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Old 08-03-2009, 07:09 AM   #1
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Default what is vapor lock?

just curious.
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Old 08-03-2009, 07:14 AM   #2
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When the fuel already burns in the carburator due to a too hot engine before it even enters the cilinder.
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Old 08-03-2009, 07:16 AM   #3
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When the fuel already burns in the carburator due to a too hot engine before it even enters the cilinder.
would a gas cooler help? And if you have vapor lock what happens to your car.
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Old 08-03-2009, 08:51 AM   #4
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would a gas cooler help? And if you have vapor lock what happens to your car.
a gas cooler would help. also using a plastic carb instead of a metal one.
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Old 08-03-2009, 09:35 AM   #5
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a gas cooler would help. also using a plastic carb instead of a metal one.
what happens when vapor lock occurs? does your engine lock up or flame out? if so i would like to know because that does not sound cool
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Old 08-03-2009, 09:43 AM   #6
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What usually happens is this:

As long as you're out on the track and on the throttle, all that fuel going through the motor is keeping the carb, crankcase and crankshaft nice and cool. But if it's running a really high head temp, you could have a problem. When you come in for a stop or for some other reason end up idling for a while, there is not enough fuel coming in to cool the bottom end of the motor and all that heat in the head quickly works it's way down. The fuel will start to boil and the motor stalls. It will not want to restart until it cools down a bit. Some people will dump some fuel on the carb and crankcase to cool it and get it restarted. This is a bit dangerous but does work.

This isn't usually a problem with .21's since they have a lot more mass to act as a heatsink but can still happen if running really hot or really lean on the bottom end. It is a BIG problem with .12's in TC onroad racing. Plastic or insulated carbs can help a bit but the biggest problem is the heat in the crank and case. A richer bottom end can really help with this problem.
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Old 08-03-2009, 10:16 AM   #7
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Old 08-03-2009, 10:22 AM   #8
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Originally Posted by dreaux View Post
what happens when vapor lock occurs? does your engine lock up or flame out? if so i would like to know because that does not sound cool


Just dont run a quali with a lean bog...IF you EVER feel something funny with the motor and it Just doesn't feel right...BRING IT IN....no sense burning down a motor in a quali for the fact you didn't want to bring it in and check it out....ive seen it all too many time's where a lean bog leads to 300+ degrees and the motor is Pooched after.

Vapour lock is more associated with lower end carb's....OS RB Nova Sirio ect ect all have the carbs figured out for the most part...its the lower end stuff that's usually the problem.
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Old 08-03-2009, 10:23 AM   #9
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Old 08-03-2009, 11:03 AM   #10
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dreaux dreaux dreaux......

I googled "vapor lock nitro engine" and the first link that came up was this, http://www.rchobbies.org/engine-tuning.htm

So I scrolled down to the last part of the page and I seen first, The Dreaded Full Tank Lean Bog that you were asking about. Then your original question, what is vapor lock? Well your answer would of taken 30 seconds to search.

Vapor Lock

If you've ever had your engine flame out after a reasonably long run and then found it nearly impossible to re-start, you may have experienced vapor lock. Vapor lock occurs most often in .12- and .15-size engines, especially when they're enclosed in a body with a 1/10-scale gas sedan or stadium truck. Vapor lock normally occurs after the engine is shut off. Heat from the head and combustion chamber transfers through the crankcase, heating the carburetor to the point that the fuel that reaches the carburetor through the fuel line boils off. This makes it impossible to start the engine because it's starved for fuel. The only way to get the engine to run is to cool the carburetor below the fuel's boiling point. If you're sport driving, you can simply wait 5 minutes for the carb to cool on it's own and then restart. If you're in the middle of an important long main, here are some creative ways racers have (including at the world championship level) cooled their carburetors preventing vapor lock:

1. A bottle of compressed CO2 (or air like those that can be purchased to operate airbrushes) with a nozzle attached, allowing cold CO2 to be directed over the carburetor even when the body is in place. We've seen several top-level race teams use this CO2 method anytime the engine flames out to prevent the possibility of a vapor lock.

2. By pulling the air filter and simply dumping fuel from the fuel bottle over the carburetor, usually bringing the temperature back to a tolerable level within a minute. Just be sure to avoid getting fuel on the brakes, radio equipment or tires or you could be in for a bad race day!
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