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  #1  
Old 01-08-2020, 03:49 PM
N546RV's Avatar
N546RV N546RV is offline
 
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Location: Brookshire, TX
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Default CPI2 current draw

Working on load planning and electrical system design, and I'm planning on dual CPI2 electronic ignition. However, there seems to be a discrepancy between sources as to what current draw to plan for.

The CPI2 product page says:
Quote:
Low current draw/ long spark duration. 4 cylinder coil pack and controller draw about 1.2 amps at 2500 rpm.
...but the installation manual, when discussing wiring concerns (page 5), says of the controller:

Quote:
The Purple 20 ga on the 14pin main harness plug, needs a 2 to 5 amp fuse or breaker. Current draw is less than 1 amp on this wire.
...and of the coil power:

Quote:
With SDS supplied coilpacks, average current draw is less than 6 amps below 5000 rpms.
Now, I do realize that, taking the "less than" wording used in the manual literally, there's no disagreement here, since 1.2 is definitively less than 7, but the manual seems to imply a higher current draw.

Long story short, I just want to verify that I'm choosing the proper values for load planning (particularly in regards to planning for various failures).

Thanks!
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  #2  
Old 01-08-2020, 04:50 PM
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rv6ejguy rv6ejguy is offline
 
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A couple of general notes here.

4 cylinder coil packs draw less current than 6 cylinder ones at a given rpm.

Current draw generally increases with increasing rpm (higher spark frequency). Pulling back the rpm in the event of an alternator failure should help extend your running time.

The CPI-2 has the ability to reduce coil charging time when a low voltage situation occurs to extend battery life. This results in lower average current draw. Coil saturation is reduced in this case which also reduces spark energy but will still fire the plugs in the relatively unchallenging environment of a naturally aspirated Lycoming engine at cruise power.

I'll try to run some bench tests tomorrow and get some more precise numbers, maybe shoot some video of both coil pack types running.

The CPI-2 controller and display don't draw much current, if memory serves me correctly, less than 0.6 amps but I will check that too so folks can get a total picture.
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Ross Farnham, Calgary, Alberta
Turbo Subaru EJ22, SDS EFI, Marcotte M-300, IVO, Shorai- RV6A C-GVZX flying from CYBW since 2003- 441.0 hrs. on the Hobbs,
RV10 95% built- Sold 2016
http://www.sdsefi.com/aircraft.html
http://sdsefi.com/cpi2.htm



Last edited by rv6ejguy : 01-20-2020 at 07:41 PM.
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  #3  
Old 01-08-2020, 07:00 PM
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N546RV N546RV is offline
 
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Thanks, Ross, that sounds great. I've got to say, your activity and willingness to help here on VAF is a big reason I decided to go with the CPI2 - it's definitely appreciated by me.
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  #4  
Old 01-09-2020, 12:32 PM
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We managed to run some tests here today so I'll try to sift the results and put up a vid and some numbers here soon.
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Ross Farnham, Calgary, Alberta
Turbo Subaru EJ22, SDS EFI, Marcotte M-300, IVO, Shorai- RV6A C-GVZX flying from CYBW since 2003- 441.0 hrs. on the Hobbs,
RV10 95% built- Sold 2016
http://www.sdsefi.com/aircraft.html
http://sdsefi.com/cpi2.htm


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  #5  
Old 01-09-2020, 09:35 PM
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rv6ejguy rv6ejguy is offline
 
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Default Current Draw Numbers

Ok here are some numbers from the testing today:

4 Cylinder, single coil pack and controller

1000 rpm- .76 amps
1500- 1.04
2000- 1.31
2500- 2.09
3000- 1.82

Current saving mode on backup battery at 2500 rpm- .77 amps

__________________________________________________ ______________

6 Cylinder, single coil pack and controller

1000 rpm- .78 amps
1500- 1.07
2000- 1.36
2500- 2.28
3000- 1.92

Current saving mode on backup battery at 2500 rpm- .89 amps


It's interesting to see the differences in current draw between the two at different rpms. These are two different coil brands. The 4 cylinder has integral drive transistors, the 6 cylinder uses an external transistor module. These transistors have different characteristics and the software is doing some things behind the scenes as well which explains the drop in current between 2500 and 3000 rpm on both setups.

