Starting a Lycoming engine

[funfly]

I have a Lycoming I0-360 injected engine fitted on my aircraft.
I start it with the mixture fully lean and the throttle open only about eigtht of an inch, as soon as it fires up I open the mixture to rich and I don't have starting problems (touch wood).
Question is why this is the technique on an injected engine when a normally aspirated engine would be started with mixture rich?
Not a catch question, I am not an engine mechanic and I can't find anything on the Lycoming website so assumed some of you clever guys can enlighten me:confused:

[Pitts2112]

Funfly,

That's a good question I've often asked myself. I'll be keeping an eye out for an answer from a well-informed person.

Cheers,
Pitts2112

[High Wing Drifter]

For the Arrow and Seneca I was told by my instructor to use full rich and full throttle and as soon as it fires bring the throttle back. It certainly seemed to work much better on crisp'n'cold mornings than the PoH method :confused:

[IO540]

Fuel injected engine starting methods can generate massive threads, even on a site that covers just one make of aircraft!

The first question to ask is why does the POH method not work. If it does not work, there is something wrong and the aircraft should not be flying. End of story. Cold starts should be very reliable.

That said, hot starts are often problematic. Especially if the engine is not quite "hot", say after being stopped for 20 minutes. I suspect that a common culprit is fuel vapour in the pipework. The POH hot start method should also work for a truly hot engine but the intermediate cases can be a problem. It can take a lot of cranking to get it going, say 5 seconds (which seems a lot).

[stiknruda]

Fuel injected starts - when hot...........................

I have a method that works for me that I use to this day: -

when I built an aeroplane with a manual fuel pressurisation pump, I opted for a purge valve on the engine driven mechical pump to allow me to evacuate hot/vapourised fuel before it reached the fuel flow controller (spider) - I used it twice in 250 hrs, once to test its efficacy!

Pitts 2112 - if you want a realy in depth, boring discussion - buy me a beer! ISTR that your kite starts quite well if swung by a Norfolk farmer!

Stik

[funfly]

The first question to ask is why does the POH method not work. If it does not work, there is something wrong and the aircraft should not be flying. End of story.
Who said the POH method did not work? All I asked for was the technical reason for lean start on injected engines and rich start on carb engines.
So another question if no-one can answer that, does anyone start an injected lycoming engine with mixture rich?

[Zulu Alpha]

I suspect its because an injected engine will continuously squirt fuel into the inlet when the mixture is rich, throttle slightly open and the pump is on. This happens whether the engine is cranking or not. Therefore this runs the risk of creating a big puddle of fuel and a fire risk.

Carburetted engines do not do this as the fuel is only drawn in when the engine is sucking air in.

Both types of engine are primed in a similar way, the carburetted engine has a manual primer to squirt a bit of fuel. With injected engines you switch the injection system on far a few seconds to achieve the same thing.

[Tinstaafl]

Not really correct to say that all injected engines use a mixture lean start. Depends on the manufacturer. As a rule of thumb Lycoming's injected opposed engines use a lean start whereas Continental's equivalent use a rich start.

I get the impression that Lycoming's injection priming leaves the engine a bit too rich so cranking with ICO eventually leans to a combustible mixture. Continental chose the opposite. Is this really correct? Damned if I know but that seems to be what's happening.

[IO540]

On an IO540-C4 the cold start is fully lean, and as the engine starts one moves the lever to fully rich.

A hot start is done with the mixture fully rich (and with full throttle!) and one has to retard the throttle VERY quick when it starts (before the C150 in the pump queue behind you gets "moved" :O )

I don't know the technical reasons, and have never met anyone who does.

[1McLay]

As Tinstaafl said, injected lycomings are generally started in the lean posy, continentals the opposite.

IO540 As for starting a hot lycoming, is that what it reallys says, use full throttle? I operate a TIO-540 and when I hot start it, I give a pump on the throttle (or 1 sec on prime) crack the throttle, mixture ICO, crank, Mixture full rich as it fires, works a treat everytime!

But every engine does have its own Idiosyncrasies!! What ever works best for you eh!;)

[slim_slag]

Zulu alpha has it.

Question is why this is the technique on an injected engine when a normally aspirated engine would be started with mixture rich?


How would you start a normally aspirated engine if you had flooded it? Mixture lean. Essentially, when you start an injected engine, you do so after it's been flooded.

[IO540]

My procedure is out of the POH. Works every time.

[funfly]

Essentially, when you start an injected engine, you do so after it's been flooded.
Slim, can you expand on this for me?

[slim_slag]

Well, it worries me to suggest the answer when so many others say they don't know, but I'll stick my neck out.

The mixture control and throttle don't do the same as on a normally aspirated engine. You will get fuel pumped into the intake even with the throttle closed, and that's what happens when you turn your pump on for a few seconds prior to startup with mixture rich and fuel flow showing.

So when you start the engine you have a liquid fuel in the intake which is all the engine needs to get going, so mixture lean otherwise it will be too rich. When it fires up, and the pool of liquid fuel has been sucked through and used up, you open the mixture and that keeps the engine going.

So that's why I used the word 'essentially', the engine isn't actually flooded in the aspirated sense of the word, but it's the closest analogy I could think of to answer your actual question. You basically have liquid fuel which needs to be got rid of.

Clear as mud? Anybody have a correct answer :)

[IO540]

This stuff has got to be highly engine and installation dependent.

On my engine, during "priming", I see virtually zero reading on the fuel flow meter, both the analog one and the Shadin flowmeter. Maybe just a miniscule movement of the needle, about 5 seconds into the operation of the electric fuel pump (this is the cold start procedure).

[slim_slag]

IO540,

You need to RTFQ :)

[IO540]

The point I am rather painfully trying to make, SS, is that any question you are going to get is going to be engine and installation dependent.

If you have an internet connection, go to www.google.co.uk and type in a few keywords and you will dig up loads of bedtime reading on engine starting. Most of that will be engine and installation dependent too, which is why these threads run for ever and ever.

[englishal]

My injected, turbo charged engine is a doddle to start. Probably due to the onboard computer controlled engine management system. I just sit there, turn the key and hey presto it roars into life, whether hot or cold. I like to keep the revs down until the oil has warmed to prolong the life of the turbo charger, but other than that it pretty much takes care of itself. I can't over speed it, mixture is accurately metered, the turbo wastegate is under the control of the computers...amazing.

I suppose the difference is that it has Audi stamped on it and it is in my car ;)

[High Wing Drifter]

...it has Audi stamped on it...
...it roars into life...
Surely an oxymoron ;)

[dublinpilot]

I can't over speed it,

Try clutching it, and pressing the accelerator to the floor and holding it there ;)

[Keef]

What, to test the rev limiter? Unless it's very different from mine, it just goes to max RPM and stays there.