altarchsa

[QUSeeOTE=Makmov;8716302]Not only, depends on if the system is all working and where the heater is set. Otherwise it blows out the wheel wells.[/QUOTE]

See my second post. I'm assuming the heater duct and fan are not to be reinstalled. Why block the duct off at all if you're leaving the heat system in place? If the heater system is not in place the hot air off the top of the engine will only be recirculated back onto the engine, not to the exterior.

Am I missing something?

yertyat

The ductwork and heat exchangers are all still installed. The heater blower is not going back in. I've found that I still get plenty of heat with just a heater bypass pipe. Enough to keep nice and toasty all year round including summer with no A.C. I made the block off plate when I had my car in for the installation of a non heat exhaust system (which ultimately didn't work) decided to leave it in place for now because I thought it looked cool and it keeps warm air out of the cabin... I still don't understand why the Rennline design is drilled w/ a hose coming out of it and why the fan shroud of the c4 lightweight has the screen..

FeralComprehension

That's an interesting tidbit. Originally I was of the school that the vents in the block off plate served no rational purpose and indeed were at *cross*purposes to engine cooling. Knowing that the factory included them on one variation of parts is telling....

yertyat

Yea, makes me wonder if it has something to do with the alternator..

FeralComprehension

I'm thinking that heat soak is the answer- run the car hard and shut it off, let the heat escape rather than keep it in there. The alternator would take it hard under those conditions....

crg53

The way I see this; Porsche designed the engine shroud to include that route for air to go to the heating system; if you remove everything and just leave an open hole, the air from the engine fan will take the path of least resistance and blow less over the engine; if you insert a restrictor plate with holes that will fix that problem. It will also give the hot air on top of the engine a place to escape after the engine is shot off; it also gives you a chance to hook up a hose to blow air through the distributor and rear lights. JMHO

Unkle

Have noticed the heat (smoke) bellowing out through the fan after I switched off (degreased the engine and ran it for a few mins to burn off the degreaser). It managed to come out perfectly ok so would it need that hole?

altarchsa

If the cabin heat duct system is installed, but the blower motor is not functional, I guess I can see how a plate with some holes might function as crude damper to allow the alternator fan to force some of the hot air from over the engine out through the wheel wells our into the cabin.This seems to defeat the design of the controls for the entire system though, and I can't understand why you would want a Porsche with this system being compromised. Its certainly not a performance mod.

yertyat

..regarding performance, the car is now 2805 lbs. and feels quite nimble. and as i stated earlier the heater blower bypass pipe will go back on after summer.

altarchsa

Please let us know how this works when you get it finished, especially with regard to engine temps. I think it would not be a good idea in our climate (100 degrees today).

c didy

Revive-a-post. This is unfinished business.

Anyone ever figure out why they, including Porsche themselves, remove the duct, go to the trouble to cover the duct, then put holes in the cover or cut a window in the shroud thereby decreasing the volume of cooling air available to pass over the cylinder fins for engine cooling?

FeralComprehension

As long as we're putting that on the table, let's talk about the tire warmers too. WTH are there vents in my wheel-wells?!

Auto_Werks 3.6

Interested to revive this one again....
I would have been firmly in the camp that the heater hole needed to be blocked off to avoid wasting airflow from the primary fan, however:
I just completed a 3.6 swap on a G-body car with a carrera tail, and I wanted to drive it around the block for a quick test before I finished buttoning up the details. i closed the heater duct on the fan shroud with a latex glove, figuring that worst case it would blow off during operation. The actual outcome was the glove sucked INTO the shroud. I may do some more testing with a go pro, but if the fan shroud somehow has negative pressure in that zone, it makes more sense why porsche would have made a vented cover there... airflow into the shroud at that point would be a net gain for cooling.