Picked up a 1LE intake elbow without the vacuum access hole for a vented opti and was wondering if that vacuum line can be connected elsewhere? And if so, any ideas of a good spot? Putting a hole in the elbow is not a problem, but if the vacuum can be accessed somewhere else it might make for a cleaner install. Unless it needs that particular state of vacuum, although I can't imagine it does.

 

That hole is not a vacuum port its a fresh air hose, so you can attach anywhere that is filtered air in front of the aircleaner

 

The air that gets pulled through the vent hose, into the Opti, eventually ends up in the intake manifold. It was placed AFTER the MAF sensor so that air would be accounted for in the A/F calculations. There is a 1LE elbow made for the 95-97 vented Opti, with the hole for the Opti vent line in the correct location.

Since you appear to have picked up the wrong elbow, all you need to do is drill a hole in the elbow, making sure it is a bit smaller than the blue elbow for the vent line, to insure a good seal.

 

I thought the air flow was the other way around, that the intake vacuum evacuated hot air from heat buildup inside the Opti?

In any case, I'll just make a hole in the non-vented elbow.

I realize I purchased the wrong elbow for my vehicle, but it was a new 25147210 intake elbow for $70 versus paying upwards of $120 for a vented elbow, if one was even found(saw one on ebay for $129). Plus, I felt very confident I could make the needed modification and I liked the idea of dealing with a brand new part as opposed to a used, possibly compromised part. I was just curious about the air-line connection point.

 

Nope. The purpose is to remove any possible moisture and ozone created within the cap.

 

Okay, so from what Injuneer stated above about the location, placing it where it is, after the MAF, means the possible moisture in the air gets factored into the A/F calculation. Although if it was before the MAF wouldn't the same moist air be headed to the throttle body anyway?

I'm curious about the why at this point, not looking for a reason to do other than what's already been said about the location, just trying to understand the science of it.

 

Here's the way the system works. There is a vacuum hose that starts at a full vacuum port on the driver's side of the intake manifold. That line creates a vacuum in the line to the Opti. The vacuum pulls air that is very slightly below ambient atmospheric pressure through the blue elbow. Since it's in front of the throttle blades, there is no appreciable vacuum at the blue elbow, other than the small pressure loss through the air filter and friction losses through the inlet ducting.

Air that has been filtered, and has been measured by the MAF sensor flows through the blue elbow/vent line, to the Opti, due to the vacuum being applied at the intake manifold. On the way, it might pick up a small amount of water vapor, but it's primary function is to remove the ozone created in the Opti cap by the high voltage discharge. That ozone is what caused the high rate of corrosion within the invented Opti.

The air pulled through the Opti ends up in the intake manifold. It gets in there through the full vacuum port on the driver's side of the manifold. Which means it goes into the combustion chambers. It needs fuel added to it, to keep the total air/fuel charge at the desired air/fuel ratio. It's a small amount, but GM engineers tend to be ****, I think. They do the same thing with the PVC system. Air used to purge the crankcase, through the PCV valve, comes from the hose attached to the passenger side of the throttle body... again - filtered air that has been measured by the MAF sensor.

If the air that flows through the Opti was taken off BEFORE the MAF sensor, it would not be included in the mass air flow reported by the MAF sensor to the PCM, and the PCM would not add the fuel required to keep the total air/fuel charge to the combustion chambers at the desired stoichiometric value or 14.7:1 (closed loop only). In effect, by locating the vent line BEFORE the MAF, you are creating a small vacuum leak.

 

Got it, and thank you for the very detailed explanation!