|
|
Data point: One of the big aviation engine/fuel injection suppliers
installs -4 lines everywhere in front of the firewall up to the
'spider', on all 4 cyl Lycs (up to 200+ hp) and if memory serves,
even on the 6cyl engines (230+ hp). The individual lines from the
'spider' to the cylinders are so small you'd be hard pressed to get
safety wire through them. This is on a Bendix style injection system
using a diaphragm type fuel pump and no return line after the pump.
These systems run at between 15 & 30 psi. Logic is that minimum
diameter line minimizes quantity of fuel that can boil on the engine
side of the firewall.
With minimum diameter lines, as long as the pump can provide
pressure it won't take long to clear any vapor as soon as cranking
begins, or you hit Tracy's 'cold start' button a couple of times.
(Vapor in the combustion chamber is a good thing anyway, right?) :-)
As Al Wick pointed out, the only place vapor should be a problem is
at the inlet to the pump itself.
Charlie
On 08/31/2011 07:35 AM, CozyGirrrl@aol.com wrote:
Interesting Chad.
The people flying Subes and using autogas were also
guessing that altitude was a factor in vaporlock. We won't be
using autogas due to variable formulation eating up epoxy
tanks.
We were thinking that if the regulator was the last item in
the chain and that the rails were hooked up serially that it
would minimize vaporlock and also a few seconds of the pump
running before a hot restart would cool and clear the rail.
Chrissi & Randi
www.CozyGirrrl.com
CG Products, Custom Aircraft Hardware
Chairwomen, Sun-N-Fun Engine Workshop
I recently researched EFI regulation a bit and
found something interesting. Many modern (post-1995)
vehicles have "returnless" EDI systems where the
regulator is in or near the tank, not the engine
compartment.
It turns out this isn't for complexity reasons,
though it does save a bit. It's for emissions. The
heating of the fuel in the engine compartment
transfers heat back to the tank. The tank's
emissions do count even though they're not huge.
It's also one less part, hose, and set of fittings
to fail- and get warranty calls on.
To deal with vapor lock they just crank up the
pressure to 65 or more psi. Very effective.
Not at all saying we should do the same, but the
purpose is interesting, no? As well as the vapor
lock" solution"...
Regards,
Chad
|
|