In this business you become a little gun-shy, a little skeptical of big numbers. World's fastest this, world's most powerful that, world's longest...never mind!
Anyway, when evosport presented its 500hp E36 Convertible at Bimmerfest '05 we welcomed it warmly but suspiciously. Since then we've been trying to track down the car and discover whether there's any truth behind the claim, and it took us 14 months to get the owner and builder together in one place.
To verify its credentials we strapped Sam into the seat (newbies are always the guinea pig) and he went for a ride. You can read about his experience over the page, but it convinced us there was a story to be told.
We then cornered evosport's lead R&D engineer, Gary Karamikian, and his infectious enthusiasm for the project quickly won us over. So we thought we'd concentrate on the engine build since it's the major aspect of this sleeper convertible.
The oily bits
Despite its appearance, the car started life as a '94 325i. During the 12 years it's been owned by 51 year-old Ivan Colon, it's taken on an M3 persona - first the 3.2 liter S52 motor and then part of the body kit. The motor was also turbocharged but Ivan was never satisfied with how the car ran, so through happy circumstance, found himself on evo's doorstep talking to Gary.
Now Ivan's pretty laid-back and you have to encourage him to open up, whereas Gary could turn telling the time into a 90min diatribe. Yet somehow these two managed to ascertain exactly what Ivan wanted.
This is how Gary approaches every job. He wears you down with unbridled enthusiasm, then goes off and builds you something special. In this instance, Ivan wanted something that could pace a 911 Turbo, yet would be reliable for everyday use - a pretty tall order from a '94 325i, it would seem. "We knew that meant at least 400hp at the wheels," Gary explained, "but we'd need to do it at low boost so it could run on 91 octane pump fuel. We decided that about 12psi would be a dependable boost pressure, so were able to choose a suitable turbocharger, which in this case would be a GT40R since it would give us enough airflow to achieve the desired manifold pressure."
We'll look at how the turbo was selected in a moment, but let's examine how the motor was prepared for its new duties. The first task would inevitably be forged aluminum pistons from CP Pistons. These would lower the compression to a safer 9:1. The pistons have gas ports around the sides to improve ring seal against the cylinder wall and give more consistent behavior on boost. The piston clearances were then set after careful long term testing that's shown Gary the tightest fit possible without the risk of the pistons binding when hot. These tests have also shown him the optimum bearing clearances and piston deck height for best performance. We'd love to share this information with you but it's one of Gary's guarded secrets and something he attributes to the quality of his engine builds.
Using tool-steel wrist pins, the pistons are attached to strong Pauter rods. The crank is stock but the rod journals were re-ground so custom bearings could be utilized. The crank was also micro-polished and the oil supply improved for durability.
The block itself was machined to accept 12mm head stud inserts. This is after evosport discovered the stock 10mm studs could allow the head to lift slightly and cause gaskets to blow under pressure. Fortunately, the bigger studs allow a greater clamping force and are less prone to blow gaskets.
Before it's clamped down the head received a mild porting to clean the airways.
The stock 3.2 cams were then refitted because Gary found they work well in turbo applications, where most aftermarket profiles sacrifice boost with too much overlap and exhaust timing.
The turbo
As we mentioned, the turbo is a Garrett GT40R. It was chosen because its size gave the best combination of manifold pressure, volumetric efficiency, compression ratio and airflow. It was mounted on an Active Autowerke cast exhaust manifold and fitted with a Tial wastegate. The engineers at evosport then fabricated a custom exhaust using their own downpipe and a Remus muffler. The 3" pipe uses V-bend flanges so there are no gaskets to leak. It also has two performance cats and all the stock emissions gear. And because the car was originally an OBD1 325i it was thought it could pass the visual and tailpipe emissions tests.
One reason the car had running problems was it arrived at evosport still using the OBD1 computer. This was always going to be discarded, especially when the tuner works closely with AEM to develop Euro applications for its standalone EMS computer. They would also fit AEM's four-channel CDI ignition system, plus a 3.5bar map sensor and intake air temp sensor.
Having worked with AEM for a while, evo has a wiring harness that allows the EMS to plug into the factory wiring. Then they wire the CDI directly to the six ignition packs and it's ready to go. The company even has a "plug-n-play" EMS for OBD1 and OBD2 cars that doesn't require the CDI system. It's sold with a base program to get the car running and you can email your log files to Gary, who will check and correct if necessary.
The bigger turbo would require more fuel, and Gary calculated that 650cc injectors from RC Engineering would do the job. At this size the injectors would be working at 60% efficiency, rather than smaller injectors where the duty cycles are strained to maximum capacity. However, they required a 250 lph high pressure fuel pump and larger fuel lines in a modified fuel rail.
To keep the turbo efficient, it would also get a GReddy Type-S blow-off valve and an air-to-water intercooler (chargecooler) with a custom heat exchanger at the front of the car.
The final mods before the car could be road tested were a custom Clutchmaster clutch in the stock M3 five-speed and a Quaife diff to distribute all that power. "The stock tranny is holding up well despite us not taking it easy. In fact, I've driven the piss out of this car and it's doing fine," Gary admitted.
