Increased efficiency

[mobile_bob]

well Guy, i am gonna keep draggin them to the water trough on this one!

sooner or later somebody will see the intracacy of my original statement

and before the avalanche comes

"yes typically larger bore engines are more efficient, but not across the board in either rpm or kwatt loading/output"

there is just more to the equation to consider than most folks are looking at.

bob g

[Andre Blanchard]

I keep telling people BHP (which is the same as watts) is just a way of measuring rate of fuel consumption.

It's like anodes and cathodes and electron flow, you can explain it a hundred times and people still don't get it.

Why does the phrase Once More Into the Fire come to mind?
Here we go.

In every engineering book I have seen the B in BHP stands for brake as in Brake Horse Power and is the horse power as MEASURED by applying a measured torque to the shaft using a BRAKE and then measuring the RPM and plugging the measured values into the formula.
BHP = torque x rpm x (unit correction factor)

BHP is only indirectly related to the fuel consumption buy the efficiency of the engine the shaft is connected to, and then ONLY under the conditions under which the test was preformed.  You can get the same BHP measurement off two different engines (or even the same engine under different conditions) but have very different fuel consumption rates.

So unless you already know the efficiency of the engine at the test conditions a BHP reading tells you NOTHING about the fuel consumption.

[GuyFawkes]

I keep telling people BHP (which is the same as watts) is just a way of measuring rate of fuel consumption.

It's like anodes and cathodes and electron flow, you can explain it a hundred times and people still don't get it.

Why does the phrase Once More Into the Fire come to mind?
Here we go.

In every engineering book I have seen the B in BHP stands for brake as in Brake Horse Power and is the horse power as MEASURED by applying a measured torque to the shaft using a BRAKE and then measuring the RPM and plugging the measured values into the formula.
BHP = torque x rpm x (unit correction factor)

BHP is only indirectly related to the fuel consumption buy the efficiency of the engine the shaft is connected to, and then ONLY under the conditions under which the test was preformed.  You can get the same BHP measurement off two different engines (or even the same engine under different conditions) but have very different fuel consumption rates.

So unless you already know the efficiency of the engine at the test conditions a BHP reading tells you NOTHING about the fuel consumption.

Andre, either take it from me, or go out and verify it for yourself, every 100 BHP engine on the planet burns fuel at about the same rate, and this rate is about ten times as fast as every 10 BHP engine on the planet.

Yes there are variations, yes there is the odd exception / statistical anomaly, but right across the board it holds true, I'd hesitate to use the phrase "rule of thumb" because it is more accurate than last thumb joint =1 inch for any human.

This BHP = rate of fuel consumption is by far the most accurate across the board description going.

I have proven this time and time again to people, for example first dyno run peak BHP for 5 minutes, precisely metered amount of fuel used, then run the bugger at lower throttle, measure amount of fuel used in exactly five minutes.

BHP at second RPM = peak BHP / ( 1st amount of fuel used / 2nd amount of fuel used) this despite torque and bhp curves and me not even needing to know the precise RPM, and not being told the Dyno indicated BHP until afterwards.

We have done this on engines as varied as japanese air cooled fours to 16 cyl MTU diesels (tank engines) of 1600 BHP, and it is surprisingly accurate, I was <5 BHP out on the MTU, which is less than the margin of error / repeatability on the dyno.

ALL INTERNAL COMBUSTION ENGINES are HEAT engines, and they ALL get their HEAT from burning FUEL.

Double the power is double the heat, ergo double the fuel.

YES there are differences between a 6 BHP honda 90cc 4 stroke petrol engine and a v8 developing 600 bhp, when both are dynoed at their respective peak, but not as much as you think.

YES there are differences between aforesaid honda developing 1 bhp and aforesaid V8 developing 100 BHP, both doing 1/6th their potential, but again, not as much as you think.

The big difference is between each engine at 1/6th power and peak power.

[Twinscrew]

Increased in efficiencies are possible, but at the price of the loss of flexibility, loss of robustness, loss of user friendliness, and at higher cost, costs that almost always outweigh any monetary gains in efficiency.

These are the words of a pessimistic, closed and feeble minded idiot. Therfore, I hope this is a qoute by someone else that you've chosen to use without regard for it's accuracy. Otherwise, you sir, are not as smart as you would lead every one here to believe.   

[mobile_bob]

an amazingly bold statement there mr. twinscrew!

perhaps you could shed some light on yourself?  who are you? what background do you come from?

i am curious to say the least, you have made yourself out to be an adversary, so as such some questions arrise.

who da hell are you?


bob g

[Andre Blanchard]

Increased in efficiencies are possible, but at the price of the loss of flexibility, loss of robustness, loss of user friendliness, and at higher cost, costs that almost always outweigh any monetary gains in efficiency.

These are the words of a pessimistic, closed and feeble minded idiot. Therfore, I hope this is a qoute by someone else that you've chosen to use without regard for it's accuracy. Otherwise, you sir, are not as smart as you would lead every one here to believe.   

I the case of a Lister(oid) I am thinking Guy is basically right in this statement.


