New ZDZ 80 w/problems-stuttering ignition, low power/thrust
04-16-2003, 09:43 PM
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New ZDZ 80 w/problems-stuttering ignition, low power/thrust
We just ran our new ZDZ 80 and are having some problems with it.
First, the engine stutters at lower RPM. We also had a problem getting a spark--sometimes it would spark, sometime it wouldn't, and this was without changing our setup at all. This was not due to the 1-minute ignition safety cutoff.
Second, we're getting a max RPM of 5000, which is corresponding to a max power of only 4 HP. This is less than half the expected power and is not enough for the planned aircraft maneuvers.
This is with a 3-bladed Zinger 22-12 prop, the Bisson inverted Pitts muffler, and with 87 octane gas and Valvoline multipurpose 2 cycle engine oil (TC-W3 certified). This oil was used instead of the Penzoil. This data came from a static test during the engine break-in period. The engine was run at around 3000 RPM for a gallon (around three hours, total). All the recommended instructions were followed as carefully as possible.
engine test
On the plus side, we're getting twice the fuel efficiency that we had planned for (at least at 3000 RPM), so that's good.
We are very concerned with these two problems. What could be causing the ignition problem? And as for the power loss, we need to solve this problem rather quickly. Is it the prop? Is it just the break-in performance? Is it due to the test being static and not in flight?
Thank you for your assistance,
Graylan Vincent
University of Washington Aeronautics & Astronautics
First, the engine stutters at lower RPM. We also had a problem getting a spark--sometimes it would spark, sometime it wouldn't, and this was without changing our setup at all. This was not due to the 1-minute ignition safety cutoff.
Second, we're getting a max RPM of 5000, which is corresponding to a max power of only 4 HP. This is less than half the expected power and is not enough for the planned aircraft maneuvers.
This is with a 3-bladed Zinger 22-12 prop, the Bisson inverted Pitts muffler, and with 87 octane gas and Valvoline multipurpose 2 cycle engine oil (TC-W3 certified). This oil was used instead of the Penzoil. This data came from a static test during the engine break-in period. The engine was run at around 3000 RPM for a gallon (around three hours, total). All the recommended instructions were followed as carefully as possible.
engine test
On the plus side, we're getting twice the fuel efficiency that we had planned for (at least at 3000 RPM), so that's good.
We are very concerned with these two problems. What could be causing the ignition problem? And as for the power loss, we need to solve this problem rather quickly. Is it the prop? Is it just the break-in performance? Is it due to the test being static and not in flight?
Thank you for your assistance,
Graylan Vincent
University of Washington Aeronautics & Astronautics
04-28-2003, 05:53 AM
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problem posibly solved
Hi Mike,
I had talked to you on thursday about a low power/hot running engine.
I think we've solved the problem. We actually broke our 3-bladed 22-12 Zinger, so we tried a Menz 26-8 and the RPM's shot up to 6,300 from the Zinger's 5,000.
The RPM's may also have been limited because we were using a power source, not batteries. I'm not sure if the power source was able to put out the current required by the ignition, so we'll have to test it when our batteries come.
As for the high temperatures, I had mentioned that we were using a thermocouple installed at the base of the spark plug. I don't know if this was calibrated, but I think the high temp was simply due to it being a different temp measuring method than with the infrared guns. We're measuring closer to the inside of the piston, whereas an infrared gun is getting the dissipative effects of the cooling fins. We ran the engine for a couple of hours, at different RPM's and it seemed fine. We watched the temps rise at higher RPMs and drop off to the same point at idle. We also pulled the muffler and checked the piston, which looked fine.
Anyways, other than a slightly low RPM, I think the engine is running well. Thanks again for your help,
Graylan Vincent
University of Washington
Here's the details which I posted in the giant engine forum:
http://www.rcuniverse.com/showthread...269&forumid=37]
I had talked to you on thursday about a low power/hot running engine.
I think we've solved the problem. We actually broke our 3-bladed 22-12 Zinger, so we tried a Menz 26-8 and the RPM's shot up to 6,300 from the Zinger's 5,000.
The RPM's may also have been limited because we were using a power source, not batteries. I'm not sure if the power source was able to put out the current required by the ignition, so we'll have to test it when our batteries come.
As for the high temperatures, I had mentioned that we were using a thermocouple installed at the base of the spark plug. I don't know if this was calibrated, but I think the high temp was simply due to it being a different temp measuring method than with the infrared guns. We're measuring closer to the inside of the piston, whereas an infrared gun is getting the dissipative effects of the cooling fins. We ran the engine for a couple of hours, at different RPM's and it seemed fine. We watched the temps rise at higher RPMs and drop off to the same point at idle. We also pulled the muffler and checked the piston, which looked fine.
Anyways, other than a slightly low RPM, I think the engine is running well. Thanks again for your help,
Graylan Vincent
University of Washington
Here's the details which I posted in the giant engine forum:
http://www.rcuniverse.com/showthread...269&forumid=37]
04-28-2003, 01:10 PM
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New ZDZ 80 w/problems-stuttering ignition, low power/thrust
Graylan, That is very good news. I was very worried there for a while. Please keep me posted.
Thanks,
Mike Dooley
RC Showcase
Thanks,
Mike Dooley
RC Showcase
