Boost Controller Roundup - Part Two

In the first part of this series (see Boost Controller Roundup - Part One) we looked at the considerations surrounding boost controllers and detailed some Do-It-Yourself type systems. Now, in the final part, we delve into the off-the-shelf aftermarket controllers we’ve tested – everything from around AUD$30 to AUD$750!

Off-the-Shelf Aftermarket Boost Controllers

Turbotech Controller

The cheapest off-the-shelf aftermarket boost controller we’ve seen is the Turbotech unit, which sells for around AUD$30 on eBay.

Sceptical? Don’t be!

As covered in the article Thirty Dollar Boost Control, the Turbotech boost valve is not a run-of-the-mill bleed valve that vents pressure from the wastegate hose. Instead, it contains a steel ball that is forced down onto a seat by a coil spring. Boost pressure enters through the bottom port of the controller and tries to push the ball off its seat. When there’s enough boost pressure for this to occur, air passes through the top port and reaches the wastegate actuator. Boost pressure is then controlled.

The advantages of this approach might not be obvious at first. But compared to a bleed, the Turbotech controller offers potentially superior boost consistency across a range of ambient temperatures and in different gears. You see, unlike a bleed, the Turbotech unit has some inbuilt intelligence – for example, in extremely hot conditions or in a low gear (where the engine will produce a relatively small volume of exhaust gas) the steel ball inside the valve body will stay closed as long as necessary until enough boost pressure is developed to lift it off its seat. And, of course, the opposite also applies – in extremely cold conditions or in a high gear (where the engine will produce a relatively large volume of exhaust gas) the steel ball will lift off its seat as soon as there’s enough pressure to do so.

In addition, the Turbotech controller gives a very quick rate of boost rise due to the spring preload applied on the internal steel ball – its impossible for any pressure to reach the wastegate actuator until there’s enough boost to lift the ball off its seat.

Installation is very straightforward. Simply remove any existing boost control system and install the Turbotech (in its specified orientation) between the compressor outlet and wastegate actuator. Turn the bolt on top of the controller to achieve your desired boost setting and secure it in position using the locking nut.

As we said in our evaluation of the Turbotech controller, anything that allows you to control boost pressure for around AUD$30 is a winning product. But let’s not sell it short. It gives a very fast rate of boost rise and, across different driving conditions, it has the potential to give better control than a conventional bleed.

PowerUp MBC

In 2002, the Powerup MBC (Manual Boost Controller) was released as a cheap off-the-shelf boost controller with a RRP of AUD$99. These days, it’s not especially cheap but it is representative of entry-level bleed valves.

Like the AutoSpeed Boost Controller #1, the Powerup MBC shares the concept of bleeding pressure from the wastegate hose to increase boost. But, unlike Boost Controller #1, there is only one valve required – it incorporates a tiny opening in the intake port which restricts airflow through the valve to allow the necessary amount of air to be bled. There’s only one point of adjustment – the dial on top of the valve body.

When we fitted the MBC to a Holden VL Turbo we saw improved rate of boost increase and an elevated boost value. But, like many bleed valves, there was a there was a boost drop off toward the redline and a substantial gear-to-gear boost pressure variation – in fact, of all the controllers covered in this series, the MBC gave the least consistent boost pressure across different gears.

Pros and cons? Well, it’s one of the easiest boost controllers to install and calibrate, it’s modest in price and looks sexier than a pair of brass valves. Unfortunately, boost pressure consistency is not a strong point – at least, as far as our testing goes.

For the full article see Low Buck Boost

Digital Pulse Adjuster (DPA)

The Silicon Chip DPA is a universal electronics kit that can be successfully used to increase boost pressure in most cars running factory electronic boost control.

The Digital Pulse Adjuster is configured to intercept the variable duty cycle signal that the vehicle’s ECU sends to the boost control solenoid. The duty cycles sent from the factory ECU are spread across 128 ‘load sites’ onboard the DPA unit; this means when the factory computer is outputting a duty cycle of 50 per cent, the DPA assigns load site 64. Boost is increased by programming the DPA to send a greater duty cycle signal to the boost solenoid any combination of load sites. The shape of the boost curve can be tailored by individual adjustment of each load site.

Fitted to a ’94 Subaru WRX with intake and exhaust mods, we were easily able to tune the DPA to hold a steady 14 psi boost to the redline. We were also able to dial out a previously existing boost spike without reducing the rate of boost pressure increase. In addition, the factory ECU retains the ability to pull back boost as a safety measure (although it can’t pull it back as far as originally).

The DPA retails for AUD$79.95 and is programmed with a separately available Hand Controller which costs AUD$59.95 - both kits supplied requiring electronic assembly. Alternatively, the Hand Controller can be bought pre-assembled and tested for AUD$139.