As far as the BHP is concerned what he says is true only if you operate the engine in the RPM/load range where the efficiency is flat.  In many types of engines this range is fairly broad but it does fail at the extremes.
Any engine at an idle has efficiency of 0%, if it is doing any work it is, by definition not at an idle no matter how fast or slow it is running.  And last friday night I was watching some tractors that were factory rated at 150HP or so, that had turbo boost pressures at 100 PSI plus and much larger injector pumps.  I would guess they had efficiencies pushed well down into the single digits.

[mobile_bob]

"Increased in efficiencies are possible, but at the price of the loss of flexibility, loss of robustness, loss of user friendliness, and at higher cost, costs that almost always outweigh any monetary gains in efficiency."

i will go on the record to support this statement!

and i will defy anyone here to prove it wrong, most especially since there are those on this thread that don't see a need to measure or test anything.

so how the friggin hell you gonna prove this statement wrong?
any increases in efficiency are likely to be quite small and will require instrumentation and a very documented approach to prove out.

checkmate!  

bob g

[Twinscrew]

who da hell are you?

Someone who, evidently, knows nothing.

[mobile_bob]

Twinscrew:

with a name like that, you must be familiar with heavy trucking and as such very conversant with hd diesel engines
to say the least.

so pop in the power divider and get back up here!

i have said it once and i will say it again.

"if one is sure of his position he should be able to relate the position without getting pissed off or calling names"

i try to follow that which i have said, but i too am human and fail miserably sometimes.

i would hope that no one here is of the thinking that i see them as idiots, quite the contrary.

i learn from everyone,,, (even Darren ),  and i think thru discussion others might learn too.

sometimes the discussion gets a bit personal, but hey that is the price of admission i guess.

seriously tell us more about yourself, and how you think.

bob g

[GuyFawkes]

Twinscrew:

with a name like that, you must be familiar with heavy trucking

I don't get that reference, to me his handle conjures up TSDY, twin screw diesel yacht

[Andre Blanchard]

Twinscrew:

with a name like that, you must be familiar with heavy trucking

I don't get that reference, to me his handle conjures up TSDY, twin screw diesel yacht

A low pressure high volume screw compressor use as a supercharger.

[GuyFawkes]

I the case of a Lister(oid) I am thinking Guy is basically right in this statement.


As far as the BHP is concerned what he says is true only if you operate the engine in the RPM/load range where the efficiency is flat.  In many types of engines this range is fairly broad but it does fail at the extremes.
Any engine at an idle has efficiency of 0%, if it is doing any work it is, by definition not at an idle no matter how fast or slow it is running.  And last friday night I was watching some tractors that were factory rated at 150HP or so, that had turbo boost pressures at 100 PSI plus and much larger injector pumps.  I would guess they had efficiencies pushed well down into the single digits.

tractor pull?

bet the efficiencies are a LOT higher than you think.

here are some dragster facts, do the math

incidentally a 500 hemi dragster motor has a single cylinder volume of about 1 litre, smaller than a lister(oid) yet it produces 750 BHP

I've added a bit at the bottom so you can do that math.

-----------------------------------------




* One dragster's 500-inch Hemi makes more horsepower then the first 8 rows at Daytona.

* Under full throttle, a dragster engine consumes 1 1/2 gallons of nitro per second, the same rate of fuel consumption as a fully loaded 747 but with 4 times the energy volume.

* The supercharger takes more power to drive than a stock hemi makes.

* Even with nearly 3000 CFM of air being rammed in by the supercharger on overdrive, the fuel mixture is compressed into nearly-solid form before ignition. Cylinders run on the verge of hydraulic lock.

* Dual magnetos apply 44 amps to each spark plug. This is the output of an arc welder in each cylinder.

* At stoichiometric (exact) 1.7:1 air/fuel mixture (for nitro), the flame front of nitromethane measures 7050 degrees F.

* Nitromethane burns yellow. The spectacular white flame seen above the stacks at night is raw burning hydrogen, dissociated from atmospheric water vapor by the searing exhaust gases.

* Spark plug electrodes are totally consumed during a pass. After 1/2 way, the engine is dieseling from compression-plus the glow of exhaust valves at 1400 degrees F. The engine can only be shut down by cutting off its fuel flow.

* If spark momentarily fails early in the run, unburned nitro builds up in those cylinders and then explodes with a force that can blow cylinder heads off the block in pieces or blow the block in half.

* Dragsters twist the crank (torsionally) so far (20 degrees in the big end of the track) that sometimes cam lobes are ground offset from front to rear to re-phase the valve timing somewhere closer to synchronization with the pistons.

* To exceed 300mph in 4.5 seconds dragsters must accelerate at an average of over 4G's. But in reaching 200 mph well before 1/2 track, launch acceleration is closer to 8G's.

* If all the equipment is paid off, the crew worked for free, and for once NOTHING BLOWS UP, each run costs $1000.00 per second.

* Dragsters reach over 300 miles per hour before you have read this sentence.

Did you know …

… that the nitromethane-powered engines of NHRA Top Fuel dragsters and Funny Cars produce approximately 7,000 horsepower, about 37 times that of the average street car?

