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New Electronic Ignition Option - Show and Tell

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toobuilder

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I recently installed Ross Farnham's new CPi ignition system and it's performing well. I figured some of you might find the installation interesting.


First off, Ross has a bunch of parts to make a complete installation kit for the 4 banger Lycomings, but he's still ramping up the 540 stuff. I've been following development of CPI for a while and just couldn't stand it anymore- so after begging him for the basic components, I had to develop my own "installation kit".


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First up is the hall sensor bracket. I came up with the .250 thick mount plate, a machined .750 dia x 1.9 spacer, and a 1.9 inch long, 5/8 hex "nut", which I machined to length, drilled and tapped for the case stud.
The extra long NAS bolt shown replaces the lower case through bolt, and the two 10-32 lock nuts complement the capscrews holding the hall sensor to the bracket. Also, the spacer and nut are machined to the exact length needed to provide the correct air gap for the hall sensor. If anyone wants to try this installation before Ross gets the 540 parts out, shoot me a PM, I can provide more specific dimensions/drawings.


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Here is the whole thing installed and ready for the ring carrier (flywheel)


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Here's the ring carier installed. Ignore the hieroglyphics on the back side. That was me trying to get my head around magnet positioning. (Quite easy, actually)


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Though the coil can be mounted anywhere, I decided to keep the wires short and mount it on the backbone of the case. Simple aluminum extruded angle stock and a couple more spacers.


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Here is the coil ignitor module, mounted just behind the coil on the backside of the baffle. The overly thick mount plate shown is my attempt at a "cold plate" heat sink. That, coupled with the large surface area of the rear baffle should ensure the ignitor never generates more heat than it can handle.


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And finally, the whole package. (And yes, the rear baffle seal is flipped out of the way for the picture).


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You will have to excuse the seemingly hasty installation shown on this picture. I'm out of room on this panel and this is one of the few places left that I can get at it easily. Eventually, the brain will be hidden. Once the curve is set, I'll lock down the settings and forget about them.


I have more than 3 hours on the system now and most of that has been taking data to figure out the best curve, and also to run some "what if" scenarios. That data is for another thread, but I do have some bottom line data relevant to this thread: What did this ignition do for me WRT fuel flow and performance?

As a baseline, my old cruise numbers used to be 191 KTAS @ 11.5 GPH. (16.6 MPG)

Economy: So for a test this morning I leaned the engine until I found my "old" 191 KTAS. Resulting FF: 10.9. (17.5 MPG) So it looks like I picked up over half a gallon of fuel per hour for the same performance.

Engine output: so let's turn up the heat a bit and use my old fuel flow of 11.5 and see what that does for speed. Resulting speed: 198 KTAS. Same fuel flow at higher speed means better MPG, or in this case, 17.2 MPG.

Not a bad improvement!

Just as another data point I also richened it up to peak EGT (12.0 GPH) and that gave me 202 KTAS (still better economy than the baseline- 16.8 vs. 16.6) and going to 100 ROP gave me 205 KTAS @ 16.0. (12.8 MPG).
 
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