Running both a supercharger and a turbo on its 2.7-litre M20, this epic twin-charged BMW E30 sleeper is a an incredible homebrew performance machine with over 600bhp!

Feature from Performance BMW. Words: Elizabeth de Latour. Photos: Jape Tiitinen

If you want to make your car faster you need to get more air into your engine to make a bigger bang and get more power as a result of that. To do that you could increase the capacity of your engine or you could add forced induction in the shape of either a turbo or a supercharger. Or, if you’re really dedicated like Sami Lappalainen, you could throw all three at your car for good measure.

The spec on Sami’s twin-charged BMW E30 is just kind of nuts, there’s really no other way of putting it. The amount of work and engineering that has gone into this build, specifically to do with what’s going on under the bonnet, is just mind-blowing and would be far beyond the capabilities of most people but, with an MSC in automotive and mechanical engineering, Sami has the knowledge to execute a build on this scale. That being said, it’s not always been easy and the car has gone through a lot of changes over the 13 years(!) that he’s been building it and now it stands before you in it most complete – and most powerful form – to date.

Not only has Sami been a BMW enthusiast and owner for almost a quarter of a century, but he’s also been into modding for as long as he can remember. “My first car was a 1985 E30 316 that I got when I had my driving license. I saved up for it and sold my motorcycle to help buy it,” he says. While it wasn’t the perfect introduction to BMW ownership as the block cracked around the head studs and Sami’s plans to turn it into a 2.0-litre turbocharged M10B20 were cut short by a lack of funds, he enjoyed it in NA form and proceeded to have some fun modding it. “We have a big forum and club here specialising in BMW tuning and I made a lot of friends that way as well, with everyone tuning, building and modding the cars,” says Sami and it’s easy to see why he’s stuck with BMW for so long and owning yet another was inevitable.

Twin-charged BMW E30

“I wanted to get an E30 Cabrio since we had some very nice summers in 2001/2002 driving around with my friend’s E30 325i Cab around town, listening to techno, seeing girls and having fun,” he grins. “Then I also had an idea to build a supercharged car, since I had started my mechanical engineering studies at uni. The plan was to get an original 325i Cabriolet in good shape and I found this one in 2004 in Germany after scouting various internet sites. It had 160,000km on the clock and it was in pretty good, almost stock, shape with Kamei front and rear bumpers and skirts, an M Tech 1 steering wheel, rear headrests, M3-look mirrors, AC Schnitzer 16” wheels, lowering springs and green-tinted windows,” he says. Sami travelled to Berlin to pick up the car and, in the process, ended up getting arrested, hit with a €380 speeding fine and had to ask his girlfriend to send him the money for the ferry crossing home so it’s fair to say it was an eventful start to what would be a very eventful build.

“The first version of the car was put together in 2005 and I fitted an Eaton M90 supercharger, an intercooler, 630cc injectors and MS1 ECU from a DIY kit. The engine was stock and was making 280hp at 0.7 bar of boost and it was quite fun to drive; I drove it for about 10,000km until the stock M20 piston ring lands gave up and I also burnt out the stock clutch unit. After this, for 2006, I upgraded the engine with hypereutectic M50 pistons and fire rings around the cylinders with the stock head gasket and 12.9 head bolts. I got the boost up to 0.9 bar and noticed belt slip from the supercharger’s PK8 pulleys and then came the second breakdown. I made a software update on the MS1 ECU and it messed up the ignition angle because there were some crossed settings in the update and four piston ring lands broke down in a split second,” winces Sami. “At the same time as fixing the engine, I made a new PK8 pulley system for the supercharger to get boost up and reduce the belt slip, ported the supercharger and fixed the engine with new used M50 pistons from Andreas at PPF. This setup gave 336hp at 1.2 bar and, after one burnout show in 2009, I seized the supercharger since I was not watching the supercharger temperature closely and it got too hot. That same year I had made a new 36mm Gates carbon fibre toothed belt SC pulley system with the help of my workplace machine shop and it kept the supercharger spinning even with melted rotor ends until parking the car, so no belt slip problems any more,” he grins. “However, the SC was maxed out on this size of engine and top-end power was suffering.

