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91 honda crx hf
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Discussion Starter #1
Hey everyone, If this is already up somewhere please point me in the right direction.

I chose this swap because I found a d15b7 and an A6 transmission for cheap and it seems to be a straight forward swap where motor mounts and transmission components match up well. This is my daily driver and not a toy, even though the car is a blast to drive.

I'm taking my bone stock 91 crx hf with a d15b6 and swapping in a d15b7 with a 91 A6 cable transmission. I will be using the 91 HF dizzy and wiring harness. I would like to stay with obd0 and was told to use an A6 ecu.

So far, I have the head work complete and the bottom end torn down. I'm holding off for money and doing some research before I proceed with buying parts to complete this build.

Now I'm being told that I will have to send the ecu off, have it base mapped to the specs for this particular setup. I see the principle of remapping the ecu to insure the air to fuel ration is correct but I'm curious as to how far off a stock A6 ecu is from what I need.

has anyone else done this swap straight from hf to b7/a6? What issues might I run into? I hear the bit about how I should skip the b7 and go right for an A6 or bigger all the time, so we can get past that and go for a thread about swapping a B7/A6 combo into an HF chassis. I am keeping an open mind to later swapping in an A6 cam, or just going for full head swap. right now I'm in it for small gain because my b6 is slowly dying of old age. I wont be taking it to any autox, flashlight drags, car shows, etc.... and...... here we go....?
 

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ministry of mayhem!
93 honda integra
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5,673 Posts
a6 and b7 heads are the same casting except cam and springs. nevertheless later b7s are known to carry a6 springs, which are stiffer than the b7.

with that said, you can swap a b7 in and get a a6 cam later down the road.
 

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91 honda crx hf
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20 Posts
Discussion Starter #5
ok, pretty much what I've already read and why I was planning to swap an A6 cam in later on down the road if I get that itch. is there anything else with this setup? o2 wires, motor mounts, etc that may be an issue or is this a straight forward swap? From what I've read it sounds like the way I have planned out should bolt up and run just fine. Does anyone know if the base map from the A6 ecu will be set up too rich for the D15b7 or will it not be enough to wet my seat covers over? i'm trying to keep it as simple as possible with as much of a factory look as possible. I don't have to worry about emissions where I'm at yet btw....
 

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91 honda crx hf
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20 Posts
Discussion Starter #7
no one had mentioned that, and I havent seen that anywhere online. so I will need the SI injectors, will the b7 injectors work? either way the harness is not the same on the hf as it is on the SI or DX/LX. DX/LX and SI take the same connector. the hf is shaped differently and will not accept the other injectors.
 

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91 honda crx hf
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20 Posts
Discussion Starter #8 (Edited)
si-hatch86, what's you're reasoning behind having to use the SI injectors with SI ecu? the flow rate is the same between the SI, B7, and B6 as far as injectors are concerned. Honda/Acura Stock Fuel Injector Flow Rates
Engine Code Year Stock Flow Rate (cc/min)

G25A4 1995-1996 235
J30A1 1997 240
C32A6 1996-1997 240
B18C1 1996-1997 240
B18C1 1994-1995 240
B18B1 1994-1995 240
B18A1 1992-1993 240
B17A1 1992-1993 235
C32A1 1997 275
C30A1 1995-1998 325
C27A4 1995-1997 235
J30A1 1997 240
F22B2 1994-1997 235
F22B1 1994-1997 235
F22A6 1990-1993 235
F22A1 & F22A4 1990-1993 235
A20A3 1987-1989 235
BT 1986 235
ES3 1985 180
D16Y7 1996-1997 240
D16Y8 1996-1997 240
D16Z6 1992-1995 240
D15B7 1992-1995 235
D15B8 1992-1995 180
D15Z1 1992-1995 235
D16A6 1988-1991 235
D15B6 1988-1989 180
D15B6 1990-1991 235
D15A3 1987 180
EW4 1986 180
EW3 1985 180
B20B4 1997 240
D16Y8 1996-1997 240
B16A3 1996-1997 240
D16Y7 1996-1997 180
B16A3 1994-1995 235
D15B7 1993-1995 235
D16Z6 1993-1995 235
F22B6 1995-1997 235
H22A4 1997-2001 290
H22A1 1993-1996 325
F22A1 1992-1996 235
H23A1 1992-1996 235
B21A1 1990-1991 235
B20A5 1988-1991 235
BT 1985-1986 235
http://www.phearable.net/tech/stockinjectorsizes.html
 

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\/Your Mom Was Here\/
Vibe GT
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OMG TOTALLY COOL TITLE!!!!
88 y49 crx
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3,888 Posts
Beerdrinkin got it. Its not flow but impedance. Obd0 a6 are 240cc like the b7 but the a6 use a resistor box and b7 dont. The hf ones are 190cc which is why I originally said switch them. But being you have the b7 ones you can either remove resistor box and use those or keeo box and source a6 ones
 

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CRX ECODiesel Ram
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1,036 Posts
how come the crx hf has a different part number as the si for injectors? it shares injectors with the 84-85 accord se-i and the 86-87 civic si.
the si however shares injectors with 83-91 preludes, 86-89 accords, and all 1.6 88-91 civics/crx. the si injectors definitely supports a 2.0 liter engine but honda did not think the hf injector should be used in anything but a 1.5 liter engine or the very early 1.8 injected accord engine.
if they were 100% for sure all the same flow rating and interchangeable it would seem honda would just have one part number.
 

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91 honda crx hf
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20 Posts
Discussion Starter #16
I've seen a lot of parts, that definitely interchange, that have different part numbers yet the specifications are the same or close enough. As a mechanical engineer / designer this drives me nuts, but I understand they have the option to change slight details to fit their needs when existing parts would work fine. cant make it easy i suppose.
 

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91 honda crx hf
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20 Posts
Discussion Starter #18
I ran into another issue, I have the stock crx hf exhaust system and it is full of holes, with the blown head gasket on the d15b6 it was smoking the entire length of the car. what reasonable alternatives would you guys consider? I'm in WV and we dont have emissions testing yet but we do have regulations on noise polution. I was looking at a full exhaust system on ebay for $173 header, test pipe, B pipe, over axle, and tuner muffler. i've watched a couple youtube videos and i'm not thrilled. I have $400 i can put toward this.
 

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Hello there fellow local ( well semi local) I'm across the river from Huntington in South Point. Don't mess with a ebay exhaust, for 400 order a good muffler and resonator (magnaflow is what I'd suggest) amd the VRS piping kit. HOME

Or if you're really cheap like me, a good muffler/resonator and the local exhaust place for some crush bent goodness (usually around 75-100 for a full 2.5 locally) I've got a Si cam/springs and some other things if you're interested. If you need some help with that ECU and getting it chipped and a basemap setup shoot me a PM, I'm not far and I don't mind lending a hand.
 

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91 honda crx hf
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20 Posts
Discussion Starter #20
well, My manifold is bad and still just an HF manifold. I'm not going for performance, just mileage. it's my DD and I need it back on the road. my truck only gets 12 mpg and i live 25 minutes from work, so driving it is tearing me a new one. I can have a full custom magnaflow exhaust (cat + catback) installed at a local shop for under $200 but would still need a header or some form of manifold.
 
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