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baw2198
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Piston Engine Fadec, Diesel Vs Avgas

Sat Oct 06, 2007 4:13 pm

Reading the other thread about FADEC systems in GA, somebody mentioned that the Mercedes diesels come with FADEC being the only option. What is different with the aviation version of the diesel that FADEC is a requirement where the avgas powered engines have it as an option or no option at all?
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TheSonntag
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RE: Piston Engine Fadec, Diesel Vs Avgas

Sat Oct 06, 2007 4:45 pm

I am not a technician, but modern Turbo Diesel engines as they are found on modern German and Japanese cars are extremely high tech. They have an electronic injection, so that they need electronics.

A Diesel engines power output is regulated by adjusting the amount of fuel injected, the more you add, the more power you get. The amount is adjusted at the fuel pump, which is a highly sophisticated piece of machinery.

I think this, and the fact that the engine only was developed recently, explains why it is only available with FADEC.
 
A342
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RE: Piston Engine Fadec, Diesel Vs Avgas

Sat Oct 06, 2007 5:38 pm

Quoting TheSonntag (Reply 1):
A Diesel engines power output is regulated by adjusting the amount of fuel injected, the more you add, the more power you get. The amount is adjusted at the fuel pump, which is a highly sophisticated piece of machinery.

Maybe I'm nit-picking, but on electronic fuel injection diesels, the amount of fuel injected is determined by the FADEC. The FADEC then transmits the signal to the injection nozzle, which, operating either by the magnetic or piezo principle, releases the pre-determined amount of fuel into the cylinder. The injection pressure is created at either a central injection pump (common rail and the older systems), or by the nozzle itself (pump-injector nozzle).

The fuel pump just delivers the fuel from the tank to the injection pump or the nozzle.
Exceptions confirm the rule.
 
ex52tech
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RE: Piston Engine Fadec, Diesel Vs Avgas

Sun Oct 07, 2007 8:10 pm

Quoting A342 (Reply 2):
Maybe I'm nit-picking, but on electronic fuel injection diesels, the amount of fuel injected is determined by the FADEC. The FADEC then transmits the signal to the injection nozzle, which, operating either by the magnetic or piezo principle, releases the pre-determined amount of fuel into the cylinder. The injection pressure is created at either a central injection pump (common rail and the older systems), or by the nozzle itself (pump-injector nozzle).

The fuel pump just delivers the fuel from the tank to the injection pump or the nozzle.

The newer Mercedes diesel engines that I have had contact with in large trucks have individual pumps that run off of the camshaft for each cylinder. There is a transfer pump that delivers fuel to each one of these pumps, and the FADEC directs each pump to the duration, amount, and timing of each fuel pulse to the injectors. I other words the injectors are just injectors, each pump is where everything happens. Most FADEC controlled big diesel engines put out more horse power when the cruise control is engaged then when the foot throttle is being used for protection purposes. So airplanes using FADEC controlled diesel engines have to be using an even more complex computer controlled system then the big trucks do.
I realize we are not talking about the same engines here, but I can't imagine the process being different, diesel injectors are buried down in the heads in considerable heat, where the individual pumps are out in the open away from the heat and the hot oil.
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A342
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RE: Piston Engine Fadec, Diesel Vs Avgas

Mon Oct 08, 2007 8:21 pm

Quoting Ex52tech (Reply 3):
The newer Mercedes diesel engines that I have had contact with in large trucks have individual pumps that run off of the camshaft for each cylinder. There is a transfer pump that delivers fuel to each one of these pumps, and the FADEC directs each pump to the duration, amount, and timing of each fuel pulse to the injectors. I other words the injectors are just injectors, each pump is where everything happens.

How far away are the camshaft-driven pumps from the injectors? Are those OHV engines with one camshaft between the cylinder banks (V-engines)? How old are they?

Quoting Ex52tech (Reply 3):
Most FADEC controlled big diesel engines put out more horse power when the cruise control is engaged then when the foot throttle is being used for protection purposes.

Seems strange to me. You don't need much power while cruising at a constant speed, except on steep grades.
Exceptions confirm the rule.
 
tlfd29
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RE: Piston Engine Fadec, Diesel Vs Avgas

Tue Oct 09, 2007 3:53 am

I'm sure that the reason for taming the horsepower when not using cruise control is due to the ECM not always knowing what the driver is going to do next. Horsepower in diesels is controlled by amount of fuel, fuel pressure, and amount of air. With todays high pressure injection systems I would guess that the engine tries to protect itself slightly when not using cruise just in case the driver really stomps on it. When using cruise the engine is a little more predictable therefore the engine can justify increasing the fuel pressure and quantity therefore increasing horsepower. Just a thought.
 
brons2
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RE: Piston Engine Fadec, Diesel Vs Avgas

Tue Oct 09, 2007 4:51 am

Quoting Baw2198 (Thread starter):
Reading the other thread about FADEC systems in GA, somebody mentioned that the Mercedes diesels come with FADEC being the only option. What is different with the aviation version of the diesel that FADEC is a requirement where the avgas powered engines have it as an option or no option at all?

