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This article was first published in 2000.
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I noticed the other day that it's just on nine months since I bought my 1995 Audi S4.... time flies when you're having fun. A purchase that involved a lot of work (see "The Audi S4"), it was also in many ways a jump into the dark - abandoning the Japanese (and Japanese-powered) cars that I'd then owned for many years, in favour of a return to the Europeans.
And am I happy with it? I sure am, but - as with all cars - it has both good and bad points. However there are a lot more entries on the credit side of the ledger than in the debits column. Firstly, there's that engine. It's probably the most unique turbo engine in the world for its combination of performance and specification; as a result, it's also one of relevance to anyone interested in turbo machinery.
The Engine
The in-line 2256cc five cylinder has a compression ratio of 9.3:1 - unbelievably high for a turbo engine - and if that's not enough, the standard boost provided by the single KKK turbo can soar to 1 Bar (14.5 psi)! The narrow DOHC alloy head sits atop a long stroke iron block, with the Bosch Motronic management including cylinder selective knock control and direct-fire ignition. The engine will rev cleanly to the cut at 7500 rpm, but the peak power of 169kW is developed at 5900 rpm and peak torque (a massive 380Nm) is achieved at just 2100 rpm.
That 380Nm torque figure is enabled only when the electronic boost control (working with a large external wastegate) allows the boost pressure to rise to 1 Bar - normally, it's about 0.7 Bar and then the max torque is 350Nm at 1950 rpm. And how is the higher boost setting enabled? Interestingly, the higher boost level comes into play only when the throttle is absolutely floored. If the engine revs are within the right window, the boost then rises to that next level. This method of boost control - keep it relatively low unless the driver is actually demanding full power - has two on-road effects.
Firstly, it probably saves fuel and reduces emissions, because the driver doesn't venture deep into boost unless they deliberately want to do so. (And that is quite different to other turbo cars, where often the driver uses a large throttle opening, gradually pulling it back as he or she gets more power than they really wanted - the so-called elastic throttle scenario.) Secondly - and it's a purely psychological plus - when you're really going for it, the turbo develops a much more serious shriek, the nose of the car rises, and suddenly you're being pushed hard down the road! It's addictive.
With this level of boost and such a high compression ratio, you'd expect the intercooler to be huge. And you'd be wrong. Like a Subaru, the Audi's engine is mounted longitudinally, with the gearbox behind it. To allow the front driveshafts to have as little angularity as possible, the complete engine is then hung out in front of the axle line. And what's that got to do with an intercooler? By the time you place a radiator and air con condensor in front of the engine, there's no room for an intercooler in the nose as well. Instead, it's tucked low down on the left side of the car, positioned almost parallel with the ground and located in front of the wheel. The lower grille beneath the bumper feeds the intercooler on one side of the car and an engine oil cooler on the other.
So with a small (but very thick) intercooler located in such an apparently poor place, and with the boost sometimes so high, what's the intake air temp like? Constantly measured and displayed with the AutoSpeed LCD thermocouple meter ("TempScreen: Part 1, Installing the Intake Air Temp Probe"), it's generally about 10 degrees above ambient in normal city traffic. I've never seen more than 20 degrees C above ambient, even straight after a heavy boost event. (During the boost period itself, the temp stays quite low.) So one of my main concerns about the car was quickly dispelled - it wasn't going to be running ballistic intake air temps.
In the driving, the most amazing characteristic of the engine is its torque. I was actually tempted to write this article as a discussion of power and torque - using the Audi as the example - so forgive me if I venture into some of that territory. As you probably know, torque multiplied by rpm is power. So, to say that the Audi's engine has a mind-boggling amount of torque - considering its modest 2.2 litre capacity - is simply another way of saying that its low-down power is excellent. (Incidentally, since I haven't yet mentioned actual performance, the Audi gets to 100 km/h in 6.8 seconds and has a top end of 244 km/h.)
