Adding redundant fuel and spark to auto/sled/motorcycle conversions.

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Daleandee

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Aha! Thanks. So, the complexity is there, just hidden under the plastic.

Dale, any feedback on the in-service reliability of the coil selector in Corvair service? And, if known, what's the typical failure mode (i.e "I can't change to my backup system", or "When the coil selector died, my backup system got fried" etc)
I incorrectly believed that most on this list were familiar with the set-up that I have that uses the MSD 8210 coil selector (yes, it has diode packs inside). Mallory used to make the same thing but I don't find them for sale any longer. My set-up uses two independent triggers for two separate ignition coils. William Wynn recommends a DPDT switch but my set up uses a SPST for each ignition system. MSD instructs that both ignitions NOT be run at the same time while the ones from Mallory said that doing so was OK. Some pilots run both ignitions for take-off & landing and I've heard no bad reports from doing so.

Mark ... I've never had any issue with my ignition set up. None. I've never heard of one of these units failing (though I'm certain it has happened as all things fail eventually). The primary ignition trigger is an electronic unit and the secondary ignition trigger is points. The secondary is timed slightly behind the primary (~ 2º) and both are advanced with the re-curved mechanical advance in the distributor. Total advance is currently 28º BTDC.

One of the VW conversions uses the Dyna S triggers for the coils of the secondary ignition:



The same sort of set up could be used with dual coils through a coil selector. Lots of ways to go at this ...

Dale
 

skydawg

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Jul 26, 2016
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this thread is getting way too complicated, me thinks. Again, I worked on an EFI system for FAA cert that used same OE automotive components for a V8 conversion that met the part 23 requirements. FAA really wanted us to use existing simple components, such as a distributor and or magnetos and carb or mechanical injection, essentially going back in technology by multiple decades. Regardless of how many spark plugs you use, there is still many single points of failures in these type mechanical systems and we tested several without much luck (and spark plugs just don't fail anymore, unless really running rich with leaded fuels which conducts electricity on electrodes at low RPM's). Mechanical components, and limited ability for real redundancy in such systems, was impossible without- as earlier post points out- causing more potential points of failures. Also, as modern OE engines were not designed for rudimentary fuel & spark delivery, only unproven aftermarket parts were available (we needed consistent QA in supply chain for FAA cert, so we didn't dwell much into the aftermarket).

As I mentioned earlier, we found OE EFI was way to go with a custom calibration and strategic redundancies. But as I also mentioned, this was an expensive process and required engine controller engineers to figure out the basic programming needed for 2 ECM's to work on same architecture and return a failed engine to operation within required time frame (we got it to less than 1 second with windmill prop). We worked for 3 years developing the system and was tested on a C172 test aircraft with great success; the test plan included a complex matrix of induced faults and never experienced any issue with the engine restarting in AUX mode or continue running with over 80% of its systems failed. It was a Delphi ECM used in millions of vehicles, and it had multiple layers of fault protection, including internal resets such as watch dog timers that reset software hangups within milliseconds. Point is, we could never of achieved this level of reliability with components currently discussed in this thread. Read my prior inputs on this thread for some more info on how we increased reliability using EFI.

I'm a former FAA DER and have seen many systems over-complicated in an effort to meet obsolete cert requirements, with many back-up designs actually adding more potential failure issues than not having back-up at all. We AB's don't have to worry about meeting cert requirements, and I'd suggest keeping a home made system simple and use quality materials and craftsmanship to mitigate failure risk, or buy a proven EFI aircraft system with a long & reliable history with some effective redundancy (but again, this is expensive process).

I got a number of messages asking about the EFI system developed for FAA cert and if its available. The engine is a GM LS series V8 heavily modified for aircraft application, including changes to lubrication systems, electrical and many other systems. It reduced the cost of operating the C172 by almost 65%, and outperformed the newest C172 model by a wide margin. The engine company that developed it is focusing on foreign market due to liability concerns in US, but will likely offer an experimental version later this year. This would be ideal for most AB's as the engine is production quality and way cheaper than trying to design and produce yourself. I'm not sure if they will sell just the EFI system as it was only calibrated for their engine, but can ask.......however, not sure what programming would be required to make it work with another engine. I think they were going to launch at Oshkosh, but not sure if event was cancelled. I can post update if anyone is interested.
 

BJC

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="skydawg, post: 523976, member: 45338" ... the EFI system developed for FAA cert ... a GM LS series V8 ... for aircraft application, ... likely offer an experimental version later this year. ... I think they were going to launch at Oshkosh, .... I can post update if anyone is interested.
Yes, please post updates.

Thanks, BJC
 

Victor Bravo

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Jul 30, 2014
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Skydawg, wasn't a V8 engine and associated systems way too much mass for the front of a 172? I would think that a 182 or 206 could handle that much weight (and whatever loads) more easily.
 

skydawg

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Jul 26, 2016
Messages
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Location
Denver, Colorado
Hi Victor
It is heavier and moved EOW CG forward about 2". Each ECM had own battery which were mounted in tail to offset. But with 400 pounds in front seats ballast was required. With just a single pilot or passengers in back seat it remains well in cg envelope.

Because the 220hp (most c172 was ever certified to) increased climb performance, MGW was increased to 2550, which was 250 more pounds more than early models, offset the increased weight and actually increased usable payload.

To increase the weight per faa, plane needed 6 ply tires and max 30 degree flaps for landing to increase go around climb rates.
 

TFF

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Apr 28, 2010
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Memphis, TN
At the right price, they will fly off the shelves. Most likely the people advocating for something like that are still going to scream “too expensive. “ Balancing our weight is not as big a deal on a fresh build or the right retro fit. It’s always the unrealistic dreamers that can’t get it through the noggin.
 
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