Dyno Bullshit!!

[ArthurPE]

60ft and trap speeds are the best metrics and NEVER lie.

amen

with awd the 60' can be skewed a bit, imho

the RS4 is very heavy, cars in the States weigh ~4000 lb

[Contigo]

I honestly don't thik that the stock B7 performs like a 414bhp car though in the real world. I've owned a B7 and driven a Cab for months and it felt down on horses. The stock B5 at 380 felt right and my remapped B5 will embarrass a stock B7.

I ain't in here to troll,. 'm relating to whaty W8PMC said that it's all about how they drive in the real world and for me it's a bit of a let down. The fact that these cars don't make the quoted manufacturers claimed BHP output does not surprise me in the sligtest.

I've been in Jims car and that now feels how mine should have been from Audi so something is amiss.

I totally disagree, my car feels full of it's claimed 420+BHP. Your car may be a bit or alot slower than mine, infact yours is a cab so it will be slower as it's around 200KG heavier than mine.

Without raising the Cab/Avant/Saloon debate, the saloon is the lightest of the 3 bodies by a fair margin, with the Avant next & Cab the heaviest. They all have the same Audi claimed power output of 414, so it's safe to assume with the same driver/conditions that the Saloon will feel closer to it's output, followed by the Avant & then the Cab.

Power & wieght will always be the biggest contributors.

Look at the stats. An E60 M5 claims the same 0-60 time as the B7 RS4 saloon, however it's 100BHP more powerful, but weighs around 300KG more. The C5 RS6 posts the same 0-60 time as the B7 RS4, but is 170BHP more powerful, however a phat 1/2ton heavier.

I've not to the cab, I've driven the cab for months and yes the weight is definitely a factor. All I'm saying is that I reckon the B7 is down on power and something isn't right. Jim's car now feels bang on.

[lengster1]

b7s are straight line slower than b5 but point to point the b7 is very very impressive.

[rjkflyer]

So, here's a view. What max speeds have you seen an unrestricted B7 RS4 do, under cool conditions????

Maximum drag-limited top speed is about the best indication of a car's power to the wheels.

At drag-limited speed ( zero acceleration), we can calculate that Vmax = 53 * cube root (Power at wheels / Cd.a) where Power = SAE hp, and Cd.A in foot sq.

So, for a RS4, where power at wheels should be ca. 80% of engine output = 414 * 0.8 = 331 hp, and Cd.A = 0.34 * 22 = 7.48 ft sq.

Vmax = 53 * cube root (331/7.48) = 187 mph

Now correct for rolling resistance, which is ca. 3% for tyres on asphalt, so Vmax = 181mph.

As another example, the 3.2 A4Q will JUST about get to the limiter (155mph). Trust me.

Let's see: Vmax = 0.97 * 53 * cube root (0.8 * 265)/(7.5) = 156mph. Correct.

All at 65 deg F and 990 mb (oddly SAE hp seems to be at that pressure).

[ArthurPE]

So, here's a view. What max speeds have you seen an unrestricted B7 RS4 do, under cool conditions????

Maximum drag-limited top speed is about the best indication of a car's power to the wheels.

At drag-limited speed ( zero acceleration), we can calculate that Vmax = 53 * cube root (Power at wheels / Cd.a) where Power = SAE hp, and Cd.A in foot sq.

So, for a RS4, where power at wheels should be ca. 80% of engine output = 414 * 0.8 = 331 hp, and Cd.A = 0.34 * 22 = 7.48 ft sq.

Vmax = 53 * cube root (331/7.48) = 187 mph

Now correct for rolling resistance, which is ca. 3% for tyres on asphalt, so Vmax = 181mph.

As another example, the 3.2 A4Q will JUST about get to the limiter (155mph). Trust me.

Let's see: Vmax = 0.97 * 53 * cube root (0.8 * 265)/(7.5) = 156mph. Correct.

All at 65 deg F and 990 mb (oddly SAE hp seems to be at that pressure).

great post & logic...

my bet is a stock RS4 tops out ~185

is the RS4 drag or gearing limited?

did you get A and Cd from sportAuto?

time to google and youtube

[SR71]

I think we're talking at cross-purposes here...

We can all make up our own minds about whether the cars produce the Audi quoted figures, but the real question is why the variance?

We have a 20% spread on cars with no VAGCOM faults thrown up.

Now if someone can confirm that the difference between running 275/30's at 25psi and 255/35's at 50psi is 40hp, then we know the answer.

Conversely, if someone can confirm that the TC was switched off on all cars prior to running, we know that there is a good chance the EDL isn't screwing with things.

Similarly, if the power flap which comes online @ >5000 rpm is f**ked on some cars (MacRS4 & Klauster?), then effectively isn't the mass flow rate choked and power will be down?

I have to say I find the RS4 study guide ambiguous because to my mind the RS4 does not have a variable intake manifold, yet the text makes reference to a "intake manifold changeover valve"...

