I must be the only person on the internet that cannot get a MW44 running. I have an autostart MW44. It will start and idle okay but once I throttle it up it flames out usually somewhere around 85 - 120K. I have replaced the fuel tank, the lines, fuel and I have run it with and without a UAT. No luck!

I emailed Sara several days ago but for some reason she has problems receiving my emails and I'm not sure she got it. I was wondering if anyone has any suggestions? Will the acceleration and deceleration delay have any effect on running?

Thanks.

Hal

yes it will!
however i am not sure you can set them try to set the acceleration delay up by 10 points and see if it goes away.
if it is gone try slowly to go back.
what is strange is that Wren always test their 44,s on each ECU.
so it could be you have a diferent problem.
i am sure Wren will read this and will help you out..

You can try to bump up your accelleration delay. That should help. Also you can put a restrictor in the fuel line. The PW will go up, but you will get a steadier running engine.

Sarah and Roger are on holiday till next week, thus the slow email response.

Increase your acceleration delay by 2-3 clicks at a time and this should help eliminate the flames. This simple adjustment slows the delivery rate of fuel to the motor. In simple terms, your motor is running "rich" on acceleration.

Hope this helps.

I will forward this thread to Wren and you will get a response next week.

Cheers

We are currently having an issue with a 44 also.

It runs fine on the ground. But when I head down the runway and gun it, it flamesout.

Once flying around its good, but once I lined up for a full throttle pass and it flamed out, destroyed an airframe because of it.

Thanks for the help.

What about the Deceleration delay? How should I set it?

Hal

Shok...
The most common cause of flame out on acceleration down the runway is air in the fuel lines. Are you using a UAT??


Set the deceleration delay the same way...decrease a tick at a time . Be careful not to get the setting to low or the motor will quit if you decelerate to fast.

I have my TP with restrictor set at 9 for deceleration.

yes using a UAT, this started after about the 30th flight

As I understand it, the problem may be with blocked fuel needle(s). Increasing the accel delay only masks the real problem AND destroys the superb throttle response. The needles are very small.

Sara is on Holiday and will be back on Monday the 19th.

Dave Rigotti

To all,

I will call Sarah early Monday morning and direct her and Roger to this thread.

Try running it again and see what the hand unit says at the exact second it cuts, look at the rpm and see if it drops a split second before the it stops. If it does then its the rpm sensor. Another way to test it is to plug the hand unit in and spin the engine over and watch the rpm reads right down to 200 if the final reading is much higher, say 800 or so then theres sensor problem . I had the exact same problem on someone elses engine the other day, flamed out at the same rpm as you and the rpm only read down to 900 but once I got a strong magnet and rubbed it round the inlet it sorted it out straight away ( a tip I got from that guy who did the RAM ecu's) , read down to 200 rpm and ran perfect.

try it it might just work!
jason

Hi, I have a similar problem with the 54 mk2. My problem occurs at idle more so than at any other setting. My rpm reading on the data terminal reads 2600 without the engine running. It didn't start doing that until I put the engine on a Y/A Stingray and used the green cowl/inlet. Do you suppose I'm having issues with magnetism as well. Also noticed that it only registers a reading when a servo appears to be under load, ie; srevo noise. When the load is taken off the servo, the data terminal indicates 0 rpms. What type magnet are you using to de-magnetize. I'm also running standard noise traps on all long servo leads.
Steve

Hi Steve
Your problem could be a result of spooke rpm readings.
I have 3 possible "spooke" generators.
Try to move the fuel and gas solenoids to another position.
My tests shows that the solenoids should be placed as far away from rpm sensor as possible.
Another possible error is bad battery, it will also give you spooke readings on the rpm also, when low voltage.
Also check the fuel pump, and relocate pump as far away from rpm sensor as possible if necessaery.
Hope this will help you.

Regards
Anders Wikman

Hal,

I have had the same problem. I have one of the initial batch of 44 autostarts (before they discontinued them and switched to the Gold).

In my Savex L-39, I have probably put twice as much fuel through it on the ground as I have in the air, trying to stop it flaming out on acceleration. As I got it from Wren, the acceleration delay was set at around 15-20. It would flame out at about 120k. Pushing the accel delay up to about 30 initially cured it, but after a couple of flights on the same day the problem returned. Upping the delay to 45 seemded to stop it flaming out. Returning to fly the next day it would again flame out on accel with the same settings that worked the previous day. I eventually had to set the delay to 60, but then started to see some other major problems, such as not being able to reach full power, erratic throttle response and one case of it not dropping below about 90k even with idle set. I spen about 10-15 starts that day trying to troubleshoot it.

