back date heater question

[krshome]

Sorry if this has been ask, I did a search and found nothing. I'm in the process of removing my A/C and have seen people talk about heat back-dating. Is this the removal of the rear heater fan and housing in the engine compartment? If yes can this be done on a 88? Would I still have heat? Is there a link on how to do this? Once again sorry if this is old hat I'm green to all this and learning through you all.

[Tidybuoy]

Backdating is done when you want to clean up the look of the engine compartment or remove items that are not needed for racing, etc..

In the case of backdating heat - people are referring to backdating to the '74 style where there is no auxiliary fan motor for forced hot air. I have a '74 and so it's the backdate style. The heat works fine but it is not pumped in as much as in a later car. It still gets hot enough to burn your toes. I think the only downfall would be if you lived in snow country and might have to wait a little longer for the windows to defog.

To backdate your car, you will have to get certain engine tin parts that block off your current areas where the electric fan blows the air. There are also engine tin parts that duct the air from the engine fan to the heat exchangers.

[krshome]

Originally Posted by Tidybuoy

Backdating is done when you want to clean up the look of the engine compartment or remove items that are not needed for racing, etc..

In the case of backdating heat - people are referring to backdating to the '74 style where there is no auxiliary fan motor for forced hot air. I have a '74 and so it's the backdate style. The heat works fine but it is not pumped in as much as in a later car. It still gets hot enough to burn your toes. I think the only downfall would be if you lived in snow country and might have to wait a little longer for the windows to defog.

To backdate your car, you will have to get certain engine tin parts that block off your current areas where the electric fan blows the air. There are also engine tin parts that duct the air from the engine fan to the heat exchangers.

I like! Sound easy. So just remove fan and housing and close off holes? Are the engine tin parts something I have to makes or buy.

[redstrosekNic]

I ended up making my pieces.

Quick heater back-date quesiton...

It wasn't too bad.

Good luck!

[911pcars]

A more accurate heat system backdate would use close-to-identical sheet metal pieces as in early 911s and factory heat exchangers, SSIs or equivalent. The following photo is mostly 3.2 sheet metal surrounds with some early 911 pieces for my 3.2.

The main differences include early sheet metal and hose pieces on the driver's side (almost a mirror image of the pieces on the right side) and the early metal piece across the rear (without a large duct hole as in SCs and Carreras).

Disregard the rear engine and muffler mount. This was a photo for subsequent powder coating.



From the top side, the engine compartment will have the same appearance of an early 911; non-cluttered and open for easier maintenance and access. The underside may appear different depending on your exhaust system (early, later-style exhaust system or aftermarket).

Sherwood

[krshome]

So are these the pieces needed from our host? Any thing else i need?
930-106-321-01-PH Left Side Heater Duct, 911 (1965-74) (1975-89 for backdated heater) NOTE: Many customers report that this part must be modified near mounting screws to achieve proper fit. $94.95

911-106-322-01-PH Right Side Heater Duct, 911 (1965-74) (1975-89 for backdated heater) NOTE: Will require modification for cars with air conditioning $89.95

[911pcars]

Originally Posted by krshome

So are these the pieces needed from our host? Any thing else i need?
930-106-321-01-PH Left Side Heater Duct, 911 (1965-74) (1975-89 for backdated heater) NOTE: Many customers report that this part must be modified near mounting screws to achieve proper fit. $94.95

911-106-322-01-PH Right Side Heater Duct, 911 (1965-74) (1975-89 for backdated heater) NOTE: Will require modification for cars with air conditioning $89.95

My part number memory isn't too sharp. Can you attach those numbers to the relevant parts?

As a starter:
Left side: the long piece under the left side intake valve cover (create hole for O2 sensor harness)
Left side: The square sheet metal piece with the duct opening (~2.5"). attached to the above
Back: The long sheet metal piece across the rear of the engine
Right side: The air duct on the right side attached to the main air shroud

Hope this helps,
Sherwood

[nickyclyde]

And maybe put levers in the cabin and lose the knob?

[911pcars]

Aren't there cabin blower motors in the floor to encourage air flow? Is the ugly, engine-mounted blower motor necessary?

And why are there so many blower motors in a Carrera? Other than the main engine cooling fan, early 911s had none which I admit is marginal in inclement weather, but three?

If you live in a moderate climate, I think the car can do with one less.

Sherwood

[krshome]

Thanks guys I got it figured out I need a 930 left side heat duct, hoses and then to make the foot blowers work I need to do the jumper on the relay. WOW my eyeballs are killing me form reading all the threads on this.

[Tidybuoy]

Originally Posted by 911pcars

And why are there so many blower motors in a Carrera? Other than the main engine cooling fan, early 911s had none which I admit is marginal in inclement weather, but three?

If you live in a moderate climate, I think the car can do with one less.

Sherwood

My '74's heat works perfect. The only issue is that it takes a little while to defrost the windshield on a rainy day due to low airflow volume (also possibly due to no a/c to dry the air).

