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Goodspeeds Twin turbo M5 hits the Media!!

  01/24/11 01:22, by Jon@GoodSpeed, Categories: Announcements , Tags: bmw, dyno, e34, fabrication, garrett, m5, proefi, twin turbo

Well once in a great wile you come upon one of those fantastic situations where a good customer lets you go all creative on their very  rare german performance car!  This is what happened to us some time back.  Many of  our customers will remember a beautiful E34 M5 waiting patiently around our shop  since we where in our old Tempe location.  This low mileage, mint condition Jem of Paul Petelin's was preparing itself for Twin Turbo greatness!  While it did take some time to design, engineer, and fabricate; it finally happened, and it received its new stroked 3.9L Twin Garrett Gt2871, inter-cooled heart.  It's been on the road as a daily driver for over 7 months now!  This was no easy task; being a year and a half project.  Now it has hit the pages of European Car Magazine!

It earned a 6 page spread labeled "Sleeper Cell" and made the front page on during January and February.  The M5's wait was worth more than just the 682 crank hp it achieved on 91oct fuel!  It got the glory and recognition a car of this caliber deserves. But enugh i will let the article do the rest of the talking!

BMW M5 - Sleeper Cell Under such deep cover, BMW won't even acknowledge its existence. From the February, 2011 issue of European Car By Peter Wu Photography by Peter Wu Share23 | | 1991 Bmw M5 Front "Drive it like you stole it." Those may have been the five nicest words anyone's ever said to me. Whether they're the wisest words to say to someone who has just gotten behind the wheel of a twin-turbocharged, 3.9-liter, E34 M5 for the first time is debatable. Even so, I felt inclined. Stepping onto the stiff clutch, comprised of a SPEC E46 M3 pressure plate and an M5 disc, and pushing and pulling through the heavy gearbox, the throws shortened with a Rogue shifter, the immediate impression is this is a man's car. As it's been stroked from 3.5 to 3.9 liters, there's plenty of torque down low to keep it drivable around town.

The turbos are so seamlessly integrated to the powerband that it's impossible to tell when they start spooling. That is, until you really nail it. 1991 Bmw M5 Rear View But all hell doesn't necessarily break loose like with many turbocharged cars; instead, there's a relentless, linear surge of power all the way to its 7000-rpm redline. Huge swaths of terra firma are consumed through each gear while the rear tries to counter the weight transfer. There seems to be no amount of wind resistance or weight liabilities that can stop it, even as the car begins to climb through the triple digits. And this is with the boost turned down to 9.5 psi during the break-in period. 1991 Bmw M5 Ac Schnitzer The E34 is the forgotten M5. It didn't make quite the splash of its predecessor, the E28, or its successor, the E39. For a while, people didn't even know if BMW was going to bring it into the United States. And when they eventually did, only small numbers arrived. Spotting one on the road was about as likely as seeing Sasquatch riding a unicorn. Then came the 540i and its big V8, relegating the E34 M5 to near obsolescence. The current owner, a die-hard BMW fan, has always admired the E34 for its understated design, and after he was tipped off that there was one for sale he jumped on it immediately. What makes this particular car unique is that the VIN number doesn't show up on BMW's database, leading to speculation that this may be one of a small batch of early, hand-built M5s never intended for sale to the public. 1991 Bmw M5 Engine Bay It's a Euro-spec model built in December 1991 that was imported and federalized by a German Air Force pilot stationed in New Mexico, but any history before that is still unknown. Shortly after buying the car, the owner blew a head gasket. He then took the car over to Jon Firpach at GoodSpeed Performance Lab in Scottsdale, Ariz., for repairs. He also wanted to put in a new chip and when they opened up the ECU, which was unlike the stock ECU, they found a few notes, written in German, wrapped in plastic and taped to the inside of the ECU box. Firpach also noticed that the idle was particularly lopey, as if it had a hotter cam. This led to more speculation on the BMW forums that this car may also be one of the rumored 400-hp E34s that M Motorsport built strictly for in-house research. It is believed that those cars were painted the same diamond metallic color as this car here. 1991 Bmw M5 Pedals While looking over the engine, Firpach took some measurements for his own curiosity and realized that there was enough room for a turbo or two.

He says he suggested a twin-turbo in jest, while the owner says Firpach tried to sell him on the idea of forced induction. Either way, a call to BMW engine guru Jim Row at Metric Mechanic was all it took for the owner to decide to go all-in. His only requirement was that engine not have any turbo lag. Metric Mechanic already offered a 3.9-liter stroker program for the engine, which the owner originally intended to buy. Turbocharging it only required a redesign of the skirt on the forged pistons.



