Where does a Top Fuel dragster accelerate the hardest? (2 Viewers)

[none]

Off topic, but did anyone notice how long it is between when the engine comes up and the driveshaft moves? There's also a split second from when the driver hits the gas and the engine comes up. All that adds up to why reaction times are slower in a fuel car than say a transbrake car. Because so much happens between the pedal going down, and the car actually moving.

Alan

 

[flapjack]

Off topic, but did anyone notice how long it is between when the engine comes up and the driveshaft moves? There's also a split second from when the driver hits the gas and the engine comes up. All that adds up to why reaction times are slower in a fuel car than say a transbrake car. Because so much happens between the pedal going down, and the car actually moving.

Alan

Is that because it takes a way for the centrifugal clutch to engage? Or just the engine spinning up and the necessary fuel system parts to engage?

 

[Nunz]

Maybe part of it is that fuel cars leave from an idle?

 

[Randy]

Fuel pressure is monitored as well, but is not displayed on the graph. Zero seconds on the graph looks like it may have been set using the first tick in drop of fuel pressure which indicates the barrel valves has opened, meaning the driver hit the throttle. I liked using fuel pressure as an indicator rather than a full throttle switch because it is slightly more instantaneous, although the combination of the two will tell you if the driver is pushing the pedal all the way down. You would be surprised to know many times that doesn't happen for one reason or another somewhere on a run.

 

[Gordon]

G-force is the measurement of acceleration that causes a perception of weight

Acceleration is the RATE of change in velocity

based on the graph provided the rate of CHANGE is the greatest on the initial hit 0-4g's in milliseconds

I'm not a physics major but I think Ken is on to something here. Is the question, "When does the driver experience the most G forces during a run?", or "When does the car accelerate the quickest?" Though they are similar questions, they are not the same thing. To answer the first, simply measure the G forces during a run - that'll tell you what you need to know. To answer the second, one must figure out a way to measure a car's speed at multiple spots down track, possibly beyond the measurements they receive now.

If, for example, a car accelerates from 0-100 in less than 60' that's a full 1/3rd of the speed on a 300 M.P.H. run with a full 940' to go to make up the other 2/3rds. And if the car is accelerating through, say 150 M.P.H prior the 330' mark, now the car is halfway there with 670 feet to go. In my mind, that means the car is accelerating the most very early in the run... but again, I'm just an average joe. I'm sure there's math out there that can explain it better, and probably prove me wrong.

 

[mick]

gordon, i follow your logic......look at a few of these 3.6 tf runs......i don't have split times in front of me, but i'll go from
memory. these cars are a tick under 300mph at 660' (1/8 mile). this is 66% of a 1000' run. lets use 330mph as top speed.
2/3 of the run has attained 300mph, while only 30mph is gained in the last 1/3. or in other words 90% of the speed is
attained in the first 66% of the track, while only the last 10% of the speed is attained in the last 33% of the track.....so all i've
tried to do here is explain acceleration.....seems to me that the hardest acceleration mite be just prior to 2/3 track?

if driveshaft speed diminishes after lockup (and engine rpm starts to increase)......are there teams out there now
trying to not get total lockup? where the rate of acceleration is constant all the way to finish line? does the rev limiter come
into play here? is this why FC's are top speed now? cuz they don't have to lock their clutches as soon as TF'rs?

if lockup is happening somewhere around the 660'-700' range; i would guess increasing g-force would be the greatest at this
point too? although g-force still increases to the finish line, it is not increasing at the same rate as it does from start to lockup? or does it increase all the way to finish line? maybe it decreases
slightly after lockup?

corrections please. this is a great thread.

 

[TooTall999]

Off topic, but did anyone notice how long it is between when the engine comes up and the driveshaft moves? There's also a split second from when the driver hits the gas and the engine comes up. All that adds up to why reaction times are slower in a fuel car than say a transbrake car. Because so much happens between the pedal going down, and the car actually moving.

Alan

Alan that's really visible in the ultra slow motion shots. You'd see the butterflies bang open, the engine torquing the chassis, the slicks wind up, then the car would move forward. Cool stuff!

 

[Gordon]

gordon, i follow your logic......look at a few of these 3.6 tf runs......i don't have split times in front of me, but i'll go from
memory. these cars are a tick under 300mph at 660' (1/8 mile). this is 66% of a 1000' run. lets use 330mph as top speed.
2/3 of the run has attained 300mph, while only 30mph is gained in the last 1/3. or in other words 90% of the speed is
attained in the first 66% of the track, while only the last 10% of the speed is attained in the last 33% of the track.....so all i've
tried to do here is explain acceleration.....seems to me that the hardest acceleration mite be just prior to 2/3 track?

if driveshaft speed diminishes after lockup (and engine rpm starts to increase)......are there teams out there now
trying to not get total lockup? where the rate of acceleration is constant all the way to finish line? does the rev limiter come
into play here? is this why FC's are top speed now? cuz they don't have to lock their clutches as soon as TF'rs?

if lockup is happening somewhere around the 660'-700' range; i would guess increasing g-force would be the greatest at this
point too? although g-force still increases to the finish line, it is not increasing at the same rate as it does from start to lockup?

corrections please. this is a great thread.

