Fuel pressure, sensor

[FastEddieB]

Wrapping also has claims of a small increase in power.

Only downside I can think of is that the wrap could make it harder to spot an incipient or developing crack in an exhaust pipe.

Regardless, my Sky Arrow and Buell both got wrapped.



Buell mainly because the pipes looked like crap!

[roger lee]

Car racer's used the wrap originally due to long exhaust pipes (not like our short ones) and as the exhaust flowed down the pipe it would cool and cause some slight back pressure causing a slight decrease in HP. The wrap helps keep the pipe hot and the exhaust gas hot all the way out. This increases the flow and helps reduce back pressure which gave them a shot of extra HP even though it was a small help. Every little tweak helps. Our pipes are only around 15" long so I don't think we get much of that benefit.

[designrs]

Cool, thanks Roger! Do you have a preferred brand of wrap?

I'd really like to know this as well, if you could please Roger?

[roger lee]

No special brand. Only a couple of MFG's. Any auto parts store. It can come in a pre-treated black or a natural tan color. It comes in 50' lengths for about $50 and you want the 2" wide. It can do 2-3 planes or if you tear it up down the road you'll have some for replacement. If you use the black it will stain your hands after you wet it unless you wear gloves. Cut 2 60" lengths and dampen them. Don't soak them. You will use a lot less than 60", but for your first time use that length. You'll need a pair of scissors to trim the end occasionally as it may fray a bit. Then you'll need to trim the final end. Do not over wrap the springs, go under them and around the knuckle. This will also stop exhaust blow-by if you have any. Only over wrap each edge as you spiral down by 3/8". You don't want a large over wrap on each layer as it will retain too much heat. It's really easy to put on, just takes a little time. About 15 minutes per pipe to make it look nice. Pull it tight as you go. After the full install start the engine and let it cook in for a few minutes. It will smell like something is burning and that will go away.

Don't let any A&P take it off for an inspection. Once off it is ruined. There will be no secret if you had a cracked pipe.

[designrs]

Thank you Roger!

[MrMorden]

Yes, thanks!

[designrs]

Sadly, I must report that the fuel line reposition did not solve my problem of low fuel pressure warnings (assumed vapor restriction). Again today a classic example which can usually be duplicated: warm day (in the 80's at ground / sea level), flying high over inland, moderate rapid descent, level flight approaching coast, persistent low fuel warnings even after electric pump switched on. Had to throttle back to bring pressure up. The VDO fuel pressure sender was replaced as well. Suggestions?

[MrMorden]

Sadly, I must report that the fuel line reposition did not solve my problem of low fuel pressure warnings (assumed vapor restriction). Again today a classic example which can usually be duplicated: warm day (in the 80's at ground / sea level), flying high over inland, moderate rapid descent, level flight approaching coast, persistent low fuel warnings even after electric pump switched on. Had to throttle back to bring pressure up. The VDO fuel pressure sender was replaced as well. Suggestions?

Fuel pressure seems to be one of the biggest bug-a-boos with the Dynon EMS setup. I have analog gauges, and don't even have a fuel pressure indication. If it's consistently causing false alarms, you could always disable the indication in your EMS.

I know some people will howl at that, but it seems the indication is showing low when a low condition is not really present, or at least not one causing a problem. Especially if the boost pump is not fixing the indication, it starts to look like an instrumentation error. I can make a good case for a recurring alarm that has no safety of flight implications to be more of a problem than simply not having the pressure indication at all.

If you really had a low pressure situation that was causing problems, at high RPM you would probably see hesitation, stumbling, higher EGTs (from an over-lean mixture), etc. If you are not seeing those things, then it's probably not a problem. Of course you want to figure out the problem, but until you do...

[drseti]

In the Dynon EMS setup screen, there is a place to program the alarm limits for each monitored function. Perhaps you can think of a reasonable value at which you would like the alarm to go off (but, of course, that is a decision to be made between you and your mechanic).

[designrs]

Re: Andy: I'd love to ignore this or just disable fuel pressure monitoring all together. It does detract from flight operations, and has me throttling back and jumping through hoops to manage the situation.

Here's the thing though... My normal cruise is 3.x psi. I see the fuel pressure start to drop into 2.x. Flip on fuel pump. Ignore it. Pressure drops 2.1 and alert. If I throttle back I see pressures come up and fucuate as I try to finesse back to normal cruise power. If I ignore it... 1.8... 1.5.... 1.2. Then what?

* I'm so angry right now, I'd love to press it to ZERO psi over an airport and see if the motor even stumbles. That would be the ultimate test!

** I did test it at altitude once but backed off when pressures fell to 1.2 psi.

Re: Paul: For now, I still like to know what Dynon allegedly says is happening with fuel pressure.

Maybe I should swap out the mechanical fuel pump. At minimum that would rule out that unlikely issue?
Paul, didn't you tell me that pumps don't fail sporadically... basically they either work or they don't?

[drseti]

That's been my experience, Richard. The ultimate test for me would be to plumb a mechanical automotive fluid pressure gauge temporarily in to the system, fly, and compare readings.

[designrs]

Might just do that Paul. I'm getting really sick of this issue.

[MrMorden]

Re: Andy: I'd love to ignore this or just disable fuel pressure monitoring all together. It does detract from flight operations, and has me throttling back and jumping through hoops to manage the situation.

Here's the thing though... My normal cruise is 3.x psi. I see the fuel pressure start to drop into 2.x. Flip on fuel pump. Ignore it. Pressure drops 2.1 and alert. If I throttle back I see pressures come up and fucuate as I try to finesse back to normal cruise power. If I ignore it... 1.8... 1.5.... 1.2. Then what?

I hear what you are saying. Well, the first thing to determine, IMO, is whether this is really a problem. How about you climb up to 4000+ AGL over your airport, and circle at high cruise RPM? Let the pressure drop. As you said: 1.8...1.5...1.2... Let it keep dropping. 1.0...0.8...0.5...0.2...?

At some point, if the pressure continues to drop, and it really *is* dropping, the engine will either stumble or lose RPM. At *that* point, throttle back, flip on your boost pump, and head in to land. You have just determined you do in fact have a fuel pressure problem that needs correcting.

If the pressure gets ridiculously low and/or down to zero, and the engine never misses a beat for a long period of time in that condition (say 5 minutes), throttle back and head in to land. You have just determined that this is an indication error. An engine can't run at full RPM with inadequate fuel!

You can try to make it better, or wherever your pressure finally stopped dropping, set your low pressure alarm slightly below that and try flying that way a while. If it went all the way to zero, you might have to disable it until you figure out the instrumentation problem.

By doing this at a high altitude, you give yourself all kinds of time to restart or glide down in a circling descent to land if the engine actually quits. I don't think that would happen though, you'd more likely just get a little stumbling or RPM loss.

[3Dreaming]

When this is happening I would try switching off electrical equipment in a systematic fashion to see if maybe you are getting some electrical interference from some outside source.

[SportPilot]

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