Other factors like Magnet Position and timing value can change the current draws slightly but in this test, we kept those the same to make it apples to apples.

Note that a dual system running twin coil packs, would draw around double the current shown here.

You can see the value of the current saving strategy here in extending flight time on the backup battery.

I'll try to get the video up shortly.
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Ross Farnham, Calgary, Alberta
Turbo Subaru EJ22, SDS EFI, Marcotte M-300, IVO, Shorai- RV6A C-GVZX flying from CYBW since 2003- 441.0 hrs. on the Hobbs,
RV10 95% built- Sold 2016
http://www.sdsefi.com/aircraft.html
http://sdsefi.com/cpi2.htm


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  #6  
Old 01-10-2020, 05:48 AM
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steve murray steve murray is offline
 
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Quote:
Originally Posted by N546RV View Post
Thanks, Ross, that sounds great. I've got to say, your activity and willingness to help here on VAF is a big reason I decided to go with the CPI2 - it's definitely appreciated by me.

I will jump on this recognition of great service!

I am installing Ross's Dual ECU with fuel injection on my -10. The support from Barry has been nothing short of outstanding. I was working through a suspect issue earlier this week and these guys overnighted a part to me in one day. Very pleasant and knowledgeable on the phone, good at helping to troubleshoot.

No regrets at all with my decision to do business with these guys. You feel you are a valuable Customer with every interaction.


Steve
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  #7  
Old 01-10-2020, 08:05 AM
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rv6ejguy rv6ejguy is offline
 
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Thank you Steve. Every customer is important to us. Customers are the ones who sign our paychecks effectively and allow us to continue improving our products which make them more functional, attractive and reliable.

I enjoy coming to work every day, talking to pilots and builders all over the world and working on our new projects, R&D and building hardware. While I put in a lot of hours, it's very satisfying to me.

Folks in Experimental aviation are the best. We see we are part of a community of friends who share a love for aviation, building and flying.

Flying the airplane you built is a very rewarding experience. We want to see folks enjoying that experience.

If we screwed up something or could improve something, let us know. We want to make it right or better.
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Ross Farnham, Calgary, Alberta
Turbo Subaru EJ22, SDS EFI, Marcotte M-300, IVO, Shorai- RV6A C-GVZX flying from CYBW since 2003- 441.0 hrs. on the Hobbs,
RV10 95% built- Sold 2016
http://www.sdsefi.com/aircraft.html
http://sdsefi.com/cpi2.htm


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  #8  
Old 01-10-2020, 10:30 AM
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Ross,

Could you expand on the effects of normal operation vs current saving mode?

Using the 4-cyl example, 2.09 amps vs 0.77 is significant. I assume the difference is entirely primary current, so the result should be a greater or lesser magnetic field. What is the result in terms of voltage rise rate and arc duration? Know if anyone has switched back and forth while running high and very lean?

Quote:
Originally Posted by rv6ejguy View Post
We want to make it right or better.
Well said.
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  #9  
Old 01-10-2020, 10:43 AM
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Default CPI-1

Ross,
Do you think us guys running two CPI-1 systems would have similar results? The thread using different backup battery types has me thinking.
Thanks,
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  #10  
Old 01-10-2020, 11:25 AM
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Toobuilder Toobuilder is offline
 
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Didn't want to hijack a CPI-2 thread, but since it was asked, I measured my CPI-1 at 1.69 amps at 2700RPM. This was a 6 cylinder, single ignition only.
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WARNING! Incorrect design and/or fabrication of aircraft and/or components may result in injury or death. Information presented in this post is based on my own experience - Reader has sole responsibility for determining accuracy or suitability for use.

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