Tom Antlfinger

My Feedback: (24)

A question for Ron, Sara, and other Wren SS owners......I am on my second season with the SS on my BC ARF.......flawless 45 runs and about 575 minutes on the cumulative run clock......

I have encountered a recent problem.......I do the recommended 5 second runup to full throttle(160K) and then slowly back down to idle(45K) after startup......PW all appear normal both at full throttle and at idle.....pump voltage is as it has been since new....

Problem is that when I land and taxi back, idle is at about 55-58K rather than back down to 45K, and it stays there......EDT show PW unchanged at idle when compared to pre-takeoff number.....

This is a new problem, in the last 10 or so flights......I have the RPM sensor well spaced by about 6" from the rest of the wires until just before entering the ECU and engine.....

Could this be a problem needing a degaussing.....haven't tried that yet......does that need a really strong magnet?.......I suppose I have to pull the FOD screen if I need to do it......seems odd that it would only affect idle.....RPM indications otherwise appear normal and unchanged......

Any ideas.....thanks in advance.......

Wren Turbines USA

My Feedback: (39)

Hi Tom,

Sounds like a pump that is possibly "freeing up".

First thing to do is check the filter between the pump and the motor for any signs. Then reteach the ECU, fire it up...let the idle stabilize, then very slowly advance to full and back to idle.
I'm sure Sara will chime in for additional support...but this would be my first thought.

Tom Antlfinger

My Feedback: (24)

Thanks for the reply Ron......I haven't checked the filter, but I will do that....I have relearned the tranny a couple of times....same result.....all the other parameters in the ECU are unchanged since factory new except, because of the "freeing" effect after a couple of hours, I did back off the minimum pump start voltage to "0" from +1 last fall......my starts are smooth as silk, no flames, and cool, never more than 450C.....I prefer to manually control the propane rather than use the solenoid.....an old habit from starting my AMT's..........zero flameouts since day 1....

For Sara and the Wrensters, my starts and flights yesterday went as follows:

Initiate the starter motor on the tranny...glow plug at 32...
Crack the propane......instantly lights off
Advance propane about 1/4 turn on the thumbscrew valve and watch temps.....keep around 400C....
As soon as starter shuts off, give about another 2 seconds of propane and then shut it off
RPM then spools up to about 55K and then retreats to about 38K and stabilizes there
Slowly run RPM up to MAX throttle.....160K
Slowly close throttle.....RPM settles at about 45K........then go fly
When I land and taxi back, idle sounds fast.....EDT indicates 55-58K......until I shut it down.....

Wren Turbines USA

My Feedback: (39)

email me your phone #

Also,
does it do this after every flight...after it cools down does it idle properly on the next startup??

WrenTurbines

Tom and Ron,

Yes, I've chimed in - but it's getting late over this side of the pond, I don't have anything else to suggest other than what Ron has already said and I'll ask the guys in the morning.


Sara Parish
Wren Turbines

Gaspar

This discards all electronics and only leave the pump and fuel installation, as the pump is receiving same power in both situations.

Could be:

a) Pump with dirty brushes that need more power to turn in "cold"
b) Fuel system. The pump have less effort to pump fuel when tanks empty than when full. Are you running tanks in series? Do you start the engine with a header tank?

Gaspar

chipperg

My Feedback: (9)

I am sorry you are having this problem. I am interested in the post due to the fact that I have an SS also. I put 1356 min on the wren last season and I just replaced my first glow plug. I hope you get the problem fixed.

fw190pilot

Try reducing you stability delay 5 points sometimes this will cure the high idle problem.

Tom Antlfinger

My Feedback: (24)

Sara and all the others....thanks for all the replies......Gaspar might have hit on something.....I recently started keeping my overflow tank hooked up until I did the throttle up/down procedure after startup as I noted I could get almost a minute more flight time by doing so......I routinely have it sitting on the ground until just before taking off where as before, I used to start on a table, disconnect the overflow and taxi the plane to the flightline before doing the runup.....definitely a different pressure head with the tank connected.......

I will followup on this tomorrow with some test runs, with and without the tank hooked up while I do the pre-flight run-up/down........

I did try dropping the stability delay already and that did not change anything......

Ron, had to leave before I got your last post.....if problems not solved tomorrow, I drop you a note with my phone #......

WrenTurbines

He often does! It really is a help to have the ECU manufacturer giving advice in person.

Sara Parish
Wren Turbines

Ray Davis

My Feedback: (1)

Sara, two questions:

Why does Wren not break in their pumps and re-check specs before shipping if 'freeing up' is truly necessary/a cause of some of the problems discussed here, and on the earlier MW-44 thread? (Very simply/cheaply done: dozens run at once at, say, 1-2VDC for an hour.....could even just immerse the pump portion in a fuel bath....or hook them up to a manifold/tank/sink. I do just that w/ all my new turbine fuel pumps before installation, as it also thoroughly flushes and eliminates minute gear wear particles, etc. I've found one bad pump that way...it just never ran smoothly.)

