New at Gas Engines; I have a Revolution 50 to go in a TF GS P-51; I have always ''Bench Tested/Break In'' my Glow Engines using an Engine Stand, I have a great Test Stand from PSP which is capably of Bench testing gas Engines; but I have heard different opinions, some say ''Bench Test'' others say ''run them on the plane only''; which is it, or what is your method and opinion?

On the airplane.

On the plane and make sure that engine gets proper cooling in that plane.

-Ed B.

I run the same setup (Plane & Engine).....make sure you get the fan and shroud to help cooling. I always test run my gas engines on the plane.

Yes, I got the Fan & Shroud; additionally I thought of using a spinner that has the holes in the backplate with the idea that the Fan may draw extra air through the spinner backplate holes and the propblade cut outs; how do you like the Engine on your P-51? what prop are you using; are you using the Revmaster CDI unit? I have opted to get one CH Ignitions.

I''m using a 20x10 prop and the plane flies like it''s on rails. The only thing I didn''t like about the engine was it was hard to start, I had to solder the hole in the choke butterfly closed so I could hand start it. I am using the Revmaster CDI unit.

Did you build any additional baffles in the cowl to help with cooling?

It won''t hurt you to test run it on a test stand but it will be better breaking it in on the airplane.

Bench is ok if you keep it cool. Use a shop vac on "exhaust" to provide a direct cooling source to the head. NOT through the prop. Spinners and/or back plates do little to nothing for directing air over and through a cylinder. Only actual ducting will handle that.

No need to do more bench running than a tank of gas through the engine. Just enough to set the needles close to what will be needed. The rest of the break in will be best performed in the air.

I didn''t use any additional baffles and didn''t have any over heating problems.

bench teat bench teat bench test go go bench test!!!
save your self all the headake to come to the field and ready to fly and get screwed because the engine have a problem
do a bech test and some breakin - for 10-15 minuts, KEEP IT COOL, than put it on the plane set to reach and you ready to go

send some pictures!!!!

enjoy

I''m confused. Are folks saying that running an engine on a test stand is going to cause the engine to over heat! Lots of airplanes have the engine just hung on the front without a cowl.

Paul

well over heating is a possebility because the engine is not in a movment -like in the air- so due to the fact that this is a AIR COOLED engine, while on the ground it will get hoter than in the air.
bench test is great as you allways keep in mind to cool the engine properly.
how? - with a fan, do it at the eveining and so on...

My understanding is that prolonged bench testing without suffecient air moving across the head will cause excessive heat. Most people don''t do breakin on a test stand which for a DA engine is 5 gallons of fuel.

I set my needles while the plane is on the ground with the cowl off but it usually only takes 1 tank of fuel.
Just my 2 cents.

I am curious why people think the airflow over the engine is any different when the aircraft is flying than when fixed on a stand. Either way, it is seeing whatever prop blast it sees. Just because the aircraft is moving a bit doesn't mean the airflow around the inner part of the prop disk is any different at all.

The reason an engine will overheat on the stand is that the LOAD is greater. Pulling full throttle static thrust is the biggest load the engine will ever see. It is the same as extended hovering at full power. This is why people use lighter load break-in props on the bench to keep the engine from overheating. When the aircraft is flying, the load is less because we seldom fly at sustained full power and the prop unloads with the forward speed. This is why a flying break in is often easier on the engine than a test stand break in, not because cooling is better. If prop load is reduced, then a test stand break in is no different than a flying break in and it is easier to control and monitor everything on the stand.

To AirWizard, how do KNOW you don''t have overheating problems? Just because the engine hasn''t died yet doesn''t mean it isn''t overheating in flight.

Mark

Thanks for setting the record straight. No house fan is going to put more air across an engine than a prop does and using a smaller break in prop is the way to go always when breaking in an engine. The cowl should also be removed so any kind of ducting is not even an issue. 3W has a recomended test stand procedure that calls for running the engine at 2000-2500 rpm for four hours. I considered it but would just as well be flying for those four hours instead.

I like bench running engines, so I would probably just bench run it for the fun of it.

