 motor. I'm going to be dropping in a D16y7 long block, pulled from--I believe--a 97 or 98 M/T hatch that had a GSR motor put in. I've spent the last week scouring forums for any potential issues that might arise, but wanted to check here before turning any wrenches. So far I have not found anything in the archives relating to this identical situation.
    As far as choosing to go with the non-VTEC y7, the main rational here was cost and labor. I toyed with the idea of hunting down a z6 or y8 head, but I'm not really interested in running oil lines to enable VTEC or doing any mini-me stuff. This EK is going to be for my gf who doesn't know how to take care of a clutch, and doesn't need VTEC anyways. (although she vehemently disagrees--yeah, what a jerk I am eh? :p ) I've only got a few free weekends to do this, so I figured the quickest fix would be to rip out the bad y8 head/block, drop in the y7, and throw on the A/T.

    Anyways, here's what I've gathered so far, I think most of it is reliable:
    1-ECU- People have told me the Auto y8 and y7 ECU's will both work with either motor (depending on your definition of 'work'). At first I thought I could just de-pin VTEC and live w/ the CEL codes....but after searching here I think the best bet would be to track down a y7 OBD2a Auto ECU and use it w/ my y8 VTEC harness: (I'm not getting an ECU with my donor motor because it's an M/T version)
    from Honda-Tech.com: Honda Civic/Del Sol (1992 - 2000): d16y7 block/head, d16y8 ecu harness,compatible??

    "Blew my y8, dropped in a y7...now car doesn't rev past 5500 and kinda bogs every now and then. Everyone says its theECu since Im using the y8 vtec one. would the y7 non vtec ECU plug in and work?"
    Reply: "use the y7 ecu. you will stop throwing codes and it will work 100% better. the ecu is still looking for vtec/oil pressure."

    I'll admit I have not studied the pinout diagrams in detail yet, but will I want to simply de-pin the VTEC wiring from the EX harness before plugging and playing a y7 ECU?

    2-Intake Manifold- Planning to re-use the y8 IM w/ a new y8 IM gasket. I understand everything should bolt to the y7 head no problem, but considering I'm looking to grab a y7 ECU, I'm a little confused on this IACV issue:
    from Honda-Tech.com: Tech/Misc: How to put a d16y8 into 96-98 civic dx...little help

    "the Y8 engine use a 2-wire IACV whereas your Y7 engine uses a 3-wire IAC. The Y7 ecu looks for a 3-wire IACV. So if you try using your DX ecu on a Y8 engine, you're going to get a check engine light for the IACV because the Y8 doesnt use a 3-wire IACV. BTW, the IACV on a Y7 engine is integrated on the throttlebody; the Y8 IACV is seperate and located on the backside of the intake manifold. Altho, an AUTO Y8 intake manifold uses a 3-wire IACV!"

    Assuming that final little note about the y8 Auto intake manifold is accurate, I should not have to do any re-wiring of the IACV system, correct? I'll have a y7 ECU on an EX harness looking for a 3-pin IACV, which luckily, I'll already have since the old IM from the blown motor is an Auto y8 version. :confused:

    3 - Exhaust Manifold - Ok I'm clear on the fact that the catalytic conv. is in different spots when comparing the y7 and y8. I want to re-use the y8 stuff from the exhaust mani down.
    from Honda-Tech.com: Honda Civic/Del Sol (1992 - 2000): d16y8 header on a d16y7?

    "on the d16y8, the secondary o2 is under the driver, INSIDE THE CATALYTIC CONVERTER
    on the d16y7, the secondary o2 is in front of the block, INSIDE THE CATALYTIC CONVERTER WHICH IS RIGHT THERE WHEN YOU OPEN THE HOOD"

    As far as extending the secondary 02, would the best bet be to simply grab some lengths of wire from a pull-apart junkyard? I read somewhere that these 02 wires are all shielded; if you don't use the right gauge to extend them you can end up with faulty/incorrect readings being sent to the ECU. I'm assuming here that both engine types are using 2-wire 02 sensors?

    I'm also having trouble tracking down a thread I saw in regards to what gasket is preferred for y7 head and y8 EM combo. Saw the answer but forgot, I think it said to use a y7 gasket.

    4-Dizzy- I can't find the links now, but I saw several posts suggesting that the y7 and y8 dizzy's are totally interchangeable. This surprised me: a dizzy wired for VTEC will work on a y7 without throwing codes? I don't doubt the guy knew his stuff, but it still seemed odd... I will have one of each kind, but the kid I'm getting the LB from mentioned his y7 dizzy had been starting to act up; if I can I'll re-use the y8.

