smartcarb

[skippydiesel]

15 minutes ago, turboplanner said:

A.       In-an-engine-we-are-assessing-less-fuel=less-power.

B.       On another engine, say a "modern injected 2 stroke outboard" with its fraction of fuel - if it's given less fuel there will be less             power.

 

I thought this discussion was about a particular fuel metering system/carburettor ("Smartcarb")  - not a specific engine.

 

Seems you are off on a tangent , as is your habit.😈

[BrendAn]

2 hours ago, Thruster88 said:

6200 static and 6500 on climb. Full throttle level flight is just under the max of 6800. 

My 618 is pretty close to that. 

Just under 7000 rpm flat out on climb. I have been thinking of giving it a bit more pitch.  So I get around 6600 on climb and bring cruise back to around 5800.  Egt around 600 now. 

[BrendAn]

17 minutes ago, skippydiesel said:

I thought this discussion was about a particular fuel metering system/carburettor ("Smartcarb")  - not a specific engine.

 

Seems you are off on a tangent , as is your habit.😈

He was quoting what I said.

Read the earlier posts

[facthunter]

Yes I wouldn't suggest over  revving that Motor. Nev

[skippydiesel]

"Oil Injection vs Premix:
• On premix engines, any change in fuel flow directly changes the oil ratio."

 

How is this statement correct ??

 

Never been a 2/ fan however my understanding of premix is that;

• The oil & fuel is added/ premixed at a certain ratio eg 50:1 in my chain saws. 
• The mixture is then put in the fuel tank.
• The fuel mix is then metered through the carburettor to the combustion chamber, where it is burnt.

 

During the above process there is no opportunity to change the fuel oil mix ratio - in my example it remains at 50:1, no matter how I tune the carburettor (rich or lean)

😈

[skippydiesel]

2 minutes ago, BrendAn said:

He was quoting what I said.

Read the earlier posts

My apologies - I understood the thrust of your questions to be; how does a claimed 30% reduction in 2/fuel ("Smartcarb")  effect the lubrication of the engine, specifically where premixed fuel is used.

 

The engine/carburettors you mentioned I took to be illustrative ie not part of the origional question.😈

[BrendAn]

6 minutes ago, facthunter said:

Yes I wouldn't suggest over  revving that Motor. Nev

The book says 7000ax on climb out so it has been setup pretty well but I would like to pull it back a bit as long as egt stay within range.

[facthunter]

I mentioned earlier that adding oil to fuel increases It's viscosity which makes it flow slower thus Leaning the Mixture/ THAT statement is NOT CORRECT as you point out.. I would suggest that they MEANT Oil  Available to the engine. Way Back a Friend of mine riding a Bultaco at Mt Panorama put a foot operated oil pump on his  bike to Prevent  engine damage down conrod straight. A chain saw should require LOAD to make it fire evenly and it should be rich enough to never scream and do high revs. Nev

[facthunter]

BrenDAn,  The MOTOR YOU Have had a reputation for breaking Crankshafts near the  drive end.  Nev

[BrendAn]

6 minutes ago, facthunter said:

I mentioned earlier that adding oil to fuel increases It's viscosity which makes it flow slower thus Leaning the Mixture/ THAT statement is NOT CORRECT as you point out.. I would suggest that they MEANT Oil  Available to the engine. Way Back a Friend of mine riding a Bultaco at Mt Panorama put a foot operated oil pump on his  bike to Prevent  engine damage down conrod straight. A chain saw should require LOAD to make it fire evenly and it should be rich enough to never scream and do high revs. Nev

This is why I started the thread. Trying to understand how they use 30 percent less fuel without leaning the engine out too much. 

Oil injection should be ok when oil is injected after the carby.

[BrendAn]

6 minutes ago, facthunter said:

BrenDAn,  The MOTOR YOU Have had a reputation for breaking Crankshafts near the  drive end.  Nev

Pretty rare I think.  Rotax rick reckons they were the best of the Rotax 2 smokes. Detuned from 135 HP in the snow mobile version.

