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Cold start options for EFI?

I was hoping I wouldn't need any additional cold start help since I live in Texas but that doesn't seem to be the case.

The obvious solution would be to use the stock idle air control valve or a Bosch IAV. I'd rather not add more hoses to my intake if I don't have to so I'm wondering if anyone has info on other options such as a cold start solenoid on the throttle body. I've heard mustangs have something like that, but I haven't been able to find anything on it.
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Old 08-03-2008, 09:43 AM
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What EFI? Why not add ordinary idle stepper motor and let the EFI control it? Then you'll have both rock steady idle and cold-start covered?
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Old 08-03-2008, 11:04 AM
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Is the idle steeper motor controlling a TB air bypass valve or the throttle itself?
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Old 08-03-2008, 11:39 AM
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You could try to source and fit an american car throttle body that has an integral Idle control solenoid but that's way more of a PITA than plumbing in a idle control valve...
Old 08-03-2008, 12:15 PM
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You will definitely need an idle air control (IAC) device of some sort. All engines are consierably "tighter" when they are cold, plus the fuel doesn't vaporize as well when the engine is cold. This adds up to needing more power to idle, which means more air when cold.

I looked around for something on another production car that integrated the throttle and the IAC (some of the GM 3.8L V6 throttle bodies in particular) to adapt to the turbo motor when I started my conversion, but they need to be welded and re-drilled to match the Porsche manifold, and then you have to re-work the throttle linkage. I decided it was too much work compared to just adding the IAC in the stock air line. I bought the Clewett Engineering IAC adaptor (see photo). Problem solved.
Old 08-03-2008, 01:01 PM
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Which EFI again?

Megasquirt, MoTeC, Wolf and Adaptronic all control an IAC valve after the throttlebody which is essentially a solenoid providing a controlled air leak under the conditions you specify to the ECU. Usually driven by a combination of coolant temp and air temp.
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Old 08-03-2008, 02:29 PM
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Wo ist die Rennstrecke?
 
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I use a GM type stepper motor (and the Clewett adapter) plus the software to control the cold start. Depending on engine temp, the software adds a shot of extra fuel during cranking and decays per the number of initial engine revolutions. The IAC is open about 200 steps when cold (at operating temp, its open only 18 steps). In addition, the engine warm up table adds a high percentage of fuel and decays up to 60C when it shuts off completely.

You probably already knew most of this, but I thought I would explain how my system works. There's nothing extra hanging off the engine to accomplish cold start.
Old 08-03-2008, 03:28 PM
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I'm using Motec so I could pretty much run anything.

I guess what's throwing me is the term stepper motor used with valve. If I understand correctly, the stepper motor is just opening the valve in an idle air control valve.

The Clewett IAC looks nice and for $200 with all the parts, it's a bit more affordable than the $300 Bosch unit Motec sells.

I was hoping to avoid adding another bung to the intake, but I guess that's the right way to go.

Do you think it'd be OK to put the bung on the IC outlet tank rather than on the tube from the IC to the TB? I think it would look cleaner and be easier to connect and disconnect the hose.

I notice the Clewett valve has 4 wire inputs. Does it use all 4?
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Last edited by David; 08-03-2008 at 03:51 PM..
Old 08-03-2008, 03:43 PM
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There are 3 main types of IAC control valves. They all work on the same principle, by bypassing the throttle plate with an adjustable amount of air. The three types just go about it in different ways:

PWM type - The bypass valve is rapidly pulsed by a high frequency current. The ratio of the time the current is on to the time it is off is called the duty cycle. The airfow is adjusted by varying the duty cycle.

Stepper type - A rotary motor moves in steps according to commands by the ECU. The rotary motion is connected to some means of adjusting the airflow.

Linear solenoid - This type has a solenoid that is controlled by current supplied to it. The solenoid directly controls the airflow.

The Motec unit supports the stepper for sure, so I suppose that is the safest route for you to go, in which case you can use the Clewett adaptor and IAC.

