3.2 Back date heat

[thorloki]

I purchased a 3.2 with 56,000 mi to replace the 3.0 that came with my wide body 911S. The 3.2 did not come with factory heat ducts and fan so I used a block off plate for a short period of time until I could develop a way of delivering heat to the cabin. I live in So. Ca. and the mornings and evenings can get a little nippy especially when granddaughter rides along.

My first task was to fabricate a hose adapter that would take the inside diameter of the factory heat boot down to a size that I could connect a standard 60mm heater hose. The adapter was fabricated out of fiberglass.



I purchased a used factory heat duct that channels hot air from the engine cowling to the auxillary fan located above the engine. The duct was cut as indicated on the following diagram and hole drilled with a 2 1/8" diameter hole saw. The open top of the duct was capped with fiberglass. Before applying fiberglass the area was roughed with 80 grit sandpaper and cleaned with grease and wax remover.

[thorloki]

A 60mm od collar was fabricated and bonded to the duct housing. During fabrication the part was trial fitted and heater hose cut and rough fitted.



The part was cleaned with soapy water to remove all dirt and grime, then cleaned with grease and wax remover, sanded with 320 grit sand paper, cleaned again with grease and wax remover and primed and painted with 500 degree engine enamel.




The process took about 6 hours not including curing and drying time for fiberglass and paint. I installed part about 2 weeks ago and I have been enjoying cabin heat. It does not blow heat as if the original factory equipment was installed but enough to warm the cabin.




I can think of a modification to this design that might deliver more efficient heat. I am going to purchase another factory heat duct, modify the same and incorporate the modification and let you know the results. Stay tuned.

[tito911s]

How long does it take to get to comfortable heat on a "nippy" night?

[thorloki]

That is hard to gauge. I haven't been opening heat flappers until engine gets up to normal operating temperature. That time also depends on if I am driving on city streets or freeway. I live a couple of minutes from a freeway so once I am on the freeway engine reaches normal operating temperature quickly and I get heat a lot sooner than if I am on city streets.

[Josh D]

Originally Posted by thorloki

That is hard to gauge. I haven't been opening heat flappers until engine gets up to normal operating temperature. That time also depends on if I am driving on city streets or freeway. I live a couple of minutes from a freeway so once I am on the freeway engine reaches normal operating temperature quickly and I get heat a lot sooner than if I am on city streets.

Just an FYI, it's pushing heat from your exhaust manifolds, which start getting hot as soon as the engine is started, so no need to wait for the engine to get warmed up. On backdated heat configurations, a heated up cabin has more to do with fan speed than engine temperature.

[Jcslocum]

I did this 4 years ago but with all stock parts:





This is great if you don't have all of the bits and looks like it will work well for you.

[thorloki]

Looks great. I really like your curved duct. Where is that from if you don' t mind? And how did you connect pieces?

[Jcslocum]

It's the stock heater duct cut down to make the short curve.



The duct was always connected at the heater feed and I sealed it with a rubber strip where is went onto the fan duct.

[thorloki]

Nice clean install. I like it and may do same. How has heat delivery to cabin been?

[JackMan]

I have backdated heat on my 1989 911. On a cold morning, say 40 degrees F, I can bake bread in my passenger footwell after the engine has been running for five min. Back dated heat rocks.