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F-family Flier

Bargain performance - a Ford TX5 Turbo with a J-spec DOHC engine conversion!

Words by Michael Knowling, Pix by Julian Edgar

Click on pics to view larger images

At a glance...

  • Originally powered by a SOHC turbo engine
  • Now converted to J-spec DOHC engine with custom turbo set-up
  • A neat and comfortable performer
  • Easy 13s
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SR20, EJ20, RB25, 1JZ, 13B - these are engine codes you’ll be familiar with if you’re into high performance. But one engine family that goes largely overlooked is the Mazda-designed F-series.

So let’s introduce you to the F-series family.

The Australian market received the turbocharged F2 2.2 litre engine in the nose of the ‘88 Mazda MX-6/626 and Ford TX5 clone (as shown here). In factory guise, the SOHC, 12 valve F2 is a low rpm slogger with a substantial 258Nm at 3500 rpm but a modest 108kW at 4300 rpm (when running premium unleaded). A natural revver it ain’t...

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Brother to the F2 is the atmo FE 2.0 litre DOHC, 16 valve engine which was never officially seen on local shores. The FE DOHC (aka FE3) benefits from a more sophisticated cylinder head and, depending on the specific version, a higher compression ratio to help produce 110 – 127kW at 6000 rpm.

Although based on similar architecture, the F2 turbo and FE DOHC atmo engines give a very different on-road feel – the forced induction engine comes on with a strong rush of low rpm torque while the atmo engine performs best above 4000 rpm.

But what happens when you add a forced induction to the free-spinning DOHC motor?

Rob Windsor’s Ford Telstar TX5 holds the answer.

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Peer under the bonnet of this mild but attractive looking TX5 and you’ll find a Japanese-spec FE 2.0 litre DOHC treated to a custom turbo set-up. Rob tells us the DOHC engine was a very straight-forward swap - no cutting was required.

About now you may be wondering about the naturally aspirated engine’s compression ratio.

Rob tells us his FE DOHC runs a fairly mild 9.2:1 compression ratio but, thanks to its free-breathing DOHC head, he extracts the same performance on ‘only’ 17 psi boost as he used to with the F2 engine running 22 psi...

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The turbocharger currently selected for the job is a T28 ball-bearing unit mounted on a custom mild steel manifold.

"The manifold is nothing special - it cost just AUD$500 for the manifold and intercooler piping," says Rob.

Boost pressure reaches a maximum of 17 psi thanks to a Goyen solenoid valve that’s triggered by an in-cabin switch. Low boost (with the solenoid closed) has been increased from 5 to 10 psi by installing spacers on the wastegate actuator mechanism.

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Charge-air temperature is chilled by a newly fabricated front-mount air-to-air intercooler, which is built from a cut-down truck core. A professional aircraft welder fabricated the end-tanks and completed assembly. A TurboSmart blow-off valve can be seen on the intercooler piping into the throttle.

The turbocharger inhales through a pod filter mounted on the end of a length of convoluted tube, while gasses are exhaled through a free-flowing mandrel exhaust - it's 3 inch diameter to the cat converter and 2 ½ inch diameter along the rest of the system.

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The fuel system is a mixture of FE DOHC and F2 components. The standard FE fuel rail has been lightly modified to accept F2 turbo injectors and the driver’s side end of the rail now incorporates a fitting to attach to a Malpassi rising rate regulator. This regulator and a Holden VL Turbo fuel pump are carried over from the previously modified F2 engine.

Engine management uses a MicroTech programmable system, which removes the airflow meter from the equation and relies on a MAP sensor load input. Again, the MicroTech system had been fitted prior to the FE DOHC motor being dropped in.

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With boost pressure set to 17 psi, Rob’s turbocharged FE DOHC motor has blasted out a creditable 167kW at the front wheels (in Dyno Dynamics Shootout mode). And note there have been no problems with the factory 5 speed gearbox or driveshafts - Rob explains the Exedy clutch he uses isn’t ultra aggressive. He also avoids prolonged wheelspin which is known to destroy the open-centre diff.

So what does a feet-on-the-ground build like this cost?

Well, it hasn’t been an ‘open chequebook’ exercise, that’s for sure. Rob paid just AUD$800 for the DOHC engine (which is an orphan in Australia), AUD$500 for the manifold and IC plumbing and a few grand for the MicroTech management, exhaust, Malpassi reg and other equipment. We’re told the bill amounts to about AUD$5000.

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This 5 grand has provided performance to carve up the majority of cars encountered on the street. An easy 13.6 second ET (at 106 mph) is proof of that.

Note that an earlier time of 14.4 seconds was recorded using the FE DOHC motor with a smaller T25G running at 12psi through a standard intercooler - a set-up that was tried immediately after the engine was plonked in.

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Granted, 13 second performance isn’t the stuff of high-end road cars these days - but it’s mighty impressive for a budget car with the comfort and practicality of the TX5. Inside, the stock TX5 Turbo is decked out with automatic oscillating centre vents, an electric glass sunroof, comfy sports seats and very high-grade trim. Rob has added a timber steering wheel, AutoMeter boost gauge, Monza pedals, staged shift lights and a custom short-shift. A Pioneer head unit is wired to a 5 channel Alpine amp and there’s a 10 inch Pioneer sub hidden in the space where the spare wheel usually resides.

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Visually, the TX5 is a long, sleek 5 door hatch that looks m-u-c-h better when lowered. Rob has slammed his car’s ride height by around 4 inches – an exercise that required shortening the struts to avoid bump-stop problems. A set of 16 inch wheels and 205/50 tyres fill the guards. It’s a subtle sporty sedan look.

Rob is understandably enthusiastic about the result he’s achieved for a relatively modest amount of money. The car cost AUD$8000 (back in 1999) and, even when you add the AUD$5000 modification cost, you’re talking about a car cheaper than a bog-stock early model WRX. Note that, today, you can pick up a ’88 TX5 Turbo for around AUD$4000, which means the same result can be achieved for less than 10 grand.

That is, so long as you’re prepared to get your hands dirty like Rob.

Previous Incarnations

Rob’s TX5 Turbo has seen many different guises - let’s take a look at them...

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In its first stage, Rob gave the original F2 SOHC turbo engine an exhaust, pod filter, upgrade front-mount intercooler, blow-off valve, T28 turbocharger, MicroTech management, Malpassi regulator and VL Turbo fuel pump. Blowing at up to 17 psi, this set-up gave 128kW at the wheels. Note that this was before the days of dyno Shootout mode.

In its second stage, the T28 turbo was replaced by a Garrett GT25 pushing up to 22 psi (!). With this change, Rob upped the ante to 180kW at the wheels (in Shootout mode) along with much improved flexibility. Amazingly, this set-up gave an identical quarter mile time as achieved with the current DOHC engine - a 13.6 at 106 mph!

Unfortunately, this fun came to an end when the F2 engine ran lean. And that’s when the DOHC FE came into the picture...

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