A mate of mine has just bought a black RS4. It's superb, but he reckons it's not as quick as he thought it would be.

I remember a thread a while back in 'other marques' where someone posted up about this. A guy had his put on a rolling road and it didn't make the claimed power of 414bhp. I remember a few people posting up saying they had heard that none of them were making the claimed output.

I can't seem to find the thread now though. Any help would be appreciated.

 

https://www.scoobynet.com/other-marq...-audi-rs4.html

 

Thanks mate, but the thread I remember was a different one to this. They guy in question had had the car tested at wo different RR's and was then thinking about rejecting the car due to the fact that it wasn't making the claimed power output.

The search function on here used to be pretty good and I could find what I looking for fairly quickly, now it's just a pile of ****.

 

No it isnt. I suggested that the new 'provided by IB' seach was crap: and I was officially told that I was mistaken.

 

Not one RS4 has made the 414bhp on a RR but does it really matter - still an amazing car Surely your mate hasn't said that it's slow! Sounds a tad better than our Scoobs too I guess ...

TX.

Edit - I'm biased though as RS4 / M5 is probably the next car

 

My mates one is slightly quicker over 100mph than my 375bhp GTR despite being heavier. So it can't be far off it's claimed output.

 

I've got one, and it has just had a new map put on the ECU by Audi.

The result is a loss of midrange grunt and loss of urgency from the engine when you put your foot down.
Reading other forums suggests the upgrade has not been done properly, and it should have been reset to remove it's learnt settings.
However, I've also been told that it should adapt to my style of driving again after about two tanks of fuel.

 

Several RS4s at Bedford today and they were bloody quick!

 

If you rev them, they are bl00dy quick, and they don't hang about even if you don't.

But look at the mid-range power of a 350bhp modded scoob. It's big. And the Scoob's low weight really scores at sub-80mph. It would be really interesting if manufacturers quoted bhp at 50% of peak revs, instead of just torque. Peak power can be so misleading. Then we'd see why Scoobs are so fast across country.

Richard.

 

same with any n/a engine, you have to rev them. there not slow buy any means.

 

What did your mate drive previously? I think the way the power is delivered masks the feeling of speed. Remember, these things rev to 8200 and don't start to make decent power until about 5500rpm when they get up on the cam on the inlet port flaps/airbox flap open.

 

Old man had one. Jumping into one from a Scoob, they do instantly feel slow. No turbo whoosh......

The engine is designed to give it's power/Torque mid/high revs. Drive it hard and get the revs up, and it starts pulling like a train.

Far froma slow car.

 

How does it compare to yours - straight line, twisties? Can't think there's much in it 'til stupid speeds??
dnc

 

A mate of mine thought the same so got MTM to supercharge his.
That sorted it out.

 

All,

I've just come out of a V3 STI into the 4.2 V8 Audi S6 avant.

As others have said, the low end doesn't feel anywhere near as quick as the scoob, but once you start working the rev range, it does pull like a train all the way up.
I do think that point to point, the STI, driven well would keep up with it, but in the S6, i'd not have a broken back, not have rattled out fillings and not have neck ache!
Saying that though, having had the S6 for a little while, it does make the scoob look frugal on fuel!

Steve

 

Is he a Millionaire?! MTM upgrade is £10k+ isn't it ... might even be £20k or £30k!

TX.

Edit:

http://forums.carolinaeuros.com/inde...&mode=threaded

 

Terminator - £85k a year trust fund helps...!!

 

RS4's are heavy at 1650kg's and have just 317lb/ft @ 5000 rpm??

Could affect the performance a touch.

 

Isnt it simply the smoother power delivery of an N/A which just makes the car feel slower? I mean, you dont get the massive rush of power like you do from a turbocharged car (obviously)

And as everyone says, you need to rev an N/A to feel its power

 

As I often state:
Assuming the car has the right gear ratios to use the power, midrange torque means very little and peak power means everything. Turbo or no turbo.
Take 2 cars of the same weight but one has higher peak power but less torque, flat out racing the one with more power wins. It gets more 'energy' to the road.

You can factor weight in to help compare acceleration up to about 100mph.

Note: When not running in 'race' conditions, the car with more midrange will be quicker as the power is more accessible.

Haven't found an example yet that doesnt adhere to this.

 

One issue with some of these road going high revving engines is that the combination of wide gaps between the lower gear ratios and peak power made right up near the rev limiter is that you get a drop off in power on a gearchange.

 

Which would be faster though (RS4 or Scoob) if both had same power to weight ratio ie turbo car vs powerful n/a car? Head hurts

TX.

