21 replies to this topic

[mariner]

A new world record

 

 

300 mph in 1/8th mile is rather impressive.

 

It's adding 2 mph per foot of track 

 

2.93 seconds for the  1/8th mile - I think that is about 4.7 G for 3 seconds 

 

 

[flatlandsman]

They are fairly serious bits of kit.  especially when someone decided to put a rather less well tuned one in a streamliner and can reach 450mph on the salt!

[gruntguru]

I still remember when 250 in the 1/4 happened. "250 Tommy".

Showing my age here.

[Bob Riebe]

Although they only have 4,000 HP, the fastest Top Alcohol run is 286 , full quarter mile I assume, and quickest 5.09, they used to be closer than that 30 years ago.

[PayasYouRace]

It’s mind boggling.

[Beri]

I have never followed any dragracing. But this is impressive to say the least!

[mariner]

With very tight , and longstanding rules, all Top Fuel gains are slowly worked out over time. The ban on competitive run data logging also affects development. It is interesting that the press conference referred to " test runs" I think you can data log on those.

 

One example of how Top Fuel can match F1 for subtlety is mentioned in this excellent video on building a 11,000 bhp Top fuel engine.

 

 

So critical is ambient weather and track temperature , sunshine driven, that the engines can be kept half built  up to 30 minutes pre race. The reason is that a last minute judgement is made on track grip and the head gasket thickness is selected at the last minute to tune the CR and hence power to  match track grip!

[flatlandsman]

It is something you should go an experience at least once in your life.  if you have an interest in engineering alone it is worth it.

 

The cars themselves are actually quite basic, they use quite basic tech to do what they do, it is all about fuel, weather, clutches and the driver!  And extra then like lane choice.

 

The top teams have insane things like blower dynos, a dyno that allows you to measure and tune the supercharger!  It is staggering the length that goes into this. 

 

The glory days are arguably gone with drivers being able to earn good livings doing match races and travelling the country, but the top levels are still very professional. And in a few places it is huge in America and also in several areas, it is one of the few Motorsports hugely taken part in by the Hispanic community, especially Puerto Ricans who love the compact and import scenes aswell as others, it is fairly big in Australia aswell, and to some extent in Europe, but not at the same level. 

[gruntguru]

. . . , it is all about fuel, weather, clutches and the driver!  And extra then like lane choice. . . . 

 . . . . and tyres!

[gruntguru]

So critical is ambient weather and track temperature , sunshine driven, that the engines can be kept half built  up to 30 minutes pre race. The reason is that a last minute judgement is made on track grip and the head gasket thickness is selected at the last minute to tune the CR and hence power to  match track grip!

 

Amazing!

You would think there was an easier way to turn the wick down a bit - throttle setting, blower pulley size, fuel metering ????

[Greg Locock]

In 1/8th mile how many combustion events do they see?

[lustigson]

I just had to do this to give some feel to these numbers for all of us who use the metric system:

 

300 mph 482.7 km/h in 1/8th mile 201.125 m is rather impressive.

 

It's adding 2 mph 3.2 km/h per foot 30.48 cm of track 

 

2.93 seconds for the 1/8th mile 201.125 m - I think that is about 4.7 G for 3 seconds

 

No matter how you measure, this is massive, indeed. 

[mariner]

To try to answer Greg's question on combustion events it is not that many which is one of the bizarre things about Top Fuel .

 

As best I know the engines are pulllng an average of 9,000 rpm. At the start the clutch slip allows these revs and clutch lock up is on a timed air pressure system set by the team. 

 

So assuming its at 9,000 for the 1/8th mile it has 3 seconds so 9000/60*3 = 450 revolutions. With 8 cylinders and a four stoke that is 1,800 combustion events if my math is right. 

 

So 1800/300 is adding one mph per 6 cylinder firings on a 2,500 lb car. A serious torque level I think 

Edited by mariner, 29 September 2023 - 08:54.

[Magoo]

How many cylinder fires in 660 feet is a wonderful question. 

 

Four-stroke, 8-cylinder engine with a crank speed of 6300 rpm at max pulldown and if everything works correctly, exactly 8000 rpm at the 1/8 mile stripe 2.936 seconds later. Then you have clutch slip and wheelspin, wild cards. 

 

I bet somewhere in the telemetry is an actual number. 

 

 

This is fairly current info, March 2023. 

 

https://www.enginebu...ds,” Flynn says.

