Electric hot air cab heater?

[SunburntLobster]

Hi, my 76 has a BITZ EFI conversion so it will need a heating system backdate or another means of heating the cabin.

Realistically I only need to demist the screen and take the edge off, the car is kept in a heated garage however it will go out on some cold mornings. Future plans will be to install a heated windshield however I need something in the meantime.

Rather than mess around trying to backdate the original system and hope it works my temporary plan would be to install one of these in the frunk and connect into the two dash ducts:

https://www.demon-tweeks.com/uk/demon-tweeks-12v-600w-ducted-electric-cab-heater-tsddech/

and blank off everything downstream to avoid wasting heat output ending up in the sill tubing.

Any thoughts?

Thanks!

[Jonny H]

To put 600W into context -

Equivalent of 12 small candles burning.

The classic Austin Mini heater (which is widely regarded as being crap) is about 2000W.

For a 911, you need at least 1600W of heat to do anything remotely useful if the outside temp is less that 10C.

You’ll need one of our alternators too. 600W is 50A at 12V. The max idle output of your alternator will be around 40A.

[SunburntLobster]

Thanks for putting 600W in to context! Sounds like it might not be useful and if my alternator can't support it then it is a dead end.

Reinstating the existing heating using backdated heating gear might be the better option.

Love your fusebox upgrades, watched Number 27 fit one to his 308 so deffo on the list for top 5 jobs-to-do when it lands (after I have stopped grinning like an idiot!)

[Jonny H]

^. We are looking at heating but it is a difficult nut to crack.

[Jonny042]

If you are only needing a slight de-misting, I think the demon tweeks unit (or something similar) might be worth a try.

Not that it will actually heat the cabin, but it would dry the air and probably be effective at clearing the window. And if it rains it should do the same.

I have heat in the Rot Rod and the only time it goes on is to clear the window.

[Bigtoe32067]

What about something like this
https://www.cabelas.com/shop/en/mr-heater-factory-reconditioned-portable-buddy-heater?GOOGLE&Google+Smart+Shopping+-+Catch+All&gclid=Cj0KCQjwvb75BRD1ARIsAP6LcqsBssKxD9GpPiM8ln1n h0VVGAq6qKVqSPtVVv4171FjvGwOHmz6jfAaArnpEALw_wcB&gclsrc=aw.ds

[Canada Kev]

Some more electric heater context or you: an electric hair dryer is about 1500 watts on high.

[Hi_Fi_Guy]

Adding a heated seat kit under the upholstery would seem a more realistic option at this point in time than full electric heat.

[Bli8]

Originally Posted by Jonny H

^. We are looking at heating but it is a difficult nut to crack.

Hope you can crack this nut Johnny as I'd like to get both an A/C and heater in a kit that can be controlled by one set of switches or be mounted where the existing sliders are. I'm doing a Tesla EV conversion on my car, thus can't use existing heaters or a/c.

[47silver]

If you have ac, you may be able to adapt it as a heat pump

[mikesarge]

Just do a heater backdate- it’s cheap, reliable, easy, and works better than some electric heater setup you’ll have to do custom work t build.

I have the heat backdated in my SC and drove it through late winter early spring including temps below 30F, never left wanting more heat.

[GH85Carrera]

Originally Posted by 47silver

If you have ac, you may be able to adapt it as a heat pump

That would be just about impossible or so complicated it would be cheaper to buy a factory heat exchanger setup new.

To make the evaporator blow heat would be a real trick.

[Jonny H]

Reverse cycle heat pump is something we’ve looked at in detail many times. The amount of pipe work, switch over valves and the control requirements would make for a very complex installation. It would be bulky, ugly and heavy.

Production cars that have this setup have a blower unit that houses both an evaporator AND a condenser along with an oversize external combined evaporator/condenser. There is simply not enough room in our tiny cars.

People read ‘reverse cycle heat pump’ and think that you simply run the pump ‘backwards’. This is nonsense. What actually happens is that the roles of the condenser and evaporator need to be swapped. Essentially extra hoses and valves that reverses the refrigerant cycle so that the evaporator ‘becomes’ a condenser and vice versa. Unfortunately, because evaporator and condenser are designed for their particular roles, operating the evaporator as a condenser is not efficient, hence why production cars have both in the blower unit.