The engine simply has an incredible degree of flexibility. Yeah, yeah, yeah, you might be saying - but isn't 380Nm/169kW only about the same as a 4 litre XR6 Falcon (the XR6's got 374Nm/172kW)? Aaah, but here's my point. The XR6's peak torque of 374Nm occurs at 3500 rpm - the Audi's is happening no less than 1400 rpm lower in the rev range! The Falcon's 172kW occurs at 5000 rpm, the Audi's 169kW is 900 rpm higher at 5900 rpm. So while the maxima are similar between the two engines, the Audi's average power is just heaps more.
I'll say that again because lots of people don't even realise that it's possible - the turbo 5 cylinder 2.2 litre Audi has far more bottom-end torque than a variable cam timed, naturally aspirated six which is over 80 per cent bigger in swept capacity! (The Audi's peak torque also occurs over 1000 rpm lower in the rev range than the supercharged Holden 3.8 litre V6....)
And how does it compare with other hi-tech turbo engines? There's obviously no other 2.2 litre turbo five cylinder engines to look at, so how about the current Saab Aero, with its 2.3 litre turbo four? The Saab's figures show 169kW at 5500 rpm and 350Nm at 1900 rpm - pretty damn close to the Audi, before the Audi's overboost comes in, anyway. But what about when the Audi's compared with a twin turbo six - surely that engine configuration would have better bottom end grunt, wouldn't it? The R32 GT-R Skyline has 355Nm at 4400 rpm and (probably a lot more than) 205kW at 6800 rpm. So the Audi's developing the pretty well the same torque as the GT-R no less than 2450 rpm lower in the rev range, and then (in over-boost mode) goes on to develop another 25Nm! (However, the GT-R's RB26DETT has of course far better top-end power.) And, out of interest, how does the Audi compare with the current twin turbo V6 Audi S4? The newer car's got more power (195kW at 5800 rpm) and more torque (400Nm), but again at much higher rpm.
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Car |
Engine |
Power |
Torque |
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1995 Audi S4 |
2.2 litre single turbo five |
169kW at 5900 rpm |
350Nm at 1950 rpm
380Nm at 2100 rpm (overboost) |
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Falcon XR6 VCT |
4 litre naturally aspirated six |
172kW at 5000 rpm |
374Nm at 3500 rpm |
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Saab 9-5 Aero |
2.3 litre single turbo four |
169kW at 5500 |
350Nm at 1900 rpm |
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R32 Skyline GT-R |
2.6 litre twin turbo six |
(at least) 205kW at 6800 rpm |
355Nm at 4400 rpm |
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2000 Audi S4 |
2.7 litre twin turbo six |
195kW at 5800 rpm |
400Nm at 3600 rpm |
Now I'm not suggesting that you can chuck your current model twin turbo V6 S4, or discard the Saab Aero, ignore the RB26DETT GT-R engine or even castigate the Falcon six. But these examples do show the point that I am making - the 2.2 Audi engine has immense bottom-end grunt.
To be honest, I'd never really considered the implications of high torque figures low in the rev range. That's probably because I'd always associated that particular engine spec with a lack of top-end power - a la a poorly breathing old V8, for example. But actually driving such a car for three-quarters of a year has really changed my perspective. It's just so effortless - and another reason that I have enjoyed it so much is the six-speed trans. Why Audi chose to use a close-ratio six-speed gearbox with an engine boasting a wider spread of torque than any 2.2 litre engine I've ever heard of is a mystery - but I'm glad that they did!
In the previously-cited AutoSpeed story (the one I wrote shortly after buying the car) I said, "Swapping cogs while paying attention to something else gives the very real possibility that you can't remember what gear you're in - often I have had to reach down and feel for the lever position...." And that's still the case. Sometimes I've been drifting along in sixth, thought that I'm in fourth, and floored it to climb a hill. Only when I'm part-way up the hill and things don't seem to be happening quite as quickly as I think they should have I realised that I'm in sixth.... Sounds ridiculous I know, but it's the case!
