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

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sotaro

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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.
If the head were shaved, wouldn't some part of the valve train be of different dimensions, such as push rod length? Perhaps the combustion chamber itself is just cast smaller.
 

TiPi

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good pick-up :) The valve adjustment screw is on the pushrod end of the rocker so it is self-adjusting for varying head thickness. The only dimension that is determining the valve geometry (rocker contact across the valve stem end) is the postion of the rocker post, and that doesn't change with shaving the head. The only influence is the valve wear or re-cutting the seat/facing the valve.
 

Vigilant1

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An observation: For whatever reason, B&S apparently sells a lot more 724cc engines (44 series) than they do 810cc engines (49 series). The 44 series engines can be found on lawn tractors as well as smaller ZTR mowers, and lawn tractors are pretty easy to find in scrapyards, etc. Seems I find at least eight 44s for every 49 I see
The 44 and 49 have the same stroke, the bore is different. I would think some of the 44 parts could be used on a 49, if desired. But, B&S doesn't make a 44 to the Vanguard spec. By going through the parts lists to find common numbers, it might be possible to find at-hand replacements.If there are enough common parts, it might make sense to buy a greasy, dead 44 just to serve as a donor engine.
Sorry, a random musing.
 
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WonderousMountain

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Yes, I've just about commited to using a Kawasaki Crank in Kohler's 725.
The one with the funny top-plate issue. The 810cc has nowhere to go, it
can't become a 900cc near liter, or a light-block 6-700 series from several
manufacturers, and it is not popular in anything yet. However, I expect it
to continue as a maybe worthwhile upgrade. If ten percent on price can
be gotten, it will pay for itself many times over. My conversion comes out
~900cc, and I intend on turbo normalizing. Leave the liters some glory.
 

Vigilant1

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Yes, I've just about commited to using a Kawasaki Crank in Kohler's 725.
The one with the funny top-plate issue. The 810cc has nowhere to go, it
can't become a 900cc near liter, or a light-block 6-700 series from several
manufacturers, and it is not popular in anything yet. However, I expect it
to continue as a maybe worthwhile upgrade. If ten percent on price can
be gotten, it will pay for itself many times over. My conversion comes out
~900cc, and I intend on turbo normalizing. Leave the liters some glory.
You are starting with a Kohler 725cc and it will end up being approx 900cc? Wow.

Push some air through those fins!
 

TiPi

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This is a YouTube clip of a transparent carburetor running on a single-cylinder engine

It is a bit long-winded but it shows some interesting patterns with the fuel/air flows. What surprised me was the amount of bubbling in the float chamber as this has been mentioned a few times as being a problem with some engines if they vibrate too much.
 

Hot Wings

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What I found interesting, and that I had never considered, is the inertia of the fuel in the delivery tube between intake strokes.
 

Vigilant1

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What I found interesting, and that I had never considered, is the inertia of the fuel in the delivery tube between intake strokes.
During testing of a new configuration, a test rig with clear parts, good lighting, and maybe a high speed camera could save a lot of time and guessing. For example, it can take a lot of trial and error to figure out if fuel is condensing in long runners, if it is pooling somewhere, etc.
Maybe the new small inspection cameras can also be used. Even a small 10mm camera inserted into the induction system might affect flows, but it still might yield useful info (and might be pretty simple to do).
Unbalanced mixture between cylinders might be easy to identify by wideband O2, but it can sometimes be tricky to figure out the cause, especially if the induction system is asymmetric.
The VW guys learned a lot when somebody built a set of valve covers with windows. Lots of oil was pooling in one side, significantly less flow/pooling on the other side. Similar tricks might be needed to see where the oil is going in an inverted 810.
 
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Vigilant1

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I was recently looking at a description and photos of the Spacek SE33 high output 810cc engine (apparently called the "SE33 EX" or the "SE35"). I know it has been mentioned here before. Can anyone offer information on whether the claimed 35 HP is time limited or continuous, and do we know how the 35hp output was determined? Thanks.

Mark
 

TiPi

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It is supposed to be the SE33 XP. Igor slightly ported the heads, 3-angle valve seat cut and compression ratio of about 8.5:1, all based on my recommendations. No other changes as far as I know (I did discuss the ignition timing with him but I haven't seen any plates to move the coils).
The power output is established empirically, based on the previous engines and the propellers used on various SD-1s. The XP does have about 80-100fpm better climb and that implies roughly 2hp more.
I put these tables together from available data (Spacek and Pireps, mainly early SE31). Best glide is at 55kts, glide ratio 13:1.
1626687881247.png
 

Vigilant1

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The power output is established empirically, based on the previous engines and the propellers used on various SD-1s. The XP does have about 80-100fpm better climb and that implies roughly 2hp more.
Thanks for that, and for the tables. There's not much dynamic pressure available at 55 knots, what are the reports on CHTs at high power levels? I'd guess at some point it may make sense to flatten out the climb a bit to improve cooling.

