So today I've been experimenting with boosting the air velocity on the heater. I'm sure I'm not the first person who has done this. There is all kinds of different fans people have rigged up on air cooled VWs. The actual heat coming from the floor vent/defroster is not that bad, it's the air velocity that "blows". The heater system is actually quite clever involving three heat sources. My main complaint is at idle there is very little air flow. It can take 10 minutes to defog the windshield in the morning. I've tried all kinds of those defogging wipes used on glasses. None of them seem to work. If I come to a stop, I can feel this sudden temperature drop in temperature on floor mode within the cabin. So I decided to mount this 4.0X10" blower fan in place of the elbow. I used the pieces below which involves a 3.25" to 4" straight transition coupler, a 3.25" to 4" 90 elbow and a 3.25" straight coupling. Not photoed is the 3" exhaust pipe. One end is 3" ID, the other end 3" OD so I used a short piece of piece of 3" silicone hose as a spacer to make up the difference at the firewall end. Using these silicone fittings reminds me of my turbocharging days! This is all this stuff mounted on the car. If this system proved successful, I was going to paint the blower and pipe black, remove the stickers, trim off the excess metal on the hose clamps and shave off the "feet" for a cleaner look. I had to delete the hose coming off the exhaust manifold going into the baffle. I was going to test to see which hose was "hotter", the one coming off the engine shroud or the exhaust manifold. But didn't get that far. This pipe had "Made in Canada" stamped on it but the sticker says "Made in Mexico"! HAH! So how did this setup work? The upside was the inside of the car did feel warmer. I was wearing my heavy coat at the time and could have removed it and still been quite warm riding around on a 40F cloudy day. Seems like without the blower, wearing a coat was a must. The downside was the heater is now noisy as hell! The fan itself is not the problem. It sounds like all the engine noise is being dumped into the cabin. I did not realize how well that baffle/elbow muffled the noise. My ears are still ringing! I also rigged up one of those outside temperature things with the probe mounted in the defroster vent. It was around 40F today and the heat coming from the defogger vent was around 135F on the highway doing 55 mph. I noticed at idle after making a hard run, the temperature rose to around 145F. Seems like with the hose that feeds into the heat exchanger from the engine shroud removed, there was a 15F difference in temperature. Deleting the hose did not make any difference in noise. So it seems all the noise generated is coming from within side the heat exchanger. So my next attempt was to mount a 3" fan after the baffle. I actually tried this fan once before but removed it. It didn't seem like it helped much with the car moving. But this time I could actually tell a difference in how much air it moved at idle. Now here is the deal. The 4" blower fan should fit in place of the short hose. All I need is another 3.25" to 4" transition coupling. The thing is, would using a larger fan make any difference in air flow? Because I'd still have to go back to a 3.25" inlet going into the diverter. So I don't know if that would act as a restrictor or not. One other thing I noticed is, when the baffle is firmly seated on the heat exchanger, the short hose does not quite line up. So the baffle/elbow has to be adjusted at the heat exchanger. I would imagine if it's not firmly seated and the clamp is not tight, some air leakage could occur. I have had the exhaust system off this car so I don't know if it's possible that I got the heat exchanger out of alignment when I reconnected it to the exhaust manifold or not (if that's even possible).