I would say that any car with drive by wire throttle has an automotive equivalent of FADEC. Every engine setting including the throttle butterfly is controlled by the computer, based on your control inputs.
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ex52tech
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RE: Piston Engine Fadec, Diesel Vs Avgas

Thu Oct 11, 2007 4:05 am

Quoting A342 (Reply 4):

How far away are the camshaft-driven pumps from the injectors? Are those OHV engines with one camshaft between the cylinder banks (V-engines)? How old are they

I am talking about the newer Mercedes in line 6 cyl. engines. These individual pumps replaced the old injection pumps. Many of the manufacturers ran injection pumps with computer controlled engines.......servos instead of mechanical linkage. When the manufacturers started getting away from injection pumps due to emission standards, they went to these individual pumps. Mack runs the same setup, and has since 1999.

These engines are OHV engines, the cam shaft is still in the same place, and the pumps run off of the cam shaft. In most cases the injection lines are shorter than the lines were on the injection pump engines.

The last of the big V-8s that had any power (Mack, 1092 cubic in.) would not make U.S.emissions after 1992, so they are becoming rare, except in Australia. So V-8s in the big trucks are a thing of the past. I have seen a Mack V-8 put out 750 H.P. and 2000 lb/ft torque.

Quoting A342 (Reply 4):

Seems strange to me. You don't need much power while cruising at a constant speed, except on steep grades

This really doesn't have anything to do with aviation, but here goes.
Yes only on steep grades is it going to work, and most times the driver has to down shift anyway, so the cruise comes off. For instance a Detroit series 60, 12.7 L engine can be set at 430 h.p max on the throttle, but will deliver 470 h.p. on the cruise. The computer will not allow any more on the foot throttle, because you could burn up a piston, or a turbo.
"Saddest thing I ever witnessed....an airplane being scrapped"
 
Grunf
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RE: Piston Engine Fadec, Diesel Vs Avgas

Thu Oct 11, 2007 10:23 am

Quoting Ex52tech (Reply 7):

The last of the big V-8s that had any power (Mack, 1092 cubic in.) would not make U.S.emissions after 1992, so they are becoming rare, except in Australia. So V-8s in the big trucks are a thing of the past. I have seen a Mack V-8 put out 750 H.P. and 2000 lb/ft torque.

*cough* Scania V8 *cough*  Wink

BTW, truck manufacturers have reused old aircraft technology and (re)introduced Turbo-Compound.

http://www.scania.com/products/newtr...turbocompound/how_does_it_work.asp
http://www.scania.de/Images/mapmap_tcm125-43342.jpg

It would be interesting to see if compounding will find its way into aircraft diesels just like in old days. Napier Nomad was using the same principle (albeit with 2-stroke diesel).

Truck engines (at least Scania) often use induvidual diesel pumps that "pump" the pressure into the injector, which is then electronically triggered to deliver specified amount of fuel into combustion chamber.

New car diesel engines often use common-rail approach, where one pump holds pressure constant in fuel-rail and injectors are triggered to deliver fuel needed.
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A342
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RE: Piston Engine Fadec, Diesel Vs Avgas

Thu Oct 11, 2007 5:59 pm

Quoting Ex52tech (Reply 7):
I am talking about the newer Mercedes in line 6 cyl. engines.

Do these engines happen to deliver about 280hp? IIRC, the really heavy trucks with 400hp and above use V-engines.

Quoting Ex52tech (Reply 7):
So V-8s in the big trucks are a thing of the past.

Maybe in America, but not here in Europe. While the vast majority of the trucks use 6-cyl engines, there are still V-8s in production.
MAN now has developed a 680hp V-8 which is Euro-5 compliant.
Exceptions confirm the rule.
 
ex52tech
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RE: Piston Engine Fadec, Diesel Vs Avgas

Fri Oct 12, 2007 4:34 am

Quoting A342 (Reply 9):

Do these engines happen to deliver about 280hp? IIRC, the really heavy trucks with 400hp and above use V-engines.

The Mercedes MBE 4000 series engines can put out up to 450 h.p., and 1650 lb/ft of torque, I do not know their exact displacement, but I think it is in the 12L size. The Bigger 14L Series 60 Detroit will put out 500+ h.p. and 1650 lb/ft of torque. The torque has actually been held to that figure because of transmission and drive line limits, not what the engine can produce. Caterpillar, Cummins, Mack, and Volvo have comparable engines offered in the U.S., but all are inline 6 cylinders in the big Semi trucks. Everyone here in the U.S. has leaned away from the big V-8s because of weight and fuel burn. Weight is huge here, and the profit margins are so slim, that fuel burn is a big deal.

I like that turbo compound engine, that is a great old idea that would probably work out well.
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A342
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RE: Piston Engine Fadec, Diesel Vs Avgas

Sat Oct 13, 2007 9:19 pm

Quoting Ex52tech (Reply 7):
Yes only on steep grades is it going to work, and most times the driver has to down shift anyway, so the cruise comes off. For instance a Detroit series 60, 12.7 L engine can be set at 430 h.p max on the throttle, but will deliver 470 h.p. on the cruise. The computer will not allow any more on the foot throttle, because you could burn up a piston, or a turbo.

A strange setup, to say the least. A modern electronically-controlled diesel will not let you burn up a piston or turbo, even with cruise control disengaged.
Exceptions confirm the rule.
 
A342
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RE: Piston Engine Fadec, Diesel Vs Avgas

Sun Oct 14, 2007 10:28 am

Quoting A342 (Reply 11):
A modern electronically-controlled diesel will not let you burn up a piston or turbo, even with cruise control disengaged.