Mark
 

TiPi

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My Rotax won't stay cool at 55kts and WOT. I only climb at that speed to 500' AGL, then usually flatten to 80kts where all temps stay in the green. The SD-1 would be similar, reports are that they have not experienced any overheating. Igor states that the CHT max out at 200deg C even on hot days (limit is 220 in Germany and 240 in the UK).
 

Vigilant1

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200degC = 392F
220 C = 428F
240 C= 464F

Pretty toasty. Obviously, much depends on where we measure, and cumulative time spent at those temperatures.


My Rotax won't stay cool at 55kts and WOT. I only climb at that speed to 500' AGL, then usually flatten to 80kts where all temps stay in the green
Yes, things are much the same in the Sonex/VW world. Most folks climb at approx 60 kts (Vy) or a 55 kts (Vx) immediately after TO, then flatten things out quite a bit and increase airspeed to help keep CHTs in check (and make better headway toward wherever they are going).

In some installations (e.g. pushers) that operate at high power levels, retaining the stock fan/blower or fitting an axial flow unit may turn out to be a good option, even at the cost of a little useable power.
 
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Vigilant1

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Tipi,
In VB's thread (on his single seat VP-21 re-imagined), you made the interesting post below regarding Vanguard 627cc engines being used in a UAV:
Forgot to add this link: Vanguard Engines Power Aid Distribution UAV | Unmanned Systems Technology

It is the Vanguard 38-series (627cm3) EFI in stock configuration, with SD-1 cowling. This EFI is single injector and open-loop but uses the same fuel pump module. Sensors are temp, MAP and rpm with electronic throttle.
Do you happen to know more about the EFI or ECU?
-- "Open loop": Sounds good, especially if it is easy to set up and has a manual leaning capability (and if we can determine what happens in various sensor failure modes).
-- "Single injector"? The OEM EFI in the Vanguard 627cc has a single injector. Any idea how they get a single injector to smoothly feed fuel to the two cylinders in this uneven fire engine?
-- Do you know if the system also manages the ignition timing? The Vanguard literature for the EFI says:
Vanguard EFI
Optimizes fuel injection and spark timing so the EFI engine delivers significant fuel savings, greater efficiency, easier starting and higher productivity.
It would be nice to have a system that could adjust timing so idle speed could be reduced and timing could be optimized for high power settings. The parts diagram for the 627 EFI engines showed two magnetron coils connected to the spark plugs. With two engines on that relatively clean UAV, both idling at a "stock" 1600 RPM, it could be hard to get down unless it has a drag brake.
-- Is this a modification of the OEM EFI (eliminating the O2 sensor)? Any idea if we can get/buy it?

Thanks,
Mark
 
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karmarepair

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From a Press Release from a rental industry magazine:

"For air-cooled marine applications <<RRY note: Mud Boats>>, an open-loop EFI system is preprogrammed to deliver fuel based on operator throttle inputs. This provides the benefits of EFI without the higher costs of a closed-loop system. An idle air control device and throttle position sensor control a low idle speed of only 850 rpm.

Vanguard also uses an open-loop system on its horizontal-shaft Small Block V-Twin engine. The 627cc engine, developed for powering fire and rescue equipment, provides 23 gross horsepower."

 

Vigilant1

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In the US, the retail price of the 49 series Vanguard EFI engine is virtually identical to the versions with a carburetor. If the OEM EFI system could be made suitable for our purposes, it might be quite attractive.
 
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TiPi

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The info that I have from the UAV project leader is they use these 2 engines in stock form (CAA requirement). This engine (and the 40hp big block) seem to be developped for the European market (New Vanguard V-Twin 40HP EFI ETC petrol engine | Vanguard® Commercial Power), to replace some of the smaller diesels. The open-loop EFI and ETC are on these 2 engines only.

The EFI and ETC operation is explained here:
Old-fashioned TBI with MAP, temp and the ETC which will have the TPS.

The Magnetron coil is stock-standard, so fixed timing. Maybe it can idle lower due to the EFI, no specs available, though.
 
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