| Author | Message | ||
| Steve Magnusson (91tr)
Member Username: 91tr Post Number: 968 Registered: 1-2001 |
Bill -- I agree that if it only takes 1 in. HG to open the diverter valve then the vacuum source doesn't matter for dumping above 4400RPM. The reason it's called a "three-way" valve (even though there are only 2 spool positions) is because it's more than a simple 2-port on/off switch: when "off" -- the end port near the top port is blocked and the far end port is connected to the top port. when "on" -- the far end port is blocked and the end port near the top port is connected to the top port. The advantage of this 3-way arrangement is that when the electrovalve is unenergized the actuator in the diverter valve will be vented to atmosphere. If it was just a simple 2-port on/off vacuum switch, and it was "on", applying vacuum to the actuator in the diverter valve, when you turned it "off" there would still be a vacuum in the diverter valve actuator. | ||
| Bill Sebestyen (Bill308)
Member Username: Bill308 Post Number: 321 Registered: 5-2001 |
Steve, I know what you mean, it's giving me a headache too. This evening I put the vacuum pump directly to the port on the diverter valve that the electrovalve feeds. At atmospheric pressure, the diverter valve flows air to the air injectors. With any vacuum applied (certainly anything greater than 1 in HG), flow diverts to atmosphere. So I guess it really doesn't matter where the vacuum signal comes from for this diverter valve, either from the vacuum system or the 3-4 manifold manifold ports. If vacuum is present, the air will dump to atmosphere. I guess any time the engine is running, air is supplied to the air injectors, unless either 4400 rpm is exceeded or a cat gets too hot, thereby supplying a vacuum to the diverter valve. Even at wide open throttle, there is likely to be a little bit of vacuum. I wonder why the OM refers to the electrovalve as a "three-way electrovalve"? I can only detect to positions, when energized it passes the vacuum signal if present and when not energized, no vaccum is passed. Thanks again for all the help Steve. I think I'll plumb it to the vacuum system as you suggested and then plumb the 3-4 inlet manifold port to the carbon canister circuit for balance reasons. | ||
| Steve Magnusson (91tr)
Member Username: 91tr Post Number: 960 Registered: 1-2001 |
Bill -- You're hurting my head  ! Actually on my ex-'78 I added the magenta hose to be the vacuum source for the electrovalve operating the diverter valve (and hooked the little 3-4 tube together with the 1-2 and 5-6-7-8 tubes to act as the vacuum source for the charcoal canister). The magenta hose is always a high vacuum source so if you go that way it always causes the diverter valve to "dump" the air injection above 4400 RPM. If you use the little 3-4 tube for the diverter valve vacuum source per McCay's diagram the diverter valve won't "dump" above 4400 RPM at high load (i.e., low vacuum). I also didn't like McCay diagram since some small amount of air will always be flowing into the 1-2 and 5-6-7-8 tubes (since the charcoal canister is open to atmosphere) yet no air will ever be flowing into the 3-4 tubes (IIRC the little tubes flow about 0.2 Kg/hr each at idle). I'll email the diagram of the modified set-up I used, but either way is probably OK. | ||
| Bill Sebestyen (Bill308)
Member Username: Bill308 Post Number: 319 Registered: 5-2001 |
Steve, Thanks for your response here and emailing me Mr. McCay's response. His diagram's do not show the magenta and lime colored vacuum lines fitted to a 78 308 and none of this stuff was fitted to my 308 when purchased. The way my car is currently plumbed is consistent with the McCay diagram in that there is only one hose to the electrovalve (item 6 in the diagram posted below) controlling vacuum muscle to the flap on the air cleaner. I recently purchased a lot of emissions hardware from a 79 308 donor car. This lot contained the majority of hoses for the vacuum system and air injection system. For this system, all the fittings shown in the diagram below were fitted, except the lime colored hose. The T-fitting for the lime colored hose was present on this system. The magenta hose was present and ran from the T-fitting on the vacuum system to a port on the side of the diverter valve. I placed the vacuum system on my car approximately as it would be if installed, and the hose corresponding to the magenta hose in the diagram could just reach the diverter valve on the opposite side of the engine, if pulled taught. The 78 Parts Catalog does not show this nipple on the diverter valve shown in TAV.9, but interestingly, the nipple does show up on the