    5 -Auto Trans- I've never really messed with yanking a honda auto trans before. I'm assuming, since it's all D-series, that this will be a relatively simple operation of transferring everything off my blown y8 onto the y7 block and then slapping the transmission in? The donor motor is having the M/T trans pulled this week, so I should be picking it up with a bare flywheel. If anyone knows of any issues I may run into installing this stuff onto the formerly M/T y7 block, plz give me a heads up!

    Well, that's about it for my long winded *expletive* post. Thanks in advance to anyone who can answer some of these questions, or confirm the info I've found.
     
  2. katman

    katman Member

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    Here's my suggestions to you...

    I'm assuming you're going to reuse the auto Y8 engine harness correct? if so...

    ECU:
    Use/find yourself an AUTO Y7 ecu for sure.
    The info is right that you've read - depinning the VTEC components will not do crap if you reuse the Y8 ecu and 'live with teh cel codes'. You'll still get a check engine light and the car will be running in limp mode (early redline, car runs rich). So forget that idea. Just run an Auto Y7 ecu. Shouldn't be too hard to find....search EBAY perhaps.

    Intake Manifold:
    Reusing the complete Auto Y8 IM w/Throttlebody is the way to go. Since the Auto Y8 TB basically uses a Y7 TB w/integrated 3-wire IACV. You may need to extend wires.

    Exh. Manifold:
    What you read is correct. You'll need to extend your 02 wiring. The whole sheilded wiring thing isn't that sensitive. You could get away with butting the extended wires together just fine..

    Dizzy:
    Whichever dizzy you decide to go with your harness will plug into the dizzy's as long as their 96-98 SOHC dizzy's. I believe the Y7 and Y8 dizzy's have the same mounting positions if memory serves me right.

    Auto Trans:
    Yes, just transfer the auto flywheel and tranny from your dead Y8 over to the Y7 and you should be good to go.

    Head info:
    I don't know what you mean by "adding oil lines for a VTEC head"....no such thing needs to be done. That's only done for LS or B20 VTEC setups. You can simply just bolt up a Y8 head to the Y7 block and be done. In fact, if just the Y8 block went bad, you can totally transfer and use the Y8 head on the Y7 block. The perk is that the Y7 & Y8 are both 1.6L blocks! Just not sure on the compression ratio differences off the top of my head. Then if you do this, you can reuse the Y8 exh. manifold and not have to worry about extending 02 wiring n' crap!
     
  3. NHBsi

    NHBsi New Member

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    Thanks so much Katman. I found an ECU from a 96-98 LX Auto in the junkyards, but I'm having a hard time determining its specific config. It was from a Canadian civic.

    Code is P2E-C81, so it's from some kind of Auto.

    Wasn't there a 3rd motor offered during this model run, like a D16y5 or b5 or something? I believe it was non-VTEC like the y7...

    In any case, it came from an Auto LX, which should not have had a VTEC motor as far as I know, so I'm hoping it will work. :ph34r:
     
  4. katman

    katman Member

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    No problem..
    I'm betting the supposed CAN ecu you have will work fine.

    The D16Y5 is the HX motor which is VTEC economy, so you don't want this ecu.
    As far as SOHC civic non-VTEC engines go, there's only one..the D16Y7.

    The breakdown is:

    D16Y5 (sohc vtec-e) = 96-00 HX
    D16Y7 (sohc non-vtec) = 96-00 CX/DX/LX
    D16Y8 (sohc vtec) = 96-00 EX

    You might be thinking of the OBD1 non-VTEC engine's which are:

    92-95 CX (1.5L sohc non-vtec) D15B8 (8 valve)
    92-95 DX (1.5L sohc non-vtec) D15B7
     
    Last edited: Apr 2, 2007
  5. NHBsi

    NHBsi New Member

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    Thanks for clearing that up. :rolleyes:

    One more quick question. I have been looking at a lot of threads around the net regarding using the Y8 Auto I-Mani on the Y7 head. Here's a statement I've only found once:

    "If you use the Y8 injectors with the Y7 ECU, you will run rich though so you will want to reuse your Y7 rail and injectors <on the Y8 IM>"

    It makes sense to me, but I found it odd that there was no mention of this on a lot of threads dedicated to swapping Y8 IM's onto D16Y7's. Have you ever heard of this issue before? Since I have a complete IM for both engines, swapping them is no huge deal, but I want to make sure it's required before taking the time to mess w/ the injectors.
     
  6. katman

    katman Member

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    I personally haven't heard of running rich issues with Y8 injectors vs. Y7 injectors, I believe both injectors have the same PSI specs.
     
  7. Dasfinc

    Dasfinc New Member

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    What do you mean Toasted? Unless it Threw a Rod or something You could probably fix it faster/cheaper than doing that swap, and just reselling the motor. I blew a Headgasket on my D15B8 a while back, and it was less than an hour job to tear it down to the block.
     
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