Maybe I should add: Except if you accidentally select the wrong gear with a manual transmission.
Exceptions confirm the rule.
 
ex52tech
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RE: Piston Engine Fadec, Diesel Vs Avgas

Mon Oct 15, 2007 4:31 am

Quoting A342 (Reply 11):
A modern electronically-controlled diesel will not let you burn up a piston or turbo, even with cruise control disengaged

That is why they are rated lower h.p. output on the throttle, no chance of burning a piston or turbo at that setting. Even with a manual transmission.
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A342
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RE: Piston Engine Fadec, Diesel Vs Avgas

Tue Oct 16, 2007 5:21 pm

Quoting Ex52tech (Reply 13):
That is why they are rated lower h.p. output on the throttle, no chance of burning a piston or turbo at that setting. Even with a manual transmission.

I'm not so sure about that. Even if only 50% of the power output is available, when the engine rpm goes say 100% beyond the specification, the ECU can't do anything about it.
Exceptions confirm the rule.
 
Analog
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RE: Piston Engine Fadec, Diesel Vs Avgas

Tue Oct 16, 2007 6:21 pm

Quoting A342 (Reply 14):

I'm not so sure about that. Even if only 50% of the power output is available, when the engine rpm goes say 100% beyond the specification, the ECU can't do anything about it.

Could the truck prevent engaging gears that would destroy the engine? Of course you could also coast with the clutch down and double your speed (can one do this in trucks?).

(Knows nothing about big rigs)
 
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RE: Piston Engine Fadec, Diesel Vs Avgas

Wed Oct 31, 2007 4:10 pm

Quoting Analog (Reply 15):

Could the truck prevent engaging gears that would destroy the engine? Of course you could also coast with the clutch down and double your speed (can one do this in trucks?)

Since almost all heavy trucks use unsynchronized transmissions, this is a non-issue. Since you have to double clutch you have great difficulty in engaging a gear that will overspeed the engine, as you have to rev it up to the speed it would be going at before it will go into gear.
As to V-8's, I do not understand why they have disappeared, as structurally they should enable a lighter engine with the same power output, as it would be shorter and stiffer with much less potential for crankshaft whipping (the same applies to a V-6.) I suspect it has to do with the fact that the only V engines that were popular were the 2 cycle Detroit Diesels, which would never have met emissions standards. The Mack V-8 had a very bad reputation for swallowing valve seats (I know about it from first-hand experience; I owned one briefly) which supposedly was solved when they went to 4 valves per cylinder, but by then its reputation was in the tank and it never recovered. I suspect that it was a case that they did not feel that the money spent in making it meet emissions standards was not worth it, rather than not being able to. All the other heavy duty engines in the US market have been in-line sixes; and it has become fixed in most trucker's minds that this is the only way to go. Personally, I think it would be possible to build a V-6 or V-8 that would perform as well or better and be lighter, but it doesn't seem likely that anyone will do it anytime soon. I would love to see the MAN V-8 for sale here.
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A342
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RE: Piston Engine Fadec, Diesel Vs Avgas

Wed Oct 31, 2007 7:36 pm

Quoting SEPilot (Reply 16):
I would love to see the MAN V-8 for sale here.

I should add that it's torque isn't that great, it is outdone by the big Volvo inline six engine with 660 hp.
Exceptions confirm the rule.
 
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RE: Piston Engine Fadec, Diesel Vs Avgas

Thu Nov 01, 2007 4:26 pm

Quoting A342 (Reply 17):

I should add that it's torque isn't that great, it is outdone by the big Volvo inline six engine with 660 hp.

Granted; but I bet it's power to weight ratio is better than any of the big 6's. Horsepower demands are probably higher in the US than in Europe, as trucks are bigger and heavier and hauls are longer. If MAN established a market here I'm sure they'd soon offer a bigger engine. The problem is getting a foothold.
The problem with making things foolproof is that fools are so doggone ingenious...Dan Keebler
 
A342
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RE: Piston Engine Fadec, Diesel Vs Avgas

Thu Nov 01, 2007 8:07 pm

Quoting SEPilot (Reply 18):
Horsepower demands are probably higher in the US than in Europe, as trucks are bigger and heavier and hauls are longer.

Are the trucks heavier on your side of the pond? I don't think so. But they're allowed to drive at much higher speeds than here in Europe. IMO that's where the power demand comes from.
Exceptions confirm the rule.
 
Mir
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RE: Piston Engine Fadec, Diesel Vs Avgas

Thu Nov 01, 2007 8:46 pm

Quoting A342 (Reply 19):
Are the trucks heavier on your side of the pond? I don't think so.

I think some of them are. I don't remember seeing that many trucks in Europe that rival your average eighteen-wheeler in the US.

-Mir
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A342
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RE: Piston Engine Fadec, Diesel Vs Avgas

Thu Nov 01, 2007 8:49 pm

Quoting Mir (Reply 20):
I think some of them are. I don't remember seeing that many trucks in Europe that rival your average eighteen-wheeler in the US.

In terms of wheels - yes. But IIRC we have higher axle loads in Europe, and maybe you have observed that the trailer wheels here are quite wide, hence you don't need four of them per axle, but only two.
Exceptions confirm the rule.
 