Do I see it as being mandatory for gas engines? No. Unlike many glow engines, there really isn''t any advantage in bench running gas engines since gas engines are close to ready to go upon arrival. Yeah, someone will find an exception to the rule, no doubt, and they will be right, but, generally, I don''t think that the gassers need to be bench ran.

Would I, yes, as stated previously, but I like to play with my engines both on and off of the model.


Ed Cregger

When my engines are new I like to check the engine temp after the first several flights.

I would not set and run 5 gallons threw an engine on the bench, but I guess you could,, but on the other hand, as expensive as my plane and gasser engine are I would run at-least 1 gallon threw my gasoline engine on the bench,,

you can give your engine a rather nice initial brake-in on the bench for it''s first gallon, then once at the field you can tune it for more power for it''s first flight without worrying about revving it to high or to long for that first flight,,

maybe for a big 100cc or 150cc fuel gulper I would run 2 gallons,, as long as you don''t over lean an engine you have no worry about getting it hot, I mean you do have a prop on it, or at-least you should,, and yes I do agree about using a smaller prop for less of a load ..

Jim

Good deal. Lots of people say they don't have an overheating problem without any actual measuring of temps. What are you using to measure yours?

Mark

I''m using a infrared temp guage called Flash Point by Duratrax.

thx mark for the inlightment

Well there is a bit of confusion here. The reasoning is flawed about where the cooling air comes from since there is actually a low pressure area created by the prop near the hub. While your statement that there is less load in the air is generally correct, this part about thinking the propwash will provide a cooling air flow is incorrect.

It may seem counter intuitive, but I promise you if you start and run a full scale on the ground with the cowl nose bowls still in place but not secured by the top section or restrained by some safety wire or something, it will pull the nose bowls into the prop.

These little engines don''t need the break in done on the ground as they''ll get hot real quick when you start pulling power with their smaller cooling fins and no significant airflow over the cylinder head/heads. Just run ''em enought to get the needles set and take it easy on the thing for the first gallon or so while flying.

Sorry about the quotation marks instead of the apostrophes, the forum still seems to be having a problem or two since it went down over the weekend...

""a low pressure area created by the prop near the hub""

well I am sure this is true "near the hub", but as long as the cylinder stays cool,,,er, it "the cylinder" will pull the heat out of the crack case, and the fresh oil/fuel/air mixture interring the engine will also help cool the lower end of a 2 stroke,,


""this part about thinking the propwash will provide a cooling air flow is incorrect"",,

I cannot agree,, I think a more correct statement would be that the average flyer would be surprised to see how little airflow an engine needs to keep it at a good running temperature, many times I have had my hands behind running engines/props, you can not tell me a prop alone will not cool an engine, a prop creates much more airflow than a flywheel-fan on a weedeater, ,, I have often put my hand behind my running weedeater and noticed "how little airflow there was yet there is so much heat being removed,,

I will agree our engines do get more cooling in flight, , but fact is, most engine damage to our engines comes in flight from tuning too lean,,

I can say I have broken-in my MVVS and my 180 4stroker on the bench and for some reason they remand cool with only a prop to create airflow over the engine,, and, how many pilots have we all seen starting and run their engines on the ground "in" their planes for quite a long time and these engines do not over heat and become damaged,, and, I am quite sure our well made plane engines have a tighter cylinder tolerances than our old air cooled dirtbike engines of the 70..

Well it doesn't really matter if you or anyone else agrees, it's just the way things are. Perhaps my statement might have been made more clear had I added "sufficient" cooling from the prop wash?

Unless you have access to cylinder head temps like the full scales to monitor engine temps while ground running, you don't know. A full scale will actually run longer without getting hot on the ground with the cowl on than it will with the cowl off as what little airflow is being produced by the prop wash in that area is directed through the baffling on the cylinder heads.

I do agree that most damage occurs from lean runs in the air, but running them on the ground for extended periods is not a good idea in my opinion. As for the manufacturers, unless 3W has changed something they recommend ground running them for quite awhile, while ZDZ will void your warranty if it fails due to heat and you've been ground running it.

So in some respects, this question is a bit like discussing oil mixes....