Sport Compact Car Comparison: Boost Controllers

[JoeThaMan]

One hundred twenty six full throttle dyno pulls. We're pretty sure Jesse Rodriguez of Diamond Star Specialties had no idea what he was getting into when he volunteered his car for our boost controller test. Amazingly, the only problem we had was paint melting off his rear bumper.

For such a seemingly simple device, boost controllers vary wildly in cost and complexity. Electronic boost controllers offer in-cabin adjustability, supposedly better boost response and advanced mapping capabilities, but some claim mechanical systems work equally well at a fraction of the cost.

In an effort to learn the real difference between $50, $250 and $750 boost controllers, we ran all the controllers we could find on Rodriguez's very angry Eclipse GS-T Spyder.

Boost Control Basics
Every modern turbocharger uses a wastegate to regulate boost. The wastegate is simply a valve that allows exhaust to bypass the turbine, limiting the energy available to drive it . When designed into the turbine housing, they're called internal wastegates, the kind found on nearly all production cars. External wastegates are located separately from the turbocharger, somewhere between the exhaust ports and turbine housing. The remote location allows the valve to be bigger and flow path smoother, resulting in better boost control and the ability to safely manage a more powerful engine.

The wastegate is held shut by a spring, and as boost builds, the wastegate actuator diaphragm pushes the wastegate open against this spring. The size of the diaphragm and strength of the spring determine how much boost it takes to open the wastegate.

All the boost controllers in this test act on the pressure signal that opens the wastegate. Reducing this pressure will keep the wastegate closed, allowing more boost to build. When the desired boost setting is reached, the controller lets pressure into the diaphragm, opening the wastegate.

Electronic controllers use either stepper motors or solenoids to do this. Stepper motor assemblies vary the opening of a precision valve, similar to a water faucet. This action is accurate, though somewhat slow. Solenoids, however, operate in either a fully open or closed position, but can change this state very quickly, feeding and releasing full pressure so quickly that the pressure in the diaphragm can be accurately controlled. Dual solenoids will give an even greater degree of precision. The HKS EVC EZ, EVC IV, and GReddy PRofec A all use an identical stepper motor assembly. The GReddy PRofec B and Blitz SBC i-D share a common dual solenoid design, though they drive them differently. A'pexi stands alone with its single solenoid design.

If a wastegate is set to 10 psi, it may start to open around 6 psi, slowing the turbo's acceleration and finally reaching equilibrium at 10 psi. Boost controllers can improve turbo response by keeping pressure off the wastegate as long as possible, making more energy available to drive the turbine. Just as boost reaches the set point, pressure is dumped on the diaphragm to rapidly open the wastegate, and hopefully keep from spiking the boost.


The Testing
Testing was performed on a 1997 Eclipse GS-T with a front-mount intercooler, big injectors, cams, a popular hybrid turbo known as a Frank Stage 3, and a 3-inch exhaust. Two key points to remember when comparing these results are that this car exhibits minor boost creep and it has an internal wastegate.

We intentionally tested a car with boost creep because it's a common problem. In a later test, we'll use these same controllers with an external wastegate.

A Dynojet was used to simulate the load of accelerating on the street in third gear. Our two basic tests tracked boost when the throttle was slammed open at 2000 rpm and at 4500 rpm. The 2000-rpm test would give the controllers a chance to highlight any improvement in response, and illustrate their stability through the rev range. Tipping in from 4500 rpm challenges the controllers ability to suppress boost spiking as the turbo is already up to speed.
Interpreting the Results
When interpreting the data, don't dwell on the final boost level. We were shooting for 12 and 17 psi, but didn't spend too much effort landing right on those values. More important is the rate at which boost builds, and the controller's ability to prevent spikes and hold a constant boost level. The tests at 2000 and 4500 rpm are shown on separate charts.


The transition from building boost to holding it is a demanding event for the boost controller. The longer boost can be kept from the diaphragm, the quicker the boost will build. Wait too long and it will overshoot, open it early and response is soft. Even if you get the timing right, there's the problem of how much to open. Again, not enough and the boost keeps going up, too much and your gauge will bounce like a basketball.
Finally, remember these tests were done on a car with an internal wastegate that does exhibit boost creep. Some controllers specifically warn against use on engines like this, and not surprisingly, they didn't work so well.


