starting SC heater backdate, but have a dumb question

[shamrok]

I was set on doing the cheap SC backdate, and after removing all old stuff, it looks like the elbow will hit the AC compressor (currently not installed).

So looking around, what exactly is the purpose of the air hose from the engine fan down to the heat exchangers? Is the cool air to the exhaust required, or could I get away with only routing the left side air to the left side exchanger to get some cabin heat?

What I'm talking about in pictures...what's the harm of just closing this hole with something like a rubber grommet


And keeping this hole open to the outside? It feels like there was a hose to this for another reason other than cabin heat, but I'm still learning this car and unsure.


Thanks!

[SkiVT]

Backdated Heat Tech Article

[timmy2]

Running A/C?
Pull the bracket and cut a clearance hole for the hose.
Only part of the rib will need to be removed. What remains is plenty strong enough.
Engine air blows out of that hose to the heat exchanger to be warmed up.

[shamrok]

Originally Posted by SkiVT

Backdated Heat Tech Article

Thanks, I'd seen that thread before and is a great reference. Still not entirely sure why we need to send air from the engine fan to the heat exchanger.

[shamrok]

Originally Posted by timmy2

Running A/C?
Pull the bracket and cut a clearance hole for the hose.
Only part of the rib will need to be removed. What remains is plenty strong enough.
Engine air blows out of that hose to the heat exchanger to be warmed up.

Plan is to run AC, but that's a work in progress. If possible, I'd like to only route from the existing left (driver) engine air outlet to the left exchanger (pic below), and not hook up the right (passenger) side heat exchanger at all.

[SkiVT]

The air from each HE goes to the 2 flappr boxes underneath by the rear wheels. Air travels from there to the cabin of the car. Use only the left side and I assume you will get roughly 50% airflow/heat. Leave the right side without hose shouldnt hurt anything but tou should have less heat in cabin.

[timmy2]

One side only, 1/2 the heat.

[pmax]

Originally Posted by shamrok

Thanks, I'd seen that thread before and is a great reference. Still not entirely sure why we need to send air from the engine fan to the heat exchanger.

You don't. I have the aux blower providing airflow on the driver side without diverting from the engine fan. Works well enough for me. The passenger side HE ducting is for passenger side heating. I routed engine fan airflow using the right side heat backdate plate for more heating as is needed on that side in my case.

Routing from the driver side duct to the passenger side means a hose over the fan or perhaps you can update to the Carrera under the engine heat ducting.

[RDM]

You have two red levers between the seats, one controls each heat exchanger's warm air to that side of the car. As long as you ride alone, your passenger will not complain about no heat on her (?) side of the car.

There may be some trickery that allows you to connect the 3.2 heater hose from one cool-air input to both heat exchangers, but I have no experience with that.

[shamrok]

Good stuff, had a local Euro mechanic telling me I was potentially damaging the motor by not sending that cooled air down to the heat exchangers, but my understanding was that they were just for cabin heat.