Mike, if you're following my logic some would tell you to get that checked.

But yes, your examples point to exactly what I'm attempting to show. Just because the clutch & tires are slipping at the hit through roughly 330' (or wherever) doesn't mean the car isn't accelerating quicker than it is once everything does lock up. Some of the initial G's, though still relatively strong and violent, are absorbed through slippage. That's why it's my contention that speed, not G forces, should be the measured variable in attempting to answer the original question. But as I stated, I could be wrong.

Yes, very interesting topic for sure.

 

[ironpony]

Also think of this, a pilot is cruising at 300 mph, there is no g force he is moving the same speed as the plane, no accell or decell..
He pulls up, creating 9g's force on his body and the plane actually slows down.......
G force and acceleration are two very different things.

 

[flapjack]

Also think of this, a pilot is cruising at 300 mph, there is no g force he is moving the same speed as the plane, no accell or decell..
He pulls up, creating 9g's force on his body and the plane actually slows down.......
G force and acceleration are two very different things.

They're related. Force = mass times acceleration (or the derivative of momentum, if you've taken calculus). G Force is a measure of force in terms of multipliers of the force of gravity, and acceleration plays into force.

 

[8sec71]

Also think of this, a pilot is cruising at 300 mph, there is no g force he is moving the same speed as the plane, no accell or decell..
He pulls up, creating 9g's force on his body and the plane actually slows down.......
G force and acceleration are two very different things.

But we're talking linear g forces here, there is no direction change. The only way to pull g's in a drag car is through acceleration/deceleration, unless of course you hit the wall or something lol. So the harder you accelerate, the higher the g force. G force doesn't always = acceleration but in drag racing they are, for all intents and purposes, one in the same.

 

[ironpony]

Never said they are not related, I said they are two very different things.
The original question was when does a T/F dragster ACCELERATE the fastest
0-4 G's in milliseconds is faster than 1.5 g's in the remaining 3.9 seconds

 

[8sec71]

Never said they are not related, I said they are two very different things.
The original question was when does a T/F dragster ACCELERATE the fastest
0-4 G's in milliseconds is faster than 1.5 g's in the remaining 3.9 seconds

Lol ok. 0-4 g's in milliseconds is still just 4 g's compared to 5.5 down track where it is in fact accelerating the hardest. Seems like you're looking at it like going from 0-40mph in a second and then taking another 3 seconds to get to 55.

 

[Cliff]

You guys are way above my pay grade. But, I was thinking about something. When T/F ran 1/4 mile, the rule of thumb was that they would pick up 50 MPH on the back half. I used to wonder why only 50 MPH? Then I realized that they faster the car goes, the more wind resistance. Maybe that is why they "only" picked up 50 MPH. I guess you could apply that to 1000' as well. How much does wind resistance affect the run? Also, I know F/C is heavier, but the bodies are way more aerodynamic that T/F. What would that contribute to MPH? Last, if T/F did not have the rev limiter, would the speeds be the same or faster than 339? Just my 2 cents.

 

[ironpony]

0-300mph in 660'

300-325mph in 340'

which is ACCELERATING FASTER?????

Force does not equal acceleration.

google is your friend

 

[ironpony]

if T/F had the same "settings" as F/C they would be similar On paper a F/C should be faster but it does not work out that way, kind of like a bumble bee can not fly based on physics.

 

[8sec71]

0-300mph in 660'

300-325mph in 340'

which is ACCELERATING FASTER?????

Force does not equal acceleration.

google is your friend

Nobody is saying they accelerate faster from the 1/8th on but they do accelerate faster from the 330 to the 660 faster than the starting line to 330. The G meter proves this, it's not debatable lol.

 

[8sec71]

A quote from Robert Hight from an interview I just read about trying to go 340mph in Brainerd this weekend.

“You don’t know it at the top end. Where you really know it is in the middle of the racetrack, from 400 feet to 700 feet. That’s when the clutch is coming hard and it sets you back in the seat,” Hight said. “To run that kind of speed you have to be 290 mph at the half track. You can really feel it. At the top end, you can’t tell much difference between 335 and 339.

That should tell you right there where it's accelerating the hardest.

 

[TooTall999]

 

[cdag]

"Where does a top fuel dragster accellerate the hardest"?

Brainerd!