Top Fuel Pics

[flynfrog]

there's nothing difficult about making measurements as outlined in the 2003 article shown by Brian

this has been off-the-shelf equipment for the last 40 years and more

or the loads could easily be measured eg at the engine mount position etc

I had never considered the possibility of measuring torque through the drive shaft in a Fuel car. Well, this certainly takes some of the difficulty out of tuning for various track conditions. The crew chiefs should have accurate baselines, a 'book', for all the tuning variables. They should have an engine output model that predicts what a change of one of the variables will do. Some of the aura surrounding the T/F crew chiefs just evaporated for me.

Brian

You are once again forgetting the cars are traction limited not power limited. You will only measure the force the tires can put to the ground. Its the same issue of spinning the tires on the dyno roller.

[Tommy Cookers]

engine power developed is the rate at which the engine does work on the load ie it is engine dependent and load dependent

if the load is limited eg by traction then the engine may not develop its max power ie will over-rev and power truncated
(a dragster has the traction matched to the motor by choice of gear ratio, to be neither traction limited or power limited ?)

the engine power in drag racing is the engine power developed in drag racing, not some higher power that (we believe) the engine could reach with an ideally matched (higher) load

check on a dyno if you think there's a difference, if there is get a new crew chief

[flynfrog]

engine power developed is the rate at which the engine does work on the load ie it is engine dependent and load dependent

if the load is limited eg by traction then the engine may not develop its max power ie will over-rev and power truncated
(a dragster has the traction matched to the motor by choice of gear ratio, to be neither traction limited or power limited ?)

the engine power in drag racing is the engine power developed in drag racing, not some higher power that (we believe) the engine could reach with an ideally matched (higher) load

check on a dyno if you think there's a difference, if there is get a new crew chief

your statement would be like saying a car only makes XX hp because that is the max the dyno can handle. The whole point of the discussion is that the engine are not suited to a dyno run.

[countersteer]

You are once again forgetting the cars are traction limited not power limited. You will only measure the force the tires can put to the ground. Its the same issue of spinning the tires on the dyno roller.

And at the top end of the run, you can hear the clutch lock up and the engine pull down as the engine is, at that point, producing all of the torque the tires can handle, on that run, under that set of conditions.

It would make sense to me that horsepower could easily be calculated at that point given torque and rpm.

Yes, the engine tune is varied to correlate to conditions at that time. But, through the course of the season, data is collected for a variety of conditions, both good and bad. Seems to me a "best case" calculation could be made.

[hardingfv32]

More of the same....

You are once again forgetting the cars are traction limited not power limited.

Once again? Maybe I am just ignoring an incorrect opinion. These cars are not traction limited in the later half of a run. The paper 'TOP-FUEL DRAGSTER WING DESIGN USING CFD AND ITS INFLUENCE ON VEHICLE DYNAMIC PERFORMANCE", on page 29, clearly illustrates and states that "In the power limited acceleration region there is so much down force that the power used to accelerate the vehicle is not large enough to spin the wheels." If the cars were traction limited, then the clutches would never lockup. You can hear the rpm drop a little when the clutch locks up at around half track.

Brian

[hardingfv32]

I'd expect the valve seating would be critical for maintaining the high compression, does that drop off towards the end of the run?

Also, how are the valves replaced in a 90 min turnaround? I guess the cylinder head is designed for a quick plug and play replacement, and you'd not have time to carefully use grinding paste for the valve and seating?

Armstrong reinforced this concept. He says, "We used to have problems with head gaskets on our old Top Alcohol engines that never happened with the fuel engines. We realized that nitro burned slower. The horsepower doesn't really come from peak cylinder pressure. It actually drives the piston farther down the hole because it [the fuel] keeps burning." This longer burn is also why the header flames are so easy to see even during daylight. Armstrong also noted that this has an effect on cam timing. "You have to be careful when opening the exhaust valve. You can't open it too early-like before 82 to 84 degrees before bottom dead center (BDC) or it will just break parts. The cylinder pressure is so high that the valve just won't open. That's also why they keep the exhaust valve small, so it's easier to open."

