Another dissapointing tear up

[lengster1]

Perhaps if you saw the ducting and system you would understand why it only works well force fed at high speed.The frontal area of an rs4 is very limited spacewise and getting good supply of cold induction air from the front of the car requires an auxilary rad to be removed to achieve this,perhaps this is something audi could not do as they have to build a car suitable for warmer climates than ours and cope under all conditions.I dont think its all about airflow if i remember correctly the cam timing etc is backed off also until over 5k in third also?? Perhaps Doug will be along and clarify?

[lengster1]

You could be on to something there icecoffee regarding the R8,audi are very aware of marketing and to offer a saloon or avant with the same perfomance would take some justifying to a potential R8 owner that was about to part with an additional 30-40k just for a different shape car? You are also quite correct in questioning why its not just 1st gear thats limitited if its to protect the drivetrain from abuse/launches.

[adsgreen]

No reason for a completely different gearbox - you could run the rs4 system and then modify the prop shaft output accordingly. I'd be surprised I'd the internals and fundamentals were that different.

I don't see Amy airflow reason why you'd bother restricting it. After all it's n/a so it's only going to take a given amount of air (ram effect (and it's not that much in comparison) aside). It's not going to take too much air.

Protecting the drive train could be valid but as above - why bother after 1st maybe 2nd gear?
R8 is a fair bit lighter so could argue that it doesn't need it.

But I agree with marketing- no different to the Porsche cayman. It could easily be a 911 beater but that sets out the wrong image. Audi are getting a bit of bashing with the rs3 and rs-tt eclipsing the far more expensive r8.

As for r8 in the wet - mid mounted cars even when 4wd are bloody tricky in the wet. The rs4's weight distribution and (iirc) narrower tyres work better in those circumstances.

[ArthurPE]

really? or are you saying the engines are entirely different? apples to oranges?
T = Displac x Cr x VolEff / 4Pi

P = T x w (w = 2Pi x rev/sec)
power is a measure of T over rotational freq
knowing T you know how much force the engine can deliver
knowing power alone you don't you need rpm

there is a reason the GTr (and others) use turbo's to boost low end torque and sacrifice hi end power/rpm
RS4 peak at 7800, GTr at 6500....which is faster?

nothing can be said with any certainty regarding 100 lb ft at 1000 rpm vs 100 at 8000...absolutley no conclusion can be draw...especially if you are saying they are entirely different engine configuration (Cr, stroke, bore, etc.)

as far as the primary variable: one is instantaneous force, the other is the measure of said force over distance/time
a better example is 100 lb ft from 4000 to 8000 rpm or 110 over 5000 to 7000 useable range
the 110 makes more power at any given point, which will be faster for a given weight?

Big assumption that the 1k engine can rev as high as the 8k one - That was the point I was trying to make. Different engines, same torque but completely different outcomes.

Take a waterwheel - thousands of lb ft/torque but spins at 0.5 rpm so relatively low power.
At the end of the day high power is what counts as with that you can apply whatever gearing you want to get the required result post gearing. High torque without the rpm to make it produce enough work means you need to run long gearing - take a look at older diesels. Lots of torque just no power. Conversely the first thing you do when you have a high revving power plant is to fit a close ratio gearbox.

So the result is saying that one car has more low down torque than another doesn't mean squat on it's own. Our cars have more low down torque than a f1 car. A truck has more low down torque than ours. So what? The only time it makes any sense is if you a comparing like with like.

Finally - I really don't get the obsession with primary variables? So what if torque can be measured on it's own? Doesn't make it so important to the point of discounting everything else. It's no different to area as measure- just because its derived from length and width doesn't make it useful.

