Lexus RC F vs. BMW M4 Performance: The final surge of the naturally aspirated engine
While, with the M4, BMW did away with its last naturally aspirated engine last year, in the Lexus RC F it's getting one more chance. It will be its last. Can it take advantage of it?
Strange, eh? After all, the German manufacturers always get the tears flowing, telling of the future emissions ordinances with which it will only be possible to comply with turbo engines. And then, of all manufacturers, along come Lexus, who aid the forest of evergreens, introduces a naturally aspirated engine. A flame in a storm, so to speak, with a trim five-litre engine capacity – proof that if you really want to do something then it is possible.
Amidst all of the euphoria: the eight-cylinder engine is not a newborn in the literal sense of the word, but rather a reincarnation of the identically dimensioned engine from the IS F – albeit a pretty expansive one. Intake manifold, throttle body housing, valve train, cylinder heads, crankshaft – everything has been completely redesigned. In addition to this, forged piston rods and titanium valves now increase the high-speed performance, which the increased compression enhances the torque range. In numbers: 470 rather than 417 HP, 530 rather than the previous 505 Nm, a maximum engine speed that has been increased by 500 rpm to 7,300 rpm – and all of this without any growth accelerators. If this was just about being likeable, the Lexus RC F would win by a mile.BMW Turbo with 40 percent more torque
However, the duel will be decided on points. And the scoring has been high since BMW triggered the fifth evolutionary phase with the M4. The record holder from Munich is the founder of the segment, a constant presence and the benchmark for all others – and so it is once again.
And what was it that we were all ranting and raving about: the turbo engine, a new name – how can they just..., they've gone nuts..., and everything was better in the good old days. Too bad that the present, in which everything must consequently be worse, has once again failed to come about. And why is that? I barely dare to put it in writing: first and foremost because the benefits of turbo charging outweigh the inevitable disadvantages. 40 percent more torque in comparison to the V8 naturally aspirated engine in the E92 stand alongside throttle response that has withdrawn no more than a few millimetres from the tip of your toe down into the path of the accelerator. Or to put it another way: in spite of the forged crankshaft and super-spontaneous monoscroll chargers, there is no way to talk yourself out of the light rubber band effect experienced in the power distribution. And at this, you drive forwards a great deal more taughtly than in – hand on heart – the rather slackly pulling four-litre engine from back in the day. In my opinion: if the 425 HP three-litre in the F32 is the benchmark for all future turbos, then as far as I am concerned, bring them on.
However,in the end there is one thing that is gone with the wind: the unmistakable sound of its predecessor, the racing-style rattle when making a cold start, the clink of the individual throttle valves and the vibrating trombone blast when putting your foot to the floor. The new model does to some extent attempt to base itself on this, with the acoustics even billowing from the audio system – however, at the end of the day it is still just a cover song. A pithy tone, no questions, but in terms of sound it is neither a typical inline 6-cylinder nor a V8. With the new titanium exhaust system from the Performance accessories package things are now at least shaken up a bit. For 4,130 Euros – plus installation – the soundtrack can enrage you on a permanent basis: sharper base, duskier undertones, metallic reverberation, and all with at a crazy volume. Without doubt this has made it more emotional, but unfortunately not more authentic.
Quite different from the Lexus: it bubbles comparatively dampened through its two-tier twin exhaust pipes, but does sound more visceral. Admittedly, it does draw a little something extra out via an amplifier. The system is called Adaptive Sound Control (ASC), which as dreadfully artificial as it looks on the page, this isn't actually the case in practice. Via a resonator in the instrument panel, the V8 tone is overdubbed according to the rev speed, accelerator position and speed: sonorous to begin, with a tenor-like tone at the peaks and with such a hefty suction engine roar in between that there sometimes is a certain discrepancy between the engine and the sound. Don't get me wrong: the naturally aspirated engine takes off with clear intent, increasing noticeably in intensity from 3,500 rpm, and has plenty of power at full throttle. What irritates more are the rhythms: the fast, almost hectic playback- the drum of the ASC on the one side and the V8 on the other, which, in spite of its short stroke, works its way up the revs rather cautiously.
The BMW M4 has a weight advantage of 240 kilograms
This is compounded by the housing that holds the V8. Even when including the optional CFRP body parts, the RC F coupé weighs 1,853 kilograms. That's almost 130 more than the IS F and far too much. It's all well and good, but even the M4 doesn't bring weigh in at its so proudly announced short weight, although at 1,614 kilogram it does have just under 240 kilos (!) less to drag around when compared to the Lexus.
And so it seems like a very one-sided match. And before we desperately try to maintain the tension: purely on paper this is exactly the case, however, with a few surprises – of both a positive and negative nature. The M4 provides the latter. The reason and cause of this is the Launch Control – the so-called Launch Control that is. For on cold Winter surfaces what you get out of the 550 Nm has precious little to do with control. Granted the starting engine speed can be manually adjusted, but even low values in the 2,000 rpm range are already too much of a good thing. The painful result: after three unwanted burn-outs, the Michelins on the rear axle would have finally reached a temperature in keeping with success, but at this stage the pair of clutches need a cooling off lap – during which the tyres cool off again. What a vicious circle!
