'Unleaded' For G/A..??
Oracle: Your earlier observation about the damage done by lead is spot on. As John Deakin has observed:
AB: Successful LOP operations do not depend on the fuel you use. Successful LOP operations are about getting each cylinder to reach peak at the same point as the others.
Once you get your multi-point thingy, you will be able to work out why your engine is behaving the way it is, and what to do to run it LOP (on either ULP or 100LL or (hopefully soon) G100UL).
Lead is not "good" for an engine, IT IS HARMFUL to engines. But if you want high performance from an engine, it is the least toxic of the presently known chemical additives that will allow high power without detonation.
Once you get your multi-point thingy, you will be able to work out why your engine is behaving the way it is, and what to do to run it LOP (on either ULP or 100LL or (hopefully soon) G100UL).
So how would PULP go with electronic ignition?
Reading the lightspeed FAQ, it looks like it does the same timing as mags at full power and as you reduce map (and rpm), it advances the timing to achieve peak power.
So advancing timing = bad for unleaded yes?
I wish gami would hurry up and get their prism onto the market.
General Aviation Modifications, Inc.
Reading the lightspeed FAQ, it looks like it does the same timing as mags at full power and as you reduce map (and rpm), it advances the timing to achieve peak power.
So advancing timing = bad for unleaded yes?
I wish gami would hurry up and get their prism onto the market.
General Aviation Modifications, Inc.
Not quite. Advancing the timing too far is always bad, irrespective of what fuel you are using. It's just that, all other things being equal, the timing of an engine running on fuel that does not have a latency addititive (like lead) will not be able to be advanced as far as it would if it were running of fuel with a latency additive.
The lack of latency addititive in the fuel has an effect equivalent to advancing the timing, because the combustion event happens quicker which means the PPP happens sooner. If you advance the timing, the spark starts sooner, which means the PPP happens correspondingly sooner.
That's why PRISM, so far as I understand it, has senors to detect detonation.
The lack of latency addititive in the fuel has an effect equivalent to advancing the timing, because the combustion event happens quicker which means the PPP happens sooner. If you advance the timing, the spark starts sooner, which means the PPP happens correspondingly sooner.
That's why PRISM, so far as I understand it, has senors to detect detonation.
Last edited by Creampuff; 3rd Aug 2013 at 00:39.
Not quite. Advancing the timing too far is always bad, irrespective of what fuel you are using.
Its a complex issue, which is why engine calibrators are paid lots of money and headhunted from company to company around the world.
Thee is nothing wrong with leaded AVGAS. I was used for decades -= and in engines far more highly stressed than the GA fleet. Many race car engines still use it.
I should add that AVGAS is also made to a tight spec. Australia has amongst the most lax fuel standard in the world. Unless you buy refined in Australia Shell, BP, Mobil or Caltex (While you can), then its a Russian roulette of imported fuel.
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sorry to drift this a bit but I needed the sleep.
wallymk2 made a pessimistic prediction that there would be a difficulty in getting anyone to make G100UL and distribute it (in Australia).
throughout the centre of Australia there is OPAL. the low aromatic fuel created to foil the petrol sniffing kids. I havent seen or burnt the stuff myself but I believe it to be in wide distribution in the "centre".
by all accounts OPAL is just avgas without the tetraethyl lead in it.
if OPAL was replaced by G100UL the combined volume may just make the stuff a viable fuel for someone like AirBP.
certainly hope so.
wallymk2 made a pessimistic prediction that there would be a difficulty in getting anyone to make G100UL and distribute it (in Australia).
throughout the centre of Australia there is OPAL. the low aromatic fuel created to foil the petrol sniffing kids. I havent seen or burnt the stuff myself but I believe it to be in wide distribution in the "centre".
by all accounts OPAL is just avgas without the tetraethyl lead in it.
if OPAL was replaced by G100UL the combined volume may just make the stuff a viable fuel for someone like AirBP.
certainly hope so.