I have spoken to a few people that have never had an issue.

I think if they are looked after and operated by the book should be good like most engines.

 

[BrendAn]

31 minutes ago, facthunter said:

BrenDAn,  The MOTOR YOU Have had a reputation for breaking Crankshafts near the  drive end.  Nev

A couple of paragraphs off a gyro forum. Shows all models can break cranks. Gyros are pretty hard on 2 strokes. Driven flat out all the time.

[facthunter]

The original Book may not be the Best reference, Currently. Nev

[Thruster88]

44 minutes ago, BrendAn said:

The book says 7000ax on climb out so it has been setup pretty well but I would like to pull it back a bit as long as egt stay within range.

The 618 needs those revs to make use of the temporarily raised exhaust ports to make the extra power. In a motorbike those valves would get plenty of action, in an aircraft not so much which may lead to sticking. 

[facthunter]

 There's a Lot of ways of helping them Last Better. Gyros need Lots of Power. Carbon Behind the rings is a Killer.  Big end Cages fail and the Hard skin flakes off the Crank Pins and the results of that are Quick and fast.  Any Holey Piston Means aluminium all through that Cylinder and case. Nev

[BrendAn]

1 minute ago, Thruster88 said:

The 618 needs those revs to make use of the temporarily raised exhaust ports to make the extra power. In a motorbike those valves would get plenty of action, in an aircraft not so much which may lead to sticking. 

True,  some people in high altitude regions run cables to operate them manually.  I flick the plastic covers off occasionally and work them by hand .  Although running amsoil full synthetic should stop carbon build up.

[Moneybox]

Slight mixture adjustment on a two stroke can make huge differences to power output. When racing dirt carts with a 100cc Yamaha we used to reach behind an lean the mixture for an extra boost of power in the straight or overtaking. You couldn't keep it lean when backing off for a corner or it would instantly raise the combustion temperature sufficient to melt the sparkplug. Slightly too rich would noticeably reduce power and slightly too lean would boost it. 

 

If that is a truly smart carburettor I can believe it could give significant improvements in performance and fuel consumption.  

[facthunter]

Telling people to lean out the mixture to get Power on a 2 stroke is NOT something I would Put my name to. It's a good way to put a Hole in the Piston.  That then requires a complete strip down. You May get More revs under Light Loads But  IT really is a NO NO for Aircraft or Chainsaws. Nev

[turboplanner]

12 hours ago, facthunter said:

Telling people to lean out the mixture to get Power on a 2 stroke is NOT something I would Put my name to. It's a good way to put a Hole in the Piston.  That then requires a complete strip down. You May get More revs under Light Loads But  IT really is a NO NO for Aircraft or Chainsaws. Nev

Agree, as someone who is a contender for taking out the most pistons in the country, I learnt the hard way. There's an acceptable risk-reward in Go Kart racing where the worst outcome is you'll roll to a stop and be busy machining a new for by next week, but the last thing you want to be doing is introducing piston seizures in the air.

 

With petrol engines, reading the plug(s) to get that light brown colour is everything.

With Methanol or Methanol-Acetone, it's designing for maximum power and cooling the combustion chamber with Methanol..

 

 

 

 

[skippydiesel]

3 hours ago, turboplanner said:

 

With petrol engines, reading the plug(s) to get that light brown colour is everything.

 

I don't disagree with the intent of this advice/comment however next to impossible with aircraft engines.

 

Rotax 912's run slightly rich at taxi RPM/shut down. This coupled with ignition, rather than fuel shut off, for engine stop,  leaves plugs with a covering of loose black soot when removed

 

I would also question if this advice works for Ly/Cons with inflight adjustable mixture control. When I did my GA training a squilian years ago (memory may be dodgy) I would take off with Full Rich (subject to airfield  pressure altitude). Make adjustments in Cruise Climb and in Cruise, go to lean of peak EGT and back (rich) a small turn.