Talking to Sarah and the team I sent it all back and they found that some of the fuel nozzles were blocked and that the NGV was cracked (probably the result of a hung start due to a failing battery). $300 of repairs later and with some of the new Gold parts installed and a FOD screen added it should be back in my hands any day now, supposedly putting out more thrust than before. It's now a hybrid configuration, not the full Gold spec. I also have had Wren replace the NiMh battery with a LiPo as after only a couple of hours the 650mAh battery had lost almost half of its capacity and could hardly support 2 starts and a run.

According to Wren the acceleration delay setting is not very sensitive with the bigger numbers, and changes in ambient temperature can significantly effect the required settings.

Good Luck

Paul

Thanks Wikman, I'll try some of your solutions.
Steve

It might be worth downloading the data from the Fadec and e-mailing it to Sara. They are pretty good at diagnosing problems from this data.

If you have fluctuating RPM readings when the engine is stationary then this can be caused by servo interference. You can get a lead to go in the RPM line that stops it. It is not a problem as the sensor signal when the engine is running is much stronger than the interfering servo. I have it on my L39 due to the close proximity of the elevator servo but it does not cause any problems with engine running.

Yep, same. A few of my servos appear to cause rpm fluctuation when the engine's not running but when it is, the fluctuations aren't registered. Hope you get your problem sorted out. As we all know, the guys and gals at wren will do all they can to help you.

Thanks for all of your help. It's comforting to know that there are people all over the world offering help. I've learned alot and will continue to learn alot through this venue. Once again, thanks for your help.
Steve

I'm having a problem along these lines that showed up on my second test run. Since pulling the engine out of my A-4 and installing in the L-39 the idle stability jumps around. It's showing between 54000 and 58000. It does not want to settle down to a very reliable 55K as when I had it in the A-4. There are two main differences, in the A-4 there were no servos near the engine and the fuel tanks and pump were located very close to the turbine. In the L-39 the elevator servos are on either side of engine center and the fuel pump is all the way up at the nosewheel firewall. I'm sure the long run of small diameter full line from pump to turbine is causing a slow response in the overall control loop. Is there something I can change to test this out. The idea of coming in to land with the power above idle , even a little bit is disconcerting. I want to maiden Saturday, so what do you guys think? Doug

I had a similar issue.

Here are a couple of things you might want to try.

Raise the idle slightly. This seems to help and doesn't affect the residual thrust.

Make sure you have the TX setup correct to give enough 'headroom' at the bottom end (i.e. idle should be above 10% from memory).

You could also try changing the stability delay figure.

I also have problems. I have a Wren 44 gold ,on board start version in a Savex L-39, I just maidened it about a month ago, and I now have 8 flights on it. From the very begining on a test stand , Brand new, the Engine was unsteady at idle I would accellerate fine but after running it up and returning to idle the rpms were 65K at idle. I e-mailed wren and Sara had me Set the stability delay to 10 and then run the engine up and down several times slowly, then shut it down and set the stability back to the standard 30 setting. This seemed to work and the next run was fine. After installing it in the plane the first flight was good and the idle after landing was 62-63k .I thought it to be a little high, Sara said it thakes the Ecu time to learn the idle. I have just put 4 flights on it on monday night,the first flight it flamed out on the first fast pass, it made a loud swoshing noise, I thought the tailpipe came out. I dead stick landed it fine and, rechecked it, everything was fine. I then refueled and flew it 3 more flights, each flight the rpms at Idle were getting higher and higher, the last flight the rpms were 91,000, This is way too high . I need to try and get this fixed or send the complete engine back to Wren, I only have flown it 8 total flights, I am hoping this can be rectified without sending it back, Thanks Jack George.

Man, wish I could remember the guy’s name that told me about this problem.
Johnny klinner

Doug, your L-39 came out great , nice scheme. Looking foward to flying them together. Hopefully we can get this engine problem resolved. Jack.

Looks like the acceleration delay may have been my problem. I set the acceleration delay to 40 and it started and ran okay. I will try and come down one click at a time. My idle is a little unstable though. The stability delay is currently at 50. Should I go down on it?

My deceleration delay is currently at 20. Should I come down on it also?

Hal

do yourself afavour first:

first start the engine let it settle to idle.
then go from idle to full throttle slowly within 10 seconds not faster not slower.
on full throttle hold it for 10 seconds.
then go down to idle again in the same matter.
the learning curve should be ok now.
let it run to idle for a minute or so.
shut down.

>> My idle is a little unstable though. The stability delay is currently at 50. Should I go down on it?

leave that it will not help you with this ..


>>My deceleration delay is currently at 20. Should I come down on it also?

if it does not flame out on throttle back dont change it


a well knows issue is for you guys who have flame outs on the runway:

most of the time when you start the engine, some fuel could get trapped in the back lower end of the turbine.
now as you nose up with the plane , or accelerate the fuel could get sucked thru the turbine wheel causing it to flame out.
so when you started the engine it would maybe a good thing to go for full thottle first tilt the nose a bit up to let the resident fuel out.