Can C/G owners tell me about priming/pumping during start?

[Hank]

23 minutes ago, carusoam said:

One thing nice about a primer pump, besides a nice measured volume of fuel being delivered closer to an intake valve...

The primer can add a little more to keep the O360 running in that first minute or so.

The IO550 has 'Low Boost' to achieve that.

My thoughts,

-a-

There are times when I think it would be nice to have a primer on my O-360, but Al left it off and added procedures to take that absence into account. Works very well most of the time--that's why there are alternate procedures in the Owners Manual.

[cctsurf]

I have the primer on my Cherokee...  the Accelerator pump works better...  No primer on the Mooney...don't want it. The rebuilt carb still works better than a primer.

[Andy95W]

3 hours ago, cctsurf said:

...does Lycoming or Continental advocate pulling the engine through a number of blades before start?  

We talk about safety, safety, safety in flying, but if your engine requires more than the book procedure to start it, there is something not right (or we have believed a wives' tale). 

+1

Very nicely put into words.

[Shadrach]

3 hours ago, cctsurf said:

I think some of these different starting techniques come from the vastly different states our planes are in.  Above 50 degrees, I really don't need to do anything for pumping or turning to start, but I have a freshly overhauled carburetor...  I have a Cherokee that is incredibly cold blooded and needs numerous pumps on the accelerator pump to start it...but that comes from a carburetor that is in need of a rebuild.

On the other hand, I also think we are just perpetuating old wives tales in a number of these starting techniques...  My instructor taught me....  My mechanic said...  For example, does Lycoming or Continental advocate pulling the engine through a number of blades before starting?  To me it seems to be unnecessary, unlubricated wear...it's not going to get the oil moving (it doesn't turn the pump enough), especially not enough to get oil on the poor cam.

We talk about safety, safety, safety in flying, but if your engine requires more than the book procedure to start it, there is something not right (or we have believed a wives' tale).  It might be time to look at it with your mechanic and fix it.

In comparison to car engines...I strongly disagree with the person who said that a liquid cooled engine was heavier...  What car engine is running approximately 2ci per hp?  You don't need a 360 ci engine to produce 180hp if you can have all of the efficiency of liquid cooling (http://www.liquidcooledairpower.com/about.shtml).  

But as was said above, the FAA stands in our way.

I agree with most of what you've said here, but I think you're looking at it from the wrong angle. How many car engines make 1 hp per 2ci at 2700rpm in stock tune. A small block chevy crate motor will make less than 150hp at 2700 out of 350ci and that's with electronic ignition.  See this list of car engine weights. Can you name one that will produce 180 or 200hp at 2700 that also weighs under 300lbs wet? None that are even close. Most cars cannot match the Break Specific Fuel Consumption of an injected Lycoming or Continental when leaned to just past peak EGT.  Airplanes by the nature of their operating environment have a surplus of fast moving cool air for most of the time they are operating. Why carry around 15lbs of water, extra parts and modes of failure to provide cooling when mother nature has it in abundance.  The only reason Porsche did it is because they're engines have gotten relatively radical in stock tune; 11.5 to 1 C/R or more is  typical for a modern Porsche, now add 2 turbos. The NA cars can easily do better than 1HP per CI (@7000RPM or more). I actually prefer the air-cooled cars. They are more reliable and easier to maintain...and certainly make good power.

See this list of car engine weights. Can you name one that will produce 180 or 200hp at 2700 that also weighs under 300lbs wet? None that are even close.

Things are never as simple as they seem on the surface.  From what I can tell, the reason O360s run on the hot side is due to cooling fin area and uneven fuel distribution. A well sorted IO will require inattention to get the CHTs above 350df in cruise (and climb for that matter). Why not just install an injected engine rather than trying to add water cooling to a carbureted engine.

The basic design of our air-cooled birds is quite sound. I agree the FAA is a hurdle to modernizing the fleet, but in my opinion, water cooling is for warbirds and racers, its overkill and just another point of failure for standard category GA recips.  

350ci Chevy Small block 

http://www.chevrolet.com/performance/crate-engines/small-block-350-290-hp.html

  

[bonal]

In comparison to car engines...I strongly disagree with the person who said that a liquid cooled engine was heavier...  What car engine is running approximately 2ci per hp?  You don't need a 360 ci engine to produce 180hp if you can have all of the efficiency of liquid cooling

That would be me, I know all about the advantages of water cooling. Modern engines can make incredible power on less displacement because of 3 primary factors water cooling and most important cylinder head design and  digital fuel injection to allow higher compression but in fact none of these "smaller" engines make full power at an RPM that is at correct prop speed. you need higher RPM which requires a gear or belt reduction. you need an effective radiator hoses water pump plus the water itself all adding weight. Look our engines are about as inefficient as they come but the one thing they are good at is making max HP at under 3000rpm and being able to take high power settings for extended periods of time. How long do you think a modern car would last if you drove it at WOT all the time. OK so lets say your right and I'm a dumb ass how much do you think this high tech engine of yours would cost in a certified application. I read the link you provided it talks a lot of virtue but provides very little in specifications. I own a car that has the exact engine you desire its 2 liters has 4 cams 4 valves per cylinder  a turbo and makes 225 HP and is a boxer design. But, maximum HP is at over 5000RPM  I would need a speed reduction. So, o360 is 258 pounds my little 2 liter is 344 pounds not counting the gear reduction and once again that damn radiator.