Twin-charged BMW E30

“After 2008 I had a new job, my own garage and more money to spend on the car and so I started to build this current setup with a turbo helping at high revs. The supercharger unit was fixed with new rotors and I got the new 2.7-litre forged bottom end and some other nice parts. I sucked up all the info I could find about building a twin-charged engine; the Group B Lancia Delta and Volvo Penta marine diesel units use this setup and later came the VW 1.4 TSI. I calculated the turbo unit size I needed and bought a lot of other new parts. The carbon fibre 36mm Gates toothed belt drive for the supercharger was made to eliminate the belt slip once and for all and it has proven to be rock solid. It has a nice belt whine also, not very sleeper-ish,” Sami laughs.

“The almost new bottom end with forged Wiseco pistons was found in good NA condition from some friends and after some new rods, dimension checks and a little piston machining it was good to go. The camshaft was chosen to get the most out of the unported head; it has high lift and with decent overlap. I tested some different factory-made ECU units on the engine but none seemed to satisfy my MSC laboratory rat INTP brains,” he laughs. “Then my friend sold me this new MaxxECU unit and it is one of the best things in the car – easy to tune and you find settings even if you don’t fiddle with it every day. The HX55 13-litre diesel truck turbo was found in new condition from Sweden and it had the perfect specs I had designed for this build. There is no turbo lag whatsoever and the turbo starts to take over from the supercharger after 3800rpm as I calculated. The setup is making around 0.9 bar of boost at 2000rpm and over 295lb ft of torque at this point, while the turbo can go over 700hp with high boost and E85 ethanol,” he adds with a grin.

Twin-charged BMW E30

“Other components have been chosen with reliability in mind, for example, the fuel regulator is an Aeromotive unit and I am using Bosch 1200cc injectors etc. so no money spared on the important little stuff and not spent on shiny fuel rails etc. I’m running triple 255LPH Walbro fuel pumps and a swirl pot, Athena fire ring head gasket and ARP head studs while the rods are, of course, H-profile,” he adds. Running on E85 and at 1.75 bar of boost, Sami’s E30 makes 607hp and 545lb ft of torque and the twin-charger setup means zero lag with massive top-end power, the perfect arrangement. The drivetrain to go with this homebrew M20 comprises a Getrag 260 five-speed gearbox with an E30 M3 lightened flywheel, Sachs 618 pressure place, PPF six-puck sintered disc, a short-shift kit and a Type 188 diff with a 3.15 final drive 75% locking LSD.

Sami has also given the chassis plenty of attention to ensure that the E30’s underpinnings can cope with all of the engine upgrades and no area has been neglected. “The suspension was chosen based on research of what would be a good compromise for track and street driving, plus the exhaust and downpipe are 4” off the ground until they get under the rear seats and that needs some ground clearance, so it is a ‘road sport’ setup using E30 M3 components with some tweaks,” he explains. E30 M3 Bilstein shocks have been mated with H&R 40mm lowering springs and there are Powerflex E30 M3 offset front and rear wishbone bushes, front negative camber correction plates and a front strut brace as well. The brakes, meanwhile, might not be a flashy off-the-shelf BBK, but performance was more important than looks for Sami; “The brakes are student budget brakes, but designed to work nicely. My setup performs well and I have not seen any reason to update it, it’s a nicely balanced system,” he says. While the rear 325i brakes have been left alone, up front sit a pair of Saab Aero calipers with 312mm Audi TT discs and Sami has also added an E32 750i master cylinder.

Twin-charged BMW E30

When it came to styling, Sami knew exactly what he had in mind for his E30; “I wanted to keep it sleeper and old-school-looking to keep the legacy of the E30 and just do something new that will not affect the original ’80s or ’90s look too much,” he says and he’s absolutely achieved that, keeping his E30 looking like a top-tier sleeper, supremely subtle but with a few individual touches. The front and rear bumpers are M Tech 2 items however they’ve both been modified slightly, the front with a custom aluminium splitter while the rear features a custom exhaust cutout cover; the side skirts, meanwhile, are custom-modified steel E39 items. In addition to that, there are Hella-style smoked headlights, genuine Startec smoked M3 rear lights and then there’s the paint itself.

