|Stepper Idle Valve Control Project
|UPDATED: June 4, 2021 CONTACT|
M A I N S
This page details the work I did on my idle air control functions for my 242 Turbo. I'm detailing and sharing it here for the benefit of others who might be interested in trying something similar.
My car uses a programmable fuel injection system from SDS (Simple Digital Systems). I began using SDS more than 20 years ago. Megasquirt is now a popular engine management system, but it didn't exist when I started using SDS, so I have stayed with SDS. And it has been bulletproof and nearly flawless for over 20 years.
SDS was originally designed for racing and it does not have nor can it control a modern computerized idle control function to control a precise stepper type idle valve, like Megasquirt or Microsquirt can. What SDS offers is the ability to trigger a simple electric air valve to enhance the idle for cold warm up or AC idle increase. A simple ON/OFF idle valve can work OK, but is crude and sometimes doesn't work as well as you like when temperature changes occur.
So this project was successful in adding some refinement to my idle functions. A welcomed addition.
For those of you using a GM stepper IAC (with a factory EMS, aftermarket EMS, Megasquirt, etc.), this extra control may be a welcomed addition for you too. Watch Jon Lamb's video. The ability to switch between normal and custom idle settings from the dash sounds like is could a pretty cool thing to me.
Your feedback or comments are welcome: CONTACT
|My Previous Idle Air Control Method in my 242|
| This is
an Ehcotech 12 volt
electric air valve. I used two of these (for two-step idle increase) for over 10 years with great results.
Both valves used manual fast
idle switches on my dash for cold starts.
The other was controlled by the AC compressor 'ON' circuit for AC idle
increase. Both were controlled by micro-switches I added to the
throttle spool to override and shut the valves when
throttle is increased above idle. So the these were set up, the idle valves are only active at idle.
These valves are found on eBay for under $10 each.
Crude but simpIe adjustment method. I'm using 1/2 inch I.D. silicone hose for the air lines from the intake tube (pre-throttle body) to the above valve and then to the intake manifold.
Tuning the airflow in the hoses can be done simply with a hose line pinch clamp like this one. It squeezes the hose in very small, precise adjustments.
In 2018 I discovered the below Youtube video made by Jon Lamb (comeinhandynow) in the U.K.. It details his method of making a stepper motor idle speed circuit that can be adjusted from the dash. Jon created the manual adjustment method for a 4-wire idle air control valve, such as one found in a GM car like he had. It sounded like a fun project, so I began planning.
So the above system allows a user to manually adjust the idle speed on the fly. This becomes useful if whatever system you're using for idle control isn't perfect. Maybe you want a higher idle during warm-ups or when the AC is on (combined with warm-ups). Being able to do an easy quick adjustment in my 242 Turbo was going to be a nice benefit.
This is a GM stepper idle motor from approximately 2003 and later GM cars or trucks.
This motor uses the 4-wire connector plug shown here.
This is an EARLIER style GM idle motor that came in cars
up until approximately 2003. It would also work, but you
would need to mount it differently since it's made with
threads to screw into a manifold, instead of the above
motor, which simply bolts on. And this earlier type uses a
different style 4-pole plug, so I won't be addressing how to use this one.
|You may have noticed this GM idle
motor is not really a complete valve. It's just a
stepper motor with a plunger. I searched and could not find an all-in-one 4-wire
idle valve with integrated IN and OUT hose barbs. Maybe one exists out there, but I found nothing
that I thought would work for me. So I started searching for an adapter housing that I
could make, buy or modify to make that stepper motor into a full stand-alone idle air valve.
There are a few housings like this out there and most are very expensive. I chose this adapter from Accufab Racing. It was more money than I wanted to pay, but it works. It's designed to allow the use of the same GM idle motor I chose. This adapter was originally designed for adapting a GM stepper idle motor for use on a Ford engine.
|Here's a view inside.
This hole starts at about .875 inch diameter. That first step is about .250 inch deep and it reduces to about .750 inch diameter. The .750 inch hole depth is about 1.1 inch and the final size beyond that is 7/16 inch (.4375 inch).
If you're handy and have the machine tools or drills, making one of these would not be very difficult either out of aluminum or maybe even a sturdy, high-temp plastic block.
Coincidentally, those IN and OUT holes on the bottom were 7/16 inch diameter, which is the correct size for a 1/4 inch NPT thread tap.
After taping the threads, I inserted 1/4 inch NPT nylon hose barbs (for using 1/2 inch I.D. hose). These hose barbs have an I.D of .375 inch.
Now I have a stand-alone idle valve (except for the circuits to run it).
I was concerned that the .375 inch I.D. of those hose barbs might be too small for the airflow needed. If this became the case, then I could optionally drill the holes in the block to 37/64 inch for larger 3/8 NPT thread. That turned out not to be needed.