So with a basic program in the AEM EMS, Gary could start road testing. He aimed for a 15:1 air/fuel ratio and gave the ignition lots of advance to make it smooth. He reckons the car will return about 20mpg on the freeway, but you can forget that if you get on it. That's because on boost, Gary was more concerned with detonation and spooling the turbo.
Tuning
With the car running cleanly on the road, it goes on the dyno to be tuned. Gary looks at the increase in volumetric efficiency at different boost levels and starts plotting curves up to 18psi, although the engine will only run to a maximum of 12psi. It's possible to plot up to 35psi with the EMS, but he prefers to concentrate its processing power on the area he wants.
With the curves plotted, the car goes back on the road for verification and is finally handed over to the customer. It's then his job to drive it in traffic with the a/c on and report back any bugs that will be ironed out. Fortunately, these are rare since Gary claims, "The AEM EMS is well suited to daily driving thanks to its continuous Lambda feedback, sophisticated idle control, as well as air temp correction, coolant temp enrichment and knock sensor feedback. You can program it to adjust both ignition and fuel under these conditions. This means the standalone won't remove the pleasure of daily driving your car."
The EMS also allows Gary to plot the boost curve against road speed. This has enabled him to increase boost as the car's speed increases. So the faster you go, the faster you go. However, he admits that even at 12psi the car is almost too powerful, but it's a very exciting car to drive as a result.
So how much power does it have? Well evosport claims 451hp at 6400rpm and 410 lb/ft at 5600rpm at the wheels.
These are very respectable numbers but they're going to cost you. An engine to this spec could be in the region of 20 grand - that's about $6500 for the motor, $6000 for the turbo conversion, another $3200 for the AEM EMS, plus labor. "The same results could be achieved for less," Gary explained, "but we build in safety margins to provide durability and daily drivability. Our engines won't throw a rod and leave you stranded."
With so much work done to his car, Ivan has no intention of selling the old girl yet. In many ways he's still getting used to the power and intends to spend the next 12 years enjoying it.
Guinea pigI had reservations about this BMW Convertible turbo. I know convertibles are heavier and the car looked close to factory. However, I'd heard stories about it annihilating other Evosport cars on the freeway, including their E60 M5, so I should have known what to expect.
Anyway, Gary took me for a spin on the way to our photo location. During normal driving the car was surprisingly smooth and unflustered. Admittedly, it possessed a deep groan that would intimidate a small child. I also noticed the suspension was firm, but not too tight. However, the interior was absolutely mint, and the re-upholstered Sparcos were astoundingly supportive.
And then it happened. We encountered a clear straightaway near Huntington Beach and Gary opened the throttle. I both felt and heard the rear tires lose traction and spin for half a second. Once we gained traction, we disappeared into what had once been the distance, leaving traffic behind us.
When Gary shifted, the noise of the blow-off valve boomed into the open cockpit, making itself heard across the city. Sadly we weren't able to do any high-speed freeway runs but the car was quick when launched off the line. Very quick. It definitely needed more traction to get away fast, but wheel spin can be entertaining in its own right.Sam
Tech SpecIvan ColonLocation: Los Angeles, CAOccupation: Accountant
1994 BMW 325i ConvertibleEngine: 3.2 liter 24v S52 i-6 with forged CP pistons, Pauter rods, evosport ported head, S54 M3 12mm head studs, evosport Garrett GT40R turbo conversion on Active Autowerke exhaust manifold, air-to-liquid intercooler with heat exchanger, evosport custom intercooler piping, downpipe, exhaust system and intake, AEM standalone engine management system and CDI ignition box, RC Engineering 650cc injectors, evosport Power Pulleys, GReddy Turbo Timer
Driveline: five-speed M3 manual gearbox, Clutchmaster Stage 3+ kevlar clutch, Quaife limited slip diff, AutoSolutions short shifter
Suspension: Koni Adjustable dampers, H&R springs and sway bars, E36 M3 control arms with Ground Control bushings, M3 x-brace, front strut brace
Brakes: Brembo Big Brake kit with 320mm drilled front rotors and four-piston calipers, drilled rear rotors, stainless steel lines
Wheels & Tires: 17x8" BBS RK two-piece wheels with 235/45-17 Yokohama AVS Sport tires
Exterior: M3 front bumper, side moldings and mirrors, stock skirts, color-matched rear apron and handles, E46 M3 trunk spoiler
Interior: Sparco Milano seats trimmed to match custom rear seat, modified for chromed Steam Chassis roll bar and subwoofer, Momo steering wheel, shift knob and e-brake, silver instrument faces, VDO boost, oil temp and oil pressure gauges in center console
Audio/Visual: Alpine CDA-9847 head unit, iPod connection, MB Quart speakers in factory locations, 8" JBL sub between rear seats, two Alpine amps in trunk, Valentine One radar detector
Contact: evosport (evosport.com, 888/520-9971)