87' Carrera 3.2 engine into 72' Coupe install question?

Bobboloo · Bobboloo's Garage

Hi Guys,

I'm installing a 87' 3.2 Carrera motor in a 72' Coupe. I'm removing the brake booster lines and capping those ports but there's an air valve on the right valve cover that I have no idea what it is used for.

What is the function of this air valve , circled in red, on the side of the motor? Is it needed? Can I just cap the ports on the throttle body where it's hoses are connected and remove it?

TIA

jbrinkley · 03-07-2008, 05:26 PM

it's suppose to be mounted on the wall over by the oil filter.
called aux air valve or warm air valve something like that.
I believe one of the hoses goes to a valve/plug at the back of the throttle body right? has 2 nipples on it.
wait
ill get some pics

jbrinkley · 03-07-2008, 05:39 PM

I read that again, the answer is yes.
that small plug in the TB with the two ports on it doesn't penetrate the TB. You just have to cap the port below where the jumper hose goes.

jcunning · 03-07-2008, 06:30 PM

The operation of the valve works like this.

When the temperature of the throttle body is cold (under 50), the valve on the throttle body (where the two vacuum hoses are connected), opens up. This will then create suction at the top of the valve, which essentially opens the aux. air valve.

The aux. air valve will then allow some extra air into the engine to help with the cold running. Once the throttle body temp rises above 55 or something, the vacuum valve closes, which then closes the aux. air valve.

This is an interesting system, as the regular Idle control valve must not be able to supply enough extra air when the engine is cold.

So to answer your question is it needed. I would say so otherwise Porsche wouldn't have bothered with this crazy type of solution.

jbrinkley · 03-07-2008, 06:51 PM

I understand they serve a purpose, it's just that they run fine without it.

Bobboloo · Bobboloo's Garage

Thanks for your insightful response. The last picture is particularly helpful.

Seems like this part is a hold over from the old CIS system that used an Aux air valve for cold running.

One more question if a may?

Here's a picture of the air valve from the PET catalog. I see the two lines that hook up to the throttle body but where does the third line #38 hookup for the source of aux air?

jbrinkley · 03-07-2008, 07:16 PM

a dorky check valve that was NLA three years ago. Don't know if it still is or not.

Bobboloo · Bobboloo's Garage

Yeah I already checked on the check valve. The air valve is NLA as well.

Thanks again.

jcunning · 03-08-2008, 03:51 AM

According to the vacuum diagram, the supply air comes from the oil tank or close to it. I haven't hooked this up yet as my engine is still sitting in the garage.

Once I get my car up and running, I'll play with this system a little more to see how much a difference it makes when cold starting the engine in cold weather.

For those that only drive their cars on nice days, you can most definitely trash this whole thing. Just make sure to plug up both the little vacuum port and the larger port.

ianc · 03-08-2008, 09:12 AM

Actually what that valve on the right side near the oil fill does is vent fumes from the oil tank into the intake. It does this to prevent icing of the throttle body in cold temps by allowing the warm air in the tank to mix with the cold intake air. Not necessary and a bit of a pain, but probably worthwhile to hook up if you can.

ianc

Jonesee · Jonesee's Garage

Where did you get that CAI? I am doing a similar conversion and the original air box is damaged.