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

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#### Protech Racing

##### Well-Known Member
FWIW. I have all of the stuff to EFI the engine. But realty is that there is a lot of stuff, pointed out above and the carbs will be simpler, lighter and until you get icing that you cant engineer around, I would stay with a carb.

#### Vigilant1

##### Well-Known Member
FWIW. I have all of the stuff to EFI the engine. But realty is that there is a lot of stuff, pointed out above and the carbs will be simpler, lighter and until you get icing that you cant engineer around, I would stay with a carb.
Yes, it's not a very clear situation. The stock carb and ignition work fine for the OEM mission of the engine, but have some shortcomings in aero use (esp wanting lower idle and higher power than stock). And yet, using some of the aftermarket automobile EFI/electronic ignition systems on these small engines can feel like overkill ("killing an ant with an atom bomb").
If the stock hardware can be adapter to work, that would be great.

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#### Basil

##### Well-Known Member
HBA Supporter
I'd be inclined to fit a pair of Mikuni VM carbs to cover the icing and power side but I think a variable timing ignition would be required to get a slower idle.

#### Vigilant1

##### Well-Known Member
I'd be inclined to fit a pair of Mikuni VM carbs to cover the icing and power side but I think a variable timing ignition would be required to get a slower idle.
The Mikunis have a good reputation. I know Tipi has another trick or two he wants to try to allow for adjusting the mixture on the OEM Nikki carb as well as giving at least two-step adjustable timing from the OEM "magnetron" ignition.
The stock stuff is "free," proven, and robust. OTOH, I've certainly wasted a lot of money and time over the years trying to make something work when a fresh approach was what I should have pursued.

#### Vigilant1

##### Well-Known Member
I’m following his [jbiplane] work, might be an option if he comes up with a simple & reliable system. Speeduino is also on the radar as well as nanoEFI.
JBIplane posted an update with a photo of the hardware in his EFI system and a proposed price ($320 US, plus shipping from Eastern Europe). As shown it has a single throat throttle body and one injector, so to work well with the uneven induction of the V-twin it would likely need a dual-throat TB and a second injector (but he says his ECU can work with a 4 cyl engine, so presumably it can support 2 injectors). It remains to be seen if some MAP averaging, "lowest MAP in last cycle", or some other logic would be needed to get the fuel flow right in the very "lumpy" V-twin induction flow. Obviously , the details will be important. His ECU does include an ignition function, so with coils and wires (more$) it could address the timing challenges with the stock B&S magnetron ignition. And for folks wanting to drive a prop from the PTO end and get rid of the B&S flywheel, a separate electronic ignition system might make things simpler (no need for magnetrons and their magnets in the flywheel).

This might eventually be another option, if all looks good in testing.

Mark

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#### LHH

##### Active Member
Kohler has an EFI series with a diagnostic app
Kohler app is on Google play, displays temps, battery, RPM and so on.

#### Vigilant1

##### Well-Known Member
Kohler has an EFI series with a diagnostic app
Kohler app is on Google play, displays temps, battery, RPM and so on.
Thanks. It probably works great on lawn products, etc. It looks similar to the B&S EFI system. Closed loop . Unspecified failure modes, limp home triggers and limp home engine output values.

#### Hot Wings

##### Grumpy Cynic
HBA Supporter
Log Member
Closed loop .
I really don't think closed loop is going to be a problem with the converted industrial engines - if you choose to use it for other than tuning.
Can't say for sure, because I've never tried it, but I suspect 100LL not going to work well in them. Those of us that do end up using industrial engines probably shjould get comfortable with hauling our own fuel.

Pictsidhe's (what ever happened to him?) idea of using a variable air leak/bowl vent to lean for altitude is still a simple option for carbs.

#### Vigilant1

##### Well-Known Member
I really don't think closed loop is going to be a problem with the converted industrial engines - if you choose to use it for other than tuning.
Can't say for sure, because I've never tried it, but I suspect 100LL not going to work well in them. Those of us that do end up using industrial engines probably shjould get comfortable with hauling our own fuel.
The 100LL issue would probably be just a minor inconvenience (unless going cross country and not being able to find unleaded fuel).
1) Having to run at stoichiometric AFR rather than "best power." That might take 2-3 HP off the table.
2) Not being able to richen the mixture for head cooling. Primarily a factor at high power levels, but also handy during refinement of baffling, high OAT, etc. It can be useful.
3) What is the failure mode when the lambda sensor does crump out?

