QUICK SPECS

Estimated Time Of Completion: 4 Hours
Material Used: eSun PA-CF
Products Used: Fusion 360, Creality K1 Max
Number of Revisions: 3
Difficulty: Low
Ease to Mass Produce: 1/10

Had a customer here with a KTuned 90MM throttle body on his 1000+HP 2005 Honda Civic Si that we did work on at the shop. The customer supplied car would not idle. Upon diagnostic, I found the throttle body itself was completely sealed, not allowing enough air to bypass the blade to keep the engine speed high enough to idle.

Typically, most throttle bodies have an adjustment screw with a lock nut that allows you to set the closing point of the throttle body before it snaps completel shut allowing an appropriate amount of air through the engine to keep the car running. Most modern cars do this using Drive By Wire, with a motor determining the throttle angle. Older cars use a cable style with a set screw and a valve that bypasses the throttle to create a controlled vacuum leak to raise the idle speed.

It’s very common in high performance applications in the Honda world for people to delete the idle control valve and only rely on the throttle stop screw to leave it cracked enough to return to idle without shutting off the engine. The company that made this throttle body recently revised the product and deleted the screw that allows you to set the idle. This throttle body also no longer has the port to accomodate for a valve. So there’s no functional way to open the throttle blade whatsoever. An interesting oversight. Looks like they broke what was fixed.

The original part to replicate and modifty

So the throttle body uses a billet aluminum stop to control the throttle open angle. This stop is not adjustable in any way whatsoever, so you’re stuck with the setting the throttle body has from the manufacture. This is a major issue because there is no one-size-fits-all opening. The amount of opening required to idle a car varies by many reasons including but not limited to, engine displacement, intake manifold, camshafts, compression, etc.

Because the piece is not adjustable in any way, I had to find a way to adjust the throttle opening. The way I approached this was to start the car, and make it idle manually by cracking the throttle by hand. I placed feeler gauges between the throttle stop and the throttle to find out exactly what thickness would be required to add onto the part to make the vehicle idle. The difference was .7mm.

So I removed the part from the throttle body, grabed a set of calipers, took measurements, and drew the part up in Fusion 360. I typically build an additional .2mm into parts to accomodate for expansion from 3d printing. However, I’ve been recently printing in eSun PA-CF (Carbon fiber infused Nylon). PA-CF is known for it’s dimensional stability, rigidity, chemcal resistance, and heat resistance. I ran the part on my Creality K1 Max with 0mm tolerance just to see how dimensionally stable it was, and the part fit perfect with no tolerance changes whatsoever.

I bolted the spacer onto the throttle body, the guys in the shop installed it back on the car, and the car idled perfectly with no further adjustment needed.

A simple part for a simple problem.