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ldj1002 Thu Nov 03, 2016 6:25 am

I would think this is a bad idea. For you pilots you know how carb. heat kills engine performance. There are many cases where a pilot trying to make a go around and didn't clear obstacles at end or runway because he forgot to turn carb, heat off, the airplane simply wouldn't climb. You also note how many rpm you lose when you apply carb. heat on run up.. Well with this heat going to our VW you have to apply more power to get the same rpm in order to get your desired speed. This should be making the engine run hotter by working it harder. Tell me why I am wrong that putting hot air in the intake is bad.

vwwestyman Thu Nov 03, 2016 7:05 am

I think the heat is supposed to be thermostatically controlled if everything is working properly.

I think the biggest reason for heat is to help keep the fuel atomized. With the long intake runners, and no heat, you'd experience icing of the intake and the fuel will not stay atomized. That, in my opinion, significantly outweighs any loss of power due to hotter air.

I know it reduces driveability. My '73 Bus came with a center-mounted carb on it's Type 4 motor. VW never intended for this, and therefore never provided any form of heat for the carb(s) in that way. That motor originally came with dual carbs with short runners, so they only needed a little heat. (The dual carb setup did have a preheat provision.)

In the Bus forums, it is pretty well known that the center mount carbs are problematic at best, and heat must somehow be introduced if you want any kind of driveablity outside of summer temperatures.

I eventually installed fuel injection.

ldj1002 Thu Nov 03, 2016 7:37 pm

you said
I think the biggest reason for heat is to help keep the fuel atomized. With the long intake runners, and no heat, you'd experience icing of the intake and the fuel will not stay atomized.


I thought those tubes from the exhaust that run up and beside the intake manifold was to take care of carb. icing. With that and the hot air being put directly into the carb. you are getting a double dose of heat.

gblair Fri Nov 04, 2016 4:01 am

The tubes under the carb from the exhaust is to help atomize the fuel after it goes through the carb. The one going to the air cleaner is to keep the carb from icing. There is a thermostatic vac pot in the air cleaner that should regulate the flap letting the correct temperature of air into the carb. I have seen a carb ice up (not on a thing) and stall the car out in cold weather first hand when i was younger and knew more than the engineers that designed the cars. I always use them when the vehicle is designed for them.

vwwestyman Fri Nov 04, 2016 5:45 am

ldj1002 wrote: you said
I think the biggest reason for heat is to help keep the fuel atomized. With the long intake runners, and no heat, you'd experience icing of the intake and the fuel will not stay atomized.


I thought those tubes from the exhaust that run up and beside the intake manifold was to take care of carb. icing. With that and the hot air being put directly into the carb. you are getting a double dose of heat.

True. The subject was asking about air to the filter, but the post was a little more generic about heating intake air in general so I guess was keeping both parts of the system in mind with my post. Though I only briefly mentioned the thermostatic valve for the carb heat.

You gotta keep the carb warm to fight carb icing, and then keep the runners warm to keep the fuel vaporized. Carbs will ice up, because you are pulling a gas through a smaller opening. Its just like how air conditioning works. Or how your small propane tank will ice up on the outside when running a grill. (Big ones do it too, but there is enough volume it isn't usually noticeable unless using a high-consuming item.)

Its all a system that works together.

Wildthings Fri Nov 04, 2016 7:06 am

I found with a fully stock engine that without the preheated intake air system working that gas mileage dropped by 10-20%. I have added air preheats to all my old rigs over the years at it greatly improve cold running/warm up.

Since the system is thermostatically controlled I see no negatives at all to having it. The VW system is a two stage system which depends on not only heat but manifold vacuum. The cold stage will hold the flap closed at all throttle positions, while the second stage will allow the flap to be closed at idle and part throttle but allow it to open at full throttle.

As far as engine life, anything that allows the engine to run smoother when cold and lets you adjust the choke to open sooner is going to mean less gasoline, water, and acids in your oil.

ldj1002 Fri Nov 04, 2016 5:28 pm

Wildthings wrote: I found with a fully stock engine that without the preheated intake air system working that gas mileage dropped by 10-20%. I have added air preheats to all my old rigs over the years at it greatly improve cold running/warm up.

Since the system is thermostatically controlled I see no negatives at all to having it. The VW system is a two stage system which depends on not only heat but manifold vacuum. The cold stage will hold the flap closed at all throttle positions, while the second stage will allow the flap to be closed at idle and part throttle but allow it to open at full throttle.

As far as engine life, anything that allows the engine to run smoother when cold and lets you adjust the choke to open sooner is going to mean less gasoline, water, and acids in your oil.

OK I'm gone fix mine factory. On the air filter does it make any difference where the vac. goes and leaves going to the vac. can

Wildthings Fri Nov 04, 2016 6:30 pm

ldj1002 wrote: Wildthings wrote: I found with a fully stock engine that without the preheated intake air system working that gas mileage dropped by 10-20%. I have added air preheats to all my old rigs over the years at it greatly improve cold running/warm up.