 

In a straight line? or on a challenging track?

 

Power to weight ratio is just one way of measuring performance. It falls down at higher speed though, as it ignores drag. If the RS4 and Scoob had the same (peak) power to weight, and the same drag (and equal gearing etc) then they would be neck and neck at the end of the strip. The big difference between these two cars is in mid-range power, and in graph form, this is revealed in the shape of the bhp curve.

NA engines tend to have a relatively flat torque curve, which means that bhp rises pretty much in line with revs, with no big peaks or troughs. Turbos, because of the nature of the way they work, tend to take a while to get going, then they blow like ****, and then they kind of choke on themselves and just can't puff any more. This means that the bhp graph is a bit 'S' shaped with low power at first, then rising steeply when the turbo gets going, before falling away quite quickly at the top.

The key to a Scoob's speed is in the mid-to-high-range and if you overlay the power graphs from say, a Scoob which produces 350bhp at the peak with an RS4 which gives 420bhp, the Scoob will be delivering significantly more bhp to the wheels at mid-range revs. That is to say, the Scoob is actually more powerful than the RS4 at all times, other than at peak revs. Combine that with quite a bit less weight and similar drag and it's no surprise that the Scoob is usefully quicker in everyday road driving, even though it might lose out in a drag race or on the track, where only peak power is used.

Back to my point about quoting bhp at 50% of peak revs, which would give an instant shortcut to this answer and would be far more revealing of everyday performance than peak bhp (for the reasons given) and torque which is actually pretty meaningless unless it is coupled to revs (when it becomes bhp of course ).

Richard.

 

Or to shorten Richards post significantly.....

Area under the curve

 

The area under the graph is not quite the full answer either. Given that the Audi has a big slug of extra headroom with an 8,250rpm redline against a typical Scoob's 7k, then the Audi is probably going to win the area contest too. It doesn't explain why, through the mid-range, the Scoob is actually putting down more bhp, so there should be no surprise that it's also faster!

Richard.

 

Not so sure about that. Sti's still rev to what 7500-7900 or thereabouts (from memory). Extra head room helps but the blown cars' line is going to be much fatter in the middle such that the overall area could be similar.

There really is no full answer unless you run a comprehensive simulation or just race the bloody things. Power, torque, tranny-losses, drag, gearing, etc are all going to play there part. Hell you could have two identical cars with equally skilled drivers but one has a clutch delay valve slowing gear changes. Multiply that little difference by the 1st-2nd, 2nd-3rd and 3rd-4th changes and you have a small difference.

I personally really want a supercharged performance car such as an Exige S with Komtech (think that's the name) 280 upgrade. Best of both worlds IMHO. I loved the purity of the F20c in the S2000 but I also loved the slam in the back from STI.

 

Thanks chaps, head still hurting though

With RS4 prices falling toward £25k ownership is a very real possibility for me however current shape M5s are also down there albeit about a year older than the RS4s so it's a tough call ... let's hope that petrol prices stay low for a few years!

TX.

 

Kenny, yes, if you're talking a high-revving STi Scoob, then this is surely the best of both worlds I should have given an example, but the kind of car I had in mind was my own UK Classic, which has a 2.5 conversion and won't rev past 7k. Mid-range is hooj though

I wonder about super-charging. What's the difference between a smaller super-charged engine and a big NA engine producing similar peak power? Isn't it effectively the same thing, with an idenitically shaped power curve, given the linear nature of supercharging that is directly tied to revs? I would expect the mid-range to be very similar, and the SC motor would not have the big turbo bulge. Isn't it just a cheap way of bolting on power? (Not that there's anything wrong with that.) Just guessing on this though.

TX, yes you'd better hope that fuel prices stay low. The S4 I've just bought is worse than I had hoped. If I drive it at the same speed as my Scoob, which is hardly frugal, I'm never going to get it out of the teens It does seem to run on 95RON okay though, which I'm suspect an RS4 will not take to so readily.

But you're right on prices. Big petrol cars are still falling, even if (as others claim on another thread) that prices have stabilised on most models. The RS4 dipped to £29k pre-Xmas and hit £27k a couple of weeks ago. Now £26k I notice on AT. I think it will be March before the season picks things up.

Richard.

 

I couldn't really say for sure to be honest as I've not researched s/c that much. The only s/c car I've driven is my auties Mini Cooper S and you can definitely tell the induction is forced. It's just got that 'fat' feeling to the acceleration but it's more linear than a turbo. I suppose it feels a lot like a big cc n/a engine, powerful, torque...but linear.