Why you should backdate your heat on a 3.2 - Page 3

carnutzzz · 06-20-2005, 09:17 AM

Ok- so let me re-ask this question.

By removing the blower, you are relying on the engine fan to push the hot air forward through the tubes and into cabin?

Might this suck in more exhaust gas? Maybe a dumb question.

I might do this and would buy the piece from Thom (would love to see a how-to" and only do the left side probably. Since I live in Atlanta and the car is garaged, I'm assuming I'll have enough heat for occasional winter use- correct?

JBO · 06-20-2005, 09:27 AM

If you only do the left side, what happens with the hose on the right that goes up over the fan to the blower (which would now be gone)?

ianc · 06-20-2005, 12:01 PM

Quote:

By removing the blower, you are relying on the engine fan to push the hot air forward through the tubes and into cabin?

Yes, that's it exactly. You might not notice the difference at speed, but one time you will notice it is stuck in a traffic jam in the rain (daily occurrence during winter in CA). Then, the idling engine will not be enough to defrost the windshield, so you'll need to carry a towel and constantly mop the windshield with it.

My A\C is long gone, but the fan stays.

ianc

mjmoran · mjmoran's Garage

carnutzzz and others.

TO answer your first question. NO. The exhaust gas is not part of the equation unless you have rusted out heat exchangers. If you do (and I doubt it on a Carrera) then you will need to replace them ASAP.

There is ample heat when getting rid of the engine fan in your Carrera -- when you keep the footwell blowers. An SC may feel a heat loss at idle as ianc mentiones. I live north of Spokane WA and have no issues with heat or defrost on brisk morning runs with the Targa top off.

widebody911 · widebody911's Garage

Quote:

Originally posted by JBO
If you only do the left side, what happens with the hose on the right that goes up over the fan to the blower (which would now be gone)?

You ditch the hose and either install an OEM or repro right-side duct.

bill3667 · 10-07-2005, 08:10 AM

Can we restart this thread since it's getting to be that time of year? I've been searching and found many threads with small tidbits of info but none of them have all the info I need to complete this.

I have an '88 3.2 Carrera. I have installed the Rennlight Fiberglass left-side 930 duct but I still don't have the hose/duct to connect to it. He has a link and mentions 2.5" heater hose but the link to Pelican's catalog has 7 possible hoses, I know 2.5" is apx. 6.3cm but which hose is correct to hook to the Fiberglass left-side 930 duct?

Also, was there ever a resolution to the resister needed to make the footwell blowers work after the engine compartment blower has been removed?

If there's another thread that has this info please let me know and I'll add it to all the other threads that seem to just die before a resolution is posted.

TIA,
Bill W.

450knotOffice · 450knotOffice's Garage

I second that. I'm interested in the same thing.

Sizzle · Sizzle's Garage

Newbie here -- so, the gist of this procedure is that the crankshaft-driven fan is completely adequate to divert a little air over the exchangers without some cheesy electric 'blower motor' clogging up the engine bay?

Jgordon · 10-07-2005, 08:40 AM

Consider me another interested party.

Also, how does this relate to backdating heat for SSIs? If you can simply go through the stock engine tin openings for this stuff, why couldn't you just use flexible tubing to hook up to the SSIs as well?

JeremyD · JeremyD's Garage

Quote:

Originally posted by Jgordon
Consider me another interested party.

Also, how does this relate to backdating heat for SSIs? If you can simply go through the stock engine tin openings for this stuff, why couldn't you just use flexible tubing to hook up to the SSIs as well?

You can.

JeremyD · JeremyD's Garage

Here's a picture of mine, unfortunately I do not have the heat hooked up yet because I have to adapt 3.2 cross tube to my 964 B & B exhaust... Probably have to come up with something custom

DW SD · 10-07-2005, 08:59 AM

On the 3.2L, I have SSi's and backdated the heat as well as simplified it to simply Defrost. I used Thom Fitzpatrick's FG parts as well as some tin work. (see picture) Came out very clean. I believe you'd be plenty warm in California or Florida at least with a similar system. To remove the air box upfront, you'd need to build a block off plate for the cowl inlet, which I'm going to do soon (so rain doesn't collect in the trunk).

I deleted my controls from the dash and the fan box, footwell mixing boxes, etc. This is a VERY clean solution. I just roll the windows down for vent fresh air and pull the heat levers which control the flapper for defrost / heat. With my SSi's, the defrost is obvious at idle. I think it would work fine in the worst San Diego Winter ;-) At speed it blazes from the defrost ports.

This setup should be easy to test for you and is easy to re-install the stock stuff later.

As far as actually doing the back date in the engine compartment...... When I back-dated the engine tins, I actually reused the Carrera ones on the side, but cut of about 3" to fit those pieces which allow the heater ducts to pass through (measure to be exact, but it is really straightforward - especially if the motor is out. Once I cut them, I had to drill holes to allow the add-on pass through tins to bolt together with my "new" backdated (chopped) Carrera tins. You really only need those pass through pieces + the FG ducting on the fan to back date. I fabricated a plate to cover the hole left by the AC compressor bracket and to cover the hole left by the old blower motor duct. The original pieces had nuts welded on the back side. I just just M6 with nyloc nuts on the back side. Welding the nuts on the backside seemed overkill and would melt the nylon anyways.

