How many G's does a supercar pull ?

I know cars can pull G's on LATERAL acceleration, but straight line?

 

of course they are generating G-forces on your body against the seat...it is merely a measure of how many times the force of gravity is being acted on you in that direction...ask the question to Mitch, apparently he's an engineer..or some type of physics guy..maybe just really good with it...anyhow, hell rub you right

 

In acceleration, probably around 1.1 or 1.2g for a little bit, which is really high. It may not sound like much, but it is. Braking is probably 1.6 or more. Top fuel dragsters will subject the driver to almost 5g's. Ive never felt an acceleration this high, but its probably really painful and not fun. To put it in perspective, lets say your head weighs about 10 lbs. Under 5g's of acceleration, it would feel like someone is pushing on your head with 50lbs. Since your head is up against a seat back, it would feel like someone is pushing on the back of your helmet with 50lbs. I think my example is correct.

 

I like watching those realtime indictors they show on SPEED during in-car video of the lmp900 cars at ALMS. From memory I have seen an Audi R8 pull 1.2-1.4 sideways and 2.2 or so braking. JJ Lehto driving.

 

i recall seeing R8's turning at over 2g's regularly. i dont think the telemetry they showed on TV for the races i saw had any g force acceleration but i do remember seeing the speed go so fast, it was jumping in increments of like 5mph.

 

Correct. As long as the vehicle is traction limited, and the driver can hold the tires slipping at 7% faster than the road surface passing under the contact patch. When the vehicle become power limited, the throttle is simply floored and the driver simply steers. While the car is traction limited, it remains at 1.2 Gs of acceleration.

However the 1.2 Gs is only in 1st gear*, something closer to 0.9* in second, and 0.75 in third. The linear tractive abilities of modern tires is equivalent to the longitudinal capabilities--unless one is traded for the other (drag race tires).

* The 600+ HP supercars will also remain traction limited through 2nd gear so 0.9 Gs is for the 400-500 HP supercars. F1 cars are traction limited into the 120 MPH range with low downforce aerodynamic package. F1 cars have tires that allow more like 1.5-1.6 Gs of acceleration before the aerodynamics begin to increase the traction levels.

Incorrect. Braking is 1.1 to 1.2 Gs for the entire duration of the braking interval. Thats why it seems more powerful than acceleration.

Top fuel dragsters hold 5 Gs for most of the run. In addition, they are traction limited up into the 240 MPH region where they become HP limited. You could double the HP of a modern dragster and not get more than another 10 MPH and 0.2 seconds out of them with current tire technology.

 

Would't they be able to change the gear ratios to bring this traction limit back within limits, but still be able to increase speed?

 

Take a look...

http://www.rs6.com/forum/showthread.php?s=&threadid=3352

the max G force for an Audi RS6 was 0.90 G....

 

The thing is they have more power than required already and are at the mercy of tire traction and aerodynamics. Top Fuel and FunnyCar have only 1 gear, and fron the line through 240 MPH the clutch is controlling the thrust that arrives at the tires, So, in effect, they are throwing away HP for 3.9 seconds of a 4.4 second run because they have too much HP most of the run! The 1 gear the have is selected for that RPM just short of engine destruction and that corresponds to the best Speed on that track plus a few MPH.

The way they could get the 10 MPH is by using more aero downforce to gain traction and accelerate faster in the first 1/8 mile while adding enormous drag in the second 1/8 mile.