Sound of top-fuellers just before launch?

[Duey]

Just looking over some of my vids of the (February) Winternationals in Pomona (when Doug Kallita won in Jesse James' rail) and they reminded me of how the Top Fuellers' idle would get strangely quiet(er) as they did the final staging, just before they launched.  I checked and every top fuel rail and funny car does it?  Definitely a "quite before the storm" kind of thing.  I couldn't confirm that this coincided with the racer's "walker" flipping a switch at the back of the car after backing up from the burnout.  Any ideas from the weekend warriors?

Cheers,
Duey

[Ghoste]

I've never noticed this but we very seldom get fuel cars at our "local" dragstrip.  Anybody?

[Charger4404spd]

I heard once that the "switch" was turning the other fuel pump on. Theres so much fuel entering the cylinders at this point, the engine is on the verge of hydraulic lock.

Another tid-bit: At full throttle, the engine doesnt need ignition to keep running.

[Lostsheep]

Another tid-bit: At full throttle, the engine doesnt need ignition to keep running.

Thats crazy!

[Wakko]

I heard once that the "switch" was turning the other fuel pump on. Theres so much fuel entering the cylinders at this point, the engine is on the verge of hydraulic lock.

Another tid-bit: At full throttle, the engine doesnt need ignition to keep running.

How do they shut it down in emergency situations, kill the fuel?

[Charger4404spd]

Another tid-bit: At full throttle, the engine doesnt need ignition to keep running.

Thats crazy!

Yep crazy for sure. Evidently, it acts much the same way a diesel engine works.

And Im sure they have a fuel shut-off, with close to 7000hp, they'd be crazy not to have one.

[psykicpup]

sure its something to do with the rev limiters......get back to you with a link or something.....

progress so far..

http://www.santapod.co.uk/index.php

when I went to the links page....and chose fansfuellers 'cos Barry Sheavalis(sp?) is a nice guy....

http://www.fansfueler.co.uk/

right now I'm pending activation on my new account there in the forum & when it comes I'll post the question above for you..ok guys?

[moparbryan]

ok this is how it works the sound mellow's as the second and high volume fuel pump is turned on just after the driver stages i.e. turns the yellow lights on also a fuel car (anthing running on nitro) requires massive spark so running at full throttle w/out ignition is incorrect these cars run duel magneto's and the driver hits a kill switch at the end of the pass which grounds the mags and end's the spark
                                                                                  moparbryan

[Charger4404spd]

I was just stating what was said on a tv program about them. They did say the engine would keep running WITHOUT the ignition.

[Ghoste]

Someone sent me a page of fueler trivia one time.  I'll have to see if I can find it and post it.  Actually I may have gotten it off the old site.

[Charger4404spd]

Here ya go, copied it from another site.

Bonus: Top Fuel Trivia:
One TF dragster’s 500-inch Hemi makes more horsepower than the first 8 rows at the Daytona 500.

Under full throttle, a dragster engine consumes 1 ½ gallons of nitro per second, the same rate of fuel consumption as a fully loaded 747 but with 4 times the energy volume.

A stock hemi will not produce enough power to drive the dragster’s supercharger.

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 nitro methane measures 7050 degrees 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 exhaust gases.

Spark plug electrodes are totally consumed during a pass. After  ½ way, the engine is dieseling from the compression â€" plus the glow of exhaust valves at 1400 degrees F. The engine can only be shut down by cutting the 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 split the block in half.

To exceed 300 mph in 4.5 seconds, dragsters must accelerate at an average of over 4G’s. But in reaching 200 mph well before  ½ 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 $1,000.00 per second.

Dragsters reach over 300 miles per hour before you have completed reading this sentence.

Top Fuel Engines turn ONLY 540 revolutions from light to light!

[Troy]

I'm pretty sure most of that was debunked on the old forum. We'll see though.

Troy

[BigBlackDodge]

Just after the cars stage in it does get alot quieter...........at least from half track. Whats really cool is that you see them hit the throttle and then a fraction of second later the noises catches up to you.

