Thief_of_Hearts

what is the top speed on a automatic GT with 4:10s intake,tune and full exhaust?
as opposed to one with the 5 speed?


and does it begin to slow down past 120 or so? with enough power it should get right up to 155 top speed correct? not planning on topping it out or anything but not exaclty wanting for it to fall flat on it's face by 120 lol.[:'(][:'(][:'(]

Jeremy05

well i may have to step down from the 4.10 to a 373 in the 1/4mile because im hitting 123mph in 4th gear, but im really getting close to the shift point maybe 8more mph to go.

I have much faith that with your mods you can get to 155 in 5th

baha

+1, if you hit 6000rpms in 5th you'll be doing 162m/h and about 175 at 6500rpms. I'm not sure though how much power is enough to pull that

kcmarti

What formula are you using to determine top speed by rpm/gear ratio?

baha

I had my 4.10s for a month now, it did hit about 125 in 4th at more than 6k rpms but didn't go beyond that.

baha

Here:

http://www.car-videos.net/tools/speedrpm.asp

kcmarti

Nice tool, thanks. Hmmm... using that calculator, I would be doing 500RPM more at posted highway speed (65) - doesn't seem like to much more to me. I may go to4.10 instead of3.73.

Norm Peterson

It's a pretty simple one based on wheel revolutions per mile times the overall gearing. Wheel revs/mile is being estimated from the nominal tire size. The 0.965 correction is pretty close for most tires but does not consider that the actual tire dimensions are allowed to vary slightly (IOW, a 235/50-18 may actually measure something like 240 mm wide and have an actual profile a percent or two different from 50.0. You can do this by hand or generate your own very similar spreadsheet, using the tire revs per mile information for your make/model/size tire from the 'SPECS' pages at www.tirerack.com .

Keep in mind that the linked calculator providesonly theoretical numbers - if there isn't enough power at whatever rpm to push the car along at that speed, you won't get up to that speed (without tailwind or downhill assistance or some such). Nor does it consider slippage across the torque converter in automatic-tranny cars. I don't know whether a lockup converter stays locked up at those speeds or engine rpms, but if it doesn't you'll lose several mph even though you might pull the full 6000 rpm.

Estimating a real-world top speed also requires halfway decent estimates of aerodynamic and rolling drag as well as torque/horsepower curves.


Norm

Norm Peterson

While you're at it, take a look at where your upshifting is going to fall and consider that if you have any drone now it'll come in at a lower speed (mph) with the 4.10's than it does now with your 3.31's.


Norm

anteyeiabazele

does installing gears on auto transmission fu*k up ur transmision?