We have a twin wren 44 powered ME-262 and have been trying to get them running for the last two days. One motor imo is rubbing and will not achieve enough rpm to get an idle. The other spools up to idle (60k) and the gsu says running but when we disconnect the glow and shut down the gas the motor starts to lose rpm and eventually shuts down?? We have not changed of tinkered with the factory ecu settings. The ecu is a fadec 302. We are also usng powermax for starting gas.

Thanks,
Vin...

Is there any way to preheat the motor, say on propane alone, then retry the start?

Wren don't recommend Propane alone as the pressure of the gas is too high, but a butane/propane mix. Its probably what you meant but just in case thought I'd raise it as there could be a safety issue. I'm not familiar with the Powermax brand.

Powermax is a mix of propane and butane.

Matt,
After the first few trys the motor was started each time with the temps around 70-80c so it had some heat in it. The motor lites off smoothly, the fuel ramp comes in and the motor spools up but kind of "choppy" with some flame out the tailpipe.
V..

Vincent,
I hope you get them figured out. I would like to hear how you end up liking them. The guys from the UK, at the FIJR, had a couple and they were awesome. They had one on a YA Stingray and it hauled the mail. I think they said it did over 200 mph. I was suprised that the engine sounded like a large turbine and didnt exhibit some anoying whining. Another show stopper was Jasons BV F86 with Wren 54 power. WOW!!! Did you buy the prebuilt ones and where did you get them from? Arent they around 1500 for the kit and 2000 for the prebuilt?
Thanks
Scott

I think the MW-44 can only be bought pre-assembled??


SJ.

Vincent,

Which ME-262 did you build?

I have a 114" ME-262 for a pair of ramtec fans. The 'kit' was from a fellow in Florida.
Glass fuse, nacalles with wood wings. great kit.

thanks,
DW_Crash

This is the 80" airworld fully molded ME-262. I have seen pics of the 114" one from fla. The guy who developed the kit had props on it??

I am working with wren and JHH on the motor issues and will let you guys know what we find. I think we need to remove one and run it on a test stand to eliminate a tailpipe issue.

V..

My comments were only meant for the one that is rubbing, and yes I meant the propane/butane mix.

In some motors, if the fit on the turbine wheel to EGV is very tight, the turbine wheel can heat up and expand faster than the EGV. the turbine wheel will then rub, and it only has to rub a tiny amount to overcome the small torque of the starter motor. If you can get the back end of the turbine hot enough, and you can ge the motor running, many times it is not a problem after that. The EGV is now up to temp and she will not rub.

As for the motor that is shutting down, sounds like the idle RPM pump voltage is not high enough, but unfortuately I do not kow anything about that ECU...that is Gaspar's , right? Maybe you can email him.

Matt,

Wren has e-mailed me and said the tolerence is VERY close and any uneven combustion could cause this problem. The tailpipes may be an issue but we will eliminate them tomorrow when we tinker again. I feel it is a PW issue with the pump pressure. Oh well, try and try again.

V..

Vincent
I was just going to say that your problem sound like your injectors not burning evenly.

Hi Guys I have wrote the program for the Gaspar ecus Fadec 302,303 for the Bee and JF100 and the problem your having isn't the Ecu, we have now Many turbines in customers hands running perfectly starting flawlessly start after start from the first start with the same controller, if you received motors that after the first few try's and phone calls isn't starting and running and the turbine is properly set up RETURN THEM! You will never get them going right you are not the manufactor and cannot solve issues with a phone call , it is the responsibility to the company producing them to make sure they are right when they ship them.Good luck Paul AJUSA

Vincent,
I have messed with turbines much smaller than the 44 and I have had the same problem in the early development of them. I will tell you what happens to mine and you can decide for yourself if this is what happens to yours.
In my engine, if there are to few propane ports in the CC you will not heat up all of the vaporization tubes, if even one does not heat up it will make hissing popping noises and not run smooth at all. This will cause the tubes beside it to cool and end up not vaporizing the fuel, this will continue until they all cool down and the flame goes out. If I hear any of these sounds going on I will leave the propane on longer to make sure all the tubes get hot and do there job,
when it does the engine will smooth out and run right. When this happens to your engine is there a orange haze in the turbine side of it?
Again, this is what goes on with my tiny turbine, without seeing yours it is to hard to tell if this is what goes on in your engine.

Hello Vincent,

As fadec ecu developper and user of a MW44 from some time now, I had think that I can give a good advice on this one.

The answer is very simple. You are using TOO MUCH starting gas (read propane/butane mix, coleman, etc). This causes 2 effects:

-One is that the gas cause a uneven heating on the turbine and EGV that can cause distortion on the egv, and the turbine can touch the EGV.