[ArthurPE]

1) who says they do?

at 2500 you only need 1/3 the air that you do at 7500
but you have 1/2 the throttle, so you have more air than you need to make max torque
they do it to increase air velocity and obtain better mixing and faster cylinder filling

2) better, more efficient dual intake system, each can be sized for a better velocity/volume efficiency or compromise
the RS4 single set-up must do both, so at low speed they optimize it by restricting throttle area

3) the peak torque rating of the engine is at 5500, but <5500 it makes the peak the engine is capable of, ~90% of the maximum (which occurs ~5500)

I have 3 questions relating to the above statement
1) If limiting the airflow does not restrict torque, then how are audi using it to protect the powertrain (ie what is it protecting the powertrain from) ?
2) how come the R8 (with our engine) does not need to do this
3) If we can make peak torque sub 5K rpm then howcome I have never seen that on any of the DYNO graphs, (it always appears above 5K RPM)

[P_G]

Torque limiters would surely be there to protect the clutch, gearbox and transmission from agreesive launches as said, not for marketing purposes.

If that were true it would only be needed in 1st (like the old cavalier and calibra turbos used to do)

Not necessarily, with the gearing in the first three beig fairly short if you are launching and then doing rapid changes dumping the clutch on each one can you imagine the torque being put through the trasmission and gearbox doing this. Forces in longer gearing isn't near the same so no need for limiter

[PetrolDave]

The Vauxhall 1.6 16v engine was designed by Cosworth

Since I was working at the company that developed this engine at the time it was being developed, I can say with confidence that the 1.6 16V (and the 1.4 16V) were NOT developed by Cosworth. The previous generation 2.0 16V engine WAS developed by Cosworth (and the head was manufactured using their thin wall casting process), and a damn fine engine it was too (I had several Vauxhall Astra GTEs with that engine as my company cars while at Lotus).

The 1.4 16v and 16.16v were developed by Lotus Engineering, and were an evolution of the engine that had previously been developed for Daewoo.

I owned a Vauxhall Corsa GSi for several years that used the 1.6 16v engine, one of the reasons for choosing that model was that I knew the engine's "foibles".

[moto15]

As intersting as this all is at the end of the day he got beat, in real world driving conditions he got beat, pisses us all off but the facts remain why oh why does Audi only give us full power over 100 mph, so how do i get full power? being a newbie i want to correct this fatal flaw on my car

[adsgreen]

really? or are you saying the engines are entirely different? apples to oranges?
there is a reason the GTr (and others) use turbo's to boost low end torque and sacrifice hi end power/rpm
RS4 peak at 7800, GTr at 6500....which is faster?

Making a n/a engine that meets emissions and endurance regs whilst producing 500+ bhp is very very expensive and leads to large capacity engines into the realms of the exotic. Turbos provide a very efficient method of solving many problems - low end torque is a secondary consideration rather than the overriding factor.
Don't get me wrong - I'm not anti forced induction (my 'ole lotus 211 is supercharged and gives gtr's a good run for their money) but n/a's need to rev and the low down torque of f/I does mask instances of being in the wrong gear.

nothing can be said with any certainty regarding 100 lb ft at 1000 rpm vs 100 at 8000...absolutley no conclusion can be draw...especially if you are saying they are entirely different engine configuration (Cr, stroke, bore, etc.)

that sounds like youre saying you can't compare two engines unless identical... I don't think that's what you mean but to say that you can't draw an outline conclusion withtwo engines producing the same torque but one redlines 8 times higher is a bit... Well, worrying.

as far as the primary variable: one is instantaneous force, the other is the measure of said force over distance/time
a better example is 100 lb ft from 4000 to 8000 rpm or 110 over 5000 to 7000 useable range
the 110 makes more power at any given point, which will be faster for a given weight?

That's the point I've been trying to make.
100 x 4000 / 5250 = 76
100 x 5000 / 5250 = 95
100 x 6000 / 5250 = 114
100 x 7000 / 5250 = 133
100 x 8000 / 5250 = 152

110 x 5000 / 5250 = 104
110 x 6000 / 5250 = 125
110 x 7000 / 5250 = 146

So yes, whilst the more torquier car initially pulls away the other will catch it. Assume same gearing and weight then the first car will murder the other after the first gear change. Add in a cr gearbox then you could have the same road speed change points for each car but the more powerful one with shorter gearing will more than make up for the lack of torque output.
To put this into reality I had a car built by a motorsport division and it had over twice the power as the standard car and was slower when compared with other cars (didn't sort itself out until 4k rpm and only really got on the boil above 5) Right up to the first gear change. On track it just dissappeard into the distance.

