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Hot weather restart idea
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Wildthings
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PostPosted: Fri Sep 16, 2016 4:02 pm    Post subject: Hot weather restart idea Reply with quote

Our present alcohol laced fuel has been giving me hot restart problems for years at this point and I have been looking for a solution. Other VW owners have had had good luck with bypassing a tiny bit of fuel back to the tank so that no pressure exists at the carb inlet after shutdown. I decided to just try and cool the carb and intake and rigged up this system which I have had in operation on my Thing for about 3 week now, but haven't seen any really hot weather. I just powered a thermostatic switch off of the B+ on the factory test plug and then feed a computer fan with it. The fan is mounted in a hole in the engine access door behind the license plate. This system seems to be effective as the engine has hot restarted nice and quick ever since I installed it, but as I said the weather hasn't been that hot.

The one down side I see is that the thermoswitch needs to be set to maybe 5°C above the daily maximum ambient temperature to get the fan to kick on and off at the ideal times, but of course the maximum ambient temp varies from day to day over the warmer months so reprogramming the thermoswitch a couple of times seasonally will be necessary. Only takes seconds to reprogram though.



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Joe 20
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PostPosted: Fri Sep 16, 2016 7:54 pm    Post subject: Re: Hot weather restart idea Reply with quote

Seems like a nice idea. Do you think it would drain your battery much? Maybe I just don't understand. It is running while your car is parked to bring the engine "box" temp down, right?
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Wildthings
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PostPosted: Fri Sep 16, 2016 8:33 pm    Post subject: Re: Hot weather restart idea Reply with quote

Joe 20 wrote:
Seems like a nice idea. Do you think it would drain your battery much? Maybe I just don't understand. It is running while your car is parked to bring the engine "box" temp down, right?


The fan is less than 2 Watts so it isn't going to put much of a drain on the battery. I don't know what the ghost draw of the thermoswitch is, but I figure that so long as the car is a daily driver during the summer that little bit of draw shouldn't hurt much.

The fan blows against the carb, manifold, fuel line, and fuel pump to keep them from heat soaking after a hot shutdown thus preventing the fuel from boiling and causing poor hot start conditions.
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doublecanister
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PostPosted: Sat Sep 17, 2016 9:12 am    Post subject: Re: Hot weather restart idea Reply with quote

hey Wildthings,

that is a interesting idea, I too pondered that a bit ago, while trying to make a redneck ac for the thing with a cooler and ice and a bilge pump fan in a tube (for hose attachment) which kept the Thing about 1 degree below sweltering,
I wondered if it would do the same thing but with more ummph as far as making a carb cooler.



using the bilge pump fan and some aluminum dryer vent hose I thought to pull air in from the engine bay vents and blow it on the carb, i'd just run the fan a few minutes before restart to see if it did anything, but a thermostat was a neat idea too.
but I've not tried an install yet...

the other note I read on that was the carb pre-heat tubes could be over heating and may need new washers with smaller holes, Rob and Dave's vw page mentioned those pre-heaters shouldn't be finger burning hot if they were it could cause a hot start issue.
but again, I've not pulled the exhaust and tried washer replacement with smaller holes.

still your idea could help. I'll post if I get time to try this crazy bilge pump dryer hose thing.
also thought of it being a ram air type deal for the vw or my truck but again, not sure how i'd get it to the carb...

let us know how it goes!

R & D at it's best! LOL

T
https://www.amazon.com/Attwood-Blower-Resist-White...lge+blower
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Wildthings
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PostPosted: Sat Sep 17, 2016 9:43 am    Post subject: Re: Hot weather restart idea Reply with quote

I had actually bought a carb cooling fan off a Toyota Land Cruiser to do something similar to what you are thinking of but had never installed it and eventually decided to try the low Wattage computer fan instead.

My thought is that you want to keep any fuel in the engine compartment cool after shutdown so it will not percolate. At shutdown the carb itself is pretty cool <100°F, but surrounded by much hotter items, particularly the intake manifold so the carb will get hotter for the first twenty or so minutes after the engine is shut off maybe reaching 150°F or so. My desire is to keep the carb from ever getting much hotter than ambient after a hot shutdown. Right now with the sensor for the thermocouple mounted on the fan shroud right in front of and above the carb it will read 250°F about 5 minutes after shut down on a 85°F day and the intake manifold is much hotter still. My goal would be to keep the fuel in the float bowl and lines no more than 15°F above ambient or around 100°F on a 85°F day by keeping the fuel system surrounded by a light flow of ambient air.

I too have wanted to try the gasket with a smaller hole, especially since I presently have a Bug muffler so am probably getting more flow through the preheat tubes than a Thing exhaust would give. I have also thought about trying to build some kind of valve into the manifold heat tubes so that I could tune the exhaust flow through them somehow, after all most American rigs of the era had a heat riser valve that automatically reduced the flow of hot exhaust as the engine warmed.
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Joe 20
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PostPosted: Sun Sep 18, 2016 7:36 pm    Post subject: Re: Hot weather restart idea Reply with quote

Thank you Wildthings. It is a very good idea. Very Happy
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vwwestyman
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PostPosted: Tue Sep 20, 2016 9:05 am    Post subject: Re: Hot weather restart idea Reply with quote

I wonder about just idling for a few minutes after arriving, before shutting down would allow the whole engine compartment to cool off enough to not heat soak the carb and gas lines?
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mondshine
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PostPosted: Tue Sep 20, 2016 9:15 am    Post subject: Re: Hot weather restart idea Reply with quote

Our modern TDI's both have all kinds of pumps and fans and who knows what else Shocked that run for a few minutes after the engine is shut off.
During the Summer months 5 minutes after my wife parks in the garage, all of that heat from under the hood is transferred to the garage, and it's over 100* out there...Amazing!
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KAmes
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PostPosted: Tue Sep 20, 2016 5:58 pm    Post subject: Re: Hot weather restart idea Reply with quote

Where did you source the thermoswitch? That looks useful.
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mondshine
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PostPosted: Tue Sep 20, 2016 8:25 pm    Post subject: Re: Hot weather restart idea Reply with quote

I used one of these $8.00 Velleman thermostat kits to control the BN2 gas heater in my Super Beetle.

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https://www.vellemanstore.com/en/velleman-mk138-thermostat-minikit

I just substituted a nicer looking potentiometer, and mounted it and the thermistor off the board (the blue blip is the temperature sensor)
The knob and the blue blip are on the left.
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Velleman kits are good clean fun!
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Wildthings
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PostPosted: Tue Sep 20, 2016 11:09 pm    Post subject: Re: Hot weather restart idea Reply with quote

KAmes wrote:
Where did you source the thermoswitch? That looks useful.


Here you go. Don't know if there is any difference between the cheaper ones and the more costly ones.

https://www.amazon.com/gp/offer-listing/B00GWFK7FA/ref=dp_olp_new?ie=UTF8&condition=new
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