# B&S 49-series (810cm3/49ci) for aircraft use - TiPi's Q&A thread

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#### Vigilant1

##### Well-Known Member
Briggs coil with large air gap (could be around 8-10deg over rpm range, might need stronger magnet)
Is this the idea of the stepped flywheel/stepped trigger spacing as you mentioned here: Simple, proven, off-the-shelf industrial V-twin? ? It seems like a clever approach, but possibly fiddly (to get the spacing right). It also seems unlikely that both cylinders would make the "hop" to the new timing at the same time.

I guess there's no practical way to have multiple selectable trigger coils per primary magneto, or to electronically delay the triggering of the main spark impulse.

#### TiPi

##### Well-Known Member
Log Member
Is this the idea of the stepped flywheel/stepped trigger spacing as you mentioned here: Simple, proven, off-the-shelf industrial V-twin? ? It seems like a clever approach, but possibly fiddly (to get the spacing right). It also seems unlikely that both cylinders would make the "hop" to the new timing at the same time.

I guess there's no practical way to have multiple selectable trigger coils per primary magneto, or to electronically delay the triggering of the main spark impulse.
That is the big question. I found some info on a kart site where they show that the timing changes quite a bit with increased air gaps (single cylinder engines).
The step is just another way of introducing a larger gap that will retard the timing at low revs. Only testing will show if they are suitable for 2-cylinder engines. As long as the timing between both cylinders is the same at idle and cruise/WOT, it should work. The rpms between idle and cruise/WOT are not used for normal operation, so the transition from retard to max advance doesn’t need to be synchronised.

#### Hot Wings

##### Grumpy Cynic
HBA Supporter
Log Member
Just one data point from history:
Some of the Quickie builders modified the Onan timing using the caveman method of mounting the ignition parts on a manually controlled plate.

I think there are more elegant ways of getting a better advance curve but if retaining stock(ish) coils and flying magnets is a priority than it is an option.

@ TIPI
Totally understand about the workspace delays. I still have some drywall and brick work to do before I can get the rest of the electrical in. To many other spring related tasks that have priority. Mother nature just doesn't care about my desired schedule..............

#### blane.c

##### Well-Known Member
HBA Supporter
I would think the first thing the crank sensor signal would go to would be a interpreter/timer. If you do your best work and you install the crank sensor so it triggers pretty close to were you want it the interpreter can fine tune it exactly (it may not matter where the sensor is the interpreter just adjusts to what you want it to be). Secondly it electronically sends out a second signal automatically timed to the first for of course the second cylinder. Then everything downstream gets two properly timed triggers. Is that how it works?

#### Vigilant1

##### Well-Known Member
Is that how it works?
I don't know about other systems, but it's not how the stock B&S magnetrons work. Each cylinder/magneteon is independent. As I understand it, it has a main coil that develops current as the magnets in the flywheel go by, and this charge is stored in a capacitor. There's a second coil that is a trigger, when the magnet goes past this and the juice it is making begins to trail off, a circuit trips the stored energy in the capacitor to go to the sparkplug. So, no delay and no linkage between cylinders. Timing is determined by the placement of the trigger coil, which is integral to all the other stuff--one clunky, fixed timing, cheap, reliable, assembly per cylinder.
Obviously, it is a "wasted spark" ignition, since the coil is charged/discharged with every revolution of the crank.

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#### blane.c

##### Well-Known Member
HBA Supporter
I don't know about other systems, but it's not how the stock B&S magnetrons work. Each cylinder/magneteon is independent. As I understand it, it has a main coil that develops current as the magnets in the flywheel go by, and this charge is stored in a capacitor. There's a second coil that is a trigger, when the magnet goes past this and the juice it is making begins to trail off, a circuit trips the stored energy in the capacitor to go to the sparkplug. So, no delay and no linkage between cylinders. Timing is determined by the placement of the trigger coil, which is integral to all the other stuff--one clunky, fixed timing, cheap, reliable, assembly per cylinder.
Obviously, it is a "wasted spark" ignition, since the coil is charged/discharged with every revolution of the crank.
So the spark advance/retard is fixed?

