[DeTomaso] NPC- Definition of acceleration
wkooiman at earthlink.net
wkooiman at earthlink.net
Tue Oct 13 19:20:15 EDT 2009
What is the a/f ratio for nitro dragsters?
Isn't 70cc of air vs. 2cc of fuel 35:1?
If this were gasoline, wouldn't it be closer to 70cc of air with ~5.5cc of fuel? (about 12:1)
Since this is nitro, wouldn't it be closer to maybe 70cc of air with 20cc of fuel? - or even more fuel?
-----Original Message-----
>From: Thomas Tornblom <Thomas.Tornblom at hax.se>
>Sent: Oct 13, 2009 1:19 PM
>To: dave at damardirect.com
>Cc: 'List Pantera' <detomaso at realbig.com>
>Subject: Re: [DeTomaso] NPC- Definition of acceleration
>
>Dave McManus skrev:
>> Ok, I sent the thread to my engineer super son-in-law for his 2 cents. He
>> says he likes ACME rockets!
>>
>> IndyDave
>>
>> Here are his thoughts:
>>
>> His thought process is wrong as far as how he is looking at the volume of
>> the engine. 500 cubic inches is not the volume of the cylinder, it is the
>> displacement. You would have to figure out how many cc the heads are. You
>> would then add that to the gap caused by the head gaskets times the diameter
>> of the piston. He may know this but he did not include it in his
>> calculation.
>
>I know that I omitted the combustion chambers in my example. In my
>hypothetical example I chose 500 cui as that is very close to 8 liters,
>or one liter per cylinder, makes it simple to calculate :-)
>
>Normal Cleveland CC:s are on the order of 60-75cc, which is orders of
>magnitude more than the amount of fuel needed in my calculation, and big
>blocks normally have larger CC:s. There is thus no chance of hydro lock
>for one missed spark, and most of the unburned fuel will be dumped
>through the exhaust so I don't see how several missed sparks would
>accumulate and cause hydro lock either.
>
>>
>> Hydraulic lock also references that the mixture is incompressible. So
>> basically you are taking 3 Liter of nitro / air (1L/cylinder compressed at 3
>> bars) and jam it a 1L cylinder. The cylinder goes through its combustion
>> cycle and further compresses the mixture. At TDC the volume of the cylinder
>> is only the volume calculated above. At some pressure point its easier for
>> the rod to set sail than continue on the compression path. The compression
>> ratio is 6.5:1. The pressure inside the cylinder is much higher than the 3
>> bars. I believe you can use pV=nRT from Thermodynamics here. Thus,
>> p1V1=p2V2. That would mean the cylinder is at 19.5 bars or 280psi. I am
>> sure they are minimizing the cc's of the head to maximize power and the
>> hydraulic lock would be the limiting factor.
>
>Yes, the pressure at ignition will be much higher, but that doesn't
>matter. What matters is the amount of air you have shoved into the
>cylinder, which happens to be 3 liters if you are running at 3 bars of
>boost. No matter how much or little you compress this, the mass stays
>the same, and thus the amount of fuel needed for stoichiometry. And I
>calculated that to around 2cc. So you have 2cc of liquid, and 3 liters
>if air crammed into a 70cc or so combustion chamber. Those 2cc:s are not
>going to cause hydro lock.
>
>I'm willing to be proved wrong, but it would need some explanation.
>
>Rich fuel blends are frequently used to keep the internals cool, but it
>appears to be orders of magnitude off, unless I've done some serious
>thought error.
>
>There is no water injection on top-fuel dragsters, or? That would add
>some liquid.
>
>>
>> http://www.motortrend.com/features/112_0502_top_fuel_numbers/index.html
>> Brandin Ray
>> Forming & Shoring Design Engineer
>> -----Original Message-----
>> From: Göran Malmberg [mailto:hemipanter at hemipanter.se]
>> Sent: Tuesday, October 13, 2009 3:35 AM
>> To: michael at michaelshortt.com; 'Thomas Tornblom'
>> Cc: 'List Pantera'
>> Subject: Re: [DeTomaso] NPC- Definition of acceleration
>>
>> I believe we could say that the air is very much only a media for the
>> supercharger to transport fuel in to the combustion chamber and not
>> really for burning. At idle it is very rich and does literally shower
>> out the exhaust. Another thing is that by using smaller diameter and
>> longer stroke we can make the engine act as a bigger than 8 litre. By
>> using larger combustion chamber we can stuff more fuel in to it as well
>> as if the diameter was larger.
>> Goran
>>
>> -----Ursprungligt meddelande-----
>> Från: detomaso-bounces at realbig.com [mailto:detomaso-bounces at realbig.com]
>> För michael at michaelshortt.com
>> Skickat: den 12 oktober 2009 23:07
>> Till: Thomas Tornblom
>> Kopia: List Pantera
>> Ämne: Re: [DeTomaso] NPC- Definition of acceleration
>>
>> I don't know anything about all that math stuff, but I do know that a
>> great
>> deal of the air used in the "explosion" is contained in the fuel mixture
>> itself ( like rocket fuel )
>>
>> And from having seen lots of them "blow up", they certainly do come
>> apart
>> with great explosive force, often removing the blower and scoop, heads
>> and
>> headers ( although nowadays they are held down by straps ) or they lose
>> fire
>> and dump loads of raw fuel out of the header pipe of the offending
>> cylinder
>> ( which you see on TV all of the time ). and sometimes the bottom end
>> also
>> comes apart ( and that's when all the action stops and the track has to
>> be
>> cleaned up ).