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RE: Piston Engine Fadec, Diesel Vs Avgas

Thu Nov 01, 2007 9:08 pm

Quoting A342 (Reply 19):
Are the trucks heavier on your side of the pond? I don't think so. But they're allowed to drive at much higher speeds than here in Europe. IMO that's where the power demand comes from.

The normal legal weight limit for an 18-wheeler in the US is 80,000 lbs. or 36,364 KG. I was under the impression it was less in Europe. Can you clarify?

Quoting A342 (Reply 21):
But IIRC we have higher axle loads in Europe, and maybe you have observed that the trailer wheels here are quite wide, hence you don't need four of them per axle, but only two.

We also have so-called "super singles" here, which are gaining in popularity. Axle loads are 12,000 lbs (5,455 KG) for a single wheeled steer axle, 20,000 lbs (9,091 KG) for a single axle with duals or super singles (also a steer axle with super singles), and 34,000 lbs (15,455 KG) for a tandem axle pair. Axles more than 10' apart are considered single axles, which has led to the growing popularity of "spread axle" trailers. Total weight capacity doesn't change, but loading flexibility does. Can you provide European limits? I would like to know what they are. (For the record, I have driven 18-wheelers here, and at one time owned a log truck.)
The problem with making things foolproof is that fools are so doggone ingenious...Dan Keebler
 
A342
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RE: Piston Engine Fadec, Diesel Vs Avgas

Fri Nov 02, 2007 12:23 pm

Quoting SEPilot (Reply 22):
The normal legal weight limit for an 18-wheeler in the US is 80,000 lbs. or 36,364 KG. I was under the impression it was less in Europe. Can you clarify?

In most of Europe it is 40,000 kg. That applies to any combination of truck and trailer having more than four axles.
In some European countries it's up to 60,000 kg, but you may need more axles.

Quoting SEPilot (Reply 22):
Can you provide European limits? I would like to know what they are.

In general:
Unpowered single axle: 10,000 kg, some countries up to 13,000 kg
Powered single axle: 11,500 kg (may require dual tyres, not sure), some countries up to 13,000 kg

In detail:
Tandem axles on the truck: between 11,500 and 20,000 kg, depending on the type of suspension, tyre setup, powered or unpowered, and distance between the axles
Tandem axles on the trailer: between 11,000 and 20,000 kg, depending on the distance
Triple axles on trailers (the most common setup): between 21,000 and 24,000 kg, depending on the distance

That's just a broad overview, there's still tonnes of differences between the countries.


Hope that helps.
Exceptions confirm the rule.
 
sv2008
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RE: Piston Engine Fadec, Diesel Vs Avgas

Fri Nov 02, 2007 12:52 pm

Quoting SEPilot (Reply 16):
As to V-8's, I do not understand why they have disappeared

I'm guessing, but I'd think it's probably cost, design and packaging. Not sure how important packaging would be in a truck, but cost is still important.

A v8 is considerably more complex to design and a lot of stuff has to be doubled, because you have two cylinder blocks basically, which means two camshafts (which somehow have to be driven). It complicates the air intakes (air filters, mass sensor...), fuel injecters and a load of other stuff.

Even all that wouldn't be too bad, except the exhaust from two blocks is now even more complicated. A straight six can have one exhaust - a V8 needs at least two (I think a V6 can either one or two, but I don't remember).

Most cars have transverse V6 arrnagement (although BMW are an exception, using longituidnal) just because there isn't space for a front wheel drive, transverse straight 6 in the engine bay, so the V6 isn't ideal but there isn't much other option.

Power isn't really an issue with a modern turbocharhed engine, you can just boost them until you get the power output you want, even from a smaller capacity, within limits.

I don't think whipping is really a problem, it can be supported and balanced, i don't remember how exactly it is done, but it's not too difficult, and manufacturers have long solved the problem.

A straight six should be much lighter than a V8, and turbocharged, can produce the same power from a lower capacity. Another advatange is less friction (less cylinders), which means more power effectivley.

It's strange how aircraft use such old technology when cars have been using electrnoics for many years. Nearly all fuel injected cars have ECU systems now (pretty much anything built in the last 12 years).
 
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RE: Piston Engine Fadec, Diesel Vs Avgas

Fri Nov 02, 2007 2:27 pm

Quoting A342 (Reply 23):
That's just a broad overview, there's still tonnes of differences between the countries.

Thanks for the info; I appreciate it. You are right, the European limits are higher. I did not realize this.

Quoting Sv2008 (Reply 24):
A v8 is considerably more complex to design and a lot of stuff has to be doubled, because you have two cylinder blocks basically, which means two camshafts (which somehow have to be driven). It complicates the air intakes (air filters, mass sensor...), fuel injecters and a load of other stuff.

This is not true; all V-8 diesels use a single camshaft, as do all older gas V-8's (located between the cylinder banks.) The block is more complex but more compact and stronger. The block is a single unit on every V engine I have ever seen. Your point on exhausts is somewhat valid, but since no modern heavy duty diesel 6 uses a single cylinder head the exhaust has to be split as well, so this is a minor issue. Look at aircraft engines; the old piston engines were radial for a reason; it meant for the shortest possible block and crankshaft which made the structure much lighter and more rigid, and the forces on opposite cylinders partially canceled each other. Modern light aircraft engines are opposed for the same reason. Radial engines present too much frontal area for the power required; so the flat opposed layout works best. A V design is not as structurally efficient but it is far superior to an inline design and fits better in most vehicles. Remember that Packard and others did produce straight 8's in the 30's and 40's; these had severe crankshaft problems because of their length. Modern diesel 6's require very rugged and very heavy cranks and blocks to avoid the problems these engines had; V engines could be built with the same strength with much less weight.