Brian

[strad]

More of the same....

You are once again forgetting the cars are traction limited not power limited.

These cars are not traction limited in the later half of a run. The paper 'TOP-FUEL DRAGSTER WING DESIGN USING CFD AND ITS INFLUENCE ON VEHICLE DYNAMIC PERFORMANCE", on page 29, clearly illustrates and states that "In the power limited acceleration region there is so much down force that the power used to accelerate the vehicle is not large enough to spin the wheels." If the cars were traction limited, then the clutches would never lockup. You can hear the rpm drop a little when the clutch locks up at around half track.

Brian

They do pull down about a 1000 rpm on lock up and at that point they often spin the tires. Top fuels cars often lay down stripes all ther way thru the timing section.
Clutch lock up has nothing to do with traction and everything to do with RPM.
Garbbed these real quick..
http://www.stradsplace.com/VIDEOS/_Ant- ... 161551.mpg
.
Watch at about 4:08
http://www.stradsplace.com/VIDEOS/T-F.mpg

[hardingfv32]

They do pull down about a 1000 rpm on lock up and at that point they often spin the tires.

Would you say it more effective to spin the tires or to use more wing (drag) and not spin the tires? I assume we are not talking about wheel spin bad enough to create smoke.

Brian

[strad]

I really don't know how much slip you'd want at that point..surely none if you could but the track and tire have to hold it,,,Remember you're up on the tire and it's pretty narrow at that point. What do you think..I have often thought the tire growing acts as a CVT of sorts?..?
edit
Too much wing would slow you all the way from 100 ft mark.

[strad]

Wheels of Fire is a 1970s drag racing movie that has a mix of fact, fiction and excellent camera work that entertains its audience with big names of the sport like "Big Daddy" Don Garlits, Shirley Muldowney, Don Prudhomme, Billy Meyer and Richard Tharp.

Kinda centers on the Tharp Muldowney rivalry iirc
Since we have a few drag racing fans, I thought there might be some interest in this..
455Mb just shy of 56Min Divx codec.
click photo

[flynfrog]

Thanks Strad. I wish I could watch more of your videos but with my terrible internet connection its a lost cause.

[flynfrog]

http://www.motoiq.com/magazine_articles ... power.aspx

Pretty good write up.

First, you may be wondering how the power is calculated. You can't strap these car's to a dyno. However, according to Mason a test was done around 2006 by a third party, and they came up with 10,000 horsepower using mathematical equations. That said, Mason reports the Matco Tools team does use a torque-measuring device in the rear differential, and it has spiked to 12,000 lb-ft of torque at times.

[Blanchimont]

The usual formula to calculate wheel power is:

Power [W] = forces [N] * velocity [m/s]

= ( mass * acceleration + ( mass * 9,81 + air_density/2 * cl * A * velocity^2 ) * rolling_resistance_coeff + air_density/2 * cd *A velocity^2 ) * velocity


Units:

mass: kg
acceleration: m/s²
air_density: kg/m³
cl, cd and rolling_resistance_coeff: -
A: m²
velocity: m/s

If all the numbers are known, estimated or calculated and if the car is able to get the power down on the road, that means tyre slip is not to high, the power at the wheels for every single speed can be calculated. If in addition you know the gear ratios, you even can plot a diagram of power in relation to rpm. I did the calculation for my road car and it got a really nice plot for the different gear, showing the efficiency factor of the gearbox is highly dependent on the chosen gear.

[flynfrog]

Read back a few pages. Those equations don't really work with a top fuel car they are slipping the clutch for most of the run. When the clutch does hook up they tend to spin the tires.

[Blanchimont]

This could be easily fixed with a few modifications.

Think about your road car, almost any car can slip the wheels in the first gear because of the gear ratio. But in second or third gear only powerful cars are able to do so.

The same can be translated to dragsters. Modify your gearbox in a way that a verly long last gear (low gear ratio) is available, change to this gear at 100 mph, close the clutch and accelerate. Tyre and clutch slip is eliminated this way.

You could also add weight to the dragster, that would also decrease the problem with the wheel slip.