Heater - Defrost

I am familiar with the early Porsche & VW heat/defrost set-up.

I am wondering if anybody has installed the small fans in the ducts to boost the velocity of the hot air. On a scale of 1 to 10 how necessary is such an add on? Does JPS, Vintage or Intermechanica install these fans? Are they standard equipment, optional or special request items? If optional, how much do they add to the cost of the build?

Bill,

I saw an article describing a auxillary heater "Add On Kit" in the latest issuee of "Hot VW's" and the kit included "Fans".

The kit was about $130.00, and I was considering it.

Let me know how it hoes-OK?

Good Luck,

Jack Blake

Jack...."How it Hoes"????????

IM's are built with a 3-speed booster fan mounted under the dash - they work well but are a bit noisy, especially on high speed. IM has a distribution box with a progressive control from heat only through heat/defrost to defrost only. Heater control is the normal cables to the heater boxes; fan is independent of the heater control.

How necessary they are will depend on where you live and how tight your heaterbox system is. I run in Dallas without them. On an occassional day they would be nice, but I get buy.

Do most state's "special construction" auto registration requirements include verification of working defrosters?

It seems I recall someone mentioning the safety checklist (brake lights, headlights, license lights, braking system, etc.) included a check of the windshild defrost system before a "special construction" registration would be issued.

I will add MTCW. I opted for beauty and performance when I built my exhaust and subbed the heater boxes for an electric heater. It is effective with the top UP. It does nothing with the top down. I have it installed on the tunnel right by my feet. I recall driving a friends Super Beatle to go skiing with the top down and the windows up. Stayed toasty.

"electric heater" can you post a pic ?

Bill: I thought you had already installed the necessary two or three-speed fans in your heater ducts, and (I assume) your defroster system also. Was I wrong? If I was correct, are the fans not up to snuff?

I have the fan with my new IM Speedster. The heat is controlled by a 356 knob-cable to oversized boxes. The defrost/heat defrost is switched under the dash and Works very well. The heat on an IM doesn't come up through a pan... (no pan) and there is a more efficient transfer of heat to the cockpit.

All of this works very well. I drove my IM during the break-in on some high roads around Vancouver, including areas of snow.... the heat worked so well, I found that I was actually turning the fan down/or off and the heat control knob down. Same thing when I went through Flagstaff AZ at 8,000'... snow and 31', I had more heat than I needed. The car seals up very tight, so when you get the interior warm, it stays that way with minimal fan and temp control. The defrost works great and I only switched it to pure defrost a few times because my feet were toasty.

Another 110% improvement in comfort, are my electric 2-stage seat heaters. They make the car seat warm in a matter of a minute... and keep your buns and back warm and are very nice on cool morning "top down" runs.

Heat, is not an issue with my IM.. it works, and it works great.

Well said Jim,

I would say that the heater/defroster works as well in my IM Roadster as the heater that I had in a first generation Miata.

Dan, you've got to be kidding. I've owned an 84Im...granted not forced fan. but I was running 1 5/8 inch heater boxes), and I now own a 1990 Mazda Miata (V8 powered), and there is NO comparison between the two cars....in that the Miata heater/defroster is FAR superior. I can't believe that the new IM multi speed fan makes THAT much of a difference. Maybe you were thinking of and pre 1970 MGB heating system, which would be on par with the newer IM system (I also owned a 1967 MGB).

Dan,

I'm with you the system in my IM is as good as the system in a 1991 Miata that I owned years ago.

Karl

Ron,

While some of the other dynamics of the Miata are unbeatable, the heater in my '90 always left me unimpressed. From what I have experienced in the comparison of my Vintage Speedster (pan and no fan), the heating system in my tube frame IM is not comparable in any way. With your Miata's powertrain, you probably have as much heat transfer throught the firewall as the heater core provides! LOL

You're right, Dan. The V8 puts heat into the car's interior even when I don't want it!

Ron O'B:

I had the same trouble in spades with my wife's Austin Healey 3000 - the Exhaust headers were right in front of the firewall, the collector under your feet and the exhaust pipe and muffler under your butt. The car was originally unbearable on even warm days.

Eventually, I followed all of the advice on Jim Werner's tech page on "Super-insulating your Healey" and it made a world of difference. Where before it was unbearable at outside temps over 70F, once super-insulated it was downright comfortable on 85 - 90 drgree (F) days cruising around pretty much anywhere - his ideas really work!!

If you're interested in some of his techniques for your Miata, you can look here:

hometown.aol.com/bgahc/myhomepage/tunes.html

Good luck!

Gordon

Thanks Gordon. The Miata isn't too bad.....and having air conditioning helps. Besides, once the top is down it doesn't matter.