Oldsragger

Just thinking of something and want to ask ppl who does racing your olds and can make wheel lift, with right slicks,raceway,gearing etc, and what minimum torque in the engine can make a wheelie ?

example 500lb-ft could be enought to make a wheelie on a dragstrip? or less/more?

Or what is your experience with your setup with a wheelie?

chadman

There is no magical equation as many, many things factor in. I can however attest that at 3825 lbs. you can get a bit of daylight under the drivers side tire with an approximately 500 hp motor with 3.73 gears and a 3000 stall.

MDchanic

+1. I am not a drag racer, but that gives you some practical sense of what it takes to lift just one wheel.
I'll post Chad's picture a bit bigger so it's easier to see:





As far as "magic equations," well, there kind of is - it's called "Physics."
You can get a sense of it from simple high school Physics, but to get truly exact numbers, you'd need to use more sophisticated equations to capture the weight shift as the car accelerates and the nose raises.
As Chad points out, even with good calculations, there are many variables involved in the real word, so even if you think you've got it figured out, a drag racer with practical experience will probably be able to give you a more accurate answer.

To get a ballpark torque figure, you need to know how much weight the engine has to lift.
I'll use "wild-*** guess" numbers here, but let's say that your car weighs 2 tons and has a 57/43% weight distribution over the axles.
In that case, you've got 860 pounds over the rear wheels and 1,140 pounds over the the front wheels, so the rear wheels have to lift about 1,140 pounds in order to get BOTH wheels all the way off the ground, with a center of gravity somewhere around 10 feet away from the rear axle.
That can be likened to a 1,140 pound force rotating the rear axle backward, which the rear axle has to overcome in order to lift the front, so, 1,140 pounds x 10 feet = 11,400 foot pounds of torque at the axle.
If you figure a 4.56 axle, which is the highest commonly available ratio (drag racers and others can get higher ratios from very expensive suppliers), you get 2,500 foot pounds of torque at the driveshaft (Hmmmmm... Why are those drag racing driveshafts so expensive again?).
If you figure a first gear ratio in a TH400 transmission (you will not be using a TH350) is 2.48, then you need 1,000 foot pounds of crankshaft torque to get the nose completely up off the ground.
This, of course, does not account for frictional losses, and does not use actual numbers from real cars.
Also, note that as the nose lifts off the ground, the force of gravity pressing it toward the ground begins working from a shorter and shorter level angle, which means that less torque is required to get it up further (and applying the same amount of torque will flip it over).

- Eric

Professur

Technically, you can wheelie with a stock 307 and stock gearing ... you just have to hang 700lbs off the back bumper... and pray the frame doesn't taco up on you.

Rallye469

Yes to no magical equation.
I see guys at the track that get both tires up there pretty well with a lot less power than I have and they run a slower #.
The right shock set ups and springs that store a lot of power can get 12 sec car's front wheels off the ground.

-pete

jims2000lt

Spring, shocks, tires, traction, gearing, and weight.
My 69 use to leave with a foot of daylight under the left front. It was hard on everything.
Now it lifts evenly and barely gets the tires off.
I reinforced the rear trailing arm mounts, added 4 more body mount bolts where it was just cusions, added hotchkiss frame braces and switched to drag radials.
Olds 60s were 1.65- 1.75
Newer 60s have been 1.55- 160
3.42 gear 3500 10inch converter, abd 275 drag radials.

young olds

ill throw some more out there. my dads old set up in his 65 nova, 355 sbc nothing special ran mid 11's, th350, 3,73 gears with 26" cheater slicks. idk what stall. i saw this set up pull both wheels, was only 6 ish inches but they were both off the ground. also the higher your car, weight and center of gravity up high, will make it easier to do wheelies. i tested this with an rc car with adjustable suspension. started as low as it could and the front would just raise. then i raised the front all the way up, the back would squat a little. the front down rear up, front would raise. last i did front and rear all the way up, would wheelie on take off.

TripDeuces

I know some low 12s cars can get the tires up. Not full wheel stands but at least daylight under there. I think that takes roughly 320-350 rwhp to get there.

