Car's acceleration-> any one size fit all formula between Torque and weight?

[JEDI]

my mazda3i automatic has 150hp, 135ft-lbs torque (Max Torque: 4500 rpm), and weighs either 2696 or 3794 lbs. (edmunds says one thing, and mazda says another.)

0-30 mph, sec. 3.6
0-60 mph, sec. 9.6

Is there any rough estimations between torque and weight to apply to all automatics to get acceleration?

btw- how much does a 2005 mazda3i automatic weigh?

 

[duragezic]

I'm guessing the lower number is the curb weight (no driver, not sure if it means a full or emtpy tank of gas, etc) and the higher one is the GVWR (how much weight it is safe for tires/suspension to support).

edit: Btw, there's tons of variables. I've never seen any sort of function to approximate them. My 1993 626 has around 110hp/127 ft-lbs, ~2750lbs, and its probably 11.5 s or so 0-60. Not sure if its the HP making the difference compared to yours or just other things like that fact that yours is much newer, geared differently, etc (tho my max torque rpm is at 4500 too, it's a 2.0L btw)

 

[Doboji]

Originally posted by: JEDI
my mazda3i automatic has 150hp, 135ft-lbs torque (Max Torque: 4500 rpm), and weighs either 2696 or 3794 lbs. (edmunds says one thing, and mazda says another.)

0-30 mph, sec. 3.6
0-60 mph, sec. 9.6

Is there any rough estimations between torque and weight to apply to all automatics to get acceleration?

btw- how much does a 2005 mazda3i automatic weigh?

It's got to be the 2696 number... 3794 is large sedan weight...

 

[Doboji]

and there is no one size fits all formula...

There are alot more factors beyond torque and weight.... gear ratios, turbo lag, etc

 

[Demon-Xanth]

http://www.caranddriver.com/roadtests/7566/mazda-3-page3.html <--about 3000LBs

 

[kaizersose]

there is no one size fit's all formula.

if a car was powered by an electric motor (completely flat torque curve) and you factored in every gear ratio (tranny, final drive, wheels, etc.) then it could be feasibly be done, but internal combustion engines performance changes as they move through their rpm band so sorry, no dice.

that being said, it's pretty easy to find the performace numbers of any car

 

[hoorah]

The torque number quoted is the engine torque output, which will be different than the torque output at the wheels due to the different gear ratios in the transmission and differential.

The only way to truly calculate your accelleration (on paper) would be to have the torque curve of the engine and multiply that by the gear ratio for each gear to get the torque at the wheels. Then you could calculate accelleration based on the weight of the car.

A much easier way to do this would be to take your car to the track and do a 1/4 mile run. Get your 60', 300', 660', 1320' times (and any inbetween they give you) and interpolate that to get a curve of position vs. time, then take the derivative, and take the derivative again.

 

[tfinch2]

Originally posted by: JEDI
Is there any rough estimations between torque and weight to apply to all automatics to get acceleration?

No, for a lot of the reasons mentioned, plus different cars put different amounts of power to the wheels due to powertrain loss.

 

[BD2003]

Originally posted by: Doboji
and there is no one size fits all formula...

There are alot more factors beyond torque and weight.... gear ratios, turbo lag, etc

Yep, there's also rotational weight, tire grip/resistance, wind resistance, aerodynamic coefficients, internal friction, torque curves of each particular engine etc etc...

The only one size formula you can know is all other things being equal, less weight or more torque = faster.

 

[Demon-Xanth]

Originally posted by: Doboji
and there is no one size fits all formula...

There are alot more factors beyond torque and weight.... gear ratios, turbo lag, etc

And torque CURVES make a huge difference.

Compare this:
http://www.kandn.com/dynocharts/69-1041.jpg (S2000)
With this:
http://www.kandn.com/dynocharts/57-1532.pdf (Ram Diesel)

I know it's hardly an apples to apples comparison, but it shows the difference between a flat and a peaked curve.

 

[JEDI]

Originally posted by: Demon-Xanth
http://www.caranddriver.com/roadtests/7566/mazda-3-page3.html <--about 3000LBs

Curb weight: 2957 lb

that's the for mazda3s model.. bigger engine than mine. but it's a manual, so should be lighter than an automatic?

 

[OS]

Originally posted by: Demon-Xanth

Originally posted by: Doboji
and there is no one size fits all formula...

There are alot more factors beyond torque and weight.... gear ratios, turbo lag, etc

And torque CURVES make a huge difference.

Compare this:
http://www.kandn.com/dynocharts/69-1041.jpg (S2000)
With this:
http://www.kandn.com/dynocharts/57-1532.pdf (Ram Diesel)

I know it's hardly an apples to apples comparison, but it shows the difference between a flat and a peaked curve.

heh, you could atleast compare gasoline to gasoline engines

 

[ballmode]

also gearing

 

[ijester]

You can do it from the HP ratings:


ET = ((Weight / HP)^.333) * 5.825

MPH = ((HP / Weight)^.333) * 234


Of course, this is in perfect conditions, so YMMV.

 

[Demon-Xanth]

Originally posted by: OS

Originally posted by: Demon-Xanth

Originally posted by: Doboji
and there is no one size fits all formula...

There are alot more factors beyond torque and weight.... gear ratios, turbo lag, etc

And torque CURVES make a huge difference.

Compare this:
http://www.kandn.com/dynocharts/69-1041.jpg (S2000)
With this:
http://www.kandn.com/dynocharts/57-1532.pdf (Ram Diesel)

I know it's hardly an apples to apples comparison, but it shows the difference between a flat and a peaked curve.

heh, you could atleast compare gasoline to gasoline engines

The point was to compare two different engines w/ the same HP (240 vs. 245) with wildly different torque curves (one at the top end of the spectrum and one at the bottom)

 

[LordMorpheus]

Originally posted by: Doboji

Originally posted by: JEDI
my mazda3i automatic has 150hp, 135ft-lbs torque (Max Torque: 4500 rpm), and weighs either 2696 or 3794 lbs. (edmunds says one thing, and mazda says another.)

0-30 mph, sec. 3.6
0-60 mph, sec. 9.6

Is there any rough estimations between torque and weight to apply to all automatics to get acceleration?

btw- how much does a 2005 mazda3i automatic weigh?

It's got to be the 2696 number... 3794 is large sedan weight...

my town car is ~4100 pounds - your little mazda 3 will be much less than that, so 2700 is probably the closer number, maybe 3000 with you and gasoline and some other goodies inside.

You could calculate your acceleration time, but you'd need the full power curve of the motor, all the gear ratios in the transmission, all the programmed shift points in the transmission, shift times in the transmission, etc. You can't just plug torque and weight in, there are too many other variables.