IO360 LCO problem Precision Servo

[lr172]

Originally Posted by airguy

That will work, to a degree - what worked a LOT better for me was to change the restrictor orifice size on the injectors to .022". This keeps the line pressure a bit higher between the servo and divider at low-flow conditions, but also requires higher fuel pressure to be able to run full-flow at full power settings. I raised my fuel pump regulator to run about 42 psig to cover that.

I already had 22 injecors and the spring does help. There was even an SB for the cessna pusher engine to improve high heat roughness. Also, all pressure produced at idle levels is from the spider. Injectors don’t offer enough restriction at idle flow levels to produce ANY pressure, which is why the spider is there.

[Tim Lewis]

Originally Posted by lr172

... i would install the 4# spring in the spider. This raises the low volume fuel pressure a bit on the post servo side and will raise the boiling point a few degrees. It helped during my remediation efforts for hot running roughness. I also insulated linesand installedheat shields on exhaust in some areaas.

Don at AFP has them.

Larry

I second that. The heavier spider spring is great.

[Mark33]

Originally Posted by lr172

.....This raises the low volume fuel pressure a bit on the post servo side and will raise the boiling point a few degrees.....

I hope I?m not drifting too far away from the O.P.?s question, but this topic does beg the question as to how much pressure does it take to actually raise the boiling point enough to ?fully? overcome the boiling point so that vapors can?t form? I?m actually thinking more in terms of a dead-head EFI/EFII electronic fuel injection system where each individual injector is plumbed from a central point/fuel distribution log where the system isn?t taking full advantage of a complete free-flowing fuel rail? e.g. a setup where the supply, regulator, and return are plumed in a fuel distribution log and each individual injector is plumed from there.

[lr172]

Originally Posted by Mark33

I hope I’m not drifting too far away from the O.P.’s question, but this topic does beg the question as to how much pressure does it take to actually raise the boiling point enough to “fully” overcome the boiling point so that vapors can’t form? I’m actually thinking more in terms of a dead-head EFI/EFII electronic fuel injection system where each individual injector is plumbed from a central point/fuel distribution log where the system isn’t taking full advantage of a complete free-flowing fuel rail? e.g. a setup where the supply, regulator, and return are plumed in a fuel distribution log and each individual injector is plumed from there.

Pretty sure the SDS customers claim zero issues with boiling fuel. I am guessing they run 40-45 PSI in their system. Pretty sure it is constant flow with return. Don't see much EFI without it. I believe fuel cooling is the larger issue driving that. A dead head setup runs the risk of fuel overheating as well as difficulty with some of the older MAP adjustments to fuel pressure (long gone in todays advanced setups, but where it started - Early EFI systems would adjust fuel pressure based upon MAP to help speed up enrichment)

Larry

[Mark33]

Originally Posted by lr172

Pretty sure the SDS customers claim zero issues with boiling fuel. I am guessing they run 40-45 PSI in their system. Pretty sure it is constant flow with return. Don't see much EFI without it. I believe fuel cooling is the larger issue driving that. A dead head setup runs the risk of fuel overheating as well as difficulty with some of the older MAP adjustments to fuel pressure (long gone in todays advanced setups, but where it started - Early EFI systems would adjust fuel pressure based upon MAP to help speed up enrichment)

Larry

Yeah, you?re right, most EFI systems have a fully flowing fuel rail, but I do know that Ross offers an option for a fuel distribution log which then feeds the individual injectors. All of the main plumbing that?s in place still has the benefits of the cool constant-flow fuel, and is maintained at that 40-45psi via a modern day fuel pressure regulator,....up to the distribution log, but from the distribution log to the injectors, it?s dead-headed. I?m curious to know if that constant 40-45psi fuel pressure along in this type of setup is enough to overcome the possibility of the fuel boiling due to heat and in turn keep it in a liquid state and not let vapors form.

[lr172]

Originally Posted by Mark33

Yeah, you’re right, most EFI systems have a fully flowing fuel rail, but I do know that Ross offers an option for a fuel distribution log which then feeds the individual injectors. All of the main plumbing that’s in place still has the benefits of the cool constant-flow fuel, and is maintained at that 40-45psi via a modern day fuel pressure regulator,....up to the distribution log, but from the distribution log to the injectors, it’s dead-headed. I’m curious to know if that constant 40-45psi fuel pressure along in this type of setup is enough to overcome the possibility of the fuel boiling due to heat and in turn keep it in a liquid state and not let vapors form.

Pressure is constant both before AND after the pressure regulator, which utilizes a return for maintaining pressure. Pressure can be maintained in either a dead head configuration or with a rail setup. Ross has mentioned several times that his system experiences no boiling issues at the pressures he is using. Might be best to ask for his input on that.

Larry