Oldsragger

Cool to read this... Well i see everything is possible with rigth setup hehe..

wr1970

The truth is no wheelie in drag racing is better. Those that have big wheelies will run slower than those who just barely have tire off the track. That is if all things being equal. Cars that have almost none the chassis is tuned correctly for the horse power. I know everyone like them wheelies!!

chadman

Theoretically I agree with you but practically I have to disagree. Many a racer has tuned their suspension to keep the front end down only to find that they run quicker times with the big wheel stands. Every car and combination is different as far as what it likes. NHRA Super Stockers are a good example. Those guys are chasing national records and would keep the nose down if it were faster for them.

wr1970

Dude they are limited is why they have that problem of what they can do!!The faster you go you have to tune plain and simple ask anyone running fast let say is 8, 7 . Your example isn't all out racing.Yes i know there is always rules !!You think John force wants a wheelie!!DUH good example.

chadman

Actually John Force is a terrible example. A top fuel funny car has practically nothing to do with your average race car. Like I said every application is different. Some cars go faster with the wheel stand and some dont. what makes sense on paper doesn't always hold true in the real world.Do a little research and you will find that I am correct.

Rallye469

Set up is everything.
This car hooks on 235 radials and is by no means a light weight.
It's a super consistent car.

wr1970

Chad i really think you know quite a bit of Stuff i am stating it one time and i am done You are wrong go ask some racers who builds and race them. Not a weekend warrior who goes now and then. I know you and you know me. i race you race but we are not professional racers. I have talked this over with chassis builders who do this for a living as well as guys who run the nhra tracks for big bucks.Good day sir if you want names who to talk to pm me. Out of here before this gets ugly.

BlackGold

Eric did a nice little back-of-the-envelope analysis above of the crankshaft torque needed to lift the front end. But he forgot that a decent torque converter multiplies crankshaft torque by about 2x (while slipping), so you really only need about 500 ft pounds at the crank. Except he also forgot to factor in the diameter of the rear tires ..... man, this gets messy.


But there's another big contributor to doing a wheelie. The torque analysis is static. The other big contributor is lateral acceleration. Simply put, the higher the car's center of gravity, and/or the quicker it accelerates, the more it will rotate backwards, ie wheelie. Picture an 8" chunk of 2x4 lying on a table. Give it a little poke on the end, down close to the table. It sill scoot forward without doing a wheelie. Now set it up on end and give it the same little poke. It'll tip over backwards gently. Now set it on end again and give it a big poke down by the table. It'll tip over backwards violently.


So you see that the better you hook, the quicker you'll accelerate, and the more "weight transfer" you'll have -- producing even more hook. A lovely, vicious circle.

MDchanic

Absolutely right. I was thinking about it in the shower, and never actually wrote it down or drew a picture, so, yeah, I completely spaced the tire diameter, and didn't consider the converter. I will admit I was thinking about a clutch, but since I used the first gear ratio from a TH400, I have no excuse.


Well, forward acceleration, actually, but, yeah, perceived weight transfer from the front of the car to the back (it doesn't really transfer, but that's not important) takes weight off of the front wheels and puts it on the rear wheels (the opposite effect is why you need larger front brakes than rear brakes), thus requiring less torque to get the front wheels off the ground.

I'm glad my very rough figuring got this discussion into at least somewhat interesting territory.

- Eric

oldcutlass

I believe a wheelie is basically torque, traction, weight transfer, and lack of forward acceleration.

TripDeuces

It's a torque moment around the rear axle.
Let's get Joe P in on this!

MDchanic

Not exactly -- You need the forward acceleration to get the weight transfer.

- Eric

chadman

Ugly? Why on earth would things get ugly? I'd like to think that both you and I are mature adults that aren't going to take it personal if we disagree on a subject. I know I won't lose any sleep over it. Here is a thread that debates this subject, as you will see you and I aren't the only two who disagree on this. And for the record I'm not saying that a big wheel stand is always faster, just sometimes depending on the situation.



http://www.yellowbullet.com/forum/sh...d.php?t=564844

BlackGold

By lateral I meant forward, trying to differentiate it from vertical acceleration.

It's good to hear someone state that weight doesn't really transfer!