[Shadrach]

11 minutes ago, bonal said:

Look our engines are about as inefficient as they come...

I agree with everything you've said but the above. A conforming Lycoming IO360 can achieve a BSFC of just .39 perhaps a bit less with perfect distribution leaned to 25LOP.  an efficient auto engine is in the mid to high .40s

[cctsurf]

18 minutes ago, bonal said:

In comparison to car engines...I strongly disagree with the person who said that a liquid cooled engine was heavier...  What car engine is running approximately 2ci per hp?  You don't need a 360 ci engine to produce 180hp if you can have all of the efficiency of liquid cooling

That would be me, I know all about the advantages of water cooling. Modern engines can make incredible power on less displacement because of 3 primary factors water cooling and most important cylinder head design and  digital fuel injection to allow higher compression but in fact none of these "smaller" engines make full power at an RPM that is at correct prop speed. you need higher RPM which requires a gear or belt reduction. you need an effective radiator hoses water pump plus the water itself all adding weight. Look our engines are about as inefficient as they come but the one thing they are good at is making max HP at under 3000rpm and being able to take high power settings for extended periods of time. How long do you think a modern car would last if you drove it at WOT all the time. OK so lets say your right and I'm a dumb ass how much do you think this high tech engine of yours would cost in a certified application. I read the link you provided it talks a lot of virtue but provides very little in specifications. I own a car that has the exact engine you desire its 2 liters has 4 cams 4 valves per cylinder  a turbo and makes 225 HP and is a boxer design. But, maximum HP is at over 5000RPM  I would need a speed reduction. So, o360 is 258 pounds my little 2 liter is 344 pounds not counting the gear reduction and once again that damn radiator.

I'm sorry, you didn't look very hard at the whole website if you didn't find specifics.  What engine is that website using for their tests?  It's a lycoming O-360.  Their radiator weighs 8 pounds.  Their cylinders are 1/2 pound lighter.  Yes, it is heavier as a whole, but I think the advantages far outweigh the disadvantages.  The consistent operating temperature allows for much tighter tolerances (who, with a modern overhaul doesn't have interference fit, choked cylinders because of the inconsistent temperature from heads to jug base, otherwise the tolerances become absolutely sloppy, even with choked cylinders it's bad when they get hot).  With tighter tolerances, we would produce far greater horsepower from the same Cubic Inches.  With the tighter tolerances allowed, we could go from 20W50 oil or similar to 5w30 or similar, robbing far less energy from the whole system.  With the tolerances as we have them now, we would burn lighter oil as fast as we burn avgas.

I also grant you that we are talking apples and oranges between cars and airplane engines from many perspectives, car engines run approximately 15% power going down the road, but that just means that we would reap greater benefits from a better design.  Your heavy car engine is almost certainly made from cast iron in certain places.  Weight that is acceptable in a car, that would be unacceptable in an aircraft engine.  It's cam timing is designed for the higher rpms you want in cars...  But we are stuck in revision 2 (approximately) of airplane engines (by liability and certification costs), where cars have again and again refined their engines and found that water cooled engines were far better than a Corvair or Bug.

I'm not interested in transplanting a car engine into my Mooney, I'm interested in moving out of the 1930's for engine technology.  I think that one of the ways we are going to do that is to move to liquid cooled engines.  Look at the Rotax 914, they cool the heads with water.  Look what engine Rutan used to fly around the world an IOL-200 in the voyager.  I was hoping for some renewed innovation with a part 23 rewrite, but it seems that the FAA is doing everything they can do to squash that.

For more on liquid cooled aircraft engines, http://www.aopa.org/News-and-Video/All-News/2002/July/1/Airframe-and-Powerplant-(6)

[bonal]

My auto engine example is all aluminum block and cylinders and heads the weights are correct. Im not saying you cant make a better engine but how much is that mother going to cost if its 3 times what a current Lyc or Cont is what's the point GA is already way too expensive you out there advocating we make it worse just to save a few pounds.

[Heloman]

 I ordered a overhauled carb from Spruce on 11/22, with a backorder expected date of 11/30, then it changed to 12/7, today the expected date simply said "call" so I did, and they say Marvel is saying at least another week; It seems Spruce and/or Marvel Schebler just makes up dates when things are back ordered, I called Qaa to and they're back ordered as well. Does anyone know someplace ells to get a Overhauled Carb?