Quoting Sv2008 (Reply 24):
Power isn't really an issue with a modern turbocharhed engine, you can just boost them until you get the power output you want, even from a smaller capacity, within limits.

This is not the issue; turbocharging increases the power output per unit of displacement but more power means more stress, and the block and crank have to be able to handle it, which requires weight. Also, wear and stress on cylinder components increases, which also requires that they be ruggeder.

Quoting Sv2008 (Reply 24):

I don't think whipping is really a problem, it can be supported and balanced, i don't remember how exactly it is done, but it's not too difficult, and manufacturers have long solved the problem.

It is a very real problem; support and balance requires added weight.

Quoting Sv2008 (Reply 24):
A straight six should be much lighter than a V8, and turbocharged, can produce the same power from a lower capacity. Another advatange is less friction (less cylinders), which means more power effectivley.

Properly designed, a V engine will ALWAYS be lighter than the equivalent straight engine for the above stated reasons.

Quoting Sv2008 (Reply 24):

It's strange how aircraft use such old technology when cars have been using electrnoics for many years. Nearly all fuel injected cars have ECU systems now (pretty much anything built in the last 12 years).

The problem is primarily certification requirements. The reliability of modern auto engines probably exceeds that of piston aircraft engines by a wide margin, but when they were designed this was not the case. The volume of aircraft engines produced simply does not justify the huge expense of certification; if someone were to try they would probably have to sell them for several hundred thousand dollars each.
The problem with making things foolproof is that fools are so doggone ingenious...Dan Keebler
 
sv2008
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RE: Piston Engine Fadec, Diesel Vs Avgas

Fri Nov 02, 2007 5:23 pm

Quoting SEPilot (Reply 25):
This is not true; all V-8 diesels use a single camshaft,

Yep your right. I should have said, i know a bit about engines for cars - i know nothing about their apllication in trucks or aircraft, so all what i wrote was based on car applications; i was just assuming some stuff would be the same or similar.

For example the exhaust problem isn't so bad if it exits on the side or something (a car it has to be routed through the vehicle to the back and through silencers.)

Quoting SEPilot (Reply 25):
This is not the issue; turbocharging increases the power output per unit of displacement but more power means more stress, and the block and crank have to be able to handle it, which requires weight. Also, wear and stress on cylinder components increases, which also requires that they be ruggeder.

Good point; again, cars have much lower stress. Yes the block has to be able to handle it, but I thought the power to weight ratio of a turbocharged engine would be higher still than than a normal engine. maybe in trucks (bigger engines) there is not so much return on this. Again, was thinknig of car engines, which don't have such a long life. (some versions of the EVO here have 400 bhp from a 2 litre four. F1 cars apparently had 1000 bhp from 1.5 litres!


I'm surprised that a V in lighter than a straight engine but don't mind being proved wrong, i'm no expert and don't have any figures. Maybe where i read that was wrong, or my memory is just wrong.
 
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RE: Piston Engine Fadec, Diesel Vs Avgas

Fri Nov 02, 2007 5:56 pm

Quoting Sv2008 (Reply 26):
Yes the block has to be able to handle it, but I thought the power to weight ratio of a turbocharged engine would be higher still than than a normal engine.

This is true to a point; but has no relevance in the straight vs. V configuration debate, as it applies to both equally. Heavy duty truck engines are all turbocharged anyway, as emissions requirements are much easier to meet with turbocharging as well as the fact that normally aspirated engines would be way too large with the horsepower of modern engines. A non-turbocharged 230hp Cummins engine of 40 years ago, for example, as a 600hp Cummins engine today.
The problem with making things foolproof is that fools are so doggone ingenious...Dan Keebler
 
sv2008
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RE: Piston Engine Fadec, Diesel Vs Avgas

Fri Nov 02, 2007 6:07 pm

Quoting SEPilot (Reply 27):
This is true to a point; but has no relevance in the straight vs. V configuration debate

It might have some releavnce, as the it makes both driving the turbocharger through the exhaust and arranging the intakes more difficult/complicated?....a twin turbo design is the obvious solution (one for each side), but of course thats heavier.....what do they use anyway?
 
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RE: Piston Engine Fadec, Diesel Vs Avgas

Fri Nov 02, 2007 6:49 pm

Quoting Sv2008 (Reply 28):

It might have some releavnce, as the it makes both driving the turbocharger through the exhaust and arranging the intakes more difficult/complicated?....a twin turbo design is the obvious solution (one for each side), but of course thats heavier.....what do they use anyway?

These are minor considerations compared to the cost and complexities of the block and cylinder design. The V-8 diesels that I am familiar with usually have a single turbocharger sitting atop the engine. This works quite well, actually, as a V engine is not as tall as a straight one, since the cylinders are angled, and it makes a convenient point to join the exhaust manifolds to a single point. Twin turbos are only useful on extremely high performance engines; they spool up faster than a single large one due to lower inertia, but on a heavy duty engine do not offer much advantage. It is easier and cheaper to just make one large one.
The problem with making things foolproof is that fools are so doggone ingenious...Dan Keebler
 
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RE: Piston Engine Fadec, Diesel Vs Avgas

Fri Nov 02, 2007 6:57 pm

Quoting SEPilot (Reply 25):
This is not true; all V-8 diesels use a single camshaft

Maybe in trucks, but not in passenger cars.
Exceptions confirm the rule.
 