Interestingly this car also illustrates the over airing point you're making (I'd forgotten about that). if you floored it out of the power band below 3k (good ole manual tb) you'd actually bog down and have less performance. You had to progressively apply the throttle until then using the engine pitch to gauge how much you could use. That car only had one wild cam with no variable valve tech so surprised something as advanced as BNS unit suffers the same but hey... Can't change physics.

[Shadow6ix]

The R8 is supposed to be a super car, despite the differing demographic it is not cool when it's common knowledge that a much cheaper estate in the same family can keep up with you.

Buyers are looking at the stats on paper R8 4.3 to 60 rs4 4.9/4.8 to 60 (you pay the extra for the exclusivity in performance)

Is it likely that an RS4 will go much quicker to 60 than an RS6 just because the torque is capped a little? Paper figure for RS6 (and now RS3 as well) is 4.6. I still don't buy the marketing thing, not for such different cars. The R8 is getting on for 200kg lighter than an RS4. It'll go faster all day.

[wrekka]

As intersting as this all is at the end of the day he got beat, in real world driving conditions he got beat, pisses us all off but the facts remain why oh why does Audi only give us full power over 100 mph, so how do i get full power? being a newbie i want to correct this fatal flaw on my car

A trip to MRC to get the car mapped. You can ask them to map out the torque limiter in the first 3 gears. Is something i'll be doing in the not too distant future!!

[adsgreen]

0-60 always comes down to how good and brave/stupid you are with the mechanicals (it's why I hate it as a metric).
4wd is especially hard to launch as the clutch takes a battering. My 211 manual advises to dial in 7k rpm to the launch control in the dry - figure something similar for the rs4 to get down to the 4.8's.
Iirc rs3/tt-rs is flappy paddle dsg so some of the guesswork taken out. For a 0-60 run it does shave a couple tenths off (although I do recall reading the manual e90 m3 being quicker off the line than the dsg version).
Rs6 is auto and these a much more consistent to launch - the torque converter acts as a damper so a smoother launch.
Gtr obviously has a very effective launch control to compliment it's already formidable armoury.

[ArthurPE]

why torque is used and not power

engine crank/tranny input = 5252 rpm, 200 lb ft, 200 HP
(always equal at 5252 since P = rpm/5252 x T, 5252 = 550 ft lb/sec (or 1 HP) x 60 sec/min / 2Pi rad/rev)
tranny out 2:1 ratio = 2626, 400 lb ft, HP = 2626/5252 x 400 = 200 HP, the same (gears multiply torque not power)
but obviously 400 lb ft will yield more thrust than 200 at a 1' radius, 400 lb (force) vs 200
twice the force ~ twice the accel since a = F/m for a constant mass, but yet, the power is the same...

[adsgreen]

Yes but when in the real world and considering actual road speed a 2:1 gearing would mean initial acceleration followed by a gearchange twice as quick. Net result would mean both cars accelerate the same.

Another way of expressing your scenario would be to have both cars fitted with cvt gearboxes but one has road wheels half the diameter than the other. Whilst yes if both cars at the same gear ratio the smaller wheels yields more force the issue is that when the system is run over a time period the cvt of the smaller car will always be twice the ratio of the larger wheel car for a given speed. Thus acceleration is the same for both cars.

Consider what would happen in a series hybrid - electric motors produce full and constant torque from zero so if you use the engine as a generator power is everything. Sure you could have a slow revving torque engine or a fast screws ing engine - really doesn't matter it's just how much energy they can put into the system. It's one reason why Australia use kilowatts as a measure instead of bhp - it's something that makes sense to people straight away.

[Ice_Coffee]

As intersting as this all is at the end of the day he got beat, in real world driving conditions he got beat, pisses us all off but the facts remain why oh why does Audi only give us full power over 100 mph, so how do i get full power? being a newbie i want to correct this fatal flaw on my car

I wasn't beaten by a 2.0, that would be preposterous, (unless it was heavily modified) , I just wasn't leaving it for dead.