[flatlandsman]

And the engines are so highly strung they are pretty much rebuilt after most runs, but they do not use brand new parts routinely, only if necessary, the quality of the parts is very good obviously so they can be used and re-used wear permitting.  it does look crazy when you see it, but dig a little deeper and they are not just burning money like you think. 

[Ali_G]

Is there a general speed at which power takes over from grip as being the limiting factor for top fuel dragsters?

Edited by Ali_G, 30 September 2023 - 13:06.

[Magoo]

And the engines are so highly strung they are pretty much rebuilt after most runs, but they do not use brand new parts routinely, only if necessary, the quality of the parts is very good obviously so they can be used and re-used wear permitting.  it does look crazy when you see it, but dig a little deeper and they are not just burning money like you think. 

 

Quite so. If the tuneup is close to optimal and the run goes well, the engine will look almost pristine on teardown with only a little smearing on the upper halves of the rod bearings.  But if much goes wrong, there will be a mess. Since they run on the ragged edge of detonation all the time, burned pistons are par for the course. 

 

On the teardown after each run, along with the inspection and maintenance they are also looking for signs that could help them refine the tuneup. Because the air pressure distribution from the Roots blower to the eight cylinders is not very good, they will alter the compression ratio on some cylinders with pistons of varying deck heights. Nobody seems to use the original Chrysler firing order anymore, choosing among a couple of alternatives. They will also vary the injector nozzle sizes for each cylinder on the three sets of nozzles pre-and-post blower. 

 

I've asked tuners why they don't simply alternate their engines between runs instead of the fire-drill teardowns after each run. They say they would quickly lose the tuneup combination that way. 

 

I always found this intriguing: They run a six-disc, five-floater centrifugal friction clutch with a tremendous amount of slip, managed by a multi-stage air-operated servo. All black art. Anyway, they resurface the discs after every run and throw them away after the second run. They work best on the second run. 

[mariner]

The great thing about TF engines is that everything is extreme .

 

they use twin magnetos with rare earth magnets to generate the spark power needed to fire the nitro fuel with extreme cylinder pressures.  44amps per plug. That is arc welder territory..

 

The multi disc clutches are driven y an air canon as Magoo says. The funny bit is that the crew chief sets the clutch up pre-run with air pressure and timing so the driver has little control over the take off , his//her initial jobs are to "beat the green" and steering it straight. unless something goes wrong like tire shake or  traction breaking.

[gruntguru]

Is there a general speed at which power takes over from grip as being the limiting factor for top fuel dragsters?

 

Yeah - about 300 mph!

Actually more than that if you believe the numbers thrown around out there. eg most sources state around 3 seconds into the run before the clutch stops slipping. (If the tyres could handle more torque, it would be given to them.)

 

This means that the 300 mph 1/8th mile run in less than 3 seconds would have the clutch slipping for the entire run, meaning some of the engine power is being wasted heating the clutch - not even needed at the wheels - for the entire run.

 

In fact, when the clutch stops slipping, the engine revs should be down to peak torque rpm - about 6,300 rpm as Magoo says - so the engine is not even making full power. (It will get up close to full power a little later if the track is longer than 1/8 mile.)

 

Sounds silly but the engine is actually closer to peak power as the car leaves the line - for three reasons. 1. Peak torque would overload the contact patches at low speed with no aerodynamic DF from the wing. 2. Peak power produces maximum gasflow through the exhaust and maximum jet-effect downforce (about 500 kg). Running the engine slower at launch (say below peak torque rpm to reduce torque) would reduce the jet-effect downforce.  3. The clutch setting at each position on the track is a defined function of torque and rpm. This will only maintain the engine at a stable rpm if the engine is operating in a region of "falling" torque - ie above the peak torque rpm not below.

Edited by gruntguru, 02 October 2023 - 02:46.

[7MGTEsup]

It's adding 2 mph per foot of track 

 

That would give you 1320 mph by the 1/8 mile (660 x 2)

 

It should be 0.455 mph per foot of track, or 2.2 feet per 1 mph increase.

[Nathan]

What blows my mind about Top Fuel is in 3 seconds, exactly how many engine revolutions took place? Maybe 400? 800 ignitions to accelerate the car that far and that fast...nuts.

Edited by Nathan, 27 October 2023 - 14:16.

[Lee Nicolle]

3 6s and 330mph plus.

As for 250 in 5.5 sec tin tops do that these days. And that in a Toyota Supra. 

"World Cup' was on last week in Maryland and the times and speeds were HUGE