>>
>>
>> Nothing else smells like Burnout tire smoke and Nitro methane, it smells
>> like.............Victory!
>>
>>
>> Michael Shortt
>>
>>
>>
>>
>>
>> On Mon, Oct 12, 2009 at 4:52 PM, Thomas Tornblom
>> <Thomas.Tornblom at hax.se>wrote:
>>
>>> Göran Malmberg skrev:
>>>> Problem arises if there is missfiering, the hydrolock is a result.
>>> Is this really true btw?
>>>
>>> I just did a quick calculation and I don't see how there could be
>> hydro
>>> lock, even if it doesn't ignite.
>>>
>>> Assume a 500 cui engine, or 8 liter.
>>> Air mass is ~9500l/kg at atmospheric pressure.
>>> Density of nitro is 1.13 kg/l.
>>> Lambda 1 AFR for nitro is 1.7:1 (by weight)
>>> Assume 3 bar boost
>>>
>>> So each cylinder gets 1 liter of air at 3 bar boost per cycle, or
>> 3/9500kg.
>>> The amount of fuel (by weight) is 1/1.7 of the amount of air,
>> 3/(9500x1.7).
>>> The amount of fuel by volume is 1.13 x the amount by weight.
>>>
>>> So the volume of fuel per cycle is:
>>>
>>> 3/(9500x1.7x1.13), which if I have calculated everything correctly
>>> amounts to 0.16cc.
>>>
>>> I don't see how this would result in a hydro lock, unless the
>> combustion
>>> chambers would have zero size.
>>>
>>> It appears that many of the items on this list are myths.
>>>
>>> Another list can be found here:
>>>
>> http://www.motortrend.com/features/112_0502_top_fuel_numbers/index.html
>>> What I find interesting is that the crank only turns 569 turns over
>> the
>>> quarter mile, and the intake valves open just 284 times :-)
>>>
>>> Thomas
>>>
>>>
>>>> Dual sparkpluggs is a good idea then.
>>>> Goran
>>>>
>>>> -----Ursprungligt meddelande-----
>>>> Från: detomaso-bounces at realbig.com
>> [mailto:detomaso-bounces at realbig.com]
>>>> För Sean Korb
>>>> Skickat: den 12 oktober 2009 20:57
>>>> Till: List Pantera
>>>> Ämne: Re: [DeTomaso] NPC- Definition of acceleration
>>>>
>>>> 58-65 degrees spark advance. By the time the piston is at TDC, much
>>>> of the charge has already burned.
>>>>
>>>> sean
>>>>
>>>> On Mon, Oct 12, 2009 at 2:28 PM, <adin at frontier.net> wrote:
>>>>> An old, old email.
>>>>>
>>>>> But, if one thinks a moment . . . .(whew) running a 1.7 to 1 fuel
>> mix
>>>>> means that over 1/3 of the charge is "liquid" ?????? At that
>>>>> compresion ratio, isn't that true hydro-lock????
>>>>>
>>>>> How does that work?
>>>>>
>>>>>
>>>>>
>>>>>
>>>>> Quoting "michael at michaelshortt.com" <michaelsavga at gmail.com>:
>>>>>
>>>>>> A friend sent this to me, fun read.
>>>>>>
>>>>>>
>>>>>>
>>>>>> For all of you old drag racers
>>>>>>
>>>>>>
>>>>>>
>>>>>> THE DEFINITION OF ACCELERATION!!
>>>>>>
>>>>>> One top fuel dragster 500 cubic inch Hemi engine makes more
>>>> horsepower
>>>>>> than the first 4 rows of stock cars at the Daytona 500.
>>>>>>
>>>>>> It takes just 15/100ths of a second for all 6,000+ horsepower of
>> an
>>>> NHRA
>>>>>> Top Fuel dragster engine to reach the rear wheels.
>>>>>>
>>>>>> Under full throttle, a dragster engine consumes 1-1/2 gallons of
>>>> nitro
>>>>>> methane per second. A fully loaded 747 consumes jet fuel at the
>> same
>>>> rate
>>>>>> but with 25% less energy being produced.
>>>>>>
>>>>>> A stock Dodge Hemi V8 engine cannot produce enough power to drive
>>>> the
>>>>>> dragster's supercharger.
>>>>>>
>>>>>> With 3,000 CFM of air being rammed in by the supercharger on
>>>> overdrive,
>>>>>> the fuel mixture is compressed into a near-solid form before
>>>> ignition.
>>>>>> Cylinders run on the verge of hydraulic lock at full throttle.