[GH85Carrera]

Originally Posted by Jonny H

Reverse cycle heat pump is something we’ve looked at in detail many times. The amount of pipe work, switch over valves and the control requirements would make for a very complex installation. It would be bulky, ugly and heavy.

Production cars that have this setup have a blower unit that houses both an evaporator AND a condenser along with an oversize external combined evaporator/condenser. There is simply not enough room in our tiny cars.

People read ‘reverse cycle heat pump’ and think that you simply run the pump ‘backwards’. This is nonsense. What actually happens is that the roles of the condenser and evaporator need to be swapped. Essentially extra hoses and valves that reverses the refrigerant cycle so that the evaporator ‘becomes’ a condenser and vice versa. Unfortunately, because evaporator and condenser are designed for their particular roles, operating the evaporator as a condenser is not efficient, hence why production cars have both in the blower unit.

This. I was too lazy to type that out.

Personally, I drive my 911 in sometimes cold weather. Last year on a fall foliage tour to Arkansas the temps got down to 16 degrees F.




The car started right up, and within a few minutes the car interior was warm, windows defrosted and for the second time in 25 year of owning my car I had to use the outside rear-view mirrors defroster. The heater on a stock 85 911 is phenomenal, and after a mile of driving I had to turn it down because I was getting hot.

If the temps get to 0F the heater has to run wide open for a while to keep the passengers warm. I have had my car in the 118 degree heat in Needles, CA and I stayed cool but the AC was struggling but I never broke a sweat. So I have had my car in a range of Zero to 118F and it kept me comfortable.

[47silver]

First of all i was only making a suggestion and did not mean to imply that it would be an easy addition.

Even though it may be hard to believe, there are "people" who understand refrigeration in the world and even this "people" realized that it would take a clever engineer to develop an elegant solution and that it would require larger coils, additional valving, controls and piping. I assume that the "un-people" of the world know it all so i will defer to them from now on.

[GH85Carrera]

Originally Posted by 47silver

First of all i was only making a suggestion and did not mean to imply that it would be an easy addition.

Even though it may be hard to believe, there are "people" who understand refrigeration in the world and even this "people" realized that it would take a clever engineer to develop an elegant solution and that it would require larger coils, additional valving, controls and piping. I assume that the "un-people" of the world know it all so i will defer to them from now on.

No doubt it might be possible to do it, but not really practical. I have replaced every component of my AC system front to back except the front condenser and the condenser over the engine. The space is just limited and tight, I have been in there, and only by using more trunk space, or leg room there is space to fit the new components. There is just no practical way to make it fit. It would be far simpler to use some other method to produce heat.

The factory figured out a fantastic heater. It makes gobs of heat, very quickly.

[Jonny H]

Originally Posted by 47silver

First of all i was only making a suggestion and did not mean to imply that it would be an easy addition.

Even though it may be hard to believe, there are "people" who understand refrigeration in the world and even this "people" realized that it would take a clever engineer to develop an elegant solution and that it would require larger coils, additional valving, controls and piping. I assume that the "un-people" of the world know it all so i will defer to them from now on.

Hey, wasn’t trying to be a smart arse but if I had a $ for every time I’ve been told that you ‘just’ run the pump backwards....

[drewr]

Originally Posted by SunburntLobster

Hi, my 76 has a BITZ EFI conversion so it will need a heating system backdate or another means of heating the cabin.

Thanks!

Not to hijack the thread, but how do you like that BITZ EFI? Are you in CA?

[tdw28210]

You could go diesel. variation on the Eberspacher petrol models form the '60's. Still used in boats and buses to this day.

https://www.amazon.com/Tseipoaoi-Thermostat-Silencer-Campervans-Motorhomes/dp/B07VT24CLK/ref=sr_1_2?dchild=1&keywords=Diesel+Fuel+Heater&qid=1597452301&sr=8-2

[porsche930dude]

do the backdate if you still have the heat exchangers. I only run one hose on the driver side and its plenty for new york winters