G-Forces at launch for 10.0 sec run?

Hot Air

E85 and S.E./Carolinas Moderator
Staff member
Does anyone know the peak (instanteous) and sustained (1-2 seconds or so) acceleration rate (G's) at launch for a 10.0 second run for a typical 3600 lb TR?
Conrad Carter
 
1G = 32.2 feet per second, so assuming a 1.4 second 60' time (60/1.4 = 42.85714286), it's 1.331 G's (42.857/32.2).

1.5 seconds = 1.242 G's
1.6 seconds = 1.165 G's
1.7 seconds = 1.096 G's
1.8 seconds = 1.035 G's
1.9 seconds = 0.981 G's
2.0 seconds = 0.932 G's


I think. Ugh, my head hurts already.
 
You are missing units. 1G is acceleration velocity- 32ft/sec^2.
Also it's not easy to get an accurate calculation just using times. Velocity is linear and changes with time (assuming a constant acceleration from 0-60ft) but you need the instantaneous rate at the 60ft mark. If we had that then we could calculate exactly what your accel is.

Averages can be calculated though,
Average velocity = 60ft in 1.5sec= 40ft/sec
Time= 1.5sec
So average accel is 40ft/sec/1.5sec = 26.7ft/sec^2
a= .83G
correct me if this is wrong. It's been a while since school
 
Welby said:
1G = 32.2 feet per second, so assuming a 1.4 second 60' time (60/1.4 = 42.85714286), it's 1.331 G's (42.857/32.2).

1.5 seconds = 1.242 G's
1.6 seconds = 1.165 G's
1.7 seconds = 1.096 G's
1.8 seconds = 1.035 G's
1.9 seconds = 0.981 G's
2.0 seconds = 0.932 G's


I think. Ugh, my head hurts already.


I don't think that takes into effect the instantaneous G's. That is an average over the 60'... It would be hard to calculate as each car is different. I would think a car with a 1.4 60' would see almost 2 G's on the start with a transbrake..
 
2G's is pretty damn hard acceleration. I would use mph readings at different points in the run to get an idea of G's. G-techs, while they blow when it comes to accurate trap speeds and horsepower numbers, the G readings are very accurate if you can stabilize the damn thing. The bracket is a terrible design. I had to add springs to the feet to keep it from banging around and getting innacurate G spikes.
 
VadersV6 said:
2G's is pretty damn hard acceleration. I would use mph readings at different points in the run to get an idea of G's. G-techs, while they blow when it comes to accurate trap speeds and horsepower numbers, the G readings are very accurate if you can stabilize the damn thing. The bracket is a terrible design. I had to add springs to the feet to keep it from banging around and getting innacurate G spikes.

I had a G-tech years ago and it would spike up near 2 G's on a 20 psi transbrake launch on slicks.
 
V6RACER said:
I had a G-tech years ago and it would spike up near 2 G's on a 20 psi transbrake launch on slicks.
Was it flopping around like they all do? It could bang back and create a G spike..although I dont doubt you could hit 2G's on that kind of launch. I cant imagine what that feels like :eek:
 
xrunner123 said:
You are missing units. 1G is acceleration velocity- 32ft/sec^2.
Also it's not easy to get an accurate calculation just using times. Velocity is linear and changes with time (assuming a constant acceleration from 0-60ft) but you need the instantaneous rate at the 60ft mark. If we had that then we could calculate exactly what your accel is.

Averages can be calculated though,
Average velocity = 60ft in 1.5sec= 40ft/sec
Time= 1.5sec
So average accel is 40ft/sec/1.5sec = 26.7ft/sec^2
a= .83G
correct me if this is wrong. It's been a while since school

If the average velocity is 40 ft/sec and the acceleration is constant, then the velocity at the end of 60' will be 80 ft/sec and the accel will be 80 ft/sec/1.5 sec = 53.3 ft/sec^2, /32 ft/sec^2 = 1.7 g

With a 1.76 sec 60' this becomes 60/1.76*2/1.76/32=1.2 g, pretty close to the GTech 1.1 g.

Turning that around I get a 1.37 sec 60' to average 2 g's.
 
VadersV6 said:
while they blow when it comes to accurate trap speeds and horsepower numbers

I dunno, I've done searches on this board and a few others, and the general concensus is that they're pretty damn accurate. In HP, 1/4, and o-60 tests. The 1/4 tests I've seen are usually within .1, and lots of times within .01
 
Antagon said:
I dunno, I've done searches on this board and a few others, and the general concensus is that they're pretty damn accurate. In HP, 1/4, and o-60 tests. The 1/4 tests I've seen are usually within .1, and lots of times within .01
They're pretty accurate with everything but trap speed and horsepower readings. I had 322rwhp in 4th gear dyno verified and the G-Tech said 155. Trap speed is usually 4mph higher than reality.
 
Antagon said:
4mph, good to know :) But 155 hp? Damn thats off
Yeah, you have to take into account aerodynamic drag, parasitic loss through the drivetrain (higher if you're in a lower gear), have to get as close as you can with putting in the correct weight of the car with you in it, etc etc. But back when my car was putting out 283rwhp in 4th, I did a 3rd gear pull on the dyno just for kicks and it was something like 268rwhp. Not exactly HALF the total power at the wheels. I think the G-Tech run was in 3rd gear. Plus I had major traction problems. I had 4.56's and crappy tires, so I would smoke the tires HARD till after 3rd gear at about 60mph. When I raced Wiked87GN (Harold/Kevin)..member of this board) with my cobra against his GN, I smoked the tires hard up to about 60mph, so getting a realistic hp number out of the G-tech wouldnt be easy. I even launched in 2nd gear and feathered the throttle but there was just no hopes of hooking. Once I hooked, I was 3 car lengths behind him and held it there. This is after I pulled the blower off and I was N/A. The video is actually on turbobuicks.net...called GNkillsCobra or something. I had ended the run and was hard on the brakes about 100 feet before passing the camera guy, (he was standing after the 1/4 mile marker for some reason) so it looks like I got stomped really bad by the time we pass the camera. Had I hooked anywhere as good as he did I would have had a chance.
Damn how did I get so far off the subject?
 
vader, was that an old model G-tech or one of the new SS or RR versions?

i found (verified with a track time slip of the same exact pass) that the RR model i used was with in .01"sec of the time slip (12.022 vs. 12.018) and only ~.5mph off and i think, not sure but the 60' time was only ~.5 off also
 
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