See Digital Pulse Adjuster, Part 1and Digital Pulse Adjuster, Part 2for more details on the DPA.

Independent Electronic Boost Control (IEBC)

Another release from Silicon Chip is the IEBC – a standalone boost controller that can be used on any EFI turbo car.

The IEBC is a trick bit of gear that receives information on injector duty cycle (which is closely related to engine load) and allows you to program a corresponding duty cycle output to drive a boost control solenoid. The output frequency from the IEBC is 10Hz, which allows you to use pretty well any garden variety OE boost solenoid. And, interestingly, the solenoid is not intended to be configured as a bleed – instead, it is placed in-line between the compressor outlet and wastegate actuator. When the solenoid is un-powered it is closed and no pressure can reach the wastegate actuator and, conversely, when the solenoid is pulsed it allows pressure to reach the actuator and boost pressure is controlled.

This graph shows the IEBC map used to control boost pressure on a Japanese import Nissan Maxima Turbo. The map shows that at light engine loads (up load site 28), the IEBC outputs nothing so the wastegate is kept closed. Then, as the turbo spools up, the IEBC sends up to a 44 percent duty cycle to the solenoid to achieve a maximum desired boost level of 11 psi. Near the engine’s maximum output, the efficiency of the factory turbocharger begins to drop off and the wastegate is almost closed to maintain steady boost pressure. This map achieved a steady 11 psi boost to redline.

The IEBC retails for AUD$79.95 unassembled (or AUD$279.99 pre-built) and you’ll need to pay another AUD$59.95 (or AUD$139 pre-built) for the associated Hand Controller. This means an all-up price ranging from AUD$139.90 and AUD$418.99.

Note that this is not a system for beginners – we suggest it only if you have experience tuning other boost control systems and understand how easy it is to accidentally over-boost an engine.

For more on the IEBC, check out The Independent Electronic Boost Control, Part 1and The Independent Electronic Boost Control, Part 2.

TurboSmart e-Boost

The most sophisticated boost controller we’ve tested – and by far the most expensive – is the TurboSmart e-Boost.

The e-Boost is a stand-alone electronic boost controller which constantly monitors manifold pressure to ensure rock-steady boost all the way to the redline. This is known as a closed-loop boost controller – it monitors manifold pressure for feedback and adjusts the wastegate accordingly.

In addition to controlling boost pressure, the e-Boost incorporates a boost gauge (with a peak recall function), an overboost alarm, overboost shutdown and an auxiliary output which can be used to trigger intercooler water sprays at whatever you chose. You can also program three different boost pressures.

Installation is pretty detailed but anyone with a good knowledge of turbo systems should be able to get through it using care. First, the e-Boost unit should be mounted inside the cabin - preferably somewhere where it’s not an attraction for thieves. Next, you’ll need to run a hose through to the engine bay and connect it to a supplied boost solenoid. Note - if your car is equipped with factory electronic boost control, this circuit should now be disabled. Now use the supplied hoses to connect the new boost solenoid between the compressor outlet and wastegate actuator. That’s the plumbing completed. Wiring involves connection to a switched 12V power supply, earth, two connections to the new solenoid and a connection for night-time illumination.

To achieve your desired boost pressure you need to program a ‘set point’ between 99 and 0 - start off with a low number to ensure the engine doesn’t over-boost. The set point should then be incrementally raised until you arrive at your desired boost level. Next, you need to program the so-called ‘gate pressure’ – the boost pressure at which the wastegate begins to open and, therefore, the rate of boost rise. Following this, you can enter the e-Boost’s various alarm and shut-down values and, if required, an axillary output.

Currently selling for around AUD$750, we’ve proven that the TurboSmart e-Boost does a spot-on job of maintaining constant boost pressure regardless of temperature and gear position. It also has the benefit of user-definable wastegate creep, though we think the head unit is a tad fiddly to operate and too large for easy mounting.

See e-Boost Evaluation for our test of the e-Boost. Note that an updated e-Boost2 (seen here) has recently been released boasting a tacho, shift light, a two-dimensional programmable output and more. Price remains similar to the first generation unit.

Warning! In an article like this we must emphasise that increasing turbo boost pressure is an easy way to destroy an engine. If you are unsure about any aspect of installing and tuning a boost control system – which includes listening for detonation and monitoring air-fuel ratios – we suggest that you enlist a performance workshop to do the job for you.

So there you have it – everything from the cheapest and easiest Do-It-Yourself boost controllers to the most sophisticated and expensive. If you chose wisely, you should be able to achieve exactly what you want for minimum $ and effort. So get boosting!