“It was a tough one to decide. I thought of a lot of different options: it had to be car age-related, but with a twist so it does not get old, boring or look out of place when the build ages. I was battling between white and black, looking at variations of both on the BMW colour charts. Then I found this Azurite black M Individual colour,” he smiles. “It seemed to have enough of a new twist/edge to it but without ruining the classic looks or jumping straight at you. I saw one of my friend’s BMWs with this colour in the sun and thought ‘This is it’. It’s nice if you don’t mind washing it every week,” he chuckles. “Dust shows, but it is a nice colour and is a little different and fresh compared to the usual E30 colours,” he says and we have to agree, the black with a blue twist being a great choice that works so well with the E30 shape and the same goes for the wheels.

“I have been constantly I fiddling with new wheels or other looks, but I always come to the same conclusion: Zenders are rare and cool,” he grins. “What would I gain by fitting BBS RSs on the car? If I would change the wheels, it would be something radical and custom-made. I have looked into making these into two- or three-piece wheels but finding the lips is difficult and custom stainless lips are pretty expensive,” he says and so the Zenders remain as they are and that’s no bad thing. They are 17” ET25 Stern wheels with polished lips and they look great on the E30, with that all-important period look and they suit the whole look of the build so well.

Finally, we come to the interior of the twin-charged BMW E30 and, much as with the exterior, Sami wanted to keep things looking subtle. “I wanted an old-school and original period look with a few little extra touches here and there,” he says. “The Alpine head unit and equaliser were a no-brainer and the ’90s front speaker system is nice and came with the car and it also had a nice leather interior so why mod it too much? For the ECU display, I wanted something cool, so I went with the Sony Xperia Z1 white glass phone and I designed and 3D-printed the stand myself since there was nothing stylish enough available. There are some other 3D-printed parts on the car as well – I only bought the printer to make the parts,” he laughs. Inside you will also spot the AC Schnitzer pedal set along with the aluminium gear knob, handbrake handle and door pins as well as a supercharger temperature gauge, and the cool period touches work really well against the modern elements.

The scale of this build, the engineering involved, the sheer amount of work that’s gone into it is just astonishing and the final result is simply awesome, a retro sleeper with some seriously cool period touches, individual flair and, of course, simply huge power courtesy of that epic twin-charger setup. Unsurprisingly, it’s the powerplant that’s Sami’s favourite part of the whole build. “The engine is phenomenal,” he grins, “hands-down the best I have ever driven if you think of something M20-based or similar displacement engines. It’s just smooth as silk, and then pure rage when you put your foot down and has a really nice progressive power curve and a lot of usable power and torque everywhere,” and it really does sound like a dream engine.

Considering the scale of the build there are, unsurprisingly, some things still left on Sami’s to-do list, along with a few future mods too. “It has always been an ongoing project and probably always will be. Maybe it is this car’s destiny. I never know if I will get some new ideas for it… Wait, I have some!” he laughs. “I might add a sub as I have one waiting, I want to add some small parts to get the engine over 700hp with 2.3 bar of boost and E85, if I get hungry for more power at least. I want to add side mouldings on top of the skirts and maybe adjustable springs to lower the rear a little,” he muses. “There have been many memorable moments with the car and with friends,” he smiles “Sometimes it has been on the road and sometimes it has been in the garage sitting partly dismantled. I think it must have some soul in it to get this far, something special,” he adds. “But what I really want to do is to enjoy driving it finally,” he grins. After spending over 13 years building it he deserves that and you know he’s going to relish every moment behind the wheel of this epic twin-charged BMW E30.