Regarding starting an interesting discussion, I thank you! I live for this stuff. It's a game I like to call Parlor Physics, where you ponder life's great mysteries with a friend and try to explain them with real physics. Preferably while drinking beer.

So, to continue the game, here's some further calculations for what we'll call Wheelie Criteria:

-------------------
Let's look at a 1970 442 which weighs 4000 pounds with driver and fuel. The wheelbase is 112 inches. We will ignore all frictional losses.

If we assume that 55% of the weight is borne by the front wheels, this places the center of gravity 5.133 feet ahead of the rear tire contact patch.

We'll also assume that the center of gravity is 24 inches (2 feet) above the ground.

-------------------
Now perform a static vector analysis (simple geometry) to determine what force must be applied at the rear tire contact patch in order to lift the center of gravity straight up. The rear tire contact patch is also the point of rotation.

The force required at the rear tire contact patch is 10267 pounds.

Assuming a 28" diameter rear tire, this equates to 11978 ft lbs of torque at the rear axle
.
Assuming a 3.90:1 rear end ratio, this equates to 3071 ft lbs at the driveshaft.

Assuming a 2.5:1 first gear, this equates to 1228 ft lbs at the input to the transmission.

Assuming a torque converter which multiplies the torque 2X, this equates to 614 ft pounds at the flexplate.

If frictional losses were included, this answer would, of course, be higher.

Also, note that unless your torque converter stall speed is very near your engine's peak torque RPM, your engine will not be launching at peak torque, so your peak torque would have to be higher than what we calculated.

-------------------
Next we look at the dynamic condition. We ignore the static forces applied through the drivetrain and instead calculate how much lateral acceleration is required to lift the center of gravity straight up.

From above, we know that 10267 pounds of force must be applied at the rear tire contact patch. We also know that acceleration equals force divided by mass. 4000 lbs is 124.2 slugs, yielding a required acceleration of 82.7 ft per second squared, which is equal to 2.57 g's.

Acceleration is a little hard to picture. I'd rather know what the 60-foot time is for 2.57 g's. We know that distance equals one-half the acceleration multiplied by the time squared. Doing the math we get a 1.20 second 60-foot time.

-------------------
So we've calculated two independent conditions which will result in a wheelie. For our example car, even if you chained the rear wheels to a stump so that the car did not accelerate down the track, 614 ft lbs of torque at the flexplate would be enough to wheelie, Likewise, even if the engine was turned off, if the example car were on a rocket sled which accelerated the car down the track with a 1.2 second 60-foot time, it would wheelie.

In the real world these two effects work together so that you get a wheelie with less than 614 ft lbs of torque and with 60-foot times slower than 1.2 seconds. My observations are that stock-type cars start to wheelie when they run high-11s or maybe low-12s, and when they have 60-foot times in the 1.5 - 1.6 seconds area. How much horsepower and torque this equates to depends on the weight. And, of course, traction is a big factor; a car with significant tire spin cannot apply the force or achieve the acceleration needed to wheelie.

-------------------
Another factor helping the wheelie is that the front wheels and the rest of the front unsprung weight is not rigidly attached to the frame and body. That's several hundred pounds which does not need to be fully lifted until the wheelie has already been achieved. Smart racers in stock classes take advantage of this by using lower-rate, longer front springs, shocks with little resistance to extension, and by trimming the rubber snubbers,
thus allowing the front of the car to rise even further before having to lift the wheels. None of this is accounted for in our crude analysis above.

Also note that as the front end rises, so must the center of gravity, thus causing an even bigger effect due to acceleration. In this manner, a wheelie is somewhat self-perpetuating. The higher it lifts, the more it wants to stay up there -- or even go too far.

wr1970

^^^^ My 3750 me in it 1970 442 390 rear gear 461 ci turbo 400 29.5x10.5x15 in drive et around 12.78 will pull the drivers side tire up about two inches. Now that is the old eng combo this spring may be different! Chadman i just think you are wrong nothing more.A good hooking well tuned car well tuned chassis can go way faster than my needs and wheels off no more than 2 inches.

Hacked Up 74

Easy....... Spray that bitch.