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SEPilot
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RE: Piston Engine Fadec, Diesel Vs Avgas

Fri Nov 02, 2007 7:24 pm

Quoting A342 (Reply 30):
Maybe in trucks, but not in passenger cars.

Right; I was not considering diesel V engines in cars; they do not exist in the US (except in pickups, and those use one camshaft). I guess there are overhead cam diesel V engines in Europe. General Motors killed the appetite for automotive diesels in the US in the 80's when they tried to make a diesel out of their 350 V-8 gas engine. It was nowhere near rugged enough and self-destructed in short order. They did come out with a decent one later, but the damage was done, and the only passenger car diesel available in the US is the VW, as far as I know. Pity; I like diesels and wish I could buy one (I don't need or want a large pickup at this point, which is the only other choice, and I won't buy a VW because of bad prior experience.)
The problem with making things foolproof is that fools are so doggone ingenious...Dan Keebler
 
A342
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RE: Piston Engine Fadec, Diesel Vs Avgas

Fri Nov 02, 2007 8:10 pm

Quoting SEPilot (Reply 31):
I guess there are overhead cam diesel V engines in Europe.

That's right, most of them are DOHC. No OHV engines over here.

Quoting SEPilot (Reply 31):
and I won't buy a VW because of bad prior experience.)

What exactly caused your headaches? Our 12-year-old VW diesel is still running fine, and none of the problems we had (there were few of them) were engine related. But I hope the exhaust system lasts longer on our new Audi (you bet it's a TDI)!
Exceptions confirm the rule.
 
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RE: Piston Engine Fadec, Diesel Vs Avgas

Fri Nov 02, 2007 9:14 pm

Quoting A342 (Reply 32):
What exactly caused your headaches?

I purchased a Rabbit (Golf over there) new in 1981. After 60,000 miles the head gasket went-not good, but not disastrous. It was repaired by an excellent independent mechanic, who told my wife to bring it back after 1000 miles to retorque the head-standard practice. She did, and as he was doing it the block cracked wide open. He was understandably surprised, and did some checking and found that that particular engine had a habit of doing just that. He then contacted VW of America, who said Yes, we know there is a problem, but no, we won't do anything about it. That is my complaint, which is primarily against VW of America. However, VW's in this country do not have a good reputation for durability.
The problem with making things foolproof is that fools are so doggone ingenious...Dan Keebler
 
A342
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RE: Piston Engine Fadec, Diesel Vs Avgas

Sat Nov 03, 2007 9:00 pm

Quoting SEPilot (Reply 31):
and the only passenger car diesel available in the US is the VW, as far as I know.

Oh, forgot to tell you, Mercedes also offers diesels in the USA:

http://www.mbusa.com/models/main.do?modelCode=E320BTEC
http://www.mbusa.com/models/main.do?modelCode=ML320CDI
http://www.mbusa.com/models/main.do?modelCode=R320CDI
http://www.mbusa.com/models/main.do?modelCode=GL320CDI

But they aren't exactly cheap...
Exceptions confirm the rule.
 
speedbird2263
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RE: Piston Engine Fadec, Diesel Vs Avgas

Sat Nov 03, 2007 9:16 pm

Quoting SEPilot (Reply 16):
Since you have to double clutch you have great difficulty in engaging a gear that will overspeed the engine, as you have to rev it up to the speed it would be going at before it will go into gear.

Double clutching with the newer transmissions of today is a good practice however is not necessary to achieve good shifts if one learns how to shift at the appropriate rpm, known as "floating" the gears. The example below shows the clutch being used only to get under way and the transmission is an 18spd Eaton-Fuller.



Even with some of the 'older transmissions' like a Quad Box on the Mack B-Model (*you said You owned a Mack), double clutching wasn't absolutely necessary so long as you timed the rpm's just right.



Quoting SEPilot (Reply 25):
A V design is not as structurally efficient but it is far superior to an inline design and fits better in most vehicles.

If the V design is far superior as you have outlined, why is it then that BMW still uses the inline design in most of its automotive product range? I do however recognize that for higher horsepower and torque applications they incorporate the V-block as is evident with the V10 used in the M5.

Quoting A342 (Reply 17):
Horsepower demands are probably higher in the US than in Europe, as trucks are bigger and heavier and hauls are longer.

As has been said, the weights are pretty much the same If not heavier, don't let the seemingly timid 'Cab-Over' designs fool You. Scanias, Volvo's and the like 'across' the pond can hold their own with the Volvo FH16 for example being offered with 660hp.
Straight'n Up 'N Fly Right Son
 
A342
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RE: Piston Engine Fadec, Diesel Vs Avgas

Sat Nov 03, 2007 10:03 pm

Quoting Speedbird2263 (Reply 35):
Quoting A342 (Reply 17):
Horsepower demands are probably higher in the US than in Europe, as trucks are bigger and heavier and hauls are longer.

False quote here.
Exceptions confirm the rule.
 
Analog
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RE: Piston Engine Fadec, Diesel Vs Avgas

Sat Nov 03, 2007 11:25 pm

Quoting Sv2008 (Reply 26):
Again, was thinknig of car engines, which don't have such a long life. (some versions of the EVO here have 400 bhp from a 2 litre four.