How We Did It
Testing is all in the numbers, and you need lots of numbers to really understand what's going on with seven different boost controllers. For this test we used an Edelbrock QwikData. Boasting a maximum sampling rate of 500 Hz, it had no problem keeping good records of our boost controllers' performance. We used two of the eight analog inputs for TPS and boost, one of the six digital inputs for rpm. The Windows-based software allowed us to monitor all the sensor readings in real-time on screen to make sure everything looked good. Watch for a complete review as soon as we get more creative with this great tuning tool.

Apexi AVC-R

A'pexi suggests having the AVC-R installed at one of its authorized Power Excel Shops. This might be a good idea, as splicing into the car's ECU harness to intercept engine speed/injector pulse width, throttle position, speed, power and ground are required to get the most out of the unit. Wiring in a momentary switch, which is not provided, is also required to take advantage of the scramble mode. If you're comfortable digging through the dash, and making good clean electrical connections, you should have no trouble installing the unit yourself. A'pexi includes ECU pin-out diagrams for most popular Japanese makes.

A single solenoid regulates the signal going to the wastegate, and a separate MAP sensor can be placed wherever it's convenient. The quality of the components is first rate, with waterproof connectors used for all engine compartment junctions. About the most annoying thing in the world is not having the right vacuum "T" fitting when trying to install your new toy at 1 a.m. A'pexi comes through with a vast goodie-bag of tee fittings and hose clamps. Also of note are the vehicle-specific install diagrams for the twin-turbo Supra and RX-7, which interestingly recommend rerouting the turbos to run in parallel.

The control unit itself is handsome, with a huge vacuum fluorescent display that's easily viewed from all angles and auto-dims in low light conditions. Contrast is adjustable from a submenu. An adjustable bracket simplifies mounting on uneven surfaces.

Basic programming and operation are straightforward with a little guidance from the 57-page English manual. The menu-driven interface is clear and intuitive. A'pexi has put a considerable effort into documenting its product and it shows. The two boost settings can be independently programmed, retained, and switched between as desired. Boost can either be set at a fixed level, or allowed to vary with rpm. Additionally, a separate scramble configuration is available for each setting to raise or lower the boost at the touch of a button (any button you want, as the unit just looks for a signal wire to be grounded).

Monitor mode provides a number of methods to display and log all the sensor data available to the AVC-R. A maximum of four digital numbers, two simulated analog dials, or a single line graph can be displayed. Maximum log time is 60 seconds. A peak hold function is also available for all displayed data.

Out of the box the AVC-R worked fine on our Eclipse. Boost response was good, but as we tried for more, things got a little weird. Getting the most out of the unit takes either lucky guessing, or real tuning time. First you set the boost, then duty, Ne-point, F/B speed... While the AVC-R is supposed to tune itself, it seems the brunt of the work is on your shoulders. If you like to fiddle with things, you'll be in heaven.

Controller: A'pexi AVC-R
Pro: Big display, tons of features, works great.
Con: Must splice ECU harness. Takes time to program well.
Cost: $629
Source:
A'PEX Integration Inc.
(714) 685-5700
A'PEXi U.S.A. - Home Page
Aesthetics: Nice big display, simple interface, clean design, big buttons.
Ease of installation: Splicing wires into a ECU harness can get hairy, but the instructions show wire locations for most Japanese cars. Installation instructions available on the company's Web site.
Clarity of instructions: Big fat book in English. Diagrams and flowcharts are intuitive.
Features: Fixed boost, rpm-based boost control, scramble up and down, auxiliary instrumentation for rpm, speed, TPS, duty cycle, boost. Data logging and replay, peak/hold display.
Support: Good on phone, answered questions.

Blitz SBC-iD

The SBC i-D is composed of three parts; a head unit, control unit and solenoid assembly. The solenoid assembly consists of two solenoids which can be operated either sequentially or in parallel, which Blitz claims gives the product an edge in both response and maximum boost authority. The control unit is scarcely larger than a deck of cards and can be mounted out of the way in the cabin. Manifold pressure is routed with supplied hardware to a small and somewhat fragile Teflon hose on the control unit. An optional harness is available which plugs into the control unit and allows for the display of three analog or digital signals such as MAF voltage, coolant temp, injector pulse-width, etc. This data can then be displayed numerically, as a bar graph, or logged over time.

The head unit fits neatly into most car stereo openings. If installing the Power Meter i-D, the two sit edge-to-edge to fill the slot. Like its name implies, the optional Power Meter offers an idea of the power output of the vehicle based on a number of input parameters along with speed data from the car's ECU.