MDchanic

Ah. Are you a flyer?


Which, by a strange coincidence, is exactly what I'm doing right now.

Eerie.


Are you sure you want to lift the entire center of gravity?
In a completely static state, 45% of 4,000 pounds (1,800 pounds) is being borne by the rear wheels, and will not need to be lifted.
Once the car begins accelerating forward, that amount will effectively increase, thus reducing the required torque further.
That means that only 55% of 4,000 pounds (2,200 pounds) needs to be lifted, and that weight is working from its own center of gravity, which will be forward of the CG of the entire car.
Of course, the rear wheels are not the farthest-rear part of the car, meaning that there is weight behind them, acting to lift the front of the car, using the rear axle as a fulcrum, and this will reduce the torque needed to achieve a wheelie as well (substantially, if the trunk happens to be full of concrete, less if it happens to be empty).

- Eric

Hacked Up 74

No spray.
See my combo on ROP : Junk 455 on the can.

TripDeuces

I like everything so far but I'm going to have to disagree about the torque converter. The TC is nothing more than a fluid coupling but it does not multiply torque. A loose converter allows engine rpms to climb before friction and a fluid coupling provided by the stator, turbine and pump reach a point of equilibrium which transfers into forward motion. The higher rpm's allowed use the engines torque at that point to transfer down the drive train.
As an example, say at 3000 rpm the engine is producing 300 lb/ft of torque and let's assume we have a TH400 for a transmission. 300 lb/ft x 2.48 (1st gear ratio) = 744 lb/ft at the out put shaft of the trans.

All I'm saying is the torque converter is not adding anything mathematically to the equation other than allowing more torque to be used at the higher rpm. It does not multiply torque in any way but rather allows more usable torque.

Oldsragger

In my opinion: i love what i see here

what setup do u have in engine like hp and torq? and driveline setup/specs? 10bolt 8,5" axle? building thread somewhere?


if you want to share then..

Hacked Up 74

Recipe:
160 K, Rusty '77 Delta 88 3950 lbs.
Steal 1 well used short block from Cutlass.
.040" L2323f , 0 deck, "N" crank.020/.020, balanced, stock rods, ARP bolts, HV pump, Smashed 7 qt. Moroso.
stock balancer and flex plate.
"C" Heads all stock, milled a **** load.
Comp Cams XE 268 Hyd. Ford roller rockers.
O-ring block but not heads. Mr. Garbage head gaskets.
Torker, milled to fit.
825 Race Demon.
Rusty A-body Hedman headers. 3" exhaust with Blow Master mufflers.
25 yr. old Unilite, MSD 6A. mis-matched wires.
3 row radiator, stock clutch fan w/shroud
TH350.
ATI 10" Treemaster : the only "real" $$$ I spent.
Quarter Master shaft.
8.5" Rear End, cheapo Auburn, 3.73 gear. stock bolt-in axles.
Swap meet Comp. Eng. shocks for early A-body.
6 cyl. front springs, worn out stock rears, air bags.
MT slicks 28x10.5 or 29.5X10.5 on steel 8".
NOS Cheater plate. jetted by instructions for 200 shot.
12.50 on motor. 11.50 on the can right out of hole. 1.51 60'.

I beat the **** out of this car street racing and at the track for 3 yrs.
until the rear control arms ripped out and the frame started to fail.
Huge buckles in the rear quarters told me it was time to junk it.

BlackGold

It all depends on the design of the fins inside. Rumor has it that for the old switch-pitch converters, what you say is true: they did not multiply torque, just let the engine get up into its powerband. But most converters DO multiply torque. Look at the opening description of chapter 7 of your Chassis Service Manual. It definitely mentions torque multiplication and, if I remember correctly, even gives the 2X number. If the factory converters did this, I can only assume that any competently designed racing converter will do the same or better.


Of course, the multiplication effect only occurs when there is a large difference between input and output speed. So as the drivetrain catches up with the flexplate, the multiplication goes away.

BlackGold

Yup, I'm sure. Your last comment about weight behind the rear axle is one reason. The CoG takes all this into account. Remember, the CoG is not just a weight -- it's a weight AND a location.