From a technical standpoint the linear solenoid it the nicest (infinite adjustment and fast), the PWM type the worst (kind of noisy and slow) and the stepper is in between, but we are not building mini-vans here! If you were happy with no IAC you will be in hog-heaven with the stepper motor.
Old 08-03-2008, 04:20 PM
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David,

I just bought the Clewett package for my Haltech.

Unfortunately, it doesn't work with Haltech so you can have it for a deal. It has literally 5 minutes run time on it before we disconnected the thing. It's a clean design, 4-wire unit. Now I'll be buying the Haltech idle unit.



Let me know, and good luck!
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Old 08-03-2008, 05:14 PM
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Look at that pile of junk Glenn ^^^^^
What hack worked on that thing? haha Glad she is runnin well
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Old 08-03-2008, 08:16 PM
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Yes you can connect your hose to the outlet of the intercooler. Ruf and Porsche do it all the time.
Old 08-03-2008, 08:33 PM
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Glenn, what are the 4 wires for on the Clewett valve?

When I built my harness I only set it up for two wires to the IAC, so I need to know what other signals I'll need.
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Old 08-04-2008, 05:33 AM
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David,

Per Richard Clewett: "The 4 wire is a stepper motor. My understanding is one pair (A&B or C&D) is high speed and the other is the slow speed."

That's about all the info I have now. He referred me to the Tec3 maual but it didn't have the pourpose of each wire, just the color-to-color match:

"In the TEC3r manual. Go to www.clewett.com , on the left select Installation Instructions, and then TEC-3r manual close to the bottom. In the manual on page 82 & 83 is the information I have. The Idle motor the I sell is # 81110 GM style."

I hope that helps.

I went through similar issues with using a Motec Hall sensor on mine, but got it sorted out fine.
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Old 08-04-2008, 07:42 AM
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The four wire stepper motor Clewett sells works like this: one set of wires opens the valve, the other two close it (actually, its closer to a plunger than an actual valve) - in steps (stepper valve) - super simple. Your ECU must be able to handle a four wire valve - some only handle solenoid types, so check your ECU paperwork and wiring. For most ECU's you don't have to worry which wires are connected to the stepper as you can reverse the action in the software. In addition, I think Clewett's only works on the TB - but ask him to verify. Here is a pic of my adapter and stepper (small motor on top of the adapter).

Last edited by DonE; 08-04-2008 at 05:28 PM..
Old 08-04-2008, 05:22 PM
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Don, you've confused me even more

It looks like your steeper motor is controlling the TB and not a valve. If so, this is what I originally wanted to do so I didn't have to add more hoses.

I have some other unused wires in the engine compartment I could use to get the 4 wires but it means I won't be able to have nitrous
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Old 08-04-2008, 06:06 PM
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The stepper IAC is actually kind of like TWO dc motors that work to balance each other at a specific "step". One acts as the driver, and one as a brake. This gives it the ability to hold at a specified point. To go in the reverse direction, the current through both motors is instantaeously reversed using a circuit all the H -bridge.

The above is a big simplification, and enough engineer talk already. Basically there are two types of GM IAC's. The two bolt kind (which people are referring to as the Clewett valve) and the screw-in kind (which Motec uses). The pins are arranged differently, but they work the same. See the diagram below.

PurpleHaze is using the Clewett valve in a Motec world. Referring to the diagram below, he just needs to reverse two pairs of wires at the IAC and hw will be cool.

125Shifter needs to add all four wires AND make sure that he has them connected to the correct pins on his ECU. I can tell him which pins if he tells us which ecu he is using.

DonE appears to have crafted a Magnificent throttle body and attached the TECII IAC adaptor to it. How did you make such a beautiful thing?
Old 08-04-2008, 10:39 PM
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Wo ist die Rennstrecke?
 
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I wish I was that good on the CNC....

Pictured is an Acufab 75mm TB sitting on top of a Marco Manzie adapter used to mate to the 3.2L manifold.
Old 08-05-2008, 01:33 PM
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