-The other effect is that the engine arrives at idle under kero and gas power, and the ecu calibrates the idle power while the full gas supply is burning. As soon as you remove the gas, the supply of kero isn't in aft to keep the idle power and the RPM drop.

You need a very little gas quantity, use a robart air restrictor or less to reduce the amount of gas. As soon as the engine begin to burn kerosene, cut the gas supply. The gas should be in aft to heat the engine up to 100-150ºC while you pulse the starter keeping the rpm between 2K and 5-8K. Once you see that the kero is triggered ("Fuel ramp" reading on the data terminal) apply full starter and cut the gas when the temperature begin to increase due at the kerosene. Remove the starter at about 35Krpm.

I'm operating this engine from some months now in my Savex L39, and it is one of the smoother and nice engines that I had own. I'm experimenting in Autostart, and typically I have complete start sequences in 15-20s without any flame at back. You will be pleased. No reason to send the engines back.

About the ecu settings, at this moment I don't know the parameters that Wren left available for the users to adjust in USA due the AMA compliance, so I can't give you an answer of about what you can modify or not, I will ask. But I'm sure that the settings that you have are OK, and your problem is the gas.

You can mail me directly at [email protected] for further advice.

Gaspar Espiell
FADEC ecu designer and firmware (program) writer.

Gaspar,
Thankyou for the info, it makes sense to me and apears to describe what is going on with our starts. In the wren instructions it says to keep the starting gas on for the entire spool up until its "running".We are also getting some weird rpm numbers when spooling with the wand.I don`t see 2k-5k but all of the 6 digit numbers are moving?? When the motor starts to ramp the rpms are more in line to what you describe?? Anyway, i bump the motor with gas supply on until i see 35k, get off the elec start and wacth it ramp up to idle but keep the gas and glow on,this is the way the instructions read.I know i am spoiled with my auto start Jetctats but ran manual start jpx for several years and understand the sequence.

I will try your start suggestion today.
Thanks,
Vin...

Definatly too much starting gas! I started mine a FIJR on propane with no problem, all you need to make sure is that there is not too much gas going in it. It needs 100 deg to start the ramp but is is easy to get it to 300 deg with too much gas. The problem is that when it is running at idle with that amount of gas and you turn the gas off quickly it will shut down because you have just taken away a large amount of the fuel it is using to run ay 60k rpm and the ecu will not react quick enough because it is regulated by the acc delay when in running mode. I start reduceing the gas slowly from just after the start of the ramp and it is completly off by the time it comes to 60k.

Brilliant little engine!

jason

OK Jason, sounds like a good idea.I ease off the gas when the fuel begins to ramp and see what we get.
Thanks,
Vin...

Before I had Auto Start on the TJTs, I had the same effect some times on the FADECs. Another option, even if you use too much gas on start, is to simply close the gas valve slowly. That way the ECU can keep up with the RPM drop-off due to the gas being removed by increasing the supply of Jet A.

HI all, a little of the topic but what weight of jet will the Wren 44 pull comfortably.Would it be rated for say a 10 pound jet.
Thanks Rcpete

The instructions say up to a 11lb jet loaded.
V..

Hi Vin,Im amazed if you been trying to start these motors with full flow of Gas?What kind of intructions,advice did you Get from the dealer factory reguarding flow rate of start Gas When you called?You been burning those motors up, to much heat the egv expands and causes the touching as I believe Matt mentioned.

Paul,
I have the gas restricted with a valve, there is just a whiff of propane going in there. The motor lights off fine on the gas, its when the kero comes on the motor spits and barks out some flames. Still no luck getting them running. Hopefully JHH can help us.

V..

Vin,

PLEASE get a hold of me on Sunday. I want to come to your shop and give you guys some help. I tried Saturday but I got no answer at your shop. I was at the field until around 4:00. Geronimo went to your shop and said that you were not there. Call me .

Willing to help,

John

Jettset 99
Wren has been Very Responsive working with us on the problem,providing On -Site assistance. Which I can say is more than I've ever received from the US Artes Rep.They unlike you ,answer the phone/e-mails & are helpful. They promise & Deliver.
All others
Still have the problem,data collected by factory rep is being forwarded to Wren as I type.
Semper Fi
Joe Balabon

Vincent::: Myself and a close friend both have Wren 44 engines running in the Savex L39's We have flown them to death this year, between us we have approx 30 hours operating these engines. (Fantastic engine!)
What you describe is not like anything i have experienced with these engines. Some times there is a bit of popping as it ramps up, but once running it is as smooth as silk.
It seems strange that you have this problem on both engines?
Can you describe your installation for me? Where are the tanks? where are the pumps? do you have a UAT? have you any filters, have you modified anything at all, no matter how small? it may be relevant.
Wren are one of the most responsive companies i have ever dealt with, if you have a problem they WILL solve it.