Pictsidhe's (what ever happened to him?) idea of using a variable air leak/bowl vent to lean for altitude is still a simple option for carbs.
Dunno where pictsidhe got to, hopefully he'll check in. Tipi had a groovy leaning gizmo fashioned from a pull rivet, IIRC.

ETA: Tipi mentions his variation on the Hacman mixture control in this post, more discussion and pictures in posts after that: Briggs vanguard conversions

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#### Hot Wings

##### Grumpy Cynic
HBA Supporter
Log Member
1) Having to run at stoichiometric AFR rather than "best power."
I think you are confusing wide band with the first generation on/off sensors?

#### Vigilant1

##### Well-Known Member
I think you are confusing wide band with the first generation on/off sensors?
View attachment 110546
Is the O2 sensor in the B&S (Delphi) EFI system or the Kohler EFI system a wideband sensor? I couldn't find a full description of it. The system operation in the B&S EFI manual was fairly sparse, but did seem to indicate that in normal running operation the mixture wasn't strictly determined only by lambda, but also be MAP, etc. That would indicate it isn't simply 14.7 AFR all the time. Yet, IIRC, previous discussions here indicated it would be in closed-loop and just stoichiometric during normal ops.
Clarification would be very welcome.

#### Hot Wings

##### Grumpy Cynic
HBA Supporter
Log Member
Is the O2 sensor in the B&S (Delphi) EFI system or the Kohler EFI system a wideband sensor?
Pulled up the B+S EFI wiring diagram:
The B+S (don't have Kohler data) O2 sensor is a heated old school unit. But that doesn't limit you to stoichiometric. Way back in the ice ages we could 'adjust' the O2 sensor output with a simple voltage divider. This can be done by the ECU..........but I suspect the stock B+S EFI doesn't.

Spoofing sensors is pretty basic. It is the graceful, or not, failure modes that will separate the aircraft EFI from ground bound.

#### Vigilant1

##### Well-Known Member
Pulled up the B+S EFI wiring diagram:
The B+S (don't have Kohler data) O2 sensor is a heated old school unit. But that doesn't limit you to stoichiometric. Way back in the ice ages we could 'adjust' the O2 sensor output with a simple voltage divider. This can be done by the ECU..........but I suspect the stock B+S EFI doesn't.
Thanks.
Yeah, I saw some aftermarket doohickies sold to allow users to improve power from their Kohler EFI engines.
It is the graceful, or not, failure modes that will separate the aircraft EFI from ground bound.
That's a biggie.

I did notice in the B&S EFI manual that at least some versions of the 49 series retain the diaphragm fuel pump (working off crankcase pressure pulses, like the ones on carb engines). Seemed surprising that such a pump could meet the pressure requirements of EFI systems. Maybe I read it wrong and these are some sort of pre-pump.
Edited to add: I re-checked. The diaphragm pump just pushes fuel to the electric EFI pump. The electric pump provides the pressurized fuel to the injectors.

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#### Hot Wings

##### Grumpy Cynic
HBA Supporter
Log Member
I did notice in the B&S EFI manual that at least some versions of the 49 series retain the diaphragm fuel pump
My version of the EFI manual says the 810 uses the diaphragm pump to lift the fuel from the tank and the electric injection pump then supplies the 39 PSI. It goes on to say that the marine version uses an electric lift pump ......... probably because those tanks may be more remote?

I haven't had 'hands on' on one of the fuel pump modules but from the manual and looks of the thing it is a mini reservoir of fuel that surrounds the high pressure pump with a built in pressure regulator. The system is a dead end type with the injectors at the end of the system. It is simple, but can lead to hot start problems if the injectors get hot enough after shut down to boil off the fuel. The fuel system up stream of the fuel module is only pressurized by the primary pump and may also be a source of similar problems, depending on the fuel system layout.

#### TiPi

##### Well-Known Member
Log Member
Pulled up the B+S EFI wiring diagram:
The B+S (don't have Kohler data) O2 sensor is a heated old school unit. But that doesn't limit you to stoichiometric. Way back in the ice ages we could 'adjust' the O2 sensor output with a simple voltage divider. This can be done by the ECU..........but I suspect the stock B+S EFI doesn't.

