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Re: [TR] Fuel percolation-Opposite effect

To: "Randall" <TR3driver@ca.rr.com>,
Subject: Re: [TR] Fuel percolation-Opposite effect
From: "Alex" <ambritts@bellsouth.net>
Date: Sat, 11 Jun 2011 15:05:38 -0400
Yes, right again. I live in Florida. And it all makes sense explained that 
way. (Randall's Law) :o).

I like the idea of introducing heat. No headers, but again the heat shield. 
At least now I know it's not me!
Thanks Randall.
Alex




----- Original Message ----- 
From: "Randall" <TR3driver@ca.rr.com>
To: <triumphs@autox.team.net>
Sent: Saturday, June 11, 2011 1:52 PM
Subject: Re: [TR] Fuel percolation-Opposite effect


>> Anyway, what happens with my car is there is an ENORMOUS
>> build up of of
>> water droplets that form all over the intake manifold and
>> carb bodies.
>
> Let me guess, you live where the relative humidity is high.
>
> There are two things that cause the carbs and intake manifold to get cold
> under cruise conditions.  One is the liquid fuel evaporating (heat of
> vaporization, same as the Dust-Off we discussed earlier).  The other is 
> the
> intake air expanding when it reaches the intake manifold vacuum. 
> According
> to the ideal gas law (aka Boyle's law although not really), when a gas
> expands, it absorbs heat (becomes cold).  This is the reverse effect to
> compressed air getting hot.
>
> Generally the water on the outside is harmless and can be ignored.  But 
> when
> the circumstances are just right, the condensation inside the carb can
> freeze and form carburetor icing.  The pilots in the audience will know 
> all
> about that, as it's a dangerous problem for small aircraft.
> The cold can also cause fuel and/or water to condense inside the intake
> manifold, which can enter the cylinders (and cause stumbling) when you
> suddenly open the throttle.  Heralds I believe actually had a drain in the
> intake manifold to prevent this.
>
> The cure is to introduce some carburetor heat.  Usually the original setup
> with the intake manifold bolted to the exhaust manifold in two places is
> enough to prevent problems.  But if that doesn't work for you (or you've
> installed tubular headers without the attachment point for the intake
> manifold), you may need to route heated air to the intake.  Something like
> the thermostatic heat stove used on Stags (and most cars of the 70s) would
> work well, IMO.  Or you could have an operator control (as aircraft 
> normally
> do) so you can apply heat only when it's needed.  The heated air reduces
> maximum power ...
>
> -- Randall
>
> 


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