[cctsurf]

I can't point you to the shop, but our a&p recommended one and they rebuilt our carburetor... It now works beautifully.

 

[mike20papa]

Heloman - the fuel pressure is taken from the carb fuel inlet just upstream of the float controlled needle valve.  There is a small dia. hose that feeds the gauge, you can see it leading from the carb.  The fuel drawn from the throttle pump is drawn from the bowl.  It is not under pressure and you won't get a pressure change until you somehow remove enough fuel from the bowl allowing the float needle valve to open and fuel starts flowing (without the elec. fuel pump on to replenish it).  I believe you can look in Trade a plane and find additional sources for OH carbs. 

This nonsense that you need the elec. fuel pump on in order to prime a non-fuel injected engine is only if it has sat for such a length of time that all of the fuel has evaporated from the bowl. And, then you only need it on long enough to fill the bowl.

[Heloman]

Airplane is running again! I had a hell of a time getting my carb overhauled; I ordered an overhaul/exchange from Spruce(Marvel Schebler) and they kept moving the date back. After a few weeks, I called and was told it'd be here soon and it didn't show, I called and said unless you can guarantee the date I need to find another option, the lady at Spruce told me she'd call MS and call me right back, never got a call back, but when I went online to my Spruce account I found they moved my back order date again for the fourth time, I'm very disappointed with Spruce for acting so cowardly. So I canceled my order, looked in trade-a-plane and found Aircraft Carburetor and Injection service of Texas, they took care of it right away between Christmas and New Years! I put put it on this week along with some new Amsafe retractor seat belts, and fixed a bunch of other minor issues I found along the way, and I'm happy to report that It started in about one blade on the test run today! Ran smooth, no adjustment needed other then half a turn to idle speed screw!

Interesting observation related to my original post; now when I turn the boost pump on before starting, the pressure comes up to six PSI then drops right back back down when I turn off the pump, before it hung and slowly bled off. And the throttle is much smoother, what happened is that the throttle/accelerator pump linkage was worn out inside the carb and was contacting the inside of the carb body preventing the accelerator pump from actuating. Surprising how well it ran with that problem!

I highly recommend Aircraft Carburetor and Injection service of Texas!

Edited January 9, 2016 by Heloman

[carusoam]

Great Pirep Heloman.

i get the feeling that there are many a carb that hasn't seen a good OH.  They soldier on like you described.

Lay up a web site or contact information if you can...

Best regards,

-a-

 

[C-GHIJ]

 

That's some good info...

 

BTW - don't google "starter vibrator" - not gonna get what you think 

WHY?  What did you get?  Plane Porn  LOL

[cctsurf]

Glad to hear it worked for you Heloman!  Sounds like your plane is better for the work.  I agree with Carusoam, I expect that there are many a carb out there running...soldiering on...without being correctly taken care of.  When I look under the cowling, I see many things that, yes...don't have to be rebuilt, but probably should be.

May I ask what the overhaul cost?

Edited January 9, 2016 by cctsurf
forgot my question

[Hank]

Heloman, your fuel pressure should stay steady when you turn off the pump before starting. If the throttle is closed. 

Before I OHed my carb, and now four years later, it's confirm throttle to idle; fuel pump on until pressure stabilizes  (6-6.5 psi); fuel pump off; then mixture to full rich. The fuel pressure drops a little each time I pump the throttle, ending around 4-5 psi after two pumps. Fuel pressure doesn't change until I push the throttle forward. 

But it sure is nice to have an engine that starts up quickly and easily! 

[Heloman]

 

Heloman, your fuel pressure should stay steady when you turn off the pump before starting. If the throttle is closed. 

Before I OHed my carb, and now four years later, it's confirm throttle to idle; fuel pump on until pressure stabilizes  (6-6.5 psi); fuel pump off; then mixture to full rich. The fuel pressure drops a little each time I pump the throttle, ending around 4-5 psi after two pumps. Fuel pressure doesn't change until I push the throttle forward. 

But it sure is nice to have an engine that starts up quickly and easily! 

 I was expecting it to work as you described after the overhaul, but it doesn't. I can't say there's anything wrong with it, but it is a head scratcher??? Yes, it sure is nice how easily it starts now!

[Heloman]

 

Glad to hear it worked for you Heloman!  Sounds like your plane is better for the work.  I agree with Carusoam, I expect that there are many a carb out there running...soldiering on...without being correctly taken care of.  When I look under the cowling, I see many things that, yes...don't have to be rebuilt, but probably should be.

May I ask what the overhaul cost?

$845 with return shipping, Spruce was about the same.

[Heloman]

 

Great Pirep Heloman.

i get the feeling that there are many a carb that hasn't seen a good OH.  They soldier on like you described.

Lay up a web site or contact information if you can...

Best regards,

-a-

 

http://www.trade-a-plane.com/detail/Overhaul/Carburetor/2047809.html