If you operated a car diesel like a long-haul truck, it would probably last quite a long time.

Quoting Sv2008 (Reply 26):
Good point; again, cars have much lower stress.

I imagine cars have higher stress. They generally have many more on-off cycles per mile and spend more time in stop and go traffic than trucks.

Quoting SEPilot (Reply 25):
This is not the issue; turbocharging increases the power output per unit of displacement but more power means more stress, and the block and crank have to be able to handle it, which requires weight. Also, wear and stress on cylinder components increases, which also requires that they be ruggeder.

More power means more stress, but that has nothing to do with whether an engine of XXX hp is turbocharged. Why would a turbocharged engine of identical output to a non-turbocharged engine put more stress on the crank? If anything, I imagine it would mean less stress, if only because the engine could be physically smaller .
 
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RE: Piston Engine Fadec, Diesel Vs Avgas

Sat Nov 03, 2007 11:37 pm

Quoting A342 (Reply 34):
Oh, forgot to tell you, Mercedes also offers diesels in the USA:

I was under the impression that they had discontinued selling diesels in the US; I had not checked as they are definitely out of my price range. Thanks for the correction.

Quoting Speedbird2263 (Reply 35):
If the V design is far superior as you have outlined, why is it then that BMW still uses the inline design in most of its automotive product range?

I don't know for sure; but it makes less of a difference on a smaller engine. I am talking primarily about 12 to 16 liter heavy truck engines.

Quoting Analog (Reply 37):
Why would a turbocharged engine of identical output to a non-turbocharged engine put more stress on the crank?

The point is that without turbocharging you need much greater displacement, which requires larger components and thus puts proportionately less stress on them. When you add turbocharging you have to beef up the components to handle the higher stress.
The problem with making things foolproof is that fools are so doggone ingenious...Dan Keebler
 
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RE: Piston Engine Fadec, Diesel Vs Avgas

Sat Nov 03, 2007 11:43 pm

Quoting Speedbird2263 (Reply 35):
Double clutching with the newer transmissions of today is a good practice however is not necessary to achieve good shifts if one learns how to shift at the appropriate rpm, known as "floating" the gears.

The point is the transmissions are not synchronized; you are correct in that you don't have to double clutch; in fact many drivers only use the clutch to start and stop (I can do this, but I usually use the clutch.) In either case it is impossible to get the transmission in a gear that will overspeed the engine without forcing it and causing quite a racket. You would not do it inadvertently. Actually I owned two Macks; the first had the six speed transmission and the second had the twelve speed (that was the one with the V-8.)
The problem with making things foolproof is that fools are so doggone ingenious...Dan Keebler
 
speedbird2263
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RE: Piston Engine Fadec, Diesel Vs Avgas

Sat Nov 03, 2007 11:51 pm

Quoting A342 (Reply 36):

Correct Quote:

Quoting SEPilot (Reply 18):
Horsepower demands are probably higher in the US than in Europe, as trucks are bigger and heavier and hauls are longer.

Terribly sorry about that mate. Didn't catch it the first time around.

Quoting SEPilot (Reply 39):
The point is the transmissions are not synchronized; you are correct in that you don't have to double clutch; in fact many drivers only use the clutch to start and stop (I can do this, but I usually use the clutch.) In either case it is impossible to get the transmission in a gear that will overspeed the engine without forcing it and causing quite a racket. You would not do it inadvertently.

Ah, now I understand your point and quite right you are.

[Edited 2007-11-03 16:54:57]
Straight'n Up 'N Fly Right Son
 
Analog
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RE: Piston Engine Fadec, Diesel Vs Avgas

Sun Nov 04, 2007 9:17 am

Quoting SEPilot (Reply 38):

I was under the impression that they had discontinued selling diesels in the US; I had not checked as they are definitely out of my price range. Thanks for the correction.

VT is CA emissions. No VW or MB diesels for you (unless you buy them used from out of state). Not until cleaner diesel fuel permits cleaner burning CARB legal engines.

Quoting SEPilot (Reply 38):

The point is that without turbocharging you need much greater displacement, which requires larger components and thus puts proportionately less stress on them. When you add turbocharging you have to beef up the components to handle the higher stress.

Wait, what? Bigger displacement -> larger components to handle the stress. Turbo-> larger components to handle the stress.What's the difference?
 
A342
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RE: Piston Engine Fadec, Diesel Vs Avgas

Sun Nov 04, 2007 11:51 am

Quoting Analog (Reply 41):
Wait, what? Bigger displacement -> larger components to handle the stress. Turbo-> larger components to handle the stress.What's the difference?

No. Turbo translates into sturdier parts, not larger ones.

Quoting Speedbird2263 (Reply 40):
Terribly sorry about that mate.

No problem!
Exceptions confirm the rule.
 
Analog
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RE: Piston Engine Fadec, Diesel Vs Avgas

Sun Nov 04, 2007 1:09 pm

Quoting A342 (Reply 42):

No. Turbo translates into sturdier parts, not larger ones.

SEPilot talked about "beefing up" parts to handle the larger stress. I guess if you use stronger materials, etc. then sturdier does not necessarily mean larger, but otherwise same material + same design + "beefier" = larger, right?
 
