[DeTomaso] NPC- Definition of acceleration

Thomas Tornblom Thomas.Tornblom at hax.se
Tue Oct 13 14:19:49 EDT 2009


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
>>> notified
>>>>> 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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>> --
>> 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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> 
> 


-- 
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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