[DeTomaso] NPC- Definition of acceleration
wkooiman at earthlink.net
wkooiman at earthlink.net
Wed Oct 14 19:24:44 EDT 2009
Yes, sorry. After I sent my reply, I re-read your thread and I saw the 1.7:1 AFR for nitro.
I didn't realize AFR was by weight, but once I reread your post, it was clear.
-----Original Message-----
>From: Thomas Tornblom <Thomas.Tornblom at hax.se>
>Sent: Oct 14, 2009 1:23 AM
>To: wkooiman at earthlink.net
>Cc: detomaso at realbig.com
>Subject: Re: [DeTomaso] NPC- Definition of acceleration
>
>wkooiman at earthlink.net skrev:
>> What is the a/f ratio for nitro dragsters?
>>
>> Isn't 70cc of air vs. 2cc of fuel 35:1?
>
>No, AFR is measured by weight, not volume.
>
>>
>> If this were gasoline, wouldn't it be closer to 70cc of air with ~5.5cc of fuel? (about 12:1)
>
>No. Recalculating those 2cc:s of nitro, with an AFR of 1.7:1 into the
>AFR for gasoline, 14.7:1, you would inject about .25cc of gas for each
>cycle if you were running at stoichiometry, but about .28cc if you are
>running a rich (12:1) AFR. Notice that this is at 3 bars (43 psi) of boost.
>
>>
>> Since this is nitro, wouldn't it be closer to maybe 70cc of air with 20cc of fuel? - or even more fuel?
>
>No.
>
>This is perhaps how this hydro lock myth started, if it is a myth.
>
>Thomas
>
>>
>> -----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
>>>>>>>>
>>>>>>>>
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