#### blane.c

##### Well-Known Member
HBA Supporter
If the spark is mechanically controlled or fixed then EFI is not likely to be much improvement if any over carburation? With the spark you described and a single engine airplane with two cylinders flying in formation with the same crankshaft (V Engines) then most likely two carbs is answer? Each cylinder is tuned as a single and so two mixture controls & cables, two chokes & cable with linkage [unless replacing with primer(s)] and two throttles with linkage that allows to dial in one cylinder independent of the other. Tuning would need to be done with two manifold pressure gages and they could be part of the engine instruments package. I imagine some of the Siamese carbs amount to the same difference depending on if they have individual mixture control and how reliable they are. Without the ability to properly lean each cylinder these (V) engines are not likely to perform as well as they should?

Part of the charm of EFI is when the spark advance/retard is also controlled by the computer. The fuel metering can be tailored to each cylinder as well by the computer eliminating the need of the pilot to do this chore.

With single engine operation one may desire to do without a computer between the pilot and the engine, just a rudimentary spark and a couple of carburetors, swilling a little extra fuel along the way is OK for the trade in reliability.

With multi engine operation the computer becomes less of an evil and more of an ally as you are not likely to lose the computer in two engines at the same time and it reduces the pilots workload and each engine can be more efficient.

#### Vigilant1

##### Well-Known Member
Apparently, previously I wrote that the B&S EFI does control spark timing. So, I misremembered that. The B-S EFI has some other attributes that make it less than ideal for acft use IMO:
1) closed loop operation, so won't achieve best power mixture, will eventually have sensor failure if running 100LL.
2) Single point failure modes (crank sensor, electrical power, etc)
3) Unidentified limp mode criteria and power output.

My description in Post 265 applies to B&S engines with carbs and magnetron ignitions.

Sorry for the confusion.

ETA: Tipi provided a link to his copy of the B&S EFI manual. See his post with link here: Forum made EFI?

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#### tunna95

##### New Member
Apparently, previously I wrote that the B&S EFI does control spark timing. So, I misremembered that. The B-S EFI has some other attributes that make it less than ideal for acft use IMO:
1) closed loop operation, so won't achieve best power mixture, will eventually have sensor failure if running 100LL.
2) Single point failure modes (crank sensor, electrical power, etc)
3) Unidentified limp mode criteria and power output.

My description in Post 265 applies to B&S engines with carbs and magnetron ignitions.

Sorry for the confusion.

ETA: Tipi provided a link to his copy of the B&S EFI manual. See his post with link here: Forum made EFI?
Could you use the BS EFI hardware and swap out the ECU with say a Speeduino with custom parameters suitable for aircraft use?

#### Vigilant1

##### Well-Known Member
Could you use the BS EFI hardware and swap out the ECU with say a Speeduino with custom parameters suitable for aircraft use?
I'd have to look back at the B&S EFI bits, but I suspect it would be easier and certainly cheaper to start with a carbureted B&S engine and add the Speeduino ECU and other stuff off the shelf. A used twin-throat throttle body with injectors from a suitable motorcycle can be had very inexpensively.