Spoofing sensors is pretty basic. It is the graceful, or not, failure modes that will separate the aircraft EFI from ground bound.
Using a conventional O2 sensor (narrow band) limits you to stochiometric, simply because the signal from the O2 sensor is either near 0 or 0.9V. You have no idea how far to the lean or rich side the mixture is. The EFI system is varying the fuel injector signal to go slightly lean/rich all the time to be able to read the 0-0.9V O2 signal.
Most cars still run conventional O2 sensors as that rich/lean oscillation is also need for the catalytic converter to function. All the other gadgets (TPS/MAP/Air Mass sensor etc) are there for the time when the engine is running outside of stochiometric (cold start, acceleration, WOT). It is not needed if you run stochiometric other than cross-checking that the O2 sensor and converter are operating correctly. Most cars now have also an O2 sensors after the converter to keep an eye on it.

#### Hot Wings

##### Grumpy Cynic
HBA Supporter
Log Member
You have no idea how far to the lean or rich side the mixture is.
You don't need that data unless you are trying to adjust fast enough to calculate injector pulse for each power stroke. We can count cross over and bias that point well enough to move the air/fuel ratio a bit. Works just fine with the old CIS systems.* Duplicating that system functionality in software should be possible?

There are other paths to the same result that may actually be simpler.

*
"Don't rush me I'll get around to adjusting the fuel flow in a few more revolutions."

#### TiPi

##### Well-Known Member
Log Member
You don't need that data unless you are trying to adjust fast enough to calculate injector pulse for each power stroke. We can count cross over and bias that point well enough to move the air/fuel ratio a bit. Works just fine with the old CIS systems.* Duplicating that system functionality in software should be possible?

There are other paths to the same result that may actually be simpler.

*
"Don't rush me I'll get around to adjusting the fuel flow in a few more revolutions."
That is not the point. With a narrow band O2 sensor, once you are on the lean side of the stochiometric (AFR14.7 - Lambda 1.0), the ECU has no idea if you are 14.8 or 18.4! Same on the rich side. It must have that oscillation around Lambda 1.0 to know where the mixture is. And it can only mainatin Lambda 1.0, no other value. If there is no converter attached and no need to meet emission targets, the frequency of the oscillations just needs to meet the needs of the engine operation (steady rpm/load or variable rpm/load). But it still can't do anything else than Lambda 1.0.

#### Vigilant1

Interesting find: This place has the 49G model engines on sale for $700 (US) . These are the engines for propane generators, they are the only model with a tapered shaft on the PTO end of the crank. Not a Vanguard, but IIRC the exhaust valves were upgraded (chrome). I don't know if the conrods and crankshaft are forged, like the Vanguard parts are. These propane models don't come with a carb suitable for liquid fuels, but if you plan to fit your own different carb or use a custom EFI... Anyway, may be of interest to someone wanting to mount a prop on the PTO end. On another note: There was some concern here a while back about the future of the 49 series. It is just one data point, but this retailer still seems to be getting plenty of them with about 60 Vanguards on hand and about 170 of the Commercial and Professional lines. Last edited: #### karmarepair ##### Well-Known Member HBA Supporter Interesting find: This place has the 49G model engines on sale for$700 (US) . These are the engines for propane generators, they are the only model with a tapered shaft on the PTO end of the crank.
I'm not sure about the 49 series, but the older K and Magnum series the propane models had heads with smaller chamber volume and thus higher compression ratios. The tractor pullers use propane heads when running Methanol or VP Racing gasoline. I would check the chamber volume before running a propane engine on gasoline, me.

#### TiPi

##### Well-Known Member
Log Member
I'm not sure about the 49 series, but the older K and Magnum series the propane models had heads with smaller chamber volume and thus higher compression ratios. The tractor pullers use propane heads when running Methanol or VP Racing gasoline. I would check the chamber volume before running a propane engine on gasoline, me.
that is correct but I have not found any info on the CR for the propane 49G. It is most likely simply be a shaved head as the head has a very deep but small chamber. The piston comes to the top of the bore and only the gasket thickness separates the piston crown from the head. Piston P/N was the same for the 49G, 49M, 49S & 49T. The 49G has a unique P/N for the heads, all other models are using either the Professional or the Vanguard heads (Vanguard has better quality valves, no other difference).
As the generator engine has the lowest forces of all applications (no side or thrust load, impacts etc), the bulk of the engine will be Professional/Commercial standard.

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