Ventus CM starting problems

Now, when cranking, battery voltage drops from 12.7 to 10.5 but on starter terminals I measured 7.5 Volts. With this, the starter runs to much faster and the engine starts as easy as when I supplied energy from the car with the car emergency wires. Never, since I have this glider, it cranked as fast and started as easily.

Maybe quit and declare success.

Or add more, nore copper.

Or measure the steady state amps to go with the similar volts and see if the loss in the wires are as expected.

The electrical parts might be working as designed and there is an extra mechanical load?

On Monday, July 20, 2020 at 7:58:24 PM UTC-4, Dave Nadler wrote:
On Monday, July 20, 2020 at 3:54:04 PM UTC-4, wrote:
Now, when cranking, battery voltage drops from 12.7 to 10.5
but on starter terminals I measured 7.5 Volts.

Lucas, 3v is still a pretty huge drop!
Keep looking!

OTH, if its really 50A steady state (at 7.5v that's .5hp!),
3V = 50A * .06 ohm
So system resistance is not crazy...

I've owned a Ventus CM for 20 years, have taken the engine from 17 hours to 67 hours and the airframe to 1200 hours without any starting difficulties. I have nothing to add to the preceding comments, and have no debate with them. I only wish to add my own experience.
As someone once said, all an engine needs is air, fuel, and spark -- in the right amounts. Here are some of the things I've learned:
1: Having the spark plug gapped correctly is critical to reliability -- 0.5mm -- I have used platinum plugs with complete satisfaction.
2: Having a charged battery -- 12.8 volts or more seems optimal.
3: Obvious but essential:
Fuel valve OPEN
Boost pump ON
Proper carburetor prime: too little and the engine won't start; too much and the plugs flood, and must be removed and cleaned because they're at the bottom of the cylinders. When the engine is cold, especially in cool weather, in my ship 4 full squeezes of the priming bulb is the minimum. If the engine doesn't start promptly, an extra squeeze or two while it's cranking may help.
In-air starts require less prime, probably because the engine retains some warmth in the engine bay.
4: As hinted by this thread, and taught to me, the #1 cause of electrical malfunction is *corroded contacts*. It is possible to check the resistance across contacts -- or simply disconnect, freshen the metal, reconnect, and spray with anticorrosion lube.
5: In-air shutdown: The manual says to let the engine cool at idle before stopping and stowing it. Years ago, I spoke to the engine designer, Wolfgang Emmerich, about this. He was *adamant* that this not be done. "I owned one of those gliders; I don't know why manufacturers give this advice. If you do not shut it down at full throttle, the carbs are over-pressured and they begin to leak."
I'd had some leakage at that point; I've ever since shut down at full power, and the leakage has never worsened, just a couple of drops.
6: I forgot to mention: both the starter button and the radio microphone button are on the stick. If one doesn't look, it is possible to be pressing the microphone button on final to the off-field landing. This has been done by at least two pilots, to my knowledge. The engine only starts if the started button is pressed... ;-)

El miércoles, 22 de julio de 2020, 0:36:05 (UTC-3), danlj escribió:
I've owned a Ventus CM for 20 years, have taken the engine from 17 hours to 67 hours and the airframe to 1200 hours without any starting difficulties. I have nothing to add to the preceding comments, and have no debate with them. I only wish to add my own experience.
As someone once said, all an engine needs is air, fuel, and spark -- in the right amounts. Here are some of the things I've learned:
1: Having the spark plug gapped correctly is critical to reliability -- 0..5mm -- I have used platinum plugs with complete satisfaction.
2: Having a charged battery -- 12.8 volts or more seems optimal.
3: Obvious but essential:
Fuel valve OPEN
Boost pump ON
Proper carburetor prime: too little and the engine won't start; too much and the plugs flood, and must be removed and cleaned because they're at the bottom of the cylinders. When the engine is cold, especially in cool weather, in my ship 4 full squeezes of the priming bulb is the minimum. If the engine doesn't start promptly, an extra squeeze or two while it's cranking may help.
In-air starts require less prime, probably because the engine retains some warmth in the engine bay.
4: As hinted by this thread, and taught to me, the #1 cause of electrical malfunction is *corroded contacts*. It is possible to check the resistance across contacts -- or simply disconnect, freshen the metal, reconnect, and spray with anticorrosion lube.
5: In-air shutdown: The manual says to let the engine cool at idle before stopping and stowing it. Years ago, I spoke to the engine designer, Wolfgang Emmerich, about this. He was *adamant* that this not be done. "I owned one of those gliders; I don't know why manufacturers give this advice. If you do not shut it down at full throttle, the carbs are over-pressured and they begin to leak."
I'd had some leakage at that point; I've ever since shut down at full power, and the leakage has never worsened, just a couple of drops.
6: I forgot to mention: both the starter button and the radio microphone button are on the stick. If one doesn't look, it is possible to be pressing the microphone button on final to the off-field landing. This has been done by at least two pilots, to my knowledge. The engine only starts if the started button is pressed... ;-)