McCay 1 drawing, as part of item B, the air relief (diverter) valve. In the McCay drawing, this nipple is shown open to atmosphere. My Owners Manual describes operation of the air injection system in 2-areas. Under �Air Injection System�, it says "The functional principle of the system is to convey air into the exhaust manifolds so that the oxigen of the air reacts with the hot exhaust gasses causing further combustion in the exhaust system. The components of the system are the following: -pallet volumetric air pump, belt driven from the engine to supply the air; - air relief valve, energized by the intake manifold vacuum properly controlled by a three-way electrovalve, to discharge the air injection at high engine R.P.M. or when the temperature of the catalyst converter reaches high values. -two check valves to protect the system from hot gases. -air injection manifolds. -Air injectors at exhaust port near the exhaust valves.� Under the section� CATALYTIC CONVERTERS�, I find the following description: �The catalytic converters are of the oxidation type with a monolith substrate. They are placed in the exhaust system and their function is to complete the combustion process of HC and CO. In order to prevent an abnormal rise of the catalyst�s temperature and to guarantee the maximum life of the exhaust system and of the air pump, there is in the air injection system, an air relief valve that shuts the air injection to the engine, releasing it in the atmosphere in the two following cases: 1) when the engine runs at more than 4400 +/-100 R.P.M.; 2) when the gas outlet temperature from any of the two catalytic converters rises at 1,508 degrees F +/- 22,5 degrees F..� So how might all this work? Bench testing. I mounted the diverter valve/electrovalve hose assembly in a bench vise. Shop air was supplied to the diverter valve inlet (where the air pump introduces air) at 5 psi. 12 VDC was supplied by a power supply and a vacuum signal was supplied to the electrovalve inlet with a hand pump. Vacuum is supplied to the diverter valve when the electrovalve allows it. The electrovalve acts as a vacuum switch to the electrovalve. It does not matter which way you hook up the leads, it works the same way. The side port of the diverter valve (where the magenta hose would presumably go if fitted) was left open as is per the McCay drawings. Case...power(VDC)...vacuum(in HG)...air flow to ..1........0..........0.............air injectors ..2........0.........15.............air injectors ..3.......12.........15.............atmosphere There are other combinations that could be tried, but from the above results I can draw the following conclusions: 1. From Case 1, the diverter valve is normally open to the air injection circuit when the car is at rest. 2. From Case 2, vacuum to the electrovalve is not passed on to the diverter valve when there is no electrical signal. 3. From Case 3, when the electrovalve is energized, the vacuum signal is passed on to the diverter valve and air is diverted to atmosphere. In the car, 12 VDC is supplied to the electrovalve by a red wire originating at the B-fuse of the left hand fuse block. To complete an electrical circuit, a white wire runs from the electrovalve to the electronic speed switch in the passenger side footwell. This speed switch also receives a signal from the coil and then passes it on to the tachometer. The white wire is extended from the speed switch to the two catalytic converter light/electrovalve, control units. If a ground is made in any of these 3-boxes (they are all electrically in parallel), the circuit will be complete and the injection air will be dumped to atmosphere, rather than the sent to the air injection manifolds. Anybody have anything to add? Does anybody still have the stock emissions plumbing on their 78 or 79 308 GT? | ||
| Steve Magnusson (91tr)
Member Username: 91tr Post Number: 953 Registered: 1-2001 |
Bill -- I think the '78 308GTB/S SPC is just not right in this case. I'm emailing to you a letter and some diagrams I received from Ken McCay (who was the FNA Technical Director at the time) when I asked the same questions and only the line going to the electrovalve (controlling the airbox flap actuator) is shown coming off the line between the check valve and the vacuum sphere. If anyone else would like a copy of Mr. McCay's response shoot me an email. | ||
| Bill Sebestyen (Bill308)
Member Username: Bill308 Post Number: 318 Registered: 5-2001 |
I need some help identifying where the 2-colored hoses connect to, on the ends not shown. Both the magenta and lime colored hoses are plumbed to the vacuum sphere line. What do the other ends connect to?  Thanks, Bill |