Just track down a Left and Right pass through ducting and you are golden. Hope that helps!!

Here are some photos which shed a bit of light.

ianc · 10-07-2005, 09:04 AM

Quote:

so, the gist of this procedure is that the crankshaft-driven fan is completely adequate to divert a little air over the exchangers without some cheesy electric 'blower motor' clogging up the engine bay?

Opinions seem divided on this. It may be perfectly adequate for Carreras that have footwell blowers, although there are problems with these as well. For SC's it's a different story. The engine fan will work fine when the car is at speed. Depending on where you live, this can be an issue. In CA, there are constant traffic jams, and at low speed or idle, the engine fan simply does not produce enough air to adequately defrost or heat. For me, replacing this fan made a huge difference in the effectiveness of my heat\defrost, and the rest of my heat ducting was in excellent shape already.

Try it both ways and see for yourself. Just unplug the connection from the fan and see if you can live with it for awhile.

ianc

KFC911 · 10-07-2005, 09:06 AM

Here's a related thread for you Carrera guys...hope this helps. BTW, even without ALL of the auxilary blowers (engine & footwell), my car still gets great heat. I might add that the A/C also works just as good setting in a box in my garage

Gratuitous pics of Carrera heater backdate...

klaucke · 10-07-2005, 09:11 AM

My '74 has "backdated" style heat stock, with early style heat exchangers (also stock for 74). No footwell blowers, etc, just the engine fan to push the air along. On the highway I need to keep the heat lever down, it'll burn me right out of the cabin. That heat cooks! But once you're down at idle, very little air is being pushed through, so if you need a lot of defrost at idle it may not be for you. Carrera footwell blowers can help.

However, one solution would be to put "inline" fans in the heater tubing. This is very common to VW bugs which have a very similar heat set-up. Fan kits are sold to help push air when the engine isn't turning quickly. If you added them to the heat tubes where they meet infront of the dash, it could likely help push some air through when idling.

DW SD · 10-07-2005, 09:16 AM

I think SSi's attribute to the quality of the heat, but also the direct routing of the ducting (see the above photos). There is a lot of primary header surface area inside the SSi heater boxes. I get hot air at idle coming from defrost. If you see the pictures, though, mine is a direct shot from the rocker tubes straight into the defrost. Maybe if you route through various diverters, mixing boxes etc the air flow is restricted enough to make it not work as well? Time will tell, but my judgement says this will work in the winter, at least in CA.

raceman · 10-07-2005, 09:17 AM

l had to backdate due to turbo conversion.Does anyone have the "Y" tube that allows the forced air from the fan shroud to "split" and feed both heat exchangers? l lost mine. Any help appreciated

DW SD · 10-07-2005, 09:19 AM

Quote:

Originally posted by raceman
l had to backdate due to turbo conversion.Does anyone have the "Y" tube that allows the forced air from the fan shroud to "split" and feed both heat exchangers? l lost mine. Any help appreciated

I was at a hotrod shop the other day. I saw something that would work. They sell aftermarket heat / AC and ventilation products for hotrods. It is probably ungodly expensive for what it is, but search on the internet and you will find. I think you could also look at aircraftspruce.com They have a lot of ducting solutions for small aircraft. I bet they have a Y connection.

Doug

bill3667 · 10-07-2005, 09:59 AM

I think we're getting scattered on this thread throwing in a bunch of non-stock exhausts which is causing confusion amongst the troups. I would be willing to copy/paste the relative comments into a NEW thread that is reserved for those of us that are trying to adapt to stock componants. This thread can then be left to al the other possable exhaust setups.

Does that suggestion work for you folks?

Bill W.

J Smith · 10-07-2005, 11:57 AM

Here's what I did:

I used the left side fiberglass piece from Thom, and kept the stock heat crossover tube (because I have yet to spring for SSI's).
The heater hoses are from Pelican (part # 902-211-921-20) available here. You will need two of them, because one won't make it. I took a trip to the Home Depot and found a piece of PVC that was close to the inner diameter of the heater hose. I cut about a 2" piece of the PVC and used some hose clamps to hold the two pieces of the hose together where they join. I know the clamps are cheesy, but they're doing the job for now.

The heater hose from Pelican fits perfectly inside the Carrera crossover piece. It's snug enough to keep it form coming out. I cut the piece of hose so that slides into the crossover piece about 3".

Now onto the footwell blowers. Another fella here found out that there is a black wire that goes to the footwell fan speed knob between the seats. If this wire has power, the blowers will run. The problem is they will run on low speed all the time, even when you're not using the heat.

Here's how I fixed that. There is a electrical contact made when the levers are pulled up to allow heat to flow into the cabin. It's easy to see the switch if you look at the lever assembly. All I did was cut the 2 wires that go the contact switch. I ran one to a switched 12+ volt source (with an inline fuse), and the other to the black wire going to the fan speed switch. Now the blowers will only work if the levers are pulled up.

So far it's working well, and there is cetainly plenty of heat. Hope this helps.