BBD

[Duey]

ok this is how it works the sound mellow's as the second and high volume fuel pump is turned on just after the driver stages i.e. turns the yellow lights on also a fuel car (anthing running on nitro) requires massive spark so running at full throttle w/out ignition is incorrect these cars run duel magneto's and the driver hits a kill switch at the end of the pass which grounds the mags and end's the spark
                                                                                                                          moparbryan

Thanks Bryan, that sounds like we're getting closer, although I don't yet have a warm technical fuzzy as to what the difference is. 

It definitely is a more muted exhaust note just seconds before the launch than the crackling open header sound as they back from the burnout, or move up towards the tree.  I watched the vids some more and the sound muffles out several seconds after the walker flips the second pump switch...usually after both cars pre-stage and one of them is still messing around to stage the second light.  Now this really has me wondering....   ?Que pasa?

Cheers,
Duey

[Ghoste]

On a not too unrelated note, a few years back Gene Snow made some exhibition passes at the Nats one year.  Well, as it turned out, one day when he was doing so, a buddy and myself were leaving the track at the back exit.  As those of you who are familiar with National Trail know, there is a sideroad behind that track and during national events, that road is cut off and the shut down area extends out into the adjoining farmer's field.
Anyway, since it was no national event, the road wasn't blocked and we happened to be exactly at the end of the track when Snow made his pass.  We got the unique experience of seeing a Top Fueler come straight for us (obviously not at full bore but still PLENTY fast).
We could barely make out the dot at the starting line.  We saw the crap shoot out of the pipes, then we saw the chutes come and THEN we heard it.  Iswear to God it seemed like he was turning off as we heard the five second roar.  It was one of the strangest experiences I've ever had.

[moparbryan]

duey,  sorry that I wasn't more clear as I was posting on my way out the door to work. When the second fuel pump comes in it actually puts a load on the engine as you probably know the best way to look at any engine is as a pump i.e.air-in air- out, add cumbustable fuel and you have a internal combustion engine.due to the huge volume of fuel passing thru the cly's the engine in effect "bogs down" if I remember right the first pump runs approx.15-17gpm (thats gallons per minute) the second pump is in the 35-40gpm range
also keep in mind this is fuel flowing thru 1/2 inch fuel lines, standard on most cars is 5/16 think garden hose but twice the volume of water. also not to be anal about this but fuel cars don't diesel per say when the driver completes the run he will kill the ignition and shut off the pumps but the pumps are not electronic they are shut off w/a valve the remaining fuel in the lines is pulled thru the motor as the car decelerates to a stop. if you have an interest in this kind of stuff check out NHRA2day on ESPN2 sunday mornings they tend to cover things like this allot hope I haven't bored you to death w/too much info
                                                                                            Bryan

[Headrope]

Are we talking about live videos that you took, or videos recorded off television?
I always thought it got quiet on television because the commentators finally shut up right before final staging, so the audience can hear the power.
No offense intended if anyone hear is a commentator.

[Duey]

duey,   sorry that I wasn't more clear as I was posting on my way out the door to work. When the second fuel pump comes in it actually puts a load on the engine as you probably know the best way to look at any engine is as a pump i.e.air-in air- out, add cumbustable fuel and you have a internal combustion engine.due to the huge volume of fuel passing thru the cly's the engine in effect "bogs down" if I remember right the first pump runs approx.15-17gpm (thats gallons per minute) the second pump is in the 35-40gpm range
also keep in mind this is fuel flowing thru 1/2 inch fuel lines, standard on most cars is 5/16 think garden hose but twice the volume of water. also not to be anal about this but fuel cars don't diesel per say when the driver completes the run he will kill the ignition and shut off the pumps but the pumps are not electronic they are shut off w/a valve the remaining fuel in the lines is pulled thru the motor as the car decelerates to a stop. if you have an interest in this kind of stuff check out NHRA2day on ESPN2 sunday mornings they tend to cover things like this allot hope I haven't bored you to death w/too much info
                                                                                                                                         Bryan

Thanks Bryan, that clear it up a bit...the engine definitely "tones down" a bit.  Would the second pump also make the engine idle slightly slower, thus changing the exhaust note?

Headrope, Nope I was there, but I was also looking recently at the vids I took...remembering how the top fuel rails and funnys sounded after listening (feeling) to the Sunday finals at Pomona.  Dang, that was fun...love the shweeeet smell of nitro in the morning! 

Cheers,
Duey