 

On Shut Down, fuel cut off  to stop engine = few moments of extreme lean running

 

The above changes in fuel air ratio, would change the colour of the plug insulation at each adjustment ie nothing to be gained by "reading" the plug colour.😈

[facthunter]

General rule with Leaning (unless operating at a high altitude aerodrome) Don't lean till below 75% Power.  Procedure...... Lean till the engine starts to run a bit rough, Correct it (make it smooth) and then richen a little bit. That way you will get the POH  consumption figures. Most engines are rich at idle. and can soot plugs which can  cause a Mag drop or Power loss. It's permissible to lean on taxi but have a way to ENSURE you go to full rich before take off Power is applied. AVAS has 2 octane ratings  like 100/110 The higher one is for a RICH mixture. Nev

[turboplanner]

17 minutes ago, facthunter said:

General rule with Leaning (unless operating at a high altitude aerodrome) Don't lean till below 75% Power.  Procedure...... Lean till the engine starts to run a bit rough, Correct it (make it smooth) and then richen a little bit. That way you will get the POH  consumption figures. Most engines are rich at idle. and can soot plugs which can  cause a Mag drop or Power loss. It's permissible to lean on taxi but have a way to ENSURE you go to full rich before take off Power is applied. AVAS has 2 octane ratings  like 100/110 The higher one is for a RICH mixture. Nev

That's GA, and there have been thousands of posts on it on GA SM

[turboplanner]

54 minutes ago, skippydiesel said:

I don't disagree with the intent of this advice/comment however next to impossible with aircraft engines.

 

Rotax 912's run slightly rich at taxi RPM/shut down. This coupled with ignition, rather than fuel shut off, for engine stop,  leaves plugs with a covering of loose black soot when removed

 

I would also question if this advice works for Ly/Cons with inflight adjustable mixture control. When I did my GA training a squilian years ago (memory may be dodgy) I would take off with Full Rich (subject to airfield  pressure altitude). Make adjustments in Cruise Climb and in Cruise, go to lean of peak EGT and back (rich) a small turn.

 

On Shut Down, fuel cut off  to stop engine = few moments of extreme lean running

 

The above changes in fuel air ratio, would change the colour of the plug insulation at each adjustment ie nothing to be gained by "reading" the plug colour.😈

 

54 minutes ago, skippydiesel said:

I don't disagree with the intent of this advice/comment however next to impossible with aircraft engines.

 

Rotax 912's run slightly rich at taxi RPM/shut down. This coupled with ignition, rather than fuel shut off, for engine stop,  leaves plugs with a covering of loose black soot when removed

 

I would also question if this advice works for Ly/Cons with inflight adjustable mixture control. When I did my GA training a squilian years ago (memory may be dodgy) I would take off with Full Rich (subject to airfield  pressure altitude). Make adjustments in Cruise Climb and in Cruise, go to lean of peak EGT and back (rich) a small turn.

 

On Shut Down, fuel cut off  to stop engine = few moments of extreme lean running

 

The above changes in fuel air ratio, would change the colour of the plug insulation at each adjustment ie nothing to be gained by "reading" the plug colour.😈

1.      Yes difficult to do with aircraft unless you cut the fuel, pull up to stop the prop and land deadstick, so much greater risk than running slightly lean           or rich.  You're looking for the colour at full power so another way to do it is on a dyno without a prop and I accept for RA tuning there's too                   much cost in that.

 

2. This discussion is not applicable to GA engines where there is a mixture lever based on adjusting to a combination of power and altitude, and the       arguments on that go on forever, with some people blowing up motors trying to prove a point.

 

3. As you say the engine must be shut down immediately from full power for the colour method.

[facthunter]

It's a Method used for Mainly Motorbikes in the Old days. It can also show whether the chosen Hot/Cold plug is the correct one. Performance (hot) Motors use COLD Plugs.   Too HOT a Plug risks Pre-ignition. Nev