Using the SBC i-D is a breeze, with nearly all navigation and adjustments made through a single dial. Rotate the dial to scroll up or down a menu, depress the dial to select, rotate the dial to make your change, depress the dial to enter the change.

The SBC i-D has two distinct modes of boost control. The Auto mode allows you to simply dial in a boost level and be on your merry way. The control unit watches the boost and carefully raises it to the target pressure. Your first time out, the turbo is going to be laggy, but with each subsequent run the boost will build faster. In our testing, the unit learned quickly and dramatically. The second mode is Manual, and allows the boost set point and gain to be individually tweaked for desired response.

With just a little work we were able to post the sharpest boost response of the test. Four programmable "channels" are available to save your different boost settings. With the Power Meter i-D, boost can also be mapped to mph in four discrete steps. In the event of an over-boost condition, a warning mode can flash the screen red, activate an audible alarm and reduce the boost a set amount.

The scramble boost feature on the SBC-iD is a unique one, shared with Blitz's DSBC spec R. Rather than having a button or switch to toggle a different boost level for some set amount of time, the system activates every time you go from vacuum to boost. The unit scrambles to a different channel where the boost can either be raised or lowered. Once scramble times out, you need to drop into vacuum again to reactivate the scramble mode. Blitz claims this system was designed for a circuit-racing environment. We don't get it. Luckily it can be disabled.

Controller: Blitz SBC i-D
Pro: Super-smooth interface, great display options, works awesome.
Con: Lame scramble boost feature, non-standard vacuum fittings.
Cost: $669, Power Meter i-D $298
Source:
Blitz USA
(714) 777-9766
Blitz-NA.com
Aesthetics: Small and simple.
Ease of installation: Power and ground, boost line into the cabin, plus some stupid pressure fittings.
Clarity of instructions: Not really needed, which is good, since they kinda suck. Available on the Web site.
Features: Four boost settings; Laggy (auto) or responsive (manual) boost mode; overboost warning and protection; sorta-though-not-really scramble boost; peak-hold boost display; choice of boost units (psi, bar, kg/cm2, and kPa); three alternate data input channels for display of digital or voltage readings (TPS, MAF, O2, etc.), logging and replay of boost and optional channels.
Support: Great on the phone. Happily answered all questions.

Greddy Profec-A

Fuzzy logic boost controllers have been out for quite a few years. The claim is that they "learn" the response characteristics of your turbocharger, and can thus build boost faster, and hold it with greater stability than conventional control methods. In reality, however, controllers based on this technology tend only to work on fundamentally stable turbo systems. This means no boost creep nor fall-off, and no sequential set-ups. Additionally, any modifications that may affect performance like a different air filter or exhaust, require the controller to re-learn the boost curve.

In the case of the PRofec-A, running through the learning process is really no big deal. You either need a good clear length of open road, or a dyno to do the required third gear acceleration runs. After a half-dozen pulls, it was clear the PRofec wasn't happy about our car's boost creep, and required us to use its alternate learning procedure. This involved tweaking an impossibly small dial on the face of the unit with the provided screwdriver, until the built-in boost gauge matched up with our aftermarket unit. With learning complete, you simply dial in your desired boost level and away you go.

In PRofec speak, "Over Take Boost" means scramble. Setting it up is a breeze with the exception of the visit back to Lilliput to turn another pair of dials. Once set, the mode can be activated by momentarily pressing yet another tiny button on the face of the controller. Holding the OTB button down will engage Hi Boost mode, which raises boost to the OTB level. GReddy offers a very cool optional wireless remote switching system that can activate OTB, toggle from high to low boost, and even activate a nitrous system or line lock. If you plan on using the OTB mode, consider the remote switch mandatory; you have no business fumbling around the dash for a little button while driving fast.

The final feature offered in the PRofec is an overboost warning alarm and protection function. If the boost exceeds a specified amount for more than one second, the system will drop the control pressure to the base boost level until the manifold pressure drops below the alarm point. This occurs in addition to visual and audible alerts

Controller: GReddy PRofec-A
Pro: Integrated boost gauge, over-boost warning, compact unit.
Con: Fuzzy logic is picky, stupid small controls, dated design.
Cost: $595, Optional Remote Switch $128.
Source:
GReddy Performance Products Inc.
(949) 588-8300
Greddy - Founded and Driven by Racers
Aesthetics: Very compact design, basic black.
Ease of installation: Yes.
Clarity of instructions: Basic but complete, nothing application-specific. Available on Web site.
Features: Fuzzy logic, "overtake boost control," boost gauge, limiter and alarm.
Performance: No better than a ball valve.
Support: Helpful customer support, answered phone the first time and provided quick and accurate information.