Twin-charged BMW E30

Tech Spec: Twin-charged BMW E30


2.7-litre M20, M20B25 block bored to 84.5mm, M20B25 cylinder head, Dbilas 284° camshaft, double valve springs, 1K Motorsport cam spring shims, adjustable cam pulley, Athena fire ring head gasket, ARP head studs, Wiseco forged pistons, Eagle H-profile con rods, ARP bolts, M21D24 turbo-diesel forged crank and oil pump, red metal crank and rod race bearings, Eaton M90 supercharger ported by 1K Motorsport, custom 36mm Gates Poly Chain GT carbon fibre toothed belt drive for SC by 1K Motorsport, Holset HX55 turbo, KKD Motorsport custom exhaust manifold, 4” downpipe plus 2×3” exhaust system, hidden side-exit exhaust tips, 450x300x76mm intercooler, 1K Motorsport 3” boost pipes and 50mm custom bypass/BOV, 60mm wastegate, 1K Motorsport custom turbo/SC exchange valve, 1K Motorsport oil return bushings in cylinder head, ITG air filter, custom throttle body, oil filter relocation kit, 1K Motorsport alternator relocation kit, 325i oil cooler, 535i radiator, Spal fan, Mercedes-Benz coolant expansion tank, custom partly stainless steel water/oil hoses, 0.6-litre oil catch can, Aeromotive fuel pressure regulator, Bosch 1200cc injectors (E85 compatible), 3x Walbro 255LPH fuel pumps, 1K Motorsport boot-mounted swirl pot, Jazz 60-litre race tank, custom starter motor (M10/M20 hybrid), custom power steering reservoir, MaxxECU V1 v.9, TT-Speed wiring loom, LS2 truck ignition coils x6 (sequential ignition), 1K Motorsport laser-cut stainless coil rack, MAC four-way boost valve, 4 bar and 2.5 bar MAP sensors for data logging, 8x K-type thermocouple inputs (EGT etc.)

Power and Torque:

607hp and 545lb ft on E85 @ 1.75 bar


Getrag 260 five-speed manual gearbox, M10 M3 E30 lightened steel flywheel, Sachs 618 pressure plate, PPF six-puck sintered disc, short-shift kit, turbo-diesel propshaft, Type 188 diff with 1K Motorsport 3.15 75% custom LSD with four friction disc pairs


7.5×17” ET25 (front and rear) Zender Stern wheels with polished lips and 225/40 (front and rear) tyres, E30 M3/M Tech Bilstein shocks, H&R 40mm lowering springs, E30 M3/325i Convertible anti-roll bars (21mm front/14.5mm rear), Powerflex E30 M3 offset front wishbone rear bushes, BMW negative correction front camber plates, Powerflex poly bushes, 1K Motorsport colour-coded front strut brace, E36 quicker steering rack (3.2 turns lock-to-lock), Saab Aero calipers with 1K Motorsport adapters and 312mmx25mm Audi TT brake discs (front), stock 325i brakes (rear), E32 750i master cylinder (25.4mm), ABS
unit relocated


Full respray in BMW Individual Azurite black, M Tech 2 front bumper with custom aluminium splitter, Hella-style smoked headlights, smoked front indicators and side repeaters, custom-made modified E39 5 Series steel side skirts, Startec smoked M3 rear lights, M Tech 2 rear bumper with custom exhaust cover, Shadowline trim, green-tinted OEM windows, carbon fibre-look boot and bonnet badges


Black leather Sport seats, four headrests, M Tech 1 steering wheel, OEM-style grey mats, aluminium gear knob, 1K Motorsport aluminium handbrake handle, AC Schnitzer pedal set, aluminium door pins, aluminium fan/temp control surrounds, chrome door handle trims, supercharger temperature gauge, Turbo XS KnockLite (warning for knock and shift light), Sony Xperia Z1 5” MaxxECU Bluetooth dash display, battery relocated to boot, Alpine 7906R CD player, ’90s Alpine graphic equalizer, MB Quart OEM-style two-way ’90s door speakers, BMW sound system rear speakers, Alpine 3555 amp


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