Thank you Danlj.
Throughout these last three years that I own my ship, I´ve learned a lot about this engine...I had plugs flooded sometimes also. I heard before about stopping the engine at full power, but never with that conviction.
After stopping it did you used to wait to cool for a while or you stowed it directly?

I also heard about pressing the wrong button to start the engine!! but mine has the PTT button not at the top of the stick but in its front, so, no mistake there.

I would like to ask you a question also. These mikuni BN 38 carburators has needle valve seat (pop off) sized 2.0. There are pop off of 1.5 and 2.5 also. The standard carburator parts drawing indicates 1.5 for Mikuni BN 38, do you remember what is the indicated one for this engine? Anyway, mine with 2.0 works ok, but I still have this doubt.
Regards.

Well.... some PC680 batteries appear to not be the same quality they were in the past. Alot of homebuilt aircraft use them an owners are complaining about the poor service life compared to what they were in the past.

If you can try someone elses battery or try your battery in a similar glider as see how it goes.

There are some devices around that can test the performance of a starter battery in cars. They measure the CCA potential of the battery in a few seconds, perhaps a local auto electrican can do this for you. It only takes a few seconds to do.

Brett

On Saturday, July 25, 2020 at 3:56:07 AM UTC-7, wrote:
Well.... some PC680 batteries appear to not be the same quality they were in the past. Alot of homebuilt aircraft use them an owners are complaining about the poor service life compared to what they were in the past.

If you can try someone elses battery or try your battery in a similar glider as see how it goes.

There are some devices around that can test the performance of a starter battery in cars. They measure the CCA potential of the battery in a few seconds, perhaps a local auto electrican can do this for you. It only takes a few seconds to do.

Brett

Google "cca tester" and you will find a bunch that are under $50.

Tom

On Monday, July 20, 2020 at 9:09:52 PM UTC-4, Dave Nadler wrote:
On Monday, July 20, 2020 at 7:58:24 PM UTC-4, Dave Nadler wrote:
OTH, if its really 50A steady state (at 7.5v that's .5hp!),
3V = 50A * .06 ohm
So system resistance is not crazy...

Something still not right Lucas.
From your wire 18 mm2 of length 2x 5m, your cables should have ~ .01 ohm total.
And its most likely less than 50A steady-state cranking, so you've
actually got closer to .1 ohm.
Matters a lot at these current levels!
Hmmm...

El lunes, 27 de julio de 2020, 21:52:31 (UTC-3), Dave Nadler escribió:
On Monday, July 20, 2020 at 9:09:52 PM UTC-4, Dave Nadler wrote:
On Monday, July 20, 2020 at 7:58:24 PM UTC-4, Dave Nadler wrote:
OTH, if its really 50A steady state (at 7.5v that's .5hp!),
3V = 50A * .06 ohm
So system resistance is not crazy...

Something still not right Lucas.
From your wire 18 mm2 of length 2x 5m, your cables should have ~ .01 ohm total.
And its most likely less than 50A steady-state cranking, so you've
actually got closer to .1 ohm.
Matters a lot at these current levels!
Hmmm...

Yes, I know something is still not right.... but I can´t find what! I´ll continue searching and let you know. Thank you

What was the actual current?