>>>>>>
>>>>>> At the stoichiometric (stoichiometry: methodology and technology
>> by
>>>>>> which quantities of reactants and products in chemical reactions
>> are
>>>>>> determined) 1.7:1 air/fuel mixture of nitro methane, the flame
>> front
>>>>>> temperature measures 7,050 deg F.
>>>>>>
>>>>>> Nitro methane burns yellow. The spectacular white flame seen
>> above
>>>> the
>>>>>> stacks at night is raw burning hydrogen, dissociated from
>> atmospheric
>>>> water
>>>>>> vapor by the searing heat of the exhaust gases.
>>>>>>
>>>>>> Dual magnetos supply 44 amps to each spark plug. This is the
>> output
>>>> of
>>>>>> an arc welder in each cylinder.
>>>>>>
>>>>>> Spark plug electrodes are totally consumed during a pass. After
>>>>>> halfway, the engine is dieseling from compression, plus the glow
>> of
>>>> exhaust
>>>>>> valves at 1,400 deg F. The engine can only be shut down by cutting
>>>> the fuel
>>>>>> flow.
>>>>>>
>>>>>> If spark momentarily fails early in the run, unburned nitro
>>>> immediately
>>>>>> builds up in
>>>>>> the affected cylinder and then explodes with sufficient force to
>> blow
>>>>>> cylinder heads off the block in pieces or split the block in half.
>>>>>>
>>>>>> In order to exceed 300 mph in 4.. 5 seconds, dragsters must
>>>> accelerate an
>>>>>> average of over 4G's. In order to reach 200 mph (well before
>>>> half-track),
>>>>>> the launch acceleration approaches 8G's.
>>>>>>
>>>>>> Dragsters reach over 300 miles per hour before you have completed
>>>>>> reading this one sentence.
>>>>>>
>>>>>> Top fuel engines turn approximately 540 revolutions from light to
>>>> light!
>>>>>> Including the burnout, the engine must only survive 900
>> revolutions
>>>> under
>>>>>> load.
>>>>>>
>>>>>> The red line is actually quite high at 9,500 rpm.
>>>>>>
>>>>>> Assuming all the equipment is paid off, the crew worked for free,
>>>> and
>>>>>> for once NOTHING BLOWS UP, each run costs an estimate $1,000.00
>> per
>>>> second.
>>>>>> The current top fuel dragster elapsed time record is 4.428
>> seconds
>>>> for
>>>>>> the quarter mile (11/12/06, Tony Schumacher, at Pomona , CA ). The
>>>> top speed
>>>>>> record is 336.15 mph as measured over the last 66' of the run
>>>> (05/25/05 Tony
>>>>>> Schumacher, at Hebron , OH ).
>>>>>>
>>>>>> Putting all of this into perspective:
>>>>>>
>>>>>> You are driving the average $140,000 Lingenfelter 'twin-turbo'
>>>> powered
>>>>>> Corvette Z06. Over a mile up the road, a top fuel dragster is
>> staged
>>>> and
>>>>>> ready to launch down a quarter mile strip as you pass. You have
>> the
>>>>>> advantage of a flying start. You run the 'Vette hard up through
>> the
>>>> gears
>>>>>> and blast across the starting line and pass the dragster at an
>> honest
>>>> 200
>>>>>> mph. The 'tree' goes green for both of you at that moment..
>>>>>>
>>>>>> The dragster launches and starts after you. You keep your foot
>> down
>>>>>> hard, but you hear an incredibly brutal whine that sears your
>>>> eardrums and
>>>>>> within 3 seconds, the dragster catches and passes you. He beats
>> you
>>>> to the
>>>>>> finish line, a quarter mile away from where you just passed him.
>>>>>>
>>>>>> Think about it, from a standing start, the dragster had spotted
>> you
>>>> 200
>>>>>> mph and not only caught, but nearly blasted you off the road when
>> he
>>>> passed
>>>>>> you within a mere 1,320 foot long race course.
>>>>>>
>>>>>> ... and that my friend, is ACCELERATION!
>>>>>>
>>>>>> --
>>>>>>
>>>>>>
>>>>>>
>>>>>>
>>>>>>
>>>>>>
>>>>>>
>>>>>> Michael L. Shortt
>>>>>> Savannah, Georgia
>>>>>> www.michaelshortt.com
>>>>>> michael at michaelshortt.com
>>>>>> 912-232-9390
>>>>>>
>>>>>>
>>>>>> This email is protected by the Electronic Communications Privacy
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>>>>>> privileged. If you are not the intended recipient, you are hereby
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>>>>>> that any retention, dissemination, distribution or copying of this
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>>>>>> have received this message in error, then delete it. Thank you
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>> Thomas.Tornblom at Hax.SE
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>
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>Real life: Thomas Törnblom Email: Thomas.Tornblom at Hax.SE
>Snail mail: Banvallsvägen 14 Phone: +46 18 444 33 21
> S - 754 40 Uppsala, Sweden Cellular: +46 70 261 1372
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