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1994 Ferrari 348 Challenge TB Twin Turbo - Force-Fed Frenzy

A 600Hp Turbocharged Near-Death Experience

Isaac Mion
Mar 17, 2011 SHARE

A lot of time and money have gone into this car. Steve Maxwell designed and fabricated more than 200 parts to get the entire package functioning.

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Stacey Slead and Steve Maxwell have always agreed that the 348 has the best handling characteristics of all Ferraris, and at a reasonable price. The only drawback is it just wasn’t as fast as newer models. They decided to remedy this flaw with a pair of T3/T4 turbos. But the road to power is never without its obstacles.

On our first test drive the throttle stuck at 150 mph and continued to accelerate, says Maxwell.

But let’s start from the beginning of that road. Slead and Maxwell met around the same time that the Ferrari you see before you, a 1994 Ferrari 348 Challenge, was being built at the factory in Maranello. Slead had stopped by Maxwell’s shop to inquire about a Maserati and the two became friends, as many of us do when we share passion for an automobile. In fact, Editor Bidrawn and I did so years ago when one of us brought up the Lancia Delta Integrale. Now he sends me a case of Jameson every Christmas. (Hint hint)

A few years later, Slead acquired a Maserati. Of course, being an obscure Italian make, it developed a noise in the steering column and when he took it to Maxwell’s shop it was determined to be unsafe to drive. At the time, Maxwell had a 348 for sale and told Slead to take it home for the night.

I drove the car once and had to have it, Slead says.

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In case you haven’t deduced it by now, Maxwell is the mechanic/builder and Slead is the owner. But his hands are just as dirty as Maxwell’s and the car is essentially both their baby.

The car needed to be serviced and we decided to do it weekends at my shop, said Maxwell. It was this that led him to come to work for me.

Maxwell had turbocharged a few other high-end cars, like Lamborghinis, that Slead had seen in action, so he decided to go ahead and let Maxwell do his thing. They removed the engine and replaced it with a spare so Slead could still drive it.

We took his engine apart and built it to the same specifications of another 348 turbo engine, Maxwell says. It got new, low-compression pistons from JE and new Inconel valves from Ferrea. I ported and polished the cylinder heads and matched them to the exhaust flanges. I also machined the guideplates to match the intake ports to the runners.

While Maxwell toiled away on the motor, Slead was making trips to Wal Mart, where he was sideswiped by a handicapped person. A disabled had disabled him. They had to look for another car and finally found one in Michigan.

I was excited because it was one of the original factory Challenge race cars, says Maxwell. It had no insulation or sound deadening to add extra weight. It had the Speedline Racing magnesium wheels that were hands-down the best wheels you could get for the car. It came with solid metal suspension joints and a factory mounted six-point roll cage.

It looked like the lining to their gray cloud was all silver (and yellow)until they took delivery of the car. Even though they had it inspected, it wasn’t all it was cracked up to be. So, they completely stripped the car and sent it to GA Coachworks to have the paint and body done. In the meantime, they picked up all the necessary trim pieces as well as seat pads and seatbelts from Group 5 Motorsport, their neighbor in San Diego and the shop responsible for alerting us to this piece of machinery.

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They then took the engine they had built for the original car and put it back into the new yellow one. While that powerplant was breaking in, Maxwell continued to build the pieces necessary to complete the system.

This is where the story gets really interesting. The amount of R&D put into this Ferrari is mind-numbing. The person responsible for the majority of this work was Maxwell, so we’ll let him take over:

First, we knew it would need much more cooling capacity, as well as intercoolers. So I ordered two much larger radiators. I then sent the front bumper out to have the A/C condenser inlet mirrored on the left side of the bumper for the intercooler radiator. Because of the space constraints of the mid-engine design, it was much easier to use a liquid intercooler. When the bumper came back, I fabricated an aluminum duct to ensure proper airflow across the radiator. The radiator placement required relocating the battery to the trunk, so I CNC machined a special mount. Then I fabricated the water tank and pump mounts for the intercooler to go under the front trunk liner. I made hard aluminum lines to the rear of the car.

Meanwhile, on the engine that came out of the 348 Challenge, I fabricated equal-length four-to-one Inconel headers from blocks of aluminum that weighed 75 pounds each. They were integrated into the oil drains of the turbo that held them in place. I made the intake manifold from seven separate blocks of aluminum. I bought Tial wastegates from Group 5 and a Tial blow-off valve. I then made the intercooler. We fitted the engine with the intake manifold that was matched to it with a much larger single plenum instead of the two smaller ones. Amazingly, even with 8.75:1 compression ratio, the engine made more power naturally aspirated than it had with the old Challenge engine.

