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Simjet 1200 SP hot starts.

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Old 10-19-2017, 08:23 AM
  #1
SJN
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Default Simjet 1200 SP hot starts.

Hi guys

How can I get my simjet 1200 SP to start better.
Gas lights up fine, and it accellerates into the 20.000`s , and then it sort of hangs there for a while, while the flames build up.....eventually slowly pulling itself up to idle.
Im running on Shell Vpower Diesel, and 4% kingtech oil. It started the same way on jet A1, but I had it installed in a rookie with no exhaust the last time I flew the engine , so the flamng stats did not bother me.
But now I want to install it in a BAE Hawk with a tail pipe, but this type of start will damage the pipe im certain.
Engine has 4 hours of running time, so its not that used, and still in new condition.
When its up and running, it delivers great thrust, and runs great.

The Start settings from the factory were "Auto+2 ", "Pump start Ramp 03" I tried lowering te settings, and think it starts best at Auto+3 and Pumps Start Ramp 01 But it still starts like crap :-)
I dont fully understand the parameters. maybe someone can explain the two ?
Autostart +4 did not work great and pump start ramp 00 did not work great either.
Im using a 2s 2200 lipo.

Also, it seems that my gas valve might be leaking. Because while the turbine is running it seems that if I open the gas bottle, the rpm`s climb. So that might also be fooling the ECU about the fuel mixture.
In my last starts when I observed this,, I closed the gas bottle at 400 degrees. When does the ECU normally shut off the gas valve ? I also remove the gas hoes from te opposite side of the valve to check for leaks when it should be shut, but it does not apear to be leaking......but at for example 40.000 rpm, and I open the gas bittle, it will give te engine a few 1000 rpms extra....so I dont know whats up with that.

What can I do to make it start better
HELP!!! :-)


Disregard the audio on the videos....my phone makes a mess of the sound.

Here is a sort of hung/hotstart, but it got going eventually.....but it is painfull to watch :-) :

This is one of teh better starts, but that is because the turbine was still quite warm after the last shutdown:

But once running, it goews quite well:
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Last edited by SJN; 10-19-2017 at 08:28 AM.
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Old 10-19-2017, 11:07 AM
  #2
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Anything in my ECU Parameter list look odd ?
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Old 10-19-2017, 11:55 AM
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The only thing that looks a bit strange is parameter 22. Is that RPM or temperature? I have seen various different units used for this and 125 could be way too high.

The starter switch off RPM also looks a little low.

Do you have a restrictor in the gas line?

The Xicoy manual will explain the difference between pump start and pump ramp: Click image for larger version

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EDIT: Do you have a video of the start where you can see the data terminal throughout the start cycle?

Last edited by siclick33; 10-19-2017 at 12:03 PM.
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Old 10-19-2017, 12:27 PM
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It says rpm.
I have a reduction valve on gas bottle, orherwise you get lots of flames.

Sorry, did not take any other videos.

A friend is giving me his parameters tomorrow to compare. His 1200 starts really well.
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Old 10-19-2017, 12:35 PM
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Yes the table says RPM but the gas switch off would often be based on temperature. If it is 125 degrees C then it seems about right. If it is 125,000 RPM then that seems quite high to me.

In the old days when I used to manually start my turbines I used to get the temp just above 100 degrees and as soon as the ramp started the gas can be turned off. There is no need for the gas when the kero is burning. I would try manually turning off the gas as soon as the kero ramp starts to see if it is any better.

Also, in your run menu the Accel delay of 090 seems very high. This won't affect the start but will increase the engine spool up time.
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Old 10-19-2017, 01:13 PM
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Yes, you are right, maybe its a mistake in the manual.
Next time, ill try cut the gas at 100 degrees.

The acc delay was 100, and I just tried to lower it to 90, and it seemed fine. It accelerstes pretty well as it is.

But I was trying to get it to start better today, so I did not bother to optimize the running of it ��
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Old 10-19-2017, 01:58 PM
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Parameters 23, 25 and 31 have weird values, these will very likely cause what you are experiencing, use the recommended values and start procedure will improve a lot
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Old 10-19-2017, 02:06 PM
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SJN
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I guess the values gaspar have ae for the MW-54 ?
This is a VERY old manual :-)
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Old 10-19-2017, 02:25 PM
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Yes the MW54 values should work
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Old 10-19-2017, 02:31 PM
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Thanks.

Hopefully, ill get the setting for this one tomorow, so I can compare :-)

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Old 10-19-2017, 11:35 PM
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Sonnich

I had one of these engines recently and flew it in a Mick Reeves Venom.

The engine is a MW54 with some modification that Lars did to the combustion chamber. He used straight sticks and there is quite a bit of silver soldering on the pipes in the chamber. The straight sticks work fine when the engine is running but as you discovered it can be not so easy to start. On my engine I resoldered one of the vaporiser sticks that has moved in the chamber. My engine did not like starting with a gas valve and I manually opened the gas just a little about 1/4 turn to make lighting the gas easier. I shut it off just before it reached the self sustain point. The combination of the size of needles and the pump tends to lead to over fuelling. Someone on my engine had added a restriction on the fuel line, but I am not sure now what the size was, possibly 1.0mm id needle. I left this and it ran fine with the short restriction.

I would have used auto plus 2 and a higher ramp of 4 or 5.

Your starter motor should be reaching a higher rpm before switching off.

Hope this helps.

John
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Old 10-20-2017, 12:15 AM
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Thanks, for all the info., I was also told the starter on off RPM`s are too low.
Will hopefully get a full parameter list his eveneing, so I can test it out tomorrow :-)
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