Z4hid, that's one hell of a compliment, thanks! It's the mantra for the coupe: it should be in line with the original design ethos, matched to the timeframe of its design, and using only materials that BMW used or could have used.
In other news:
RvsBmw was both kind and mad enough to let me have a go in his lovely Z4M Coupe. Driven back to back, you really get a feel for the differences between the Si and M. Some observations in no particular order:
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Engine. The S54 dominates the experience of the M. Where the N52 is smooth and linear in its power delivery with plenty of low-down torque, the S54 demands more thrashing to get the most of it. Under 3.5k rpm, they're not all that different in the way they pull. Get up above that point and the S54 just gets better and better. By no means does the N52 feel underpowered, but the S54 just keeps getting better with every 1000 rpm right up to the red line. Bonus: the supersprint exhaust really allows the oldschool sound of the M to come into its own. My Si has the aFe intake and a Bastück backbox, but it sounds eerily quiet compared to the M-chorus. Very addictive...
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Gearbox. The manual box in the M is more mechanical in feel. Notchy in first and second, but very precise in the rest. The N52 is smoother to operate, which on a day to day basis would certainly be a benefit. Given that I'd spent an hour in traffic before that drive, I was glad I did it in the Si. The M isn't by any means impossible, it's just that the Si is a lot easier to use.
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Steering feel. The M just has spades of it, whereas the Si is just lacking in that regard. Numb is too harsh a term, but the electronic power steering isn't nearly as communicative as the hydraulics in the M. The suspension of the M feels well-sorted, though my Si is on STX coilovers so it doesn't feel like a boat either. Can't really compare the two honestly because of it.
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LSD. When you throw the Si into a turn you need to feather the throttle lightly, as the open diff tends to push you into understeer. The rear of the M just comes round under power, pushing you through the turn. It's an addition that transforms the way you take corners and massively boosts the driving experience.
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Tyres. Something that did catch me off guard was the behaviour of the Michelin PS4S: they've got boatloads of grip, but need to "set" themselves on their sidewalls a bit more compared to the Vorti R's. The slightly softer sidewalls of the Michelin's had to load up a bit before achieving their full bite, whereas the Vorti R has stiffer sidewalls and load up more sharpish. Out and out grip of the PS4S is excellent, but their feel building up to the limit (so not actually on the limit) is something you need to get used to.
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Styling. One thing that instantly made me go: "I need that", was the view over the bonnet. The two creases just finish off the view over that long nose. Interesting to see was the variation in the front bumpers. Not just the obvious differences in lines, but also in depth and dynamics: the Si has protruding outer areas with a recessed central area, giving a flatter, wider front. The M has rounder sides with a positive central area stepped up from the sides. The kidneys also lay further back into the nose of the M compared to the Si, which further boosts the flat front of the latter. The recessed grills are design queues we see with other M-models as well.
Another interesting difference is between the halogen and xenon lights. The halogen's outer and inner lens are placed side by side, whereas the two projectors in the xenon headlight are stepped in design with a curve around their inner edges. Coupled with the bumper design, the M has a more pointed, rounded nose compared to the somewhat "blunt" Si. As for the rears: I actually liked the look of my diffuser more than the original M-bumper now. It looked more aggressive, sportier. It only lacks the 4 pipes, something which I'll be tackling this winter with a custom project on the diffuser. Final styling point: the dials. Really like the red needles and white lighting, looks special. Oil temp gauge was another addition I miss in the Si.
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Like I said above: the rear end of the Si actually looks better -to my eyes- with the diffuser now fitted. The M looks great, if perhaps a little restrained. Although, M-cars of the era hadn't yet fallen prey to the over-designed looks of the 2020's, so perhaps my perception is a bit tainted by modern M-cars.
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As for the front: I lose that battle by quite a margin. The Si just looks a little "flat" compared to the more rounded, stepped design of the M. I like the way the xenon's tie in with the raised central area of the bumper, further offset by the increased depth of the kidneys. Classic looks that have aged brilliantly, especially confronted with the modern radiator grills (can't really call them kidneys anymore can you) we see today.
All in all, a great day out with a few key take-aways for me: hydraulic conversion just got bumped up the list, "comfort" seats really aren't so I need to get a move on with the Pole's, an M-bumper should really complement the new rear-end of the Si, xenon-style stepped housings are in order, and I've got a few plans in my mind for this winter that neither car originally had; exciting times ahead!
Big thanks to
RvsBmw for letting me take his pride and joy for a spin, an absolute gent