… that one cylinder of the eight cylinders of a Top Fuel dragster or a Funny Car produces 750 horsepower, equaling the entire horsepower output of a NASCAR engine?

… that the gasoline-powered engines of NHRA Pro Stock cars produce about 1,200 horsepower, about eight times that of the average street car?

… that an NHRA Top Fuel dragster accelerates from 0 to 100 mph in less than .8-second, almost 11 seconds quicker than it takes a production Porsche 911 Turbo to reach the same speed?

… that an NHRA Top Fuel dragster leaves the starting line with a force nearly five times that of gravity, the same force of the space shuttle when it leaves the launching pad at Cape Canaveral?

… that an NHRA Funny Car is slowed by a reverse force more than seven times that of gravity when both parachutes deploy simultaneously?

… that NHRA Top Fuel dragsters and Funny Cars consume between four and five gallons of fuel during a quarter-mile run, which is equivalent to between 16 and 20 gallons per mile?

… that NHRA Top Fuel dragsters and Funny Cars use between 10 and 12 gallons of fuel for a complete pass, including the burnout, backup to the starting line, and quarter-mile run?

… that NHRA Top Fuel dragsters and Funny Cars travel the length of more than four football fields in less than five seconds?

… that NHRA Top Fuel dragsters can exceed 280 mph in just 660 feet?

… that from a standing start, NHRA Top Fuel dragsters accelerate faster than a jumbo jet, a fighter jet, and a Formula One race car?

… that a fuel pump for an NHRA Top Fuel dragster and Funny Car delivers 65 gallons of fuel per minute, equivalent to eight bathroom showers running at the same time?

… that the fuel-line pressure for NHRA Top Fuel dragsters and Funny Cars is between 400 and 500 pounds, about 20 times greater than the pressure on passenger-car fuel pumps?

… that depending on size and angle, the large rear wing on an NHRA Top Fuel dragster develops between 4,000 and 8,000 pounds of downforce?

… that the 17-inch rear tires used on NHRA Top Fuel dragsters and Funny Cars wear out after four to six runs, or about two miles? Some brands of passenger-car tires are guaranteed for 80,000 miles.

… that it takes just 15/100ths of a second for all 7,000 horsepower of an NHRA Top Fuel dragster engine to reach the rear wheels?

… that it's desirable for an NHRA Top Fuel dragster to race with its front wheels inches off the ground for about the first 200 feet of the run? This ensures proper weight transfer to the rear wheels, a crucial part of a good launch and quick run.

… that the nitromethane used to power the engines of NHRA Top Fuel dragsters and Funny Cars costs about $30 per gallon?

Sources: NHRA Communications and Technical Departments, NHRA race teams, motorsports equipment manufacturers

-------------------------------------------

Nitromethane is a fuel that is used in racing, particularly in drag racing, to provide more power. When you hear the term "nitro-burning funny car" or "top-fuel dragster", that means that the engine burns nitromethane. Model aircraft fuel contains from 0% to 65% nitromethane.

Nitromethane's chemical formula is CH3NO2. For comparison, gasoline is typically C8H18. The oxygen in nitromethane's molecular structure means that nitromethane does not need as much atmospheric oxygen to burn -- part of the oxygen needed to burn nitromethane is carried in the fuel itself.

You need 14.6 kilograms of air to burn a kilogram of gasoline, and only 1.7 kilograms of air for the same amount of nitromethane to burn. A cylinder can only hold so much air on each stroke, and with that amount of air you can burn 8.7 times more nitromethane than gasoline. By pumping in 8.7 times as much nitromethane per stroke, you get about 2.4 times more power per stroke. Gasoline provides 18,000 BTU/pound (42 MJ/kg). Nitromethane provides 5,000 BTU/pound (12 MJ/kg). [1] The amount of nitromethane also provides some cooling, making the charge a bit denser and increasing power.

The flamefront does not move as quickly in nitromethane as it does in gasoline, meaning that there is not enough time to burn all the nitromethane in the cylinder when the engine is running at high RPM. When the exhaust valve opens, burning nitromethane flows out through the exhaust pipe. That is why Funny Cars and dragsters "spit fire" from their exhaust pipes.

[GuyFawkes]

Twinscrew:

with a name like that, you must be familiar with heavy trucking

I don't get that reference, to me his handle conjures up TSDY, twin screw diesel yacht

A low pressure high volume screw compressor use as a supercharger.

aha, obvious when smacked in the face with it, cheers

[Twinscrew]

i learn from everyone,,, (even Darren  ),  and i think thru discussion others might learn too.

Bob, honestly, how do you learn from anyone if you're always right? Debate is one thing, but dammit man, it seems like your hobby is to hang out by the computer and shoot down anything not accompanied by a forensic report. Are you compensating for something? Some of my current projects might actually amaze you, but then again probably not. You've probably already done everything I'm attempting. We don't know each other. Maybe that's not a bad thing.

[slowspeed1953]

Guy, this is a really tasty tidbit!

* Nitromethane burns yellow. The spectacular white flame seen above the stacks at night is raw burning hydrogen, dissociated from atmospheric water vapor by the searing exhaust gases.

Peace&Love , Darren