Ever since getting the the car running and driving there have been a few drivability issues that made driving it less desirable then it could be. The car bucked and jerked when engaging the accelerator and it could not return to idle without dying. Needless to say it was not a very refined driving experience.
The idle issue was easy enough to diagnose. I had tried adjusting the idle screw in the throttle body multiple times. This allowed me to get the idle stable but any time I touched the throttle and the engine returned to idle it would die. I quickly realized I was missing a critical component which is standard on all K-series applications — the idle air control valve (IACV).
The Skunk2 Ultra Race does not come with a provision for mounting the Honda IACV but once again, KMiata came to the rescue with their IACV Mounting Block. This allows you to mount the IACV anywhere in the engine bay. It has two ports, one for the intake and one for the manifold which are neatly engraved so you don’t accidentally plumb it the wrong way around. This nifty little device allows you to use a stock IACV to control the air flow for maintaining the target idle RPM set by the ECU.
I built a simple bracket to mount the IACV mounting block to and bolted it to an existing bracket that held an oil catch can. This allowed the IACV to be out of the way without needing excessively long hoses to connect to the intake and manifold.
The Skunk2 Ultra Race intake manifold comes with multiple vacuum ports which made plumbing a cinch. I simply removed a 1/4 NPT plug and added a barbed fitting in its place. A silicone hose was used to connect this fitting to the “manifold” side of the IACV mounting block.
On the intake side I wasn’t really looking forward to disassembling everything to tap another bung for a barbed fitting. Instead I chose to tee an existing line which is a breather for the fuel system. Ideally each line should have a direct connection to the intake but it seems to work just fine with a tee and I have plans to clean this all up using a vacuum block or something similar down the road.
As you can see the IACV has made the return to idle rock solid. No more do I have to constantly babysit the throttle when I’m moving the car around at slow speeds. This really made the car feel less like a slapped together Frankenstein build and more like it was supposed to be this way.
The second drivability issue was the throttle engagement. When I first built the throttle cable bracket I just took a couple pieces of steel out of the scrap bin and made it work. The only constraint I was aware of was coming up and over the ABS module. Not really understanding how where the throttle cable is mounted relative to the throttle body actuator would effect the behavior of the car, I just built something that resulted in my foot being able to move the throttle. As I mentioned earlier the car would buck and jerk as I engaged the throttle which made me realize I probably overlooked something in my hasty design.
The flaw in my design was the angle at which the throttle cable pulled on the throttle — it was too steep. This caused the slightest movement of the accelerator to pull on the throttle too quickly and too abruptly. By redesigning the bracket to make that angle more shallow it significantly smoothed out the throttle engagement and made it feel more like a factory fresh Honda. Although I’m a big fan of making things lightweight the only material I had the ability to work with was steel. After realizing how over-engineered this little bracket was I drilled a few large holes in it to help me sleep at night. Now I only dream of smooth driving Honda powered rear wheel drive goodness.