Have to agree with Al W. on this one. I have never seen smoking gun evidence that vapor lock occurs in the fuel rails. I have seen MANY smoking guns pointing at problems in the pump inlet circuit.
That pump inlet filter on Bobby Hugh's installation raised a big red flag for me as a possible cause of his power failure. It looks like the identical filter that caused the same problem on my 20B. Ed Klepis talked with me about the problem but unfortunately Bobby is not communicating about it AFAIK.
BTW, Here is one piece of advice when you experience a power loss at high throttle. All engine systems are under maximum stress at full power and it is often the case that if you ask a bit less of them, they might work better. I understand the urge to firewall the throttle when power sags at takeoff but TRY reducing throttle momentarily to see if you get better engine performance. This has saved me from at least three aircraft accidents. When that clogged inlet filter caused a power sag in the RV-8, backing off on the throttle lowered the fuel demand of the engine and the fuel pressure recovered enough to let the engine run normally at reduced throttle. Same thing applies to other situations. When my Rotax powered Twinstar started loosing power on climb out I reduced throttle and the engine recovered. Piston seizure was the problem but reducing throttle let the piston cool a bit and total seizure was avoided. I replaced rings & scuffed pistons after nursing it 80 miles to home.
Tracy
Sent from my iPad
<if there is not a method to bleed down the rail the risk of vapor lock
exists
So you are saying every car built since 1990 has this "vapor lock" problem?
We would see thousands of cars unable to start at every desert truck stop. This
concern for fuel rail is a myth.
Vapor lock is not a myth. It occurs at the fuel pump inlet. Very important
to minimize pressure drop there. You can actually measure how far your design is
from vapor lock. You don't have to guess.
The bleed helps if you totally blew the plumbing from tank to fuel
pump. But much better to fix that plumbing error.
-al wick
----- Original Message -----
Sent: Tuesday, August 30, 2011 9:14
PM
Subject: [FlyRotary] Re: CG Products
Intake Manifold
HOWEVER..... if there is not a method to bleed down the rail
the risk of vapor lock exists, as the rail heats, the fuel boils, and the
vapor gets trapped in the line.
If you DO put the regulator upstream of
the rail, its imperative to be able to be able to flow fuel past the injectors
and to a return line to avoid any possibility of vapor lock. The easiest way
is simply to put the regulator downstream of the rail and injectors, but
again.. this arrangement is more about preventing vapor lock, not ensuring
adequate pressure.
Chris and I were forced into the upstream approach
by the Mistral fuel rail configuration, and I didn't want to mess with
drilling out the pinhole and then running a regulator downstream - Mistral was
hard enough to get the intake from, and we didn't expect getting a replacement
part if we had an OOOPS would have been easy. As others have now found out,
Mistral isn't selling parts.
So... anyways.. just wanted to clarify
previous post. 1) can regulate pressure anywhere in the fuel circuit
between pumps and injectors. 2) Must provide for mechanism to flow fuel past
injectors to prevent vapor lock.
Dave
On 8/30/2011 11:06 PM,
Dave wrote:
No... at the flows
and pressures we are using (and barring any major obstructions between the
regulator and the injectors), the regulator can be anywhere in the circuit
and adequately regulate the pressure.
On Chris Barber's install, I
purchased the Mistral intake for use on his engine. The fuel rail was a dead
end tube with a pinhole on the end. Presumably the pinhole was to prevent
vapor lock in the fuel rail. The regulator HAD to be upstream of the
injectors when using the intake. We had stable fuel pressures and no
problems getting fuel to the engine.
We had return lines from the
pinhole end of the rail, as well as from the pressure regulator, that fed
back to the sump tank. Since there were not check valves running from the
wings to the sump, there was no chance of pressurizing the sump.
Dave
On 8/30/2011 10:30 PM, CozyGirrrl@aol.com wrote:
Ed, I must have mispoke to give this impression, I thought the
pressure reg HAD TO be last in line to maintain pressure in the fuel
rail?
Chrissi
& Randi
www.CozyGirrrl.com
CG Products, Custom
Aircraft Hardware
Chairwomen, Sun-N-Fun Engine Workshop
If the pressure regulator is place before
the injectors then there is less fresh fuel flowing through the
rails.
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