Big turbo Fiesta ST - Borg Warner 6258 EFR

New Mods:

Borg Warner 6258 .64AR TURBO

MWR custom exhaust manifold

PTP turbo blanket

MWR custom downpipe

MWR custom A/N oil lines

MWR custom air intake + lower intercooler piping

JST Performance custom tune

Borg Warner EFR 6258 .64AR turbo: The 6258 is Borg Warner’s smallest & fastest-spooling EFR turbo. This is one of the few Fiesta STs running a Borg Warner EFR turbo. Most ‘big turbo’ Fiestas out there run Garretts. And the reason they’re running Garretts, is because most of the turbo kits available in the aftermarket, use Garrett turbos, so you kind of tend to get funneled into Garrett. Motor Werks Racing exclusively deals with Porsche chassis. They believe in the real-world results of Borg Warner turbos so much, that they offered to fabricate an exhaust manifold for the Fiesta. Darn tootin I jumped at that offer.

MWR custom exhaust manifold: Motor Werks Racing made a custom manifold to mount the Borg Warner EFR 6258. They used an OEM donor manifold to retain the shape off base & mounting points, and then fabricated larger & better flowing piping (log style manifold). The manifold is constructed from thick-walled schedule tubing rather than thinner 304 or 316 stainless. It may look a bit more industrial, and less ‘pretty’. But on a street car, the minimal weight gained is well worth the added longterm durability, and resistance to cracking under heat & vibration.

People want to believe they need an equal-length header, because the looks sell themselves. But the racer’s tested truth is, there’s no benefit to equal length headers until you’re real high up in the RPM range. Specifically – high 6s to low 7,000rpm and beyond. This Fiesta ST is a street car that’s going to live most of it’s life under 7,000rpms. And until then – equal length makes no difference. On an normally aspirated car – yeah sure. But not on a forced-induction car where where the exhaust is literally being force-fed through the system… AND has to go through a turbo wheel.

Both the common 304 and 316 steel used in a lot of the aftermarket equal-length headers will most likely fatigue & crack under heat cycles & vibration (think back to all the cracked headers on boosted Hondas over the years). That’s just the harsh nature of the environment. And reality is – it’s hard to make the tight bends on these headers if you’re using thick-walled steel… unless you’re using insanely expensive materials. Not to mention, really dialing-in & testing a true equal length header will probably take 500-1000 hours. Combine the time + price with the 1-2hp gain… and you can get better results for your money pretty much anywhere else.

PTP turbo blanket: PTP makes a tailored blanket for the Borg Warner 6258. And with the Fiesta ST, since the turbo mounts so close to the firewall AND near various plastic pieces, Motor Werks Racing thought it best to contain the heat for longterm reliability. Plus – the blankets actually improve turbo performance. It may seem as if you’d want the turbo’s heat to dissipate, but keeping it contained allows expansion, thus allowing the wheel to spin as absolutely freely as possible. It also lessens the hot/cold temp cycles, which can wear on metals.

MWR custom downpipe: Motor Werks Racing made a custom downpipe, running from the new Borg Warner 6258 to the Cobb Tuning exhaust. The car previously had the Cobb downpipe, but getting that downpipe to fit the Borg Warner would have required so much cutting/pasting, that it seemed easier to just keep the Cobb downpipe intact, and start fresh.

MWR custom stainless/AN lines: Being Porsche-exclusive mechanics, MWR was confused by some of the cheaper plastic-y materials used in Ford’s water & oil lines. Especially being so close to the heat of the turbo. So MWR upgraded the lines to braided stainless steel with AN fittings. They also rerouted the oil line so it didn’t run directly above the hot turbo.

MWR custom air intake + lower intercooler piping: New pipes were made, just for better routing to & from the new 6258 turbo.

JST Performance custom tune: I didn’t come into this with any specific horsepower-gain expectations. But on Brian Tyson’s (JST Performance) very first dyno run, the FiST made an eye-opening 280whp. And even Brain, who tunes 50+ ST’s per month, was really amused by this setup. Brian was able to dial it in with the Cobb Accessport, and actually lower the boost to 25psi, while getting the horsepower leveled up to a safe & happy 292whp on a 65-degree day. That’s on the STOCK fuel system.

‘Numbers’ are always going to be somewhat arbitrary on a dyno, but just for reference, this is roughly a 100hp increase from the stock turbo on a Stage 3 setup (torque held about the same).

But it’s SO MUCH MORE THAN THAT! …when put to the real world.

On the tiny stock turbo, the FiST was able to hit full boost by 3,000rpms. And that’s why these stock Fiesta STs are so much fun redlight to redlight! However, that OEM turbo just can’t flow through the higher RPMs, and it completely gasses-out around 5,000rpms. So there’s not much time to bask-in-boost, before it falls flat on its face.

But – because of the EFR’s superb efficiency, you can go bigger, without losing much response. The car now rolls into full boost by 3,500rpm… rather than slapping full boost at 3,000. That may seem like a 500rpm ‘boost-lag’ on paper, but it’s not. Because even at 3,200rpm, the car is now making as much power as the old OEM turbo ever could. And – the EFR flows effortlessly STRONG STRONG STRONG all the way to the 7,200rpm redline.

Simultaneously, the ‘roll into boost’ is less jerk on the drivetrain, and it’s surprisingly keeping tire spin at a real minimum… at least with the Toyo R888Rs. I can’t overstate how stupid-fun this car is!