The fuel consumption's also a really interesting point. While in normal around-town driving, the trip computer shows the consumption to be in the low to mid-tens (in litres per 100 km), in hot weather the consumption just goes berserk, rising as much as 30 per cent! It not at all unusual to see an average of 13 litres/100 km, in the same sort of driving conditions that in cool weather results in 10 litres/100 km. The responsiveness and power of the engine stays very good in hot weather, but I can only assume that the ignition timing is being pulled w-a-y back to prevent detonation, resulting in very poor efficiency. Strangely enough, in the heat the over-boost function is not dropped - in fact, the ECU will allow boost to a massive 1.1 Bar (16 psi) in very hot conditions. Yep, on hot days boost goes up, not down! Weird. I expect that when Shell Optimax (higher octane) fuel becomes available locally, my hot weather fuel consumption will improve.
The Handling
The Audi is a constant four wheel drive car that uses a Torsen centre diff. This is unusual - most four wheel drive cars use a viscous coupling as the centre diff. The fact that the diff can sense changes in torque - rather than just changes in relative speed - gives the car more throttle control than other constant four wheel drives that I have driven. However, the basic handling characteristic remains the same - get the car to turn in by using a relatively slow entrance speed and then get on the power early.
At 1650kg and with a length and width of 4790 and 1804mm respectively, it's quite a lot of car to throw around - though still smaller than a current Falcon and Commodore. But unlike (say) a current 5.7 V8 Commodore, the Audi never feels nimble and light on its feet. The suspension is set up a little softly, giving a very good ride but at times also feeling a little underdamped. The corollary of the power, four wheel drive grip and a suspension a little softer than desirable is that the tyres suffer. Worn on standard 16 x 8 alloys, the 225/50 ZR Goodyear Eagle GS-D's are having their shoulders absolutely torn to shreds.
The high rate of wear that I was causing became obvious quite soon after I bought the car. I had John Keen of DAT Racing perform a four-wheel alignment - I would have liked more castor in addition to a check of toe and camber. Unfortunately, castor is not adjustable, and is a measly 0.5 degrees. This results in basically no additional camber coming to bear when cornering - the static camber is all that you've got. And in the Audi's case, that's a max of about a degree. I've not seen any suspension geometry 'kits' for the car (one of the problems in owning a Euro car in Australia) and so effectively I'm stuck with these settings. Without having the dough to put in slightly stiffer dampers (which would stop some of the body roll, and so lessen the demands on the tyres) and being reluctant to change the sway bars at this stage, I'm basically stuck with chewing up tyres. 'Course, as a friend gently pointed out, I could always change my driving style ....
Incidentally, one of the controls that people often notice when they get into the car is the centre diff lock, a button mounted on the console. However, its use is quite limited - it's only for slow travel in very slippery conditions. In fact, the lock switches off automatically at speeds over 20 or so km/h. For moving away from a standstill in snow and ice it's probably useful, but here in Australia I've pressed the button only once. That was when after a sudden, heavy downpour, there was some minor flooding across some Adelaide roads. Traffic was detouring through a dirt carpark covered by about 30 cm of water. As we entered the slippery area I stabbed my finger at the button, locking the front and rear axles together. A-ha! I thought; bet there's no other driver here doing that! My glee was somewhat reduced when I realised that I was following a middle-aged woman in a FWD Corolla - and that she was negotiating the slippery wet earth surface with no apparent problems at all...
The Car
In my job I do a lot of kilometres. Many of those aren't 'fun' kays - you know, fun kays are where you're just out in the car playing. Instead, I might be dropping off film or picking it up or visiting a workshop or going to a photo shoot location or driving through the city. In other words, there are lots and lots of kilometres where I just wanna sit back and let the car take me there - quickly, quietly and easily. The Audi does that better than any other car I've owned. At other times I might want to play - and then the Audi is highly competent. It doesn't have that steer-me-by-the-fingertips feel of a tactile and sensitive car - in fact, it's more of a blunt instrument in terms of its nimbleness and the adjustability of its handling. But its power and grip and driveability are just superb.
So yes, I'm still happy.
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