Half Heater Backdating

[Guardsred911]

Anyone done a "half" heater-backdate? I am in Washington State, with a good need for a strong heater for defrost. What I hear is that a full backdate ends up keeping the defrost from working well. I thought that if I eliminated the passenger side tube that comes from the manifold, blocked it off with the correct tin under the AC compressor, but kept the left tube to the blower, it would clean up the engine compartment, but also give me some defrost functionality. Obviously, I would need to block off the respective inlet at the blower motor.




Example in the picture of where I tore off the paper tubing. Thinking of leaving that permantly off. anyone done that?

J

[Elombard]

Daily driver?

Consider doing the full backdate, I think you will find the only time your defrost is week is when you sit at idle for long periods. Lots of air is still moving through their. I am trying to think, on an SC you can back date and then if its a problem reverse it pretty easily.

[timmy2]

My defrost works fine with a full backdate. I get strong heat and defrost within 2 minutes of driving and have to turn it down to almost off after 5 minutes driving my suburban route to the main arteries going to work.
The key is knowing how your blower control panel works and your flapper boxes are fully closing.
You won't get any air through the passenger side Heat exchanger with the method you are suggesting.
You will lose 1/2 of your heat.

[Craig_D]

My backdate was done with the addition of SSI headers. The heat that comes into the cabin, from engine fan only, is very hot and is very effective for defrost. It's only when you're at idle that the flow slows down, but once you're moving, the air flow is very good.

- Craig_D

[will hung]

It's a bad idea. You need air flow through both heat exchangers at all times. Otherwise you'll have heat concentration areas under your car resulting in engine issues. Even when you're heat is turned off, the flapper boxes at your frame rails open and allow air to pass through the heat exchangers but escape before it enters your cabin, allowing a cooling effect for the engine.

When I still had the stock exhaust on my SC, I backdated my heat and had no issues with the defrosters.

[porsche930dude]

i only have the driver side hooked up. i dont even have the engine bay electic blower in there. the tube runs right from the shroud down to the heat exchanger. Works good enough for me. Takes the chill out. If you want more heat just rev it up but like they said. you dont get heat or anything on the passenger side and no air movement through the heat exchanger. I have both ends open and there are lots of holes so im not too woried about it getting really hot on that side. Im not sure how effective the defrost is . I always just crack the window open if it starts fogging up. if you put a Y pipe underneth the car to get air to both exchangers that might work

[redstrosekNic]

Just do the full backdate. It is quite easy, and you can make/get everything you need quite cheaply. My backdate cost me a total of around $20.


For the driver's side, simply have an exhaust shop make a reducer to go from the output on the driver's side to the hose that connects to the heat exchanger. For the passenger side, do this...




No complains about the heat. It cooks me! I'm happy to answer any questions you might have

[Guardsred911]

nice picts. thanks all! I will take a think about where I want to take it from here.... good to know that the back date doesn't kill the defrost

[spuggy]

WA? With stock H/E's, you should be just fine, even in the mountains. My 930 has no motor compartment blower, and the tub doesn't have footwell blowers - with factory H/E's, the windshield would be literally steaming within a couple of minutes with ice on the ground.

Now I have aftermarket headers with much less effective H/Es (why are *all* the guys building/designing these in hot climates like AZ?) - for defrost I use a plastic scraper, and have found the squirrel cage to be the most effective for demist.

[Guardsred911]

Sounds like there can be some issues with fitting the tin under the AC compressor.. how have people dealt with that? (aside from removing the compressor! )

[timmy2]

I removed the compressor and bracket and then had part of the bracket cut out with a plasma cutter. Just enough for the hose to pass underneath.

[F.G.]

not using the engine compartment blower? I need one, willing to part with it? (if it works obviously) also if air always needs to be flowing through there then why do people install block off plates?