how do all you high hp cars increase the top speed of the GT?

I know the top speed varies from GT (145), Roush (150?) to the GT500 (160?) so it's not all due to lack of aero-dynamics.

How to increase the top end to 160-165 in the GT?

 

Like you said, more hp. Gearing plays a big role. Your gearing and rpms will give a theoretical top speed. The more hp you have, the closer you can get to that theorectical top speed. Less hp means you will get to the velocity where aero force against you equals your engines force (hence zero acceleration).

You can also get numerically higher gears to give your car a better torque multiplier, but this is at a cost of a lower theoretical top speed. Sometimes this result can net you a higher "real" top speed with the same engine output.

There is a point where your car's hp will exceed the high gearing and then, instead of hp being the limiting factor for top speed, the gearing becomes the limiting factor.

 

if by top speed, you mean on a track or the autobahn top speed, you first need to remove the speed limiter with a a flash tool, like the SCT XF3(what i used), and then you are just limited by 1st the amount/condition of the road in front of you, i.e. Mustangs do not like turning off camber corners in speed > 150mph!, next is the amount of grip your tires have, better tires=better turning, next is the amount of air going under your car mine gets light at ~150mph and pot holes at that speed can be very scary!. after you address that then, you run in to HP/Aerodynamics limitations of the mustang.

Keep in mind my mustang has better tires, but stock suspension and no chin spoilers and no wing/spoiler in the back (both spoilers in route now).

 

also it should be noted that I find that driving at speeds > 125MPH very tireing, you have to watch everything, all the damn cars on the road, and at that speeds braking becomes an issue. Personally i would upgrade your braking before you worry too much about going faster. Its better to out stop the car in front of you 99% of the time, then it is to out run the car in front of you. I dont know how many times i have been cut off buy cars going half my speed on the autobahn. I normally cruse at ~ 200KmPH (120mph) but at times i do go ~250KmPH (155mph) and i have been cut off by Nissan Micras and VW Polo's that are only going <120KmPH. It is times like that that having great tires/brakes and reacting to them has saved my life a lot.

 

The GT is a combination of being power- and drag (aero+rolling)- limited to mid, maybe upper 140's. At about 4700 rpm with 3.55's is where the fun stops. If you were to change the axle gears such that you hit peak power rpm (6000) at the same time that you stopped accelerating, you might be going another 5 mph. 4.30's might do this for you.

To get any more speed than that you need either quite a bit more power (properly geared) or a substantial reduction in aero drag. You'd be a bit past 6000 rpm with 4.30's at low/mid 160's, though the extra 60 - 80 hp required would be found above 6000 rpm anyway as long as the engine remains normally aspirated.


Norm

 

ah, I'll stick to acceleration and not so much top speed.

Who cares if I can go 180+ when I can go 11.2@125 in the quarter??

It bugs me when I hit top speed and the car just halts. 145 is faster then what I should be doing anyways ( empty highway). It 'feels' like it should be either building up more speed or has enough ***** to anyways. By then, with the O/D off and the 4.10s it's damn near redling so it's not like I have anymore powerband left and with only 270 whp right now, tops, it's not going to break any speed records lol.

 

It's always amusing to read comments like that, having done some mathematical simulations of acceleration. Until you get up into the last couple of mph, you simply cannot see the aerodynamic wall that's waiting for you. Only when it takes, say, a quarter to half a mile to add the next mph to the dial do you start wondering "where'd the power go", "am I going up a hill" or something similar. At that point, it's over.


Norm

 

Do you have a one piece driveshaft? If not the Oetiker clamp holding the grease in the cv joint bewtween the two shafts will come apart creating quite a show at speeds over 150mph

 

So does this mean the funky cool GT/CS hood scoop isn't gonna cut it?




jk