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Wildthings Samba Member
Joined: March 13, 2005 Posts: 50255
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Posted: Fri Sep 16, 2016 4:02 pm Post subject: Hot weather restart idea |
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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 Samba Member
Joined: August 27, 2005 Posts: 655 Location: Ohio
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Posted: Fri Sep 16, 2016 7:54 pm Post subject: Re: Hot weather restart idea |
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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 Samba Member
Joined: March 13, 2005 Posts: 50255
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Posted: Fri Sep 16, 2016 8:33 pm Post subject: Re: Hot weather restart idea |
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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 Samba Member
Joined: September 23, 2008 Posts: 1184 Location: Richmond, Va
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Posted: Sat Sep 17, 2016 9:12 am Post subject: Re: Hot weather restart idea |
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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 _________________ ****************************************
2020 - Mustang Eco Boost [High Performance]
1973 - Thing
1966 - Mustang GT- Fastback
1951 - Ford F1 pickup Flathead V8 |
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Wildthings Samba Member
Joined: March 13, 2005 Posts: 50255
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Posted: Sat Sep 17, 2016 9:43 am Post subject: Re: Hot weather restart idea |
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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 Samba Member
Joined: August 27, 2005 Posts: 655 Location: Ohio
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Posted: Sun Sep 18, 2016 7:36 pm Post subject: Re: Hot weather restart idea |
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Thank you Wildthings. It is a very good idea. |
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vwwestyman Samba Member
Joined: April 24, 2004 Posts: 5680 Location: Manhattan, Kansas, USA
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mondshine Samba Member
Joined: October 27, 2006 Posts: 2765 Location: The World's Motor Capital
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Posted: Tue Sep 20, 2016 9:15 am Post subject: Re: Hot weather restart idea |
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Our modern TDI's both have all kinds of pumps and fans and who knows what else 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 Samba Member
Joined: February 16, 2014 Posts: 876 Location: Illinois
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Posted: Tue Sep 20, 2016 5:58 pm Post subject: Re: Hot weather restart idea |
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Where did you source the thermoswitch? That looks useful. |
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mondshine Samba Member
Joined: October 27, 2006 Posts: 2765 Location: The World's Motor Capital
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Posted: Tue Sep 20, 2016 8:25 pm Post subject: Re: Hot weather restart idea |
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I used one of these $8.00 Velleman thermostat kits to control the BN2 gas heater in my Super Beetle.
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.
Velleman kits are good clean fun! |
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Wildthings Samba Member
Joined: March 13, 2005 Posts: 50255
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