erieqc

I"ve not found much info on these little engines nor have I found a forum on them. I would like to hear from the people that have these and if they are a good engine or not. What to watch out for and what to expect out of these engines.

w8ye

My Feedback: (16)

It might be a few days before both of them show up but there are at least two very knowledgeable people on this engine that often post here. They are sure to have something to say.

http://www.aircraftinternational.com...5/Default.aspx

aussiesteve

I am not one of those that Jim refers to but here is my $0.02 from personal experience with them
Some time ago, I asked one of the people Jim is referring to as to what is the best choice of engine in the size range. I was pointed to the 3W 28i. I purchased one to try it.

I now have many hours run time on that engine (well in excess of 200 hours) and it has not once missed a beat. I have since purchased 2 more of them and they also have in excess of 100 hours on each one and neither of those has missed a beat either.
One has been crashed twice and survived with no damage.

When properly tuned and propped, These are the most powerful engine in the 26cc to 32cc size range that I have experienced (and I have tried quite a few engines in that size range). Power curves are exceptionally good right through the range.
They can be a little fiddly to tune but if small adjustments are made at a time it is not too bad.

The genuine 3W ignitions can be a problem (I have yet to have one fail on me but I am sure I have just asked for trouble by saying that). However when it happens, an RCExcel ignition (and Hall sensor) will bolt straight on and work fine.

They have a 3 standoff mount that takes some people a little time to get their head around but it is plenty strong enough.
The long carb / intake setup can also be a little daunting to some as it is slightly offset but take time with the install and the effort is well rewarded, it really is no more work than any other rear carb to install. The other annoyance to some is the 6 bolt prop hub.

Overall quality is extremely good. The only minus for some people is the initial purchase price.

It is the 3W 28 that initially triggered my signature line. That thought got reinforced with some other offerings later on.

Tired Old Man

My Feedback: (1)

Steve hit most of the good points. If the engine has a weak point it's the ignition but those are said to have been improved. The 3 point mounting system bothers some people but in thousands of engines I have not seen that to be a problem. Anyone that so desired could make a 3 to a 4 point mount if they wanted to, but being "different" has nothing to do with adequate mounting security.

About a true (on dyno) 2 HP, or 1,600 watts or so. Intended for a max RPM of about 8,000 using an 18" prop, keeping the engine within its best torque to RPM curves. Propped correctly they'll fly a 40+ pound plane for 24 hours at a time and come back for more over and over. Two sizes of cylinders and pistons, labelled "A" and "B" on the back of the cylinder and the top of the piston. The 28i has been a continuous evolution of improvements over the years. They started out a little shakey with some machine tolerances but those were all but eliminated a couple years ago.

They've gotten away from the "legged" wrist pin circlips to eliminate any of them breaking off and seizing a cylinder. That was very rare but was the most likely point of failure if and when an engine went bad. About 1 in 3,000 (numbers from experience) engines might experience a bearing failure where the bearing seal gets ingested by the bearing. They use very good bearings. If that ever happens it's always an "outer" bearing and easy to fix. Never seen a wrist pin bearing fail in one. 600-800 hours of easy life cycle before needing to change the ring. The piston and cylinder will still be fine at that time if you keep oil in the fuel and didn't run it hot all the time. Haven't gone beyond 1,000 hours myself so for this discussion I'll limit the ring life to 800 hours. Typically they are within about .003" of max wear at that point. Handles heat extremely well and will run up to about 180C-190C without too much wear. Performs best when run between 130C and 160C.

Pricey, but you definately get what you pay for. Hard engines to break and reliability is off the scale to the good side.

wesaysoracing

i would say one of the two has spoken

erieqc

Thanks guys for the info I really appreciate it. I plan on running Sthil HD oil whats the best ratio to run it at. Again Thanks

Tired Old Man

My Feedback: (1)

50-1, and there's about 300,000 running hours to support that ratio.

rc bugman

My Feedback: (30)

TOM hit all of the points. The only thing I can add is that 3W engines preform better on 91+ octane (US) than 87-88 octane. You usually gain about 400-500 rpms with the higher octane fuel

Elson

Tired Old Man

My Feedback: (1)

You also avoid detonation... Under extreme conditions some run 100 octane no lead racing fuel but maybe 1 in 500,000 modelers might ever operate to that level of severity

Good call Elson.

erieqc

With the velocity stack on the carb do I need to put some holes in the back of my fuse to let air flow threw for that or just leave it alone.

Tired Old Man

My Feedback: (1)

The stock, black intake stack should be clear and unobstructed for best performance. You should have at least 1" of free space between the intake and the firewall. If you do not, make it so. Just in case I misunderstood your previous post, do not drill holes in the black intake stack.

erieqc

No I mean if the stack extends threw the firewall into the fuse along with a part of the carb is there enough volume of air for it to opperate correctly or do I have to have an air flow for it. It stated it in the online manual that if extends into the fuse you need to open a hole in the back of your fuse for airflow for it. Or did I read into something thats not there.

Rear induction
Carburetors, whether front or rear, require a steady supply of fresh air. The best way to supply
air to a rear carburetor is by installing an air scoop. Some have thought to drill holes into the
fuselage near the carburetor area rather than creating an air scoop for the carburetor. This does
not work, it fact it will create a vacuum effect that will draw the air away from the carburetor! Again,
you should install an air scoop into the front of the plane which will supply air into the fuselage.
This air will then need to flow out of the fuselage. Drill exit holes into the rear area of the fuselage
24i / 28i Engine Manual
more infos: www.3w-modellmotoren.de
for this purpose. Important: The interior of the fuselage must be sealed to prevent damage from
gasoline that sprays from the carburetor. Use a thin epoxy or other appropriate fuel proofing
method. Do not overlook this step as gasoline will melt some materials like Styrofoam very quickly.

Tired Old Man

My Feedback: (1)

It does not take much of an opening to provide all the air required. Fuselages are generally not vacuums unless they can hold pressure, positive or negative. I can't think of any wood framed models that fit that description. A small scoop on the side of the fuselage could work well in minimizing any potential diaphragm pressure issues and provide a little better balance with the induction system if you chose to install one.

So no, you don't have to have a scoop but it might work out a little better for tuning if you did.

ollie witt

Hi, sorry for digging up an old thread.

I am just about to install a 28i and canister in an extreme flight 74" yak. I am trying to CAD up a support bulkhead for the engine but am not sure what angle to put the engine at to ensure the canister sits directly below the prop shaft? From picture's of installs I've seen it looks like when the bottom and top right bolt holes (when looked at with cylinder upright) are horizontal to each other gives this canister position.

If anyone could help that would be great!
Thanks,
Ollie