Top speed on the B7.

[quattrosteph]

What is the top speed on a B7 with the limiter and without limiter?

[wellzieRS4]

ive had 170

[sonny]

I think I answered this on another forum. But will post again. I saw 180mph on speedo, so that's around 173ish GPS.

MRC had run bottomed out RS4s at 193 due tot he limitations of the 6th gear.

So for me, 180 speedo, limiter removed.

[PetrolDave]

What is the top speed on a B7 with the limiter and without limiter?

quattro gmbh do not carefully calibrate the 155 limiter, in reality many people have reported seeing a GPS verified 168 with the limiter.

[S4Player]

193 car won't go any faster until there's a new 6th gear made which is in the pipeline

[PetrolDave]

until there's a new 6th gear made which is in the pipeline

Will that give a higher mph per 1000rpm? Even a standard RS4 needs a higher 6th IMHO (or a 7th gear).

[Brooner]

Possibly why the RS5 has 7 gears?? wonder what that would be flat out?

[ArthurPE]

imo top speed is limited by drag and power ~ 180-185
a different gear won't help...the car is drag limited....at peak power ~7500 rpm...you have less power >7500

180+ is pretty fast though

[S4Player]

Sorry Arthur as much as always agree with most of your opinions I feel your wrong here reason being I look at my s4 on a standard box it will run 191 tops but with a modified 6th it will run 215 on a long enough strip. So if we modify a b7 box 6th ofcourse It will run more than 193 it will top 200mph

[S4Player]

Also your 180-185 is wrong I've all ready had mine at 193mph

[ArthurPE]

7500 is ~ 180-185 mph
power decreases after that, so you will go slower...you hit the 'wall'

now lets look at the thrust
torque = 5252/7500 x 420 ~ 295 lb ft
at the wheels ~ 295 x 4.11 x 0.78 / 1.08 ~ 870 lb (force)
now let's say you change the 6th to 0.72 from 0.78, in theory you should move 7500 rpm to 0.78/.72 x 185 ~ 200
but now you have only 295 x 4.11 x 0.78 x / 1.08 ~ 808 lb (force)...you can't go faster with less force
this does not factor driveline loss, friction or slip for tires, drag

in fact some cars go faster in 5th than 6th becasue of this
here's a pretty good calculator...the 60-120 times are spot on to the magazine tests...
I entered the RS4 specs, top speed ~185 (not sure if tire slip is factored 2-3% loss)

give it a shot http://vlsicad.ucsd.edu/~sharma/Potpourri/perf_est.html

a car with stock gearing that can move the HP peak up the power band a few hundred rpm could get another 3-4% speed 5 mph or so...

[ArthurPE]

another way to look at it power required = power loss drag + power loss friction + power req to accel (we can ignore accel since we are a constant top speed...)
this by no means is exact, but close for order of magnitude evaluation, std equations Bosch and others...pretty typical

speed = v = 180 mph
wt ~ 4100 ~ 3900 + some stuff (like the driver)

HP drag = v^3 x Cd x A /151130 = 180^3 x 0.31 x 23.36 / 151130 ~ 280 HP (the Cd and A are from the sportauto supertest)
HP friction = 0.015 x wt x v / 375 ~ 0.015 x 4100 x 180 / 375 ~ 30

total 310 HP....and this is pretty close to what a healthy RS4 will deliver to the wheels on a dyno

190 mph ~ 360 wHP

[S4Player]

My car was supercharged at the time so that would have played a factor surely

[ArthurPE]

8000 rpm w/3% slip is 187 mph with stock gearing

gents, 180+ mph is fast...a 997 Turbo can 'only' do 192-193 (as verified in several tests)...it has much more torque...

I'd be content with being able to cruise 140-150 range without fear of loss of life (due to a stupid driver) or license...


the oem tire is rated Y or 300 km/hr ~ 186 mph,,,,Audi would not put a tire on the car lower than it's unrestricted top spped...
not that you could sustain that speed for long...
there are higher ratings (Y) in parenthesis is rated in excess of 186

[ShaneyB]

183 on GPS and ran out of road.

No limiter.