Since the system is thermostatically controlled I see no negatives at all to having it. The VW system is a two stage system which depends on not only heat but manifold vacuum. The cold stage will hold the flap closed at all throttle positions, while the second stage will allow the flap to be closed at idle and part throttle but allow it to open at full throttle.

As far as engine life, anything that allows the engine to run smoother when cold and lets you adjust the choke to open sooner is going to mean less gasoline, water, and acids in your oil.

OK I'm gone fix mine factory. On the air filter does it make any difference where the vac. goes and leaves going to the vac. can



The thermostatic valve has two fitting and yes it matters which way the hoses are hooked up. One fitting is brass and the other is plastic, but right off I don't know which one hooks where. The valve may be all gummed up inside and need a good soak in solvent and/or getting a goodly squirt of carb cleaner.

Windisch Thu Jan 12, 2017 3:58 pm

Wildthings: Did you ever determine which hose goes to which of those two fittings (one brass, the other plastic) on the air cleaner? I've seen pictures showing them hooked up both ways, but nowhere does anyone seem to discuss which is the CORRECT hookup for the hose coming from the manifold and which hookup is correct for the hose going to the cleaner's hot/cold air flap. Most confusing, since if, as you say, which way they are hooked up CAN make a difference, it would be great to put his controversy to rest once and for all! Thanks.

74 Thing Thu Jan 12, 2017 4:58 pm

http://kubeltreffen181.com/gallery/a-near-perfect-74-thing-2/

There are plenty of photos of orig VW Things on the Dominic Brothers sites.

Wildthings Thu Jan 12, 2017 7:06 pm

Windisch wrote: Wildthings: Did you ever determine which hose goes to which of those two fittings (one brass, the other plastic) on the air cleaner? I've seen pictures showing them hooked up both ways, but nowhere does anyone seem to discuss which is the CORRECT hookup for the hose coming from the manifold and which hookup is correct for the hose going to the cleaner's hot/cold air flap. Most confusing, since if, as you say, which way they are hooked up CAN make a difference, it would be great to put his controversy to rest once and for all! Thanks.

Plastic toward the manifold and brass toward the dashpot on the intake. When cold if you suck on the hose that goes to the manifold the flapper should close and stay closed even once you quit sucking on the hose.

Windisch Thu Jan 12, 2017 11:13 pm

Excellent! That also confirms what I spotted on pages 43 & 45 of the VW '73 Thing Owner's Manual (Operation & Maintenance), which shows the connections conforming to exactly that pattern (1-3, 2-4). Much appreciate that help! Cheers! =D>

citroen Sat Jan 14, 2017 7:58 am

74 Thing wrote: http://kubeltreffen181.com/gallery/a-near-perfect-74-thing-2/

There are plenty of photos of orig VW Things on the Dominic Brothers sites. and yes there are many pictures of the engine setup on our site http://kubeltreffen181.com from the Domeck brothers

Windisch Sat Jan 14, 2017 10:49 am

Thanks for that reminder of your 'Treffen' site. I've been there before and true...lots of great images showing 'Things the way they needz ta be'....Vielen Dank! =D>

BJT Sat Aug 10, 2019 7:13 pm

Just curious if there is a way to test the thermostatic valve? Other than wait for cold weather. And how does the Thing’s air cleaner decide what is “cold” weather?

Al Capulco Sat Aug 10, 2019 10:20 pm

Cold weather really has nothing to do with it. It purpose to to warm the motor up faster by inducing warm air into the air cleaner instead of cold air . The thermostat controls the flap. Easy to test, before starting the engine, see if the flap is up in the opening of the air cleaner not allowing outside air into the air cleaner. As the motor warms up the flap will move to close the opening on the bottom (heated air) and allow outside air to carburetor. Good luck!

BJT Sun Aug 11, 2019 4:25 am

Well, mine is never up to allow the warmed air in, thought maybe the ambient air temp was too warm or something. I wouldn’t say it moves “freely” either, unlike the other intake flap, the weighted one.

Is there a spring or something that holds it open? Mine takes a good couple of pounds of finger pressure to push it up. The PO has removed the warm air intake pipe and elbow, along with the vacuum hose from the intake, just trying to put it all back together.

BJT Sun Aug 11, 2019 6:04 pm

Took it apart a bit, and got a better look, the flap is definitely closed, and after pushing on it, it would take a pretty strong vacuum to suck up the bladder type thing in the vacuum canister. Seeing as how my vacuum hose is hooked up to my carb and not the intake, I’m not sure if there is enough vacuum to pull it open.

Wildthings Tue Aug 13, 2019 9:01 am

The vacuum can should hold vacuum when you suck on a hose hooked to it, zero leakage. You could tee a vacuum gauge into the hose and tell us at what level of vacuum the valve operates.

Al Capulco Tue Aug 13, 2019 10:37 am

The vacuum ports on the carburetor are all different for different reasons, none are for that air cleaner flap. Use the one on the intake manifold and just reduce it or get the right manifold.



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