Greddy Profec B (Now Profec Type S)

PRofec stands for Pressure Offensive Controller. What that means we're not really sure, and we don't care. The PRofec-B is really good. GReddy's "basic" model features a dual solenoid design similar to the Blitz SBC i-D. The solenoid assembly is somewhat bulky, but mounts easily enough in the engine compartment. An additional pressure signal must be brought to the back of the control unit in the cabin. Our tester came housed in a translucent blue case, which lets you see all the electronic bits inside. When lit up at night, it looks like a cross between a UFO and a holiday ornament. Basic black is available for a few bucks more.

Where the PRofec-A must be trained in the ways of your turbo, the B model comes out of the box smart. GReddy specifically recommends this unit for sequential cars and problem cases. Straight-away boost is responsive, though further tuning can be made with the balance dial. High and low boost each get their own dial, all of which normally sit flush, and pop out for adjustment. Toggling between high and low boost is accomplished either by the mode button on the control unit, or through the use of GReddy's optional wireless remote switching system. Mount it on your steering wheel, shifter, key chain or girlfriend.

Controller: GReddy PRofec-B
Pro: Super simple, works great.
Con: Sensitive knobs.
Cost: $420 in black, $399 in blue, remote switch: $128.
Source:
GReddy Performance Products Inc.
(949) 588-8300
Greddy - Founded and Driven by Racers
Aesthetics: Looks like a Xmas tree ornament.
Ease of installation: Yes.
Clarity of instructions: Fine. Available on Web site.
Features: High, low boost, adjustable response.
Performance: Grrrreat!


HKS EVC-EZ

The EVC EZ is out there for those who just want a dial in the cabin, and that's all you get. Be forewarned, however; it's a mighty sensitive dial. HKS claims the EZ can take you to 35 psi, which is probably true.

The stepper motor used for boost control is the same as used on the EVC IV. Installation is a simple case of hooking up power and ground. Three hoses need to go to the intake manifold, compressor discharge and wastegate. If you have a twin turbo Supra or RX-7, you can find vehicle-specific instructions in the Japanese manual. They're in Japanese, of course. Unless you purchased the optional installation kit for your vehicle, run out and get a 6mm vacuum tee before you start working, as one isn't supplied. Finally, flip the switch on the back of the unit to select internal or external wastegate and you're all set.

Much like the volume knob on a high-end stereo receiver, the EVC EZ is ready to rock, so tune in cautiously. There's no mention in the one and a half pages of English instructions about problems using the EZ on cars with minor boost creep, but it sure doesn't seem to like it. To be fair, we've had no boost spiking problems on our externally wastegated test car.

Controller: HKS EVC-EZ
Pro: CARB legal. Adjustable from inside the cabin.
Con: Significant boost spike.
Cost: $395. Installation kit, $20-135.
Source:
HKS USA
(310) 763-9600 x203
HKS USA Driving Performance - Homepage
Aesthetics: Simple and clean.
Ease of installation: Two wires, three hoses.
Clarity of instructions: It missed the most important one, "be careful with the dial." Otherwise, fine.
Features: In-cabin adjustable boost. CARB legal.
Performance: Boost control not as good as a ball-valve.

HKS EVC-IV Silver Edtion

The HKS EVC is the granddaddy of electronic boost controllers. Many still consider the EVC II to be the best boost controller out there because it's so simple to use, thanks to high and low presets on its face and a knob that lets you manually dial in a third boost level. It would work with both internal and external wastegates if you knew which dip switches to flip around inside. For years it was the only option, because everything else out on the market didn't work.

The EVC IV shares its case size with all the other HKS electronic components back to the original EVC I. It still has the high- and low-boost modes, but now you also get a scramble mode, integrated boost gauge, over-boost alarm and protection feature. The limited edition silver model we're reviewing here incorporates a handy additional Peak/Hold function on the boost gauge. Peak/Hold is key for programming the EVC IV, because like the PRofec A, it tries to take advantage of a fuzzy logic to optimize boost characteristics. Unlike the PRofec though, programming is a pain.

