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Man Maths: BMW 320iS

18 hours ago

Writer:

Andrew Frankel | Ti co-founder

Date:

7 March 2026

As statements of the bleedin’ obvious go, ‘I’d like an E30 BMW M3’ is right up there, making it a poor choice for a story like this. Problem is, even in these straitened times, they are somewhat pricey, to put it mildly. The cheapest cars go for around £50,000 now, even at auction, while six-figure sums for Evo IIs and some other limited edition cars are to be expected.

But if I were to say there was another E30 you could have, still with Paul Rosche’s fabled S14 engine under its bonnet and still with Getrag’s dog-leg five-speed gearbox joining you in the cabin, but which could be yours for little more than half what you pay for an even quite scruffy M3? It’s called the 320iS and you have the Italians and Portuguese to thank for it.

For those were the countries applying punishing tax rates to any cars with engines of greater than 2-litre capacity, meaning the 2.3-litre M3 didn’t stand a chance there. So BMW took its engine and instead of taking the easy, cheap, boring and obvious option and simply sleeving it down to the required capacity, Rosche decided instead to take the more difficult, expensive, exciting and unpredictable route instead, and made the engine internals not narrower, but shorter. He left the bores untouched but fitted a short throw crank, different pistons and rods, reduced the stroke from 84mm to 72.6mm and made an already oversquare engine considerably more so. He created, in other words, a screamer.

The 320is was a rare special edition made for the Italian and Portuguese markets

But he created something else too: a real Q-car, because the 320iS didn’t have the M3’s big rear wing or dramatically flared arches – the powertrain was slipped into a standard 3 Series shell, with only a different rear spoiler to give the game away, and plenty soon removed that. This also meant that, unlike any E30 M3, you could choose to have your 320iS with four doors or two.

That engine is an absolute pearl and because its shorter stroke allows it to rev higher, it develops just eight fewer horsepower than the M3. Indeed former Williams F1 team principal Jost Capito, who was working at BMW Motorsport at the time of its development, has been quoted as saying they actually had to hold the engine back to stop it really treading on its big brother’s toes.

Short-stroke S14 engine makes a 320is almost as powerful as the M3

I’ve only driven one, it wasn’t a great example and it was a very long time ago, but I still had a ball in it. Its suspension is essentially that of a 325i with the Sport pack option, but back then that meant lower and stiffer springs, different roll bars and re-rated dampers too. It had the M3’s limited-slip differential and a shortened final drive to make the most of the rev-happy but torque-limited motor. On a track I’m sure the M3 would ease away from it but at road speeds I expect its advantage to be barely noticeable. And yes, while all 320iSs were left-hand drive, so too were all E30 M3s.

The biggest problem I suspect is finding a good one. People quote different numbers but it seems that for every 320iS BMW made, it produced at least five E30 M3s. And those are hardly common. So iSs are very scarce indeed. The good news is that the one most people want – in this case the two-door – is for once not the rocking horse rare example, outnumbering four-doors by approximately two to one. Looking around Europe, cars seem to have been sold over the last few years in the £20,000-£35,000 bracket, though my old friend Barney Halse at the Hero Motor Company has one up for £49,000. Knowing Barney it’ll be the best of the best, and for that money it will need to be.

A proper 1980s Q-car – if you can find one...

I doubt it will ever be a hugely appreciating asset because it lacks the M3’s look and, above all, racing pedigree, but if you want something that’s damn near as quick, good to drive but a great deal cheaper just to smoke about it, I still think it’s highly tempting. If I had one I’d remove the M Technic bodykit (as had been done to the one Barney has for sale) and just love almost everyone thinking it’s bog-standard 3 Series and I’d never enlighten them. Then, once in a blue moon someone would look again, squint, wander around to the back, see the badge and ask immediately to look under the bonnet, hoping to find an S14 there. I’d really enjoy that.

BMW E30 320iS at Hero Motor Company

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