HENRX7

Ok I already took off my BAC and now I'm left with the Air Bypass Solenoid valve. Both the BAC and ABS valves get air from the snorkle that connects to the throttle body. Since the snorkle is after the Air Flow Meter (AFM), it is then metered air. Now my question is, do I really need to get a metered air for my ABS valve or the BAC valve(if i still had it) or can I just use a small air filter and stick it in the opening of the ABS valve. The reason I'm asking is, I wanted to get rid of that brass tube behind the TB where the BAC and ABS valves connect to.

HENRX7

anybody?

Keith

Oh yes, you must use metered air, otherwise you will not get fuel for the increased air drawn by the engine. These valves do the same thing as opening the throttle a little bit. What you will be simulating here is a hole in your intake path. You might be able to compensate for this with idle mix adjustments, but you will have a very confused ECU.

Irv, Keith's dad

HENRX7

So Mr Irv, if I am understanding it correctly, you wanted to get the air from the intake path(snorkle) because when the ECU asks for more air, it has to be well distributed to the throttle body and to the AIR BYPASS SOLENOID valve. Meaning, if I only stick a filter right at the ABS valve, there will be too much air going to the TB.

Hmmm, so that's why the idle becomes erratic when either the BAC valve or ABS valve is not working. Because the excess air in the intake path is too much and it is not being bypass through either one of the valves. I think that makes sense now.

So the only fix to this is to NOT inform the ECU if you wanted air to come thorugh the BAC or ABS valve. Then it will be independent to the ECU.

Keith

Here is what I was trying to point out. In the simplest system, you have a rotor creating a suction. A throttle plate puts a variable restriction in its path (depending on how much it is open). Less restriction, more air is drawn into the engine. The ECU must know about this somehow, so a device called an air flow meter is used - the more air drawn into the engine, the higher the voltage signal sent to the ECU. The ECU then uses this signal to figure out how much fuel to inject into the engine. Now lets add these valves to the picture. They are all basically small holes from the front of the throttle plate (normal atmospheric pressure) to the vacuum on the other side of the throttle plate (after the restriction). So, if a hole opens, there will be a very slight drop in restriction (just like opening the throttle plate a little - touching the gas). Now, this is done in a completely seperate part of the ECU. It only knows to pick a solenoid if a condition is satisfied (example, you just started a hot engine). Now here is what happens - slight drop in restriction, the engine draws a little more air. The AFM senses this, sends the signal to the ECU, which adds more fuel.

Now, if you got the extra air from other than the air being pulled through the AFM, the engine would be getting more air, but the AFM would not sense it, and your engine would go lean. This is what I meant by a "confused ECU".

Sorry about being unclear.
Irv, Keith's dad

HENRX7

ok, I got it. thank you for all these information.