To do anything you must depress some combination of poorly labeled buttons, and do it quickly. Almost every time the dial is turned, it must be calibrated by turning fully to the right or left. Having used the menu-driven interfaces from other companies, operating the EVC feels like a game of Memory. Plus, all four buttons are fairly small, and pretty close to each other, making it easy to hit the wrong one.

There's an optional harness to remotely mount the scramble trigger, which is great. If you're too cheap, just connect a momentary switch between the orange ground and yellow trig wires.

For weeks we've had the EVC IV running on our externally wastegated test car with no problems. Installing it on the Eclipse was straightforward; it went in just like the EVC EZ. We could get through the learning procedure just fine. Once a boost level was dialed in however, the EVC just seemed to sit back and watch the show. Boost would build quickly, and just keep on going right past our set point. Peak/Hold recorded only a fraction of the pressure run, which was probably the reason the alarm didn't activate. Luckily, we had good fuel in the car, and it was able to survive the 25 psi of boost. We tried reprogramming, swapping out the harness, even using the actuator from the EVC EZ. All the settings were checked by a number of people. Replacing it on the other car proved the unit works fine. It just didn't like our Eclipse.

HKS as a company has been very aggressive in perusing CARB-exempt status on all its products. This effort is by no means trivial, and we applaud its efforts. Here in California, vehicles are being pulled over more and more often for suspected vehicle code infractions. Bottom line: If your car gets inspected by the state, you want an EO number for every aftermarket part you have. HKS is the only one that offers this security.

Controller: HKS EVC IV Silver Edition
Pro: CARB legal, peak / hold boost gauge.
Con: Won't work on a boost creeper. Adjustment dial from hell.
Cost: $735 silver, $675 std. Installation kit, $20-135. Scramble trigger $80.
Source:
HKS USA
(310) 763-9600 x.203
HKS USA Driving Performance - Homepage
Aesthetics: Nice size, clear display, meaningless button labels, totally lame dial.
Ease of installation: Yes.
Clarity of instructions: Japanese book gets 62 pages. English book gets 5. We must be missing something.
Features: Low, high and scramble boost settings. Boost gauge (peak/hold on silver model). Overboost warning and protection. CARB legal. Adaptive control.
Performance: Needs to be manually set, then doesn't hold true. Scramble works well, though.

Ball Valve Manual Boost Controller

Here it is, the hardware store homebrew that could. DSS' manual boost controller is a simple ball-spring system that delays pressure from getting to the wastegate. An adjustable spring holds the ball bearing against a seat, blocking off pressure from reaching the diaphragm. Once the spring is overcome by boost pressure, most of the air makes its way to the actuator, while a bit is allowed to bleed off to atmosphere. This bleed is necessary, as once you're back out of boost, you don't want the ball-spring to act as a check valve and hold the wastegate open. If you're handy and want to build your own, try these numbers to start: 0.065-inch bleed, 0.375-inch ball, 3 lb/in spring.

In all honesty, it kind of looks like a plumber got his hands on your car, but it sure does work. Turning the black-oxide coated bolt down against the spring makes adjustments. We gained around 1.5 psi of boost per turn. Two springs come with the kit; one is good for about 20 psi, the other even more. We never had a chance to try the other.

DSS has an improved design going into production that should eliminate much of the boost spiking experienced in this unit.

It'll also look much better, is manufactured from billet aluminum and be available in a number of anodized colors.

Controller: JBC/DSS MBC
Pro: Works pretty darn good.
Con: Some boost spiking. Can't adjust inside the car.
Cost: $65. You can get six of these for the next closest competitor.
Source:
Diamond Star Specialties
(805) 541-4483
www.diamondstarspecialties.com
Aesthetics: Looks like your uncle the plumber got his hand on your car.
Ease of installation: As easy as it gets.
Clarity of instructions: See above. Written for DSMs, applicable to all.
Features: Makes more boost.
Performance: Simple, effective and consistent.

[Billyburnout]

Wow, that was really informative. Can I still make fun of manual boost controllers?

[Gaslight]

Joe!

I did not see Innovatives boost controller in there?

Jake

[JoeThaMan]

This was a test done by Sport Compact Car.

[patman]

good info...
im sure everybody knows about them, but ive sorta go the best of both worlds with a turboxs dual stage MBC. Its basically 2 manual boost controllers in one package, with an electric solenoid that switches between the two, so you mount a switch in the car, and can instantly switch from low to high boost and back.