Thanks to the broader power delivery and the striking weight advantage, it can, however, be turbo boosted to well beyond the capability of the RC F: the M4 gains five tenths in the sprint to 100 km/h alone, 1,8 seconds in the race to 200 km/h – and this in spite of the fact that in comparison to the super test car (sport auto7/2014), on the last rev peak the M4 clearly sags towards the 2,000 rpm range.
But even the Lexus doesn't come close to delivering everything it promises. The eight-speed automatic transmission somewhat arrogantly calls itself the Direct Shift, but at times it is quite the opposite. Especially when cruising, in manual mode it feels like when you're calling one of these service hotlines: please wait, you are being connected. All joking aside: even if the reaction time slows a little with increasing load conditions, the converters are worlds apart from the explosiveness of the DCT in the BMW, whereby you practically slam the gears directly into the pinions using the paddles. And the Japanese could have also done with finding a more fitting name for the "Slalom" option on the electronic rear axle locking system. On country roads it is a cheeky turn-on with regard to handling behaviour, however, in the actual slalom the considerable pulses of power cause nothing but turbulence at the back of the vehicle.
Lexus RC F with inaccurate steering
In any case, it really only becomes truly dynamic in the Track programme: both when weaving between the cones and – and this is the positive surprise we spoke of – on the track. It's not that the RC F would embarrass the M4, its just that you no longer notice its heavy set build – provided it's handled properly.
That is to say: those who drive it strictly according to the manual, brake first and then turn towards the apex of the curve - they will find the ideal line, but without any great inspiration. The trick: you have to – as our fast-driving men so nicely put it – "compensate for the brakes", that is, continue to steer and countersteer during the deceleration phase. Then the RC F really lets rip and hurls the side window forwards into the corner. However, there are two problems with this: firstly the spaciously geared steering whereby you really have to crank the wheel, when the car inadvertently slips into a drift when cornering.
And secondly the sinking chassis, which causes an unpleasant jolt in the steering movement when springing back. Just a moment! There is another problem, a third: as entertaining as this driving from the hips may be, it does not result in record times. At least not when used exclusively. The art is in finding the right balance – the balance of clean and dirty. Okay, that is hardly an astounding new discovery, except that in the Lexus it is such a fine line between under and oversteer that you are at risk of wobbling back and forth. To express it clearly: achieving the perfect lap is Sisyphean task.M4 with controlled drift
The M4 makes this easier. It makes no provisions for understeer whatsoever, instead continually swinging its rear section outwards: before corners, when the active limited slip differential pushes gently in the same direction, in corners where it consequently scythes through the apex at a slight angle and after corners, when the rear axle surfs over the outside of the corner on the wave of charging pressure. Put emphatically: the steering only provides the rough direction, you actually steer using the accelerator pedal.
It is particularly impressive how easily controllable it remains. Regardless of whether in a powerslide when leaving the Sachs corner or when moving quickly into a drift in third gear – drifts can be drawn out as long as you want or immediately steered into the proper lane, in case you ever overdo it. So fun without remorse which can even be experienced in part in the ESP's M-Dynamic mode with its residual protection. Just between us: we really had to pull ourselves together on the test day as otherwise we would probably have worn the rear tyres right down until they were full slicks.
Lexus RC F with maximum speed from 4,800 rpm
The difference from the RC F, which is ultimately perhaps a little larger when it comes to seconds than when it comes to entertainment value, is not, however, down merely to the handling. With a more rigid chassis design and the nippier steering that is still too dogged in Sport-Plus mode, the BMW lays the foundation for its victory. However, it gets its clarity first and foremost from its turbo engine.
Is the killer argument in favour of the naturally aspirated engine about to be resurrected? By no means! For the impotence of the Lexus V8 is not so much down to the engine itself, but rather the fact that its concept-related disadvantages are enhanced even further by the extremely unfavourable framework conditions. Specifically: the enormous weight of the RC F weighs down like lead on the cars free-revving character.
And it is precisely this that is the lifeblood of an engine, that has to clamber up to 4,800 rpm to reach its maximum torque. In this regard the RC F would definitely have the equipment required of a Performance- Coupé – even a good one. Its lap time is just two tenths behind that of the Audi RS 5. In spite of its lacking traction, in spite of the more gentle transmission and a good 70 kilos of additional weight.
Therefore our appeal is this: put the RC F on a diet. Out with the opulent seats, out with the generous insulations, out with the infotainment from the 1990s and out with the bulky wheels. That's easy to say? Correct! But as the naturally aspirated engine has already proven: if you really want to do something then it is possible.Among the naturally aspirated engines, the RC F is right out in front
Although the Lexus doesn't quite manage the lap times of the RS 5 and C 63, it keeps up with them in terms of points. It manages to tie with the 444 HP Audi, while the Mercedes with 480 HP is even a point behind in the test on account of the poorer braking values. The catch: both naturally aspirated cars are or are to be discontinued models. In the AMG the new biturbo generation is imminent, Audi will also follow suit in 2016 with two turbo-charged vehicles.
Date20 July 2015