EFE: What's it do?
01-13-2002, 12:29 AM
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EFE: What's it do?
When I bought my 84 Berlinetta LG4, I replaced all the vacuum lines. According to the emissions routing sticker there is a valve in the exhaust between the manifold and pipe and there is an actuator on the valve. Well, I don't have the actuator. So I plugged the vacuum line. 1.) What position should that valve be in and 2.) what are the implications of me not having the actuator?
Thanks,
(edited for ease of reading. I'm tired!)
Thanks,
(edited for ease of reading. I'm tired!)
Last edited by GregN; 01-13-2002 at 12:32 AM.
01-13-2002, 01:02 AM
#2
Greg,
EFE 101
The Early Fuel Evaporation system is installed to help your engine warm up as quickly as possible, to enable the engine to run on as lean a mixture as possible, as soon as possible after a cold start. (Is that possible?) Auto manufacturers discovered a long time ago that most hydrocarbon pollution created by an engine was from the excessively rich mixture required to run an engine while it is cold. This system was the solution to reduce that problem and help them meet emission standards (and fuel economy numbers).
The EFE system includes an exhaust gas passage in the intake manifold that is routed under the carb/throttle body well. The passage connects the two internal exhaust port openings in either cylinder head. There is also a heat riser valve in one of the exhaust manifolds. The valve is operated by either a thermostatic spring (old method) or vacuum servo (later method). There is either a Temperature Vacuum Switch (TVS) to control vacuum or a solenoid operated by the ECM.
When the engine is started cold, the thermostatic spring maintains tension on the heat riser valve to hold it closed, or on newer systems the TVS or ECM routes vacuum to the heat riser valve servo. The vacuum servo closes the butterfly valve in the exhaust manifold, effectively closing that exhaust passage so that all exhaust gasses from one of the cylinder banks must travel through the passages in the intake manifold to exit the system. The hot exhaust gasses quickly heat the intake and throttle body, allowing for better fuel evaporation and atomization in cold air temperatures. As the engine warms, the thermostatic spring relaxes and opens the valve, or the TVS of ECM removes the vacuum from the servo, the heat riser valve opens, and the exhaust system returns to a "normal" state of full flow from both manifolds.
The older thermostatic spring systems were prone to corrosion and sticking valves, rendering the system useless, or worse yet, stuicking in the closed position and creating an exhaust restriction. The newer vacuum servo systems are designed so that the valve defaults to the open position, and vacuum is required to close it. A failure in the system may create a longer warmup period, but the chance of an exhaust restriction is minimized.
If you cannot get your system to function properly, you can at least cap the vacuum line and verify that the valve is in the open position. You'll run rich a little longer at every cold start, but you shouldn't be concerned about a restricted exhaust. Unfortunately, the return spring in your vacuum servo was the device that assured that the valve was in the open position. With the servo missing, it is difficult to guess the current position the heat riser valve. There should be a line etched in the end of the heat riser valve shaft, corresponding to the position of the butterfly valve. You may have a little rust removal to do before you can see it clearly.
Another, potentially less significant problem is that you may not pass an emissions inspection without the valve, depending on just how observant the inspector may be. I belive the servos are fairly universal among most SBC V-8s, so finding a replacement might not be too difficult if necessary.
EFE 101
The Early Fuel Evaporation system is installed to help your engine warm up as quickly as possible, to enable the engine to run on as lean a mixture as possible, as soon as possible after a cold start. (Is that possible?) Auto manufacturers discovered a long time ago that most hydrocarbon pollution created by an engine was from the excessively rich mixture required to run an engine while it is cold. This system was the solution to reduce that problem and help them meet emission standards (and fuel economy numbers).
The EFE system includes an exhaust gas passage in the intake manifold that is routed under the carb/throttle body well. The passage connects the two internal exhaust port openings in either cylinder head. There is also a heat riser valve in one of the exhaust manifolds. The valve is operated by either a thermostatic spring (old method) or vacuum servo (later method). There is either a Temperature Vacuum Switch (TVS) to control vacuum or a solenoid operated by the ECM.
When the engine is started cold, the thermostatic spring maintains tension on the heat riser valve to hold it closed, or on newer systems the TVS or ECM routes vacuum to the heat riser valve servo. The vacuum servo closes the butterfly valve in the exhaust manifold, effectively closing that exhaust passage so that all exhaust gasses from one of the cylinder banks must travel through the passages in the intake manifold to exit the system. The hot exhaust gasses quickly heat the intake and throttle body, allowing for better fuel evaporation and atomization in cold air temperatures. As the engine warms, the thermostatic spring relaxes and opens the valve, or the TVS of ECM removes the vacuum from the servo, the heat riser valve opens, and the exhaust system returns to a "normal" state of full flow from both manifolds.
The older thermostatic spring systems were prone to corrosion and sticking valves, rendering the system useless, or worse yet, stuicking in the closed position and creating an exhaust restriction. The newer vacuum servo systems are designed so that the valve defaults to the open position, and vacuum is required to close it. A failure in the system may create a longer warmup period, but the chance of an exhaust restriction is minimized.
If you cannot get your system to function properly, you can at least cap the vacuum line and verify that the valve is in the open position. You'll run rich a little longer at every cold start, but you shouldn't be concerned about a restricted exhaust. Unfortunately, the return spring in your vacuum servo was the device that assured that the valve was in the open position. With the servo missing, it is difficult to guess the current position the heat riser valve. There should be a line etched in the end of the heat riser valve shaft, corresponding to the position of the butterfly valve. You may have a little rust removal to do before you can see it clearly.
Another, potentially less significant problem is that you may not pass an emissions inspection without the valve, depending on just how observant the inspector may be. I belive the servos are fairly universal among most SBC V-8s, so finding a replacement might not be too difficult if necessary.
01-13-2002, 01:16 AM
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Wow! EFE-101. That's the info I was looking for. I wonder if that's why the engine seems a bit weak, because of the restriction. Well, maybe it's the measly stock 140 hp. :-0 I'll try to hit the junk yards on Monday to see if I can find a replacement. With headers I assume this system has to be removed, eh?