A342
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RE: Piston Engine Fadec, Diesel Vs Avgas

Sun Nov 04, 2007 2:18 pm

Quoting Analog (Reply 43):
but otherwise same material + same design + "beefier" = larger, right?

I'm no expert, but this is how I imagine it.

Let's have a look at a piston, for example. If we want to make it sturdier without using other materials, we'd have to add material to the piston walls, the piston head etc. Now the question is: Where do we add that material? If we add it on the inside of the piston, the piston doesn't become larger, only heavier. It can be used in the existing cylinder.

Or does this contradict "same design"?
Exceptions confirm the rule.
 
Analog
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RE: Piston Engine Fadec, Diesel Vs Avgas

Sun Nov 04, 2007 8:06 pm

Quoting A342 (Reply 44):
If we add it on the inside of the piston, the piston doesn't become larger, only heavier. It can be used in the existing cylinder.

Or does this contradict "same design"?

Adding material inside the cylinder decreases displacement.

I was talking about "larger" in the sense of individual parts. Clearly turbocharging effectively decreases an engine's physical size and weight, given the same HP and torque.
 
A342
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RE: Piston Engine Fadec, Diesel Vs Avgas

Sun Nov 04, 2007 8:53 pm

Quoting Analog (Reply 45):
Adding material inside the cylinder decreases displacement.

That's why I used the example of a piston.  Wink
Exceptions confirm the rule.
 
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RE: Piston Engine Fadec, Diesel Vs Avgas

Sun Nov 04, 2007 9:16 pm

Quoting Analog (Reply 41):

VT is CA emissions.

That is news to me. I have bought most of my cars in New Hampshire (because that's where the dealers are) and have had no problem registering them in VT; I just bought a brand new Subaru for my wife in NH. There are VW diesels in VT; I just won't buy one for reasons stated above. Diesel pickups are fairly common; I just don't need one at this point.

Quoting Analog (Reply 41):

Wait, what? Bigger displacement -> larger components to handle the stress. Turbo-> larger components to handle the stress.What's the difference?

The point is that when you take a small displacement engine and turbocharge it you have to beef up the components, which is what happens since most heavy duty diesels on the market today started out as naturally aspirated and had turbochargers added on. Engine design has been largely evolutionary rather than revolutionary; although there have been a few "clean sheet" designs that started turbocharged, most notably the Detroit Diesel Series 60 engines

Quoting Analog (Reply 45):
Clearly turbocharging effectively decreases an engine's physical size and weight, given the same HP and torque.

True, but since the higher stresses need to be dealt with the components do need to be beefed up, so you lose some of the weight savings, but not all.
The problem with making things foolproof is that fools are so doggone ingenious...Dan Keebler
 
brons2
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RE: Piston Engine Fadec, Diesel Vs Avgas

Mon Nov 05, 2007 6:39 am

Quoting SEPilot (Reply 38):
I was under the impression that they had discontinued selling diesels in the US; I had not checked as they are definitely out of my price range. Thanks for the correction.

The MB 3 liter CDI (Common Rail, direct injection) is sold in the E, R and M class ranges, and also in the Jeep Grand Cherokee. It's a wonderful engine, I have driven one in a Jeep. Has 215 HP and TONS of torque, while getting 23 mpg in town and 28 on the highway according to my friend. It can also tow 7,000 pounds in the MB ML320 CDI version.

But on the downside, every vehicle that offers it costs at least $35,000. And it does have some rather specialized requirements, for example ultra-low sulfur diesel and motor oil that is compliant with MB oil standard 229.51 (costs $11 per quart!!!) Also, the MB diesels are only 45 state compliant. Any state that has adopted CA emissions won't be able to sell them.

The VW diesels are really nice and extremely efficient, however, I share your concerns on VW reliability. A lot of the VW's sold in North America are assembled in Mexico. Also, the product support in the USA is not very good. If I lived in Germany I would definitely drive a VW, but not so much over here.
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speedracer1407
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RE: Piston Engine Fadec, Diesel Vs Avgas

Mon Nov 05, 2007 5:04 pm

Quoting Speedbird2263 (Reply 35):
If the V design is far superior as you have outlined, why is it then that BMW still uses the inline design in most of its automotive product range? I do however recognize that for higher horsepower and torque applications they incorporate the V-block as is evident with the V10 used in the M5.

You're comparing apples to oranges. The design of a large diesel engine in a highway tractor or any other industrial/commercial truck will be dictated entirely by cost, packaging, durability, maintenance, and efficiency. If (and I don't have the apparent expertise that SEPilot does) a V design is superior to an inline six given those criteria, then that's what they'll use. Though the popularity of inline 6 designs in that application suggests that there must be something to it.

Anyway, BMW and pretty much every other car manufacturer also consider factors like smoothness, fun, and tradition. BMW sticks with the inline 6 because it's inherently balanced (silky smooth), sounds great, and it's become BMW's signature design. The fact that BMW's inline 6s have been exceptional engines for decades speaks to the potential of the inline 6 design, but you can bet that there are probably engineering and cost challenges associated with cramming that long block into 3 and 1 series engine bays. Witness, for example, that when faced with the challenge of busting through the 400HP mark for the latest M3 to stay on par with their competition, BMW went to a 4 liter V8 and ended up with an engine that's actually lighter and more compact than the less powerful 3.2L I6 of the previous M3.
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