Surefly electronic ignition

[jliltd]

I put a SureFly on an angle-valve IO-360 and set it up for fixed-timing at the listed 25*. No manifold pressure line attached. The reason for this was after communicating with experienced people in the field it was found angle-valve engines don't respond as favorably or innocuously to advance timing curves like the more typical parallel valve Lycoming. I think Dan was more or less alluding to the same idea above (but I haven't ever been or propose to be as technically deep as Dan). Whether at altitude or coyote-chasing levels my angle-valve stays well behaved. When I swapped a mag out for a SureFly I was looking for reliability and easy hot starting more than anything. That's what I got.

I also have an RV with dual P-Mags and with the mild-curve jumper in place and I have been very satisfied with that. The SureFly is bulkier and more mag-esque and doesn't have a built-in dynamo to keep the sparks going without battery power like the P-Mag. They each have their place. As do a good quality set of CMI/Bendix mags (sacrilege!). I have been happy with all of them. You may note I leave out mention of Slicks, which in my personal opinion are **** throw-away at 500 hours no matter the model.

[DanH]

Two examples, return flights from OSH, 2018 and 2019. It's about a four hour run for me, so I usually schedule some kind of experiment so I won't get too bored. The ignition I'm using stores two complete, independent ignition maps. For this sort of test I load one at fixed 23 BTDC, and another with the experimental schedule. Back and forth is just the flip of a switch.

A little lean of peak at 9500, a common RV cruise configuration. 28 BTDC vs 23 BTDC, same flight, back to back. Note times, CHTs, oil temps, and speeds. BTW, these temperatures were all taken with the cowl flap closed, so cooling exit area was down around 30 sq in, about half a standard RV-8.



Again a bit LOP, this time at 16,500 feet and 23 vs 35 BTDC, the kind of advanced timing typical at this altitude (i.e. manifold pressure) for several of the EIs with mystery maps. Again note CHTs and oil temps vs speeds.



The higher CHTs correspond to high peak in-cylinder pressure. It's significant additional engine stress for no gain, and quite contrary to GAMI-APS philosophy, for those who respect George Braly, John Deacon, et al.

[sailvi767]

I am curious why the fuel pressure is so different between the two pics. The actual fuel flow is virtually the same.
G

[Scott Hersha]

Wow! That was the kind of actual data I was hoping for. I will be removing my manifold pressure line from my SIM and reconfiguring for fixed timing. The only question remaining for me is will I get a fixed 25* timing the way I have it set - 30* fixed dip switching, timed to 5*ATDC. I like the way this setup starts the engine. Bette to me anyway, than when I had my timing set at TDC (with a 25* dip switch setting). SureFly tech to answer this question, I hope.

[DanH]

Originally Posted by sailvi767

I am curious why the fuel pressure is so different between the two pics.

VDO mechanical sender was crapping out.

[Carl Froehlich]

Dan,

Good data. Can you provide your thoughts as to why you got these results?

Carl

[rv6ejguy]

Nice data Dan. Thanks for posting.

[bjdecker]

Thanks Dan -- What do the numbers look like if the RPM is the same (2nd set of pictures -- 2430 vs 2530).

[Scott Hersha]

I spoke with a SureFly tech rep today about my setup with my SIM/Slick mag on my O-360 RV4, namely start timing set 5*ATDC, and dip switch set to 30* (25* engine). His response - some of that is OK, and will work like I think it will - but only partially. With a wasted spark EI system, when I set my timing to 5* ATDC, that also influences the wasted spark on the opposite cylinder. That wasted spark is supposed to occur at TDC on the exhaust stroke of the opposite cylinder when the exhaust valve is fully open. When I fool it to fire 5* later, that wasted spark is occurring after the exhaust valve is starting to close. How much is it closed? Who knows, but it is not the way they recommend operating it, and granted, that modification of the recommended setup is only occurring during the start cycle because the run cycle is still 25* actually. But, he told me they have experienced zero reported incidence of engine start kickback when installed as designed, and they have plenty of light weight props in the field.
Today I reconfigured my SIM to 25*, fixed timing (manifold pressure port disconnected and capped). One other thing he asked me that I hadn’t considered was how I am timing my ignition. I timed it just like I would time a Slick. He said there is quite a bit of slop in the gearing in the engine and in a traditional mag that doesn’t exist in the SureFly SIM - it is very precise. He recommended finding TDC on cylinder #1 compression stroke using a dial indicator riding on the piston to find the exact TDC. Using the marks on the flywheel will get me in the ball park and is OK for an equally inaccurate Slick, but that should be fine tuned to the actual accurate piston TDC. Maybe others do it this way normally, I just never have. That’s part of my task tomorrow before test flying to see if I can notice any difference with these changes.
Bottom line - I wouldn’t recommend setting up your SIM the way I did it with retarded start timing. Install it the way the factory recommends.

[BlndRvtr]

Originally Posted by Scott Hersha

...fixed timing (manifold pressure port disconnected and capped).

FYI Scott, last time I talked to SureFly they no longer recommend capping the MP port when running fixed timing, just to leave it open.

George