You and I just went about it differently. You took 55% of the weight but located it 112 inches away from the rear axle. I took all of the weight but located it 55% of 112 inches away from the rear axle.

BlackGold

One last comment:
As analyzed above, we define a wheelie as lifting BOTH front wheels off the ground. Getting daylight under one wheel is impressive (my car doesn't do it), but it's not really a full wheelie. It's more of a twist.

Oldsragger

i agree with that,, but what makes it twist than lift both wheels in front? To soft supsension than the power from the engine?

TripDeuces

It most certainly does not multiply torque. The angle of the vanes is what determines stall speed but it's not multiplying anything. It's a fluid coupling that has predetermined built in slip. Gear boxes and transmissions multiply torque through gear multiplication and reduction.
A torque converter is nothing more than a wet clutch. Just like a clutch allows you to rev the engine to gain a higher toque band the TC does the same but does it by slipping. The amount of slip is determined by the angle of the stator blades. The switch pitch just allowed you to utilize the higher rpm where more torque is generated by the engine.
A 66 Toronado made 475 lb/ft at 3200 rpm. A stock TC would only flash to maybe 1800 rpm before it essentially 'locked up' and won't let the engine rev any higher until forward motion takes over. Don't confuse my use of the term 'locked up' to mean there is some mechanical device within the converter. Although that applies to newer cars it didn't exist in 66 and was basically a fluid pressure lock between the turbine, stator and pump. At 1800 rpm you're only using a fraction of the available torque but let the TC flash to 3200 and now you have the full 475 lb/ft acting on the drive train.
At no time does the TC multiply the torque. It just slips allowing the higher torque band to be utilized

BlackGold

Thanks for the PM, Trip. We won't argue, just discuss.

I'm not a mechanical -- nor certainly a hydraulic -- engineer, so I can't prove that torque multiplication occurs. But there seem to be some smart people who agree it does. I suggest everyone go read the Wikipedia entry for torque converters (and yes, there's even math in there, not just words). I won't claim everything in Wikipedia is true. But it is a juried encyclopedia; BS usually gets ferreted out. I'll quote a couple relevant sections here:

When you consider a solid gear set, which achieves torque multiplication by reducing the speed from input to output shaft, I don't know why anyone should be surprised that the same effect can be achieved through hydraulics.

BlackGold

Some of the twist is real, with the frame, body, and body mounts actually flexing. But some of the apparent twist at launch is really just the body and frame rotating on a diagonal with respect to the rear axle. The rotation of the drive shaft wants to spin the rear axle assembly like a propeller, driving the left rear tire into the ground and lifting the right rear tire. Newton's equal and opposite reaction is the engine trying to spin the entire frame/body the other direction, lifting the left side and driving the right side down. The end result is the right rear spring compressing and the left front corner of the frame//body lifting, thus pushing the right rear corner of the frame/body down.

On stock cars, much of this action can be reduced by using anti-sway bars front and back. On more serious drag cars, the rear control arm geometry is set up so that both sides of the rear axle are driven down into the ground with near equal force. Without this, you have unequal traction in the rear, and a car with front wheels up heads for the wall.

gearheads78

I can tell you this my buddy with the 85 Camaro I work with 600 hp motor with a 400 shot on 275 drag radials will go right to the bumper if we leave on much more than 40% on the controler. It will still go to the bumper it we ramp it in too fast. Its a balancing act. It been a best of 5.20's but looking for 4.90-5.0's this year with some changes made.

coppercutlass

Ok now according to the ron sessions book on the th350 it say's "The stator redirects and accelerates the fluid passing from the turbine back into the impeller. This increases velocity and force of the fluid against the turbine fins , multiplying or converting the tq supplied by the engine". "With the engine in gear , brakes applied , and the car is still the tq. Converter is capable of multiplying the tq. By a 2:1 ratio . It mentions this only happens at low speed and maximum tq. Inputs . Its minimal at lock up. That's by the book. Now it sounds like if you where to leave at maximum rpm for the converter to flash you won't bang off of the converter. Which makes sense since you always want the converter to "flair" . Since tq. Multiplication does not happen at lock up it makes sense.