You can take the lead out and make the problems go away by retarding the timing. (Therefore, the magneto timing is definitely lubricating the valves ) But if you do that, you’ll create other problems.
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Akro, the 40 degrees advance is probably happening on engines at 5000+ RPM if I were to bet on it 
So lets not confuse the issue.
We have aeroplanes, with props (yeah wally props are for boats
) and those props want to turn at 2500+/- 10% so that has pretty much fixed the speed/advance thing.
The next issue is how much HP do we want? The engine designer starts with this, works out a BMEP and peak pressure and starts designing back from there.
So the relevance of what happens next door while technically interesting only has the science in common, the application of it for your average Chieftan or 414 is different.
Not really, the spec on making AVGAS is not that tight at all and BP98 would be a tighter spec. One of my flying buddies here at YCAB actually fiddles the knobs on the fuel factory and is paid a heap to do it, nice job, but the production of AVGAS makes him laugh compared to other fuels when it comes to spec. It has to meet certain specifications, but that is about it. Quality control after that is where the expense comes from.
So lets not confuse the issue.We have aeroplanes, with props (yeah wally props are for boats
) and those props want to turn at 2500+/- 10% so that has pretty much fixed the speed/advance thing.The next issue is how much HP do we want? The engine designer starts with this, works out a BMEP and peak pressure and starts designing back from there.
So the relevance of what happens next door while technically interesting only has the science in common, the application of it for your average Chieftan or 414 is different.
I should add that AVGAS is also made to a tight spec.
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W8
Sorry the G100UL will not replace OPAL. The kind of compound that makes G100UL work is definately not going to be suitable for that target market. The compound is called
Hope you understand
Sorry the G100UL will not replace OPAL. The kind of compound that makes G100UL work is definately not going to be suitable for that target market. The compound is called
Hope you understand
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The compound is called
Hope you understand
Hope you understand
...so if it isnt suitable for breathing uncombusted, why is it going to be suitable for breathing once it is combusted?are we going to see a disaster in the making like one of the current additives in unleaded that is yet to have a bacteria evolve that can break it down in the environment? serious question actually. we do need exhaust products to be biodegradable.
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Shagie,
Well it works to a point but you can't have a fixed spark engine retarded all the way back far enough to erode the detonation issue without turning it into a problem for many engines.
The big engines already run in the 20-25 BTDC range, and they run two plugs. In terms of flame fronts that is twice as much as the car engine Old Akro refers to above. So when you consider a Turbo 540/550 engine at say 22d BTDC, it is already in its sweet spot full rich, so if you advance or retard the timing by say 3 degrees, it will lose HP.
As a by product, if you advance the timing, EGT will drop and CHT will go up. If you retard the timing the CHT will drop b the EGT will go up. We want less CHT and hence more detonation marging but we have a Turbine that has a limit of say 1650dF. So we are caught in a small window of reality physics. The lower compression TC engines (compared to 8.5:1 in say a TN) will always have higher EGT to begin with so the have less of a window.
Now if you get in your trusty C414 or a pressurised Baron or 402 and retard the timing enough to un on ordinary UL, life might be fine when running really rich or very LOP but the TIT will be on the limit and you can't use a mixture in-between, but you are OK because the power loss is only 30HP or there about, but what about when you have to shut one down or it does it for you
Does a sizeable ROD concern anyone?
So in essence, changing the spark timing matters, there is only a small range of timing values that are useful on a fixed speed engine, and that is around 20-25 and at high powers you can't have more, although you can have a bit more when running well LOP or at low powers, but you need to take off first!
That help?
Forgive my ignorance but what problems does retarding the timing make? Jaba mentioned hotter egt but I'm not following why...
The big engines already run in the 20-25 BTDC range, and they run two plugs. In terms of flame fronts that is twice as much as the car engine Old Akro refers to above. So when you consider a Turbo 540/550 engine at say 22d BTDC, it is already in its sweet spot full rich, so if you advance or retard the timing by say 3 degrees, it will lose HP.