And why should 'movement' in the pump wires be any kind of a issue?! Certainly Wren's connectors are of sufficient integrity/quality to prevent mechanical problems....or if it's RFI, can't the pump/ECU (or whatever is affected) be protected by better design? Or any problem pumps simply rejected after a simple test procedure?

Wren does everything else so well(!).....don't stop there .......as I'd think this major problem source could be rather easily caught and eliminated before shipping. Tx!

Ray

WrenTurbines

Ray,

The pumps are run here at the factory, and if they are "tight" then they don't go out, they have to be working properly. However, some of them seem to free up more over time and that's something we don't have any control over. Likewise, the fact that they are sensitive to movement in the wires is a manufacturing issue, we can't control that either. We are talking to the manufacturers about it and are all trying to improve things.

Sara Parish
Wren Turbines

Tom Antlfinger

My Feedback: (24)

I have always checked my fuel pumps and run them in before installing them......I use my Duratrax I.C.E. charger which has a motor run-in mode, actually designed for electric ground(trucks, etc.) operation and is calibratred in 0.1 v......I usually run them at 3.0v for about 30 minutes......sometimes get a few flecks of filings, but most often nothing.....

I think I remember someone stating that the factory built Wren motors like the SS do have the pumps tested and run-in, but suggested that the owner should do this on the kit MW 54's which I did on mine.....

I also check the minimum pump start voltage at the same time......

I am waiting for the winds gusting to 30 MPH to subside, probably not till tomorrow to go out and test fly without the overflow connected when I do the pre-flight run-up.....

yeahbaby

My Feedback: (21)

don't be a sissy!! Get in there amigo, just think how slow your ground speed will be, much like mississippi

Vincent

My Feedback: (61)

Tom,
Just run it up in the drive way....why wait till you get to the field and have a problem ??
V..

Tom Antlfinger

My Feedback: (24)

Sort of like the "Sheeeet!" moment before I harriered the UB into the ground.......AS=30........GS=0.......

And Jane said to remind you that Desitin Butt Cream works better than draggin' it on the carpet after a mudbug fiesta......

Tom Antlfinger

My Feedback: (24)

Heading out there right now Vin...neighborhood's been too quiet today anyway....had to wait for the rain to stop earlier today.......

yeahbaby

My Feedback: (21)

perhaps, but the reaction from my buddies isn't quite the same when scratching with my hand vice creating the goal posts with my feet.


[quote]ORIGINAL: Tom Antlfinger

Tom Antlfinger

My Feedback: (24)

Problem solved by eliminating the startup tank while doing the throttle up/down after start.......made little difference if tank was on the wing of the BC ARF or on the ground.......

I have my main tanks in parallel, into a 16 oz midline hopper tank, and then into the UAT, but adding that BVM overflow tank really increases the resistance to flow, even though everything, except from the fuel solenoid output to the engine, is 6mm tubing......that was driving up the pump voltage at idle......

Thanks for the comments......

causeitflies

Glad you got it sorted out.
Is it recommended to do the 5 sec run-up on every engine run?

Tom Antlfinger

My Feedback: (24)

Mark:

It is recommended in the manual to get the best throttle position to RPM match under changing ambient conditions. I am not smart enough to know why it is recommended on my AMT NL's and Wren's and not on the JetCats I run.....If Gaspar is following this thread, maybe he can chime in..

Tom

Gaspar

No, it is not necessary, just start and go. It is only reccomended after changing something, like new install or new pump, etc. But when the engine have been run once in a given setup, it don't need any other full power run before take off, the ecu remember the last flight. From what I heard, AMTNL ecus need to go full power each run to calibrate the pump, in the fadec it is not neccesary, the ecu remember it.

Gaspar

Tom Antlfinger

My Feedback: (24)

Thanks for the information Gaspar.......

Gerald Rutten

Very nice to read all this, I was just starting doing the same thing to lenghten my flight-time or better, have more safe reserves. My Orbit ECU doesn't seem to bother very much as it's not a constant calibrating unit as the fadec is I guess. However I will use Gaspar's fadec's for my new homebuilt MW's so I will have to take care on that, good to learn here!

Also from the older day's it was reccomended to do the full-power check before every flight to make sure all parameters where as they should be and on my homebuilts I still do so today. Lot's of things could happen during sequential flight but it was just a way to make sure everything is ok before the flight is commenced. Noweday's market turbines are increadable reliable so the full-power run would only do harm as it eats-up the costly maintenance interval time.....

Best regrards,
Gerald

Tom Antlfinger

My Feedback: (24)

I agree Gerald, especially after Gaspar's comments.....I was just following the instructions in the Wren manual......