#### Urquiola

##### Well-Known Member
EFI is still an option if I can’t get a single carby to work properly (single or dual barrel). The challenge with EFI is to identify and address all possible and likely failure modes while keeping it simple. No point in designing an EFI system that will cost the same as the actual engine.
If my information is still right, FAA did not allow EFI in General Aviation, if rules differ for ultralight and homebuilts, I don't know. www.ecotrons.com has a line of EFI for small engines, in Italy, they sell Turbocompressors for Vespa Two-Stroke engines. You may like this SAE technical paper: 2003-28-0017 'Altitude Performance Comparison of A Wankel Engine with Carburetor and Fuel Injection', can be downoald from SAE for $33, membership not needed. Wankel News, magazine from Hercules Wankel IG, has some documents about EFI for Sachs small Wankel engines. Blessings + #### TFF ##### Well-Known Member EFI is allowed in general aviation in the US. It is not economically feasible to certify it, because it would require recertification of each aircraft to add that system. Homebuilts US rules is any risk you want to take is up to you as long as you can get the paperwork signed. 103 ULs no rules except speed and weight. #### Urquiola ##### Well-Known Member EFI is allowed in general aviation in the US. It is not economically feasible to certify it, because it would require recertification of each aircraft to add that system. Homebuilts US rules is any risk you want to take is up to you as long as you can get the paperwork signed. 103 ULs no rules except speed and weight. The issue could be if your flying machine falls, it can harm not only you, but third parties. Also insurance companies avoid any daredevil attitude. Blessings + #### TFF ##### Well-Known Member You can build a homebuilt out of bread in the US. Wing folding is your problem. If you did stretch the engineering to that, the FAA can restrict passengers and other things. There are safety valves to keep it your own problem. If you need insurance on a baked bread airplane, don’t land where there is animals. That’s your insurance. #### WonderousMountain ##### Well-Known Member You won't be cleared for landing if tower is gluten intolerant. #### Urquiola ##### Well-Known Member You won't be cleared for landing if tower is gluten intolerant. Perhaps for risk analysis, budget spread, Insurance companies are classifying diseases to the minor detail, they have different codings for human bites, for bites from a cow, a dog,.. Blessings + #### Protech Racing ##### Well-Known Member Some points . I race and sell Microsquirt EFI. I have a standard template now and have a bunch of cars using the same bits. Tunes vary with actual fuel pressure but overall the maps are very similar . As a rule , if it starts and runs , failures have not happened. Failures that have happened. include the LS coils, I now use standard OTS VW waste spark smart coils. I race these and power/results are crucial for me to make a living . Any AFR between 12.2 and 12.6 make effectively the same power . I tune in closed loop , race in open loop. I dont use a TPS. Simply a GM map sensor, NIssan or Ford RPM trigger. The Nissan bolts up more solid and vibration can lead to a high RPM trigger fault. The Nissan trigger and pig tail is robust. Use a wide band O2 sensor and the deal can tune it self . You may use a flying bolt for a trigger or a toothed wheel . These little engines will not burn enough fuel to worry about lean cruise. The map can be tailored for lean RE to the map . You simply will not need to tune each cylinder. The system will allow you to time each cylinder as you see fit . There is a "kick start " timing set. at 0 or 1 BTDC. If you find that the heads flow better than the other , you can trim the AFR with inlet tube length. It is a simply system and would work fine on these engines . As usual, desk engineers are overthinking it. #### Flyguyeddy ##### Well-Known Member HBA Supporter Some points . I race and sell Microsquirt EFI. I have a standard template now and have a bunch of cars using the same bits. Tunes vary with actual fuel pressure but overall the maps are very similar . As a rule , if it starts and runs , failures have not happened. Failures that have happened. include the LS coils, I now use standard OTS VW waste spark smart coils. I race these and power/results are crucial for me to make a living . Any AFR between 12.2 and 12.6 make effectively the same power . I tune in closed loop , race in open loop. I dont use a TPS. Simply a GM map sensor, NIssan or Ford RPM trigger. The Nissan bolts up more solid and vibration can lead to a high RPM trigger fault. The Nissan trigger and pig tail is robust. Use a wide band O2 sensor and the deal can tune it self . You may use a flying bolt for a trigger or a toothed wheel . These little engines will not burn enough fuel to worry about lean cruise. The map can be tailored for lean RE to the map . You simply will not need to tune each cylinder. The system will allow you to time each cylinder as you see fit . There is a "kick start " timing set. at 0 or 1 BTDC. If you find that the heads flow better than the other , you can trim the AFR with inlet tube length. It is a simply system and would work fine on these engines . As usual, desk engineers are overthinking it. Which coils are the ones you speak of? #### Flyguyeddy ##### Well-Known Member HBA Supporter These? Vw 032 905 106B #### Vigilant1 ##### Well-Known Member Lifetime Supporter Microsquirt: How much to get into the game?? ECU and harness:$360
Used throttle body and injectors: $100 Fuel pump (45 psi):$150
Misc fuel hose and fittings: $40 Wideband O2 sensor for tuning:$200
Sensors: ?? CAS, MAP, temp, etc.
Lots of connectors and fittings, relay, fuse block, etc. You'll need a good crimper.

This is fuel side only. If you want to use it for ignition, add more wires, coils, connectors, etc.

You'll also need a laptop, but most people have one.

People converting a car to full Megasquirt/Microsquirt from old school carb spend $800+ Microsquirt might work great. Aeromomentum uses Microsquirt for their aero engines. The stock B&S Vanguard 810cc engine is available brand new for about$1200. Whether builders will choose to discard the OEM ignition system and carb and invest another \$800+ (about 2/3 the price of the complete original engine) for a MicroSquirt EFI and ignition system for their 2 cylinder, 30 HP motor remains to be seen. It probably depends on whether the advantages are seen as being worth the cost, and if it is the best overall option available. I would expect that perceived reliability would be an important criteria.

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