91 civic si

[Xist]

Good luck!

[Stacygifford]

Ok sweet! Good news fellas! I have everything on its way, along with a little surprise!

It is a CRX HF trans on a d15b7 with obd0 injectors and disy. So no conversion needed for me!! (I will still probably swap to obd1 for other reasons though.)

AND, I threw together a kammback that will also incorporate a rear corner airflow trip feature. It may be about a month until this is under production, but with some CAD (cardboard aided design) tried to get a general idea. My dads body shop has a few roles of carbon fiber/ kevlar weave, so.... the final piece will weigh next to nothing!!!

Let me know what you guys think!!

[Stacygifford]

I'm sorry but its been awhile since I've updated this, I've been busy house shopping. My move in date is May 29th!I realized that my cars fan was wired on the ignition switch, so now I set it up to where it is on a temperature switch and the fan only turns on after a 185 degrees.

when I get off work tonight I will be updating this some more with pictures!

[Stacygifford]

Let me elaborate on the ignition switch idea, anytime the key is on the fan would be on. I have had some wiring bugs, but I have sorted them out for the most part. Here are some of the pictures of what I did.

This is how much crap wiring I removed, along with 2 non-functioning relays.



Here is the temp probe poking through the radiator.



I reused the the factory fan plug for easy removal.



I mounted the new relay behind the headlight on a factory bolt.


Also, I have been playing with the idea of killing 2 cylinders while cruising ( not while idling or accelerating) My car runs OBD0 so I only have 1 o2 sensor, and because I have tubular headers the o2 sensor only reads cylinder 3. so I do not have to worry about it trying to richen the mixture, because 2&3 are not affected. If I kill 1 & 4.

This is the firing order


When I disconnect 1 and 4 it remains balanced, and will idle and run (slightly rough at an idle) and will sloooooowly get me up to 75mph without a problem. above 2000 rpm you can not feel/here the dead cylinders. Also, it will pull small hills without a problem.
You do have to have a more aggressive throttle position, but that is to be expected with half the effective displacement.

By shifting the load of all 4 to just #2&3 (by deactivating them) to the remaining cylinders should operate under higher higher effective compression ratios.

Does this sound like it would work ok?

As a way to avoid the CEL, I will not be simply "Cutting the power" to the injectors, I plan on making the go to an alternate circuit with a ~6ohm resistor to fool the ecu to saying the injector is firing.

Any feedback would be awesome and appreciated!

[Stacygifford]

Well, I guess people Aren't that interested in my civic/thread...

Nonetheless! I will keep this thing updated.

I am off work tomorrow so I will be wiring in the injector kill switch.
This is my diagram of how I plan on fooling the ECU into saying the injectors are "firing"
sorry, I am not an artist, or good with diagrams :P

[Stacygifford]

IT WORKS!!!!!!!!

Awesome news ! My cylinder management system actually works!

<object width="640" height="360"><param name="movie" value="http://www.youtube.com/v/hjAGmZx-lyc?hl=en_US&amp;version=3"></param><param name="allowFullScreen" value="true"></param><param name="allowscriptaccess" value="always"></param><embed src="http://www.youtube.com/v/hjAGmZx-lyc?hl=en_US&amp;version=3" type="application/x-shockwave-flash" width="640" height="360" allowscriptaccess="always" allowfullscreen="true"></embed></object>

Variable displacement experiment. 91 Civic Si B18 - YouTube

The first thing that I did was checked the resistance of my injectors. They were all between 2.4 and 2.6 ohms. (92 - 95 should be around 8 ohms FYI) it being that I could not find any 2.5 Ohm resistors that could handle more than 1/4 watt of power I wired four 1/2 watt 10 Ohm resistors in parallel, which yields a final resistance of 2.5 ohms.





The next thing that I did was remove the plug from injector one and unplugged the two plugs in the wiring harness that go to the injectors. (see next picture)
The green one goes to the resistor box (nonexistent in 92-95 Hondas) the large white plug is where you test what wire goes to where. They are also color coded, I always check with a volt meter to be certain before I go cutting the wiring harness.



To make sure that this would fool the computer, and to prevent myself from wasting a few hours of wire in something that would not work; I simply put the resistor directly on the cut wires and completely bypass the injector.



I went in the car turned the key and to my amazement it started with no check engine light!!!

Granted, it did run a little rough or in just three cylinders Lol..
Now, it was just time to wire it all in!
To make the alternate circuit I used a DPDT switch from radio shack (On-Off-On) I was hoping to find a DPST On-On switch, but it is just as easy to skip the center of position.



On this style switch there are six terminals. The three on the left and the three on the right are completely independent of one another(one circuit for each injector)

On the upper two terminals I connected the resistors and spliced into the constant power to injectors 1 & 4
The middle terminal I connected to the ecu side of the injector ground wire (brown in the first picture)
And on the lower terminals connected to the injector side of the ground wire (brown in the first picture)
As a side note the wire color for cylinder number four is yellow.



Listed tools and items needed
• Resistors equal to resistance of injectors (2.5 ohm in 88-91 civic 8 ohm in 92-95) ~$4*
• Soldering iron with Souder
• Good wire (12-18 gauge, I used about 30 feet....) ~$6*
• Heat shrink ~$4*
• Wire cutters/ strippers
• 1 DPDT On-Off-On switch (Or a DPST On-On switch) ~$4*
* cost is assumed if buying new.

Most people who do wiring should have all of these with the exception to the switch and possibly resistors, all I purchase were the resistors and the switch.

[Stacygifford]

Not to spam the board, but can anyone think of a way to make this transition automated? that would be the next logical step.

[t vago]

Let's see some fuel economy improvement figures from your cylinder management circuit, first.

[Stacygifford]

Originally Posted by t vago

Let's see some fuel economy improvement figures from your cylinder management circuit, first.

Just filled up, after this tank, I will be throwing some numbers out there.

[Stacygifford]

As an update, on the variable displacement. it didn't work as well as hoped.. I gained about 1.3 mpg.. not enough to be worth the risk to the engine, and the added trouble.

However, I have better news!!!! I just finished swapping back to d series with a CRX HF trans, And I was paid to do it!!

My buddy has a 1991 civic dx with a d15b1. Me and him worked out a trade to where we trade ECU's, wiring harnesses, motor mounts, axles, shift linkages , and he pays for everything, and buys me the crx hf trans. the reason it was worthwhile to him is because he wanted by b18b1.

here are some pics!

The hf trans


My motor


My engine bay


Lowering it in


Hell... *cough* wiring


His engine


We took the valve cover off the b18 and look how clean this thing is!!! this is after I have had it for + 15k miles and it needed an oil change!


here is my prototype kambak... the angle is to steep, I made it with some spare fiberglass. i wanted to test it with glass before I use my Kevlar.