Hi guys I need your help directing me to a site or something to help me determine what kind of speed my car can do, or what kind of power I need to get there.

94 RX7
440 HP wheels
275/40/17 tires
6th gear final ratio is .50
Rear end is 3.90
So final drive ratio is 1.95

I would appreciate any help you can give me. I am trying to build a car that will do 180+. I know I may need aerodynamic mods, but I am trying to find out if the gearing I have will work, as well as what kind of power will be required.

Spank

 

Alrighty, I found a site to calculate speed based upon gearing and using a ZO6 as the car. Now how much power (is there a way to calculate it) will it take our 3rd gen to hit 180+

Additionally any suggestions on auro mods to keep the car stable?

Spank

 

there's a thread where somebody calculated this using simple drag calculations. What kind of tranny are you using that has a 6th gear and a ratio of .5? That's pretty insane

 

This is my street RX7 with a modified LS6 and a 6 speed with the .50 6th gear. I purchased this as well as changed the gears in the rear to 3.9 to improve milage, increase top speed, and make gears 2-3 the main gears to use in racing.

 

with a 6spd and 3.90 you should hit 180 easily but it may take a while to get there with that 6th gear ratio

 

All this stuff is in the Suspension and Handling Links sticky:

Gearing Calculator The Race Technology Gear Calculator will calculate vehicle speeds in the different gears at various engine speeds, as well as calculating the rolling circumference of the tyres and rev drops when changing gears.


Aero Drag and Rolling Resistance CalculatorThis tool will calculate the aerodynamic CD and Rolling Resistance of a vehicle by performing deceleration tests.

Gearing rarely limits top speed, horsepower does. You can gear for 200 mph but you'd never attain it. You're trying to figure top speed bass ackwards. First you must know the cD and that will dictate the amount of power needed to attain a given speed. Once you have the power you need you compute meaningful gear ratios. Even then you must realize the power of the engine is not flat through every gear so the engine must have reserve power available to pull the car up through the gears. You also need an actual dyno graph so you know true power at every RPM. Even if you have enough total power if you go too far down the curve at each gear change the engine will not be able to keep accelerating the car. Drag will overwhelm the car before the engine gets back up to peak RPM.

For instance you may find out you need 600 hp to hit 210 mph. Actually that means 600 hp to maintain 210 mph. You have to get there first and that will take more than 600 hp.

 

440 hp to the wheels in a stock geared RX-7 will already do better than 180mph.

 

The fastest i've got my 7 was 170, and it was not done. It didn't take long either. My mods were basic bolt ons; intake, exhaust, intercooler.

 

Fastest I've been was around 160, out running Alabama state trooper..
I would never do that again..

 

Did you make it?

 

100% stock except for HKS filters 265km/h and a little left under the foot (10km/h)

that's 165mph for you US guys...

 

i had a stock rx7 with intercooler and rebuilt motor...at the time i had a fuel problem with the car and it wasnt even my car...and i got it up to 150 i am sure 180 will be a cinch...my t78 rx7 could have hit 180 with out a problem...stability well thats another factor...make sure your car is lowered and you have a belly pan and any other kind of under carriage cover because you dont want any wind gusts catching an air pocket under you car and flipping you...

 

can I see pictures of this LS7 rx7 ?

 

He said LS6, the LS7 isnt released yet...Soon though.

 

Are we talking about a big block here or the new LS motors?