As a by product, if you advance the timing, EGT will drop and CHT will go up. If you retard the timing the CHT will drop b the EGT will go up. We want less CHT and hence more detonation marging but we have a Turbine that has a limit of say 1650dF. So we are caught in a small window of reality physics. The lower compression TC engines (compared to 8.5:1 in say a TN) will always have higher EGT to begin with so the have less of a window.
Now if you get in your trusty C414 or a pressurised Baron or 402 and retard the timing enough to un on ordinary UL, life might be fine when running really rich or very LOP but the TIT will be on the limit and you can't use a mixture in-between, but you are OK because the power loss is only 30HP or there about, but what about when you have to shut one down or it does it for you
Does a sizeable ROD concern anyone?So in essence, changing the spark timing matters, there is only a small range of timing values that are useful on a fixed speed engine, and that is around 20-25 and at high powers you can't have more, although you can have a bit more when running well LOP or at low powers, but you need to take off first!
That help?
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W8
I can't reveal any more but the compound blended with an existing high octane unleaded base stock is very readily available in refineries now and is no more a problem than anything else. It is made from the same basic elements of the periodic table that most other petroleum products have.
It is incredibly common. But I would not pour it on my corn flakes as much as I would any other petroleum product.
I can't reveal any more but the compound blended with an existing high octane unleaded base stock is very readily available in refineries now and is no more a problem than anything else. It is made from the same basic elements of the periodic table that most other petroleum products have.
It is incredibly common. But I would not pour it on my corn flakes as much as I would any other petroleum product.
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It is incredibly common. But I would not pour it on my corn flakes as much as I would any other petroleum product.
BP98 would be a tighter spec
Although, my engine tuning mates get the best power from the United Racing fuel. We used to use AvgAS in the rally car until we turned to Philip racing fuel in pursuit of more power. I think it cost us $15 / litre and I haven't rallied for over 10 years.
Don't confuse company specs with Govt. specs. Australia has only had a National fuel spec for a handful of years.
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A few things that ARE in harmony with the laws of physics:
1) Lead does NOT slow the burn rate of avgas. It increases the latency, which is the time it takes for the flame front to become organized after the spark event. This is why it suppresses detonation. After the flame front is organized the flame front moves at the same speed with or without the lead.
2) The iso-octane study done by the FAA took two NEW engines, one on the right, one on the left in a twin. One engine was run on 100LL; the other on 100 octane (iso-octane) with no lead. After several hundred hours, there was NO difference in the wear patterns in the two engines. NONE. This proved that lead had no effect on wear or exhaust valve life or performance. Lead is NOT needed in ANY way to help valves. Period. Parade Rest. It is used ONLY to widen the detonation margin.
3) The reasons seats were changed in auto engines when unleaded fuel came about was that the existing seats were not hard (like aircraft engines have always had). These issues are not in any way applicable to aircraft engines.
4) 100 octane unleaded fuel performs exactly like 100LL. Why? If you remove the lead in 100LL it is not 100 octane.
5) John Deakin is right. Everything he says about this topic is in harmony with Taylor, Haywood, and all other known sources of DATA, including the most advanced engine test facility in the world.
6) Many SAE papers on the topic of the effects of lead in combustion are flawed in that the studies did not control for internal cylinder pressures (which ARE the cause of the observed problems).
7) Healthy exhaust stains are a very, very light tan (almost whitish) because this indicates that the engine is being run at BSFC(min) mixtures (LOP).
I have data to support all of the above. I have been showing it during the APS classes for over a decade to thousands of pilots, mechanics, OEM engineers and combustion engineers from the engine manufacturers. Not once has anyone taken issue with the hard data or presented any contrarian data.
If you have any contrarian data (respectfully, no opinions, please) I would deeply appreciate seeing it.
If you would like to see this data, we will be presenting it in Ada, Oklahoma in October and Sidney in November (I think it's November--can't recall at this instant).
It seems as though everyone has an opinion on this topic, but it is worth remembering that the data has no opinion. It is what it is.