[caldy]

Aaaah but it does - 1 per bank. Surely this refers to the vacuum operated valves which open/close the vanes in the inlet manifold?

[Gazzer68]

I think we're talking at cross-purposes here...

We can all make up our own minds about whether the cars produce the Audi quoted figures, but the real question is why the variance?

We have a 20% spread on cars with no VAGCOM faults thrown up.

Now if someone can confirm that the difference between running 275/30's at 25psi and 255/35's at 50psi is 40hp, then we know the answer.

Conversely, if someone can confirm that the TC was switched off on all cars prior to running, we know that there is a good chance the EDL isn't screwing with things.

Similarly, if the power flap which comes online @ >5000 rpm is f**ked on some cars (MacRS4 & Klauster?), then effectively isn't the mass flow rate choked and power will be down?

I have to say I find the RS4 study guide ambiguous because to my mind the RS4 does not have a variable intake manifold, yet the text makes reference to a "intake manifold changeover valve"...

Just ran some vagcom logs on my car....
Reports my air intake power flap is not opening at 5000rpm
my vagcom results, best so far with esp off and s button on....
1/4 mile 13.3 @104mph
weight 4221
calculate this with a hp calculator (dragtimes.com)
equates to 362.59 bhp at flywheel !
tyres at f41 r38 checked today at cold
(car produced 343hp at paramount)

Also you CANNOT switch off EDL, it do's NOT switch off with the ESP

[ArthurPE]

using the same calculator with 4200 and 108 yeilds 413 HP...

sounds like you found your problem, the intake flap..
dosn't that set a check light or code?

for reference mine comes up with 370 HP using 4220 and 104

[SR71]

caldy,

But those vanes are there to introduce "swirl/tumble" for the purposes of operating in stratified mode correct?

Like here: http://sankaranv.blogspot.com/2009/01/f ... ction.html

I can't understand how the action of these vanes "shortens" the intake path?

They're not responsible for acoustic tuning of the manifold from a performance point of view are they?

Gazzer,

How do you get 4221lbs?!

The saloon weighs 1650kg, so with me onboard, I'd be looking at ~1750kg or ~3900lbs...

PS: I know you can't switch off the EDL (or for that matter the ESP - the system as I understand it will re-activate if limits are exceeded regardless of switch position), but it stands to reason that for comparison purposes all the cars should have been run with either TC on or off. How that actually affects the ABS, TC, EBD & EDL is anyones guess...

[SR71]

http://www.stealth316.com/2-calc-hp-et-mph.htm

[ArthurPE]

caldy,

But those vanes are there to introduce "swirl/tumble" for the purposes of operating in stratified mode correct?

Like here: http://sankaranv.blogspot.com/2009/01/f ... ction.html

I can't understand how the action of these vanes "shortens" the intake path?

They're not responsible for acoustic tuning of the manifold from a performance point of view are they?

Gazzer,

How do you get 4221lbs?!

The saloon weighs 1650kg, so with me onboard, I'd be looking at ~1750kg or ~3900lbs...

I'm not sure of euro wts, but every US test had the curb wt close to 4000, Audi specs it at 3957...not sure of fuel load...

intake path: depends
if the 'flap' acts as a baffle, doesn't the path the air has to travel become longer to circumvent it?

we use this in treating wastewater, we add baffles to the tank, so the water has to travel a longer path to achieve longer chlorine contact time to kill the bacteria...

[ArthurPE]

http://www.stealth316.com/2-calc-hp-et-mph.htm

that's the best set of equations around...nice
it's the one I use

[Gazzer68]

caldy,

But those vanes are there to introduce "swirl/tumble" for the purposes of operating in stratified mode correct?

Like here: http://sankaranv.blogspot.com/2009/01/f ... ction.html

I can't understand how the action of these vanes "shortens" the intake path?

They're not responsible for acoustic tuning of the manifold from a performance point of view are they?

Gazzer,

How do you get 4221lbs?!

The saloon weighs 1650kg, so with me onboard, I'd be looking at ~1750kg or ~3900lbs...

PS: I know you can't switch off the EDL (or for that matter the ESP - the system as I understand it will re-activate if limits are exceeded regardless of switch position), but it stands to reason that for comparison purposes all the cars should have been run with either TC on or off. How that actually affects the ABS, TC, EBD & EDL is anyones guess...

Yep sorry got that wrong...

Kerb weight avant 1845kg(4068.2pounds) + my weight 16.5 stones (231pounds) + guess of additional stuff in the car (20pounds)
Recalculate = 371hp
i will take the car up my mates weighbridge and get an accurate figure this week.

Arthur, No lights or codes apart from 1 (See Vagcom subject)

[duud40]

It`s still guesstimation people, stop grasping at straws. Are drivetrain losses linear with rpm ? linear with speed maybe? obviously not. Stop torturing yourselves with this , it`s also bothering me but there is simply no other solution to knowing engine hp than taking the engine out and puting it on an engine dyno .