I suspect that Porsche added the additional blowers to combat the above and because the 911 was becoming more luxurious in the later years.

One more thing to think about....I occasionally will have an oil smell in the cabin if my car leaks a little or the engine is not spotless. I believe that the later electric fan powered systems eliminate this problem as the air is fresh and not passed over the engine to feed the heat exchangers. Just one more reason I keep the engine clean.

[KFC911]

Originally Posted by krshome

Thanks guys I got it figured out I need a 930 left side heat duct, hoses and then to make the foot blowers work I need to do the jumper on the relay. WOW my eyeballs are killing me form reading all the threads on this.

Great...sounds as if you found the Carrera specific threads. I would suggest removing the blowers in the foot wells also (as they impede air flow) and not worrying about the relay either. My car will still "roast" ya and I don't need 'em

[911pcars]

Originally Posted by Tidybuoy

My '74's heat works perfect. The only issue is that it takes a little while to defrost the windshield on a rainy day due to low airflow volume (also possibly due to no a/c to dry the air).

I suspect that Porsche added the additional blowers to combat the above and because the 911 was becoming more luxurious in the later years.

One more thing to think about....I occasionally will have an oil smell in the cabin if my car leaks a little or the engine is not spotless. I believe that the later electric fan powered systems eliminate this problem as the air is fresh and not passed over the engine to feed the heat exchangers. Just one more reason I keep the engine clean.

Vern,
Yes, fresh air to the cabin interior has a different source than heated air. It's been that way for the air cooled engines for quite awhile.

Sherwood

[will hung]

I think some folks are getting it wrong. The point of the auxiliary blower is that it assists the traditional heating system. The old system used the cooling fan to drive the heat out of the heat exchangers. It worked fine, but at low engine speeds didn't move as much air. The auxiliary fan helped move air when the car is setting at or near idle speed.

If one needs to have a heater to defrost the windows, but lives in an area where ambient temperatures can get quite hot, it might be a good idea to keep the auxiliary fan and wire it to turn on when the heat is not on so that you can move more air out of the heat exchangers on hot days to help keep engine temperatures down.

As far as parts go, you might want to consider getting this duct for the driver's side.
Pelican Parts - Product Information: 930-106-321-02-OEM

It will have no issues fitting behind the distributor. I have the duct you bought, and it didn't take much hitting with a hammer to shape to clear the distributor. It's just nerve racking to hammer away at a brand new Porsche part.

[KFC911]

Will, your point about low rpms, etc. are valid, but have never been an issue with my "toy" as I don't sit at idle very often. I've had mine this way for years (before the relay solution, etc. was worked out), and I have no regrets whatsoever. The "best" (imo) Carrera solution is using the 930 hot air duct...no mods required. Here's an old thread from the archives....

Gratuitous pics of Carrera heater backdate...

ps: My Carrera runs "cool"...even on the hottest of summer days...no auxiliary fan needed for that either.

[Hellraiser]

I did it last week:

SC Heater backdate part question

[will hung]

Oh, I backdated my 911's heat about 2 weeks after I bought it. One of the best mods I ever made. I was just stating the reason for it and why it might be a bad idea to remove. In fact, I backdated it with my stock exhaust and after reading so many horror stories about not being able to defrost windshields, the first time I got into it after it was parked outside on a cold fall night, it had a totally frosted over windshield and to my surprise, I had no issues with the windshield not defrosting immediately. I mean, literally, a couple seconds after starting my car and turning on the defrosters, my windshield was clear.

[NYNick]

When backdating/removing the engine blower on an '89, what must be done to the wiring or relay to insure the footwell blowers work correctly?

Mine was done by the PO and is messed up.

Nick

[krshome]

Hey nick here you go! Carrera - Removing Engine Compartment Heater Blower

[911pcars]

Seems like Porsche's cabin heating system was either anemic (early 911) or over-engineered (Carrera).

A simpler system of inline duct blowers can reduce the complexity and weight of the current (Carrera) pieces. BTW, anybody have a total weight for all the factory pieces: two footwell blowers, one engine-mount blower, air splitter and related ducts and associated hardware?

Maybe something like this inline blower mounted in the ducting between the heat exchanger outlet and the cabin ducts. Robust enough for harsh winters? Good enough for mild climates?


Inline Fan / Blower 2.5 - £33.33 : T7Design.co.uk, Lightweight Kit Car Heaters

The motor assembly would have to:

- Operate in a hot atmosphere, ~150ºF
- Produce enough air volume (cfm) to include a multi-speed switch for more control. Typical bilge blowers are more powerful but larger.
- Provide adequate shielding from road debris

This seems to be a computer-type fan with a couple of reducer cones attached to adapt to the duct hose.

Some potential drawbacks: Volume - 87 cfm. Enough? Location: The factory cable-controlled diverter valve (or equivalent) should be in front of this unit - hot air from the heat exchangers needs an open path to atmosphere when heat is OFF.

Sherwood