Top Speeds in Different Gears (6MT)

m4a1mustang

It's possible but the stock body is really slick. I don't think you'll do much better without a strong tail wind.

__________________
- Steve

Zs & Coffee - Saturdays at 10AM in Fairfax, VA and Columbia, MD (Click the banner!)
LIKE us on Facebook!

jchammond

1-35
2-55
3-85
4-125
5-158,,per speedo at 7,000rpm.
all other gears shift at 7500 in automatic.
5th is 1:1 ratio
6th-.862
7th-.771
mine will go 0-158 in 30sec. pretty fast/thinking of getting rid of the 3.36:1 pumpkin & putting a 3.69:1 from a manual car.
then
1st-32
2nd-50
3rd-79
4th-114
5th-still would speed limit at 158/but closer to 7500 redline
i never push in either 6 or 7th.

BGTV8

I have attached a zip'd XLS which will give you the numbers you want.

Plug in tyre width, section and wheel diameter and you get speed in each gear - I have arbitrarily set rpm to 7000 in all gears apart from 6th which is 6500, but you can fiddle with the values to your hearts content. Diff ratios included are 3.7 and 4.08 to 1. Just change the pinion/ring gear tooth counts for other ratios.

Vmax in my car has never exceeded 250kph (+ or - a few kph) in either 5th or 6th (at Philip Island GP Circuit which has a slightly down-hill main straight which you come onto at 180-190kph). Without a tail-wind, 5th is higher Vmax.

This thread has confused torque (which is the available force which can be applied to move/accelerate the car - i.e.: increase speed) and horsepower which the rate at which work can be done (i.e. affects max speed).

It is torque which sets the rate at which a vehicle is accelerated and hp (torque in lbs/ft x engine rpms/5252) which is doing the work of pushing the air out of the path of the accelerating vehicle and ultimately sets maximum speed - when hp and air resistance reach equilibrium. NOTE: Air-resistance varies as the square of vehicle speed - double the speed requires 4 times the power.

Gearing comes in to play as it affects the engine speed (and it is the amount of torque available at a given engine speed which determines the amount of power available to push the air out of the way of the moving vehicle bodywork).

The bottom line (depending on additional variables such as wheel drag - wider front tyres will always go a tiny bit slower that narrower tyres), is that horsepower available (given the gearing) in a 6MT and stock engine runs out somewhere around 255kph, give or take 10kph depending on relative wind-speed (tail or head-wind and how much). Ultra lo-rolling resistance tyres will improve Vmax by a few %.

In my own case, the car will run faster into T1 at PI in 5th (will pull red line give or take 100rpms) and 6th is a tad slower because of taller gearing.

If gearing is too short (higher numerical number for diff ratio) it is possible to "run out of revs" in that available power is greater than that required to push the air out of the way f the body when the engine reaches its max rpms.

Attached Files

Z34 MT6 Speed in Gears.zip (7.6 KB, 14 views)

jdsto

Its not just gearing. Gearing may give the theoretical maximum but horsepower to overcome the wind resistance becomes critical as the speed increases.

Here's the theory
Part 6: Speed and Horsepower

Which is why a Bugatti Veyron needs 1000hp to get to 250mph and a lot of space.

__________________


Gone but not forgotten

Duc_Z09

+1. At extremely high speeds you need to start adding a LOT of horsepower to go just a LITTLE faster.

__________________
2009 370z #206 (all mods are Home Depot)
2009 Ducati 848 (full Ohlins, Termignoni, etc)
2003 Grand Cherokee (long arms, big tires, 4.56, lockers)