I've got a 78Z that has had a larger throttle body and AFM added. The air control valve has been removed and, the TB doesn't have a port for the ACV. (runs terribly cold - thermotime & cold start are fine) The EGR has also been removed and been replaced with a metal plate. (we don't have emissions testing in this part of TN.) I'm wondering if I could replace the ACV and plumb it somewhere other than into the TB. Would it do the job plumbed for example to where the EGR used to be or does it need to be near the front of the intake?
air control valve modification question
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It has to be plumbed around the TB. That's how you get the fast idle. Its basically a controlled vacuum leak, which has the effect of increasing idle speed.
Kevin
Kevin
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Kevin is right it needs to be plumbed around throttle plate but it isn't really a vacuum leak, it is just a controlled source of measured air (air that has passed through the AFM so the ecu knows how much fuel to add). You might add an air line from the duct in front of the t/b to a point behind the t/b (just about any vac fitting should work as long as it is behind the throttle butterfly) and put some sort of manual control valve in the line so you can open or close the line yourself. One could use some sort of solenoid normally used to control a/c or such and connect it to a switch in the cockpit. That way you could switch fast idle on or off as needed.
Thanks for the help. Yo2001 has basically the same setup so I'll consider changing the ACV when everything else is right on. The former owner said this car was "nearly restored". It is close but, he restored the head gasket with stop leak and misdiagnosed the brakes as rotors only. A valve job, timing chain/gears, calipers AND rotors & it's nearly ready to drive. Easier starting would help....Oh well, what's more fun than working on the Z????
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working on an air cooled vw with dual carbs. wou gotta pull those suckers any time you do anything that requires pulling the motor or getting behind it, then you have to synchronize them every month. i'm selling a 74 superbeetle if you're interested,,,,,,pascagoula, MS
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OOOH OOOH! I know the answer!!!
Get yourself some of the "T"'s or a boot from a 280ZX with the two holes between the AFM and the TB.
You plumb the second hole (or "T" off the line from the PCV) to your air control valve. From the ACV, stick it into one of the holes to the rear of the manifold, there is usually one right next to the Vacuum point for the Brakes.
You don't really need a big line, you can plumb it with Brake Hose if need be, and use an old brake hose for the passage.
This is similar to using the stand-alone idle bypass from a late ZX when you install the 240SX T/B on an early car.
It sounds FUBAR, but it will work!
You can mount the thing on your FENDER if you want. You really don't need a lot of air to bypass either. I set one up using 5/16" vacuum lines, and fittings tapped into the ACV with threads! The 5/16 is a bit more sanitary, and easier to work with than the other items. Take a look into that ACV: there is only a little little shutter that moves and uncovers a hole. It's enough bypass when you start that you don't puke a lot of black soot out the back. And the electric thermal element turns it off quick enough. thermal soak keeps it off after you've been running, if you want it to stay off afterthe car is warm (because it will restart the cold-start sequence every time you do it if it's on the fender well) make a bracket and place it under the manifold, with the 5/16 lines runnig up to to your vacuum ports.
You can make the bracket out of 1x1/4" flat stock, and mount it with the hardware used on the exhaust manifold heat shield. You can sandwich the water heater part between the bracket, and run the hoses down there too, and it will work like original.
I assume you are doing this to clean up the TOP of the manifold!
Get yourself some of the "T"'s or a boot from a 280ZX with the two holes between the AFM and the TB.
You plumb the second hole (or "T" off the line from the PCV) to your air control valve. From the ACV, stick it into one of the holes to the rear of the manifold, there is usually one right next to the Vacuum point for the Brakes.
You don't really need a big line, you can plumb it with Brake Hose if need be, and use an old brake hose for the passage.
This is similar to using the stand-alone idle bypass from a late ZX when you install the 240SX T/B on an early car.
It sounds FUBAR, but it will work!
You can mount the thing on your FENDER if you want. You really don't need a lot of air to bypass either. I set one up using 5/16" vacuum lines, and fittings tapped into the ACV with threads! The 5/16 is a bit more sanitary, and easier to work with than the other items. Take a look into that ACV: there is only a little little shutter that moves and uncovers a hole. It's enough bypass when you start that you don't puke a lot of black soot out the back. And the electric thermal element turns it off quick enough. thermal soak keeps it off after you've been running, if you want it to stay off afterthe car is warm (because it will restart the cold-start sequence every time you do it if it's on the fender well) make a bracket and place it under the manifold, with the 5/16 lines runnig up to to your vacuum ports.
You can make the bracket out of 1x1/4" flat stock, and mount it with the hardware used on the exhaust manifold heat shield. You can sandwich the water heater part between the bracket, and run the hoses down there too, and it will work like original.
I assume you are doing this to clean up the TOP of the manifold!
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