SCANS AutoBild Sportscars - Audi S4 vs. BMW 335i, Mercedes C350 & Volkswagen CC 3.6

Assuming a fixed percentage parasitic losses to derive the engine output has led to numerous people deducing the wrong engine output.
The parasitic loss is a fixed torque loss through the tyranny ie you have to calculate this loss and add it to the wheel torque to ascertain what your engine output is.
To elucidate what I am saying, if you measure torque at the wheel to be 100 ft.lbs:

• using a fixed percentage loss of 20% will give you engine output of 125 ft.lbs at that rpm

• applying a fixed torque loss of 20ft.lbs will give you an engine output of 120 ft.lbs at that rpm.

Let us now tune that engine such that we now have 150ft.lbs of torque at the wheel, then
applying a fixed percentage of 20% parasitic losses will falsely give us an engine output of 188 ft.lbs at that rpm.
applying a fixed torque loss of 20 ft.lbs will give us an engine output of 170ft.lbs of torque at that rpm.
Torque loss is a function of mass,rpm,diameter,friction.

The question then is how do we know what the torque loss is since dynometers measure the torque at the wheel?
Well, you take what the torque from the manufacturer's torque-curve and subtract your dyno torque from it reading off the rpm abscissa. The difference is your total torque loss through the system.

So chonkoa, in S4 putting 333whp, what does it put at crank?

Here's a typical S4 dyno graph.



300hp at the wheel with an estimated 360hp at the crank over 2 runs shown.

I can't find a link to the 330whp but after doing quite a few searches the 300whp seem to be typical for the car so best ignore the other as either a one off or a misprint that has done the Internet rounds.

Well if the N55 puts a average of 280whp and the 335i weights much less than the S4, BMW should be embarassed. Only 20whp more get's to wheels on the S4.

embarassed by what exactly?

It is a big gap but 122hp is just over a third of the S4's 333hp, given that the 2.0T has a third smaller capacity this is not entirely unreasonable. That said, the 2.0T needs a bump to around 245hp if it wants to even get close to the 328i imo. If the BMW 3.0 335i output had the same specific power as the 2.0 328i, then the 335i would be running around 368hp instead of 306hp. The 335i needs more power to distinguish itself from the excellent and lighter 328i.

Yes, the 328i won easily

Mainly for being almost 2sec slower to 200. And more than a second on hockeinring with only 2.6km. Should be much closer to the S4.

^ It almost sounds like in your opinion BMW have somehow failed this time round instead of accepting that the S4 is exceedingly good.

Well, it would be hard not to share his opinion. Almost 2 seconds to 200km/h is A LOT in that category.

Not to mention Mercedes C350. Ok it's NA, but jeezuz.

Yeah, they should make something like they did with B7. The A4 DTM B7 had 220hp, +20hp on the normal 2.0T.


So they should do a tuned DTM version that would put out 240hp. That would give the 328 a match. But for now, there is no match. Not with 211hp.

Yeah. As I mentioned before, its a great looking car... But the engine...? What is going on there? Embarssed by even the CC. (which nobody cares about here hehe)

which is suppose to be faster than 335. You are not saying that audi should be embarassed because s4 will be slower than new m3? s4 should be more sporty and faster than 335, thats why it cost more

Embarrassed? Just like 328i is quicker than a 211 hp Audi. Does this mean Audi should be embarrassed?

The S4 only puts 300whp on average. Is supposed to be faster but the difference is big, considering the weight the S4 carries. Don't know if the ZF8P gearbox affect the outcome too much but BMW should come with a faster 335i.

Just Me. Of course, Audi has to do best.

In your country you mean..........see the argument is all relative.

It would have been silly to expect the 335i quicker in acceleration compared to the S4 since the older E90 couldn't do it and really very little had changed between these two (E90 vs F30) apart from a different gearbox, weight had for the most part remained unchanged as is the engine...........on the track now that's a different matter cause it's an entirely new chassis that stiffer, here I expected the 335i to have been much closer.

This just shows how the range of these two model differ so much, performance for the most part doesn't pair up though I do feel Audi needs to pull it's finger out and up the power of it's 2.0L engines both petrol and diesel.

In my country the S4 costs 79.753,85€ and the 335i F30 costs 61.025,08€

maybe because 335 doesnt have m pack so its suspension is probably nowhere near sporty as s4's. you guys make such a big deal of this, it is how its suppossed to be, s4 has always been faster than 335i's hasnt it?

This is totally wrong. The S4 competes straight to the 335 and the M3 competes with the RS4/RS5. If you thing different, you are very wrong.

Is it a stock engine? I doubt with the above number.
When was the dynometer last calibrated and is it calibrated properly?

Let us assume 333whp is correct, you are still going to be wrong applying a fixed percentage parasitic loss, to ascertain the engine output you will have add total losses to what is measured at the wheels.