1) Lead does NOT slow the burn rate of avgas. It increases the latency, which is the time it takes for the flame front to become organized after the spark event. This is why it suppresses detonation. After the flame front is organized the flame front moves at the same speed with or without the lead.
2) The iso-octane study done by the FAA took two NEW engines, one on the right, one on the left in a twin. One engine was run on 100LL; the other on 100 octane (iso-octane) with no lead. After several hundred hours, there was NO difference in the wear patterns in the two engines. NONE. This proved that lead had no effect on wear or exhaust valve life or performance. Lead is NOT needed in ANY way to help valves. Period. Parade Rest. It is used ONLY to widen the detonation margin.
3) The reasons seats were changed in auto engines when unleaded fuel came about was that the existing seats were not hard (like aircraft engines have always had). These issues are not in any way applicable to aircraft engines.
4) 100 octane unleaded fuel performs exactly like 100LL. Why? If you remove the lead in 100LL it is not 100 octane.
5) John Deakin is right. Everything he says about this topic is in harmony with Taylor, Haywood, and all other known sources of DATA, including the most advanced engine test facility in the world.
6) Many SAE papers on the topic of the effects of lead in combustion are flawed in that the studies did not control for internal cylinder pressures (which ARE the cause of the observed problems).
7) Healthy exhaust stains are a very, very light tan (almost whitish) because this indicates that the engine is being run at BSFC(min) mixtures (LOP).
I have data to support all of the above. I have been showing it during the APS classes for over a decade to thousands of pilots, mechanics, OEM engineers and combustion engineers from the engine manufacturers. Not once has anyone taken issue with the hard data or presented any contrarian data.
If you have any contrarian data (respectfully, no opinions, please) I would deeply appreciate seeing it.
If you would like to see this data, we will be presenting it in Ada, Oklahoma in October and Sidney in November (I think it's November--can't recall at this instant).
It seems as though everyone has an opinion on this topic, but it is worth remembering that the data has no opinion. It is what it is.
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it may not seem it but I have no problems with decisions based on data.
which fuel are you talking about???
octane rating is the detonation characteristic. octane rating has no effect on the energy released by the fuel which is about the same in all the petrols.
in all of this we still only have engines using about 25% of the energy and dumping out the exhaust 75% of the energy unused as waste heat.
it would be really lovely if people would see the big picture and engineer fuels that led to more thermally efficient engines.
now what I really wanted to do was ask a question.
80/87 avgas ran perfectly using REM40E massive electrode plugs.
the same engine will run 100/130 avgas quite well using REM38E plugs.
what plug is going to be needed for G100UL if it becomes widespread?
Healthy exhaust stains are a ...
100 octane unleaded fuel performs exactly...
in all of this we still only have engines using about 25% of the energy and dumping out the exhaust 75% of the energy unused as waste heat.
it would be really lovely if people would see the big picture and engineer fuels that led to more thermally efficient engines.
now what I really wanted to do was ask a question.
80/87 avgas ran perfectly using REM40E massive electrode plugs.
the same engine will run 100/130 avgas quite well using REM38E plugs.
what plug is going to be needed for G100UL if it becomes widespread?
Healthy exhaust stains are a very, very light tan (almost whitish)
When I was young I used to tune Weber carburettors by plug cuts and the looking at the colour of spark plug insulators. Many of the drag racing guys still do.
TEL is never good for the engine. Why do you think they add in Bromine? Well to scavenge the lead after it finished with the latency issue they want it out! The result is Lead Oxybromide which is a salt.
Originally Posted by John Deakin
In my opinion, the ATSB has taken junk science, pure speculation and profound ignorance to levels seldom before seen. They have not only perpetuated "Old Wives' Tales," but they have invented a few new ones. I'm afraid we'll be hearing about "lead oxybromide deposits" for all eternity. As best I can tell, that term seems to have been INVENTED in this accident report. (Try a search on the Internet for "lead oxybromide"!)
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Walter, correct me if I'm wrong, but this colour is only true for leaded fuel. Alas, you'll never see a road car with this colour exhaust any more.