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About this time I heard about a 355 Challenge race car that had been crashed and was being parted out, so I bought all the suspension pieces and the gearbox from the car. I brought them back thinking it would be easy to fit them to the car. The suspension took a bit of doing and I made bushings from Teflon. I then set about making the gearbox fit. I was told that it fit right in. It didn’t. That was by far the most difficult part of building this car. I had to make new crossmembers and machine arms for the gearbox mount. Then I had to cut a hole in the frame and put in a tube for the shift rod to go through. Next, I had to get an engine pan from a 355 and fit it to the engine by moving a couple of studs. I then had to machine brackets for the Toyota Tacoma alternator. Then I bought a smaller A/C compressor and made everything necessary to make it work. I used a 355 shifter and machined a new center console that moved the climate control to make room for boost and EGT gauges, and added a switch for the computer to operate the traction control, launch control, wet traction control, and added a switch to raise boost, turn on a fan for the intercooler, and make the exhaust louder.

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Wiring and injection came next. I wanted reliability, so I used Toyota coil-on-plug coils. I made the entire wiring harness and machined brackets and plastic covers to keep water out of the coils. I used a computer from DTA Fast in England. I chose this computer for its features. It has traction control, launch control, wet traction control, boost control, idle motor control, enough drivers for sequential injection, and drivers for each individual coil. For the most part it worked well with all the existing Bosch sensors.

As we said, there’s been a lot of time, money, and R&D put into this Ferrari. Maxwell designed and fabricated more than 200 parts in order to get the entire package functioning, from the turbo plumbing to the custom engine mounts. These were designed to limit movement, and had to be as a result of the mishap during the first test drive.

As the speedometer climbed past 160 mph, Slead announced with increasing fervor that the car wasn’t slowing down. Maxwell sat beside him with a laptop hooked up. His pants may have been soiled a little as well as the speedo went past 170 mph. Only as they hit 180 mph Maxwell hit the emergency stop button to cut engine power.

A lot of Toyota parts have been used in this build as they are reliable, readily available and of high quality. But after the throttle incident, a few guys started saying that maybe a Toyota ghost had gotten into the Ferrari. Maxwell laughed along with them when they teased Slead that his car was going to Go Toyota on him and take off on its own, until he took a closer look at the engine.

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We put it back on the dyno and when it went up on power I saw the whole engine lift up about 3 inches, said Maxwell. I realized then the engine was making so much power it had broken the front mounts. When it lifted it rotated back and the throttle jammed under the intercooler.

There’s a moral to this story somewhere.

1994 Ferrari 348 Challenge TB Twin Turbo

Layout
Longitudinal mid engine, rear-wheel drive

Engine
’89 Ferrari 3.4-liter V8, Ferrari 75mm crankshaft, Carrillo rods, 8.75:1 JE pistons, Mahle bearings, Ferrea valves, twin Turbonetics T3/T4 K26 turbos, CNC-machined intake manifold by Steve Maxwell, mandrel-bent equal-length headers and custom stainless steel exhaust, DTA PS pro fuel injection

Transmission
Ferrari 355 five-speed manual

Suspension
355 Challenge springs, 355 Challenge with CuC links and rocker arms, revalved Bilstein shocks (f); 355 Challenge rear end, springs and antiroll bars, revalved Bilstein shocks (r)

Epcp_1104_07_o+1994_ferrari_348_challenge_tb_twin_turbo+front_seats Photo 8/8   |   1994 Ferrari 348 Challenge TB Twin Turbo - Force-Fed Frenzy

Brakes
AP Racing six-piston calipers, 362mm rotors

Wheels And Tires Speedline Ferrari Challenge alloys, 8x18 (f), 12x18 (r)
Pirelli P Zero, 245/35 (f), 315/30 (r)

Exterior
Front bumper inlet for intercooler, BASF Fly Yellow paint

Interior
Refurbished OEM interior with seat pads and seatbelts from Group 5 Motorsport

Performance
Peak Power: 609 hp @ 7700 rpm
Peak Torque: 486 lb-ft @ 5700 rpm

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By Isaac Mion
38 Articles

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