After the engine came back to GoodSpeed, Firpach bolted on a pair of GT2871 turbos to a custom stainless-steel exhaust manifold and 3-inch stainless downpipes. To get more air in, they modified the OEM intake manifold and also made two 3-inch ram-air intakes to feed the airbox.

Firpach went with a liquid-to-air intercooler instead of an air-to-air unit that would've required cutting into the core support. Aside from a few stainless pipes, the engine bay looks next to OEM. The turbos are hidden discreetly down low, completely out of sight.

The engine uses a Proefi stand-alone ECU; an uprated, in-tank fuel pump and an Aeromotive fuel pressure regulator. Many of the hard-to-find OEM replacement parts were sourced through Saliya Ukuwela at Euro M Cars.




The exhaust is a custom GoodSpeed fabrication utilizing E60 M5 cats and a Supersprint muffler and is completely emissions legal. 1991 Bmw M5 Interior View As mentioned earlier, I drove the car during the break-in period, so boost was set at 9.5 psi. Since then, they've turned it up to 16.5 psi and registered a corrected 682 crank horsepower on GoodSpeed's Maha dyno. This is with 91 octane pump gas. A high-boost race gas tune is in the works. Row at Metric Mechanic said he'd guarantee the engine to withstand up to 1,000 hp. Both the owner and GoodSpeed's Firpach say that with the boost at 16.5 psi, the power is now too much for words. A Ground Control suspension setup keeps it planted to the ground, but because there was so much weight transfer to the rear, new, stiffer springs have replaced the ones I drove on. Powerflex bushings and Dinan sway bars replace the stock units. Eighteen-inch M Motorsport Parallel wheels from a 7 Series have replaced the Throwing Star five spokes. They're wrapped with Toyo Proxes RA1 tires, 245/40 in front, 275/35 in back. 1991 Bmw M5 Wheels One revealed weakness was that the Wilwood six-piston brake calipers simply weren't up to task.

Although better than the stock setup, they started to fade after a few hard stops from high speeds during my brief drive. A pair of Brembo eight-piston calipers and carbon-composite discs from a Mercedes-McLaren SLR remedied the problem. A taller, Dinan 3.64 rear differential was also added, which Firpach says increases the load on the turbos and also lowers the revs for quieter highway cruising. The owner has said he has yet to come up against a car that can run with him. To date, his list of victims includes a couple of E60 M5s, a Z06 Corvette and a GT3. Odds are, they thought he was easy prey and are probably still wondering what hit them. And it's that sleeper quality that appeals to him the most.



1991 BMW M5 Layout Longitudinal frontengine,rear-wheel drive Engine 3.5-liter I6, dohc, 24-valve. 3.9-liter stroker conversion, custom GT2871 twin-turbo kit by GoodSpeed Performance Lab, liquid-to-air intercooler, custom ram-air intakes, custom exhaust manifold and 3-inch downpipe, custom GoodSpeed exhaust w/ Supersprint muffler, Proefi stand-alone ECU Transmission Five-speed manual, Dinan 3.64 differential Suspension Ground Control coilovers, Dinan antiroll bars, Powerflex bushings Brakes Eight-piston Brembo calipers, carbon-ceramic rotors Wheels and Tires M Motorsport Parallel alloys, 18-inchToyo Proxes RA1, 245/40 (f), 275/35 (r)

Performance Peak Power: 682 hp @ 6445 rpm* Peak Torque: 616 lb-ft @ 5000 rpm GoodSpeed Data

GoodSpeed Performance Lab 480.747.6150


Comment from: Rick Touton
Rick Touton

Beautiful build makes the car Beautifully unique and very desirable. Great Job!

01/26/11 @ 06:09 pm
Comment from: Chris Lee  
Chris Lee

OUTRAGEOUS…. Got to love it. I know what I want when I hit the lotto. Sleeper ? Don’t wake the beast .

09/18/11 @ 09:29 am
Comment from: DEEDEE478

I have a 1991 318is BMW, and I’m looking to put a 1991 E34 m5 twin turbo engine and gearbox. Will it fit or will I have to do alot of cutting….

12/10/11 @ 04:40 pm
Comment from: Greger

682 crank bhp? Got a couple of e34 M5 with over 1000 whp in Sweden.

08/28/12 @ 05:43 pm

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GoodSpeed Performance Lab located in Scottsdale, Arizona offers professional, high quality installation, custom tuning and design solutions for the performance enthusiast. We are authorized distributor of such trusted brands as RennTech, APR, ESS Tuning and AMS Performance. Nobody will work harder to accommodate your aspirations for high speed and high excitement for your Audi, BMW, Mercedes, Porsche, Subaru or other high-end vehicle. Never settle for less than the very best!


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