Jon Lamb's video has a hand drawn diagram showing all of the components he used to complete his project. He will also email you a PDF document showing more detail if you like. Check his video description for that.
My version uses a few less parts, since I don't already have an existing GM ECU or an EMS that uses this type of motor for primary idle control. So I don't need the relay or the toggle switch Jon used to switch from Auto to Manual Idle Control.
I initially had a little trouble interpreting and following Jon's hand-drawn diagram, so as I figured out how these all these components went together, I decided to create a new, cleaner, easy to read diagram below showing each component that went into my project. This diagram below is a little different from Jon's diagram. It doesn't include the relay Jon used to switch between his factory EMS and manual idle control, since I'm not using that relay. Creating this diagram helped me to better visualize the task, since so many of these components were new to me. It should help you understand better too.
If you need any help with this diagram or with the one in Jon's video, contact me.
A printable PDF version of this diagram is available: CLICK HERE (1.2 mb)
Before actually building the circuits, I hooked up the raw circuits on a solderless breadboard to make sure I had it right. It worked as promised. If you check out the below video, you'll get to see my test in action.
If this is new stuff to you, more basic information on working with BREADBOARDS like this can be found here:
Here's the mini rocker switch I used for the idle increase/decrease adjustment. It's to be mounted in a dash switch blank panel for my 240.
The mini rocker switch has .187 inch tabs on the back. I had some uninsulated female .187 inch terminals, so I covered them with heat shrink tubing.
Here's a view below from the left side. Pinouts on this side from top to bottom are: 12V OUTPUT (top), 12V INPUT (middle), and 12V OUTPUT (bottom).
I decided not to solder everything together like Jon did in his video. This is a personal preference thing. You might like soldering stuff. I don't particularly care for it. Solder joints are prone to cracking when used in a vibration environment, like a car. When that happens, you'll have a hard time finding the problem.
I bought a JST mini pin connector kit (see parts list below). It worked out nicely. This connector will connect the project box (which I put in the dash) with four wires going through the firewall to the engine bay for the idle valve.
Here's the project box I stuffed everything into. When testing again at a final stage, things suddenly stopped working. I discovered that the 5V regulator was no longer working. Maybe I shorted it when moving stuff around. I replaced the regulator and it all worked perfectly again. Good thing I bought two of them.
Next step was installing all this in the car.
I mounted the new idle valve under the intake manifold here.
More close up view.
Here's the adjustment rocker switch. It's set up to adjust the fast idle #1 circuit. Idle #2 is an extra circuit that can be used during warm-ups.
After trying the new idle setup using the two small Ehcotech valves shown at the top of this page, I found the small Ehchotech air valve (with a 3/8 inch I.D.) that was being used for this new idle circuit was not allowing quite enough airflow during high airflow demand (cold idle with the AC on). I decided that the valve not big enough, so I bought this valve pictured below. It's a larger valve, also with a plastic body, with an inner diameter of 3/4 inch. It solved the problem and now the engine gets plenty of airflow in any cold idle condition. I found this valve on eBay for about $25.
|If you have
any comments or questions, please feel free to
motor for GM (2007 Chevy Silverado and many others).
4-pole connection. Cost will be $10 to $90, so shop
|Connector plug with pigtail for above. Cost is
Stepper Motor Driver Board or Module. Size is typically
less than an inch long. Typical input may be 5-45 volts.
Cost is about $2.00 to $4.00.
Pulse Module Square Wave Signal Generator Board with LED
Indicator. The LED is
needed for this project. There are a lot of these boards
without an LED. Get one with it. Size is
typically about an inch or so wide. Typical input will be
5-15 volts. There are three required connections:
VCC, GROUND and OUT. Cost is around $5.00 to
5.0 volt regulator to reduce voltage to the Generator
Board. Cost is around $2.00.
(Double Pole, Double Throw) mini rocker switch, 6-poles on
the back. Momentary (ON), OFF, (ON) function. Front
size is about 1/2 x 1 inch. Cost is about $5.00.
Carbon Film Resistor. 0.25 Watt. TWO NEEDED. Cost
Carbon Film Resistor. 0.25 Watt. Cost is
(0.1uf) Ceramic Disc Capacitor. THREE NEEDED. Cost is small.
|100uf 25 Volt Radial Electrolytic Capacitor. Cost is small.|
fuse and fuse holder for 12V input to the rocker
1591BSBK ABS Project Box Black. 4.4 x 2.4 x 1.1 inches (112mm x 62mm
x 27mm). $5.00.
2.54mm Pitch JST Pin Housing Connector Kit. About
Not required. You can solder things also.
Micro Open Barrel Crimping Tool for JST Terminals.
Not required. You can solder things also.
12 volt electric valve, normally closed, 1/2 inch hose
barbs, 3/8 inch inner diameter. Under $10.00.
12 volt electric valve, normally closed, 3/4 inch NPT
female, 3/4 inch inner diameter. About $25.00.
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