Boost controllers can be simplistic and complex, vary in features and cost, as well as work excellent in some applications while doing poorly in others. Evans Tuning has gotten literally hundreds of emails over the past few years concerning which boost controller we recommend to use, and while it would be nice to recommend a single boost controller to do it all, no such one exists. First and foremost as the consumer, you have to make an honest and educated decision as what you want out of a boost controller. What are you going to do with your car? Daily driver? Road course/Auto-x? Drag race? Dual purpose? Once you can accurately decide which application you’ll be using the car for, you’ll need to know what features you are after. This is where Evans Tuning can help. Below is a chart listing some of the major features to look for in a boost controller.



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Data logging: Data logging is an essential tool in getting the best performance out of your vehicle. Most of the boost controllers on the market do not come with the ability to data log without the use of a programmable engine management system or other auxiliary data logging device such as PCS or Racepack. The NLR AMS-1000 boost controller allows for on board data logging to give a graphical boost vs. time comparison in order to set up the time based boost feature (drag race only). This is invaluable in setting up the various stages, and ramp rate features of the AMS-1000. With AEM EMS and Hondata systems using the AEM boost solenoid, you have the ability to view boost vs. time, speed and gear with the on board data logging (among countless other parameters). With the AEM EMS system this allows for setting up vehicle speed based boost more accurately and efficiently. With the Hondata s300 and Kpro system using the gear based boost feature this allows you to accurately set up the maximum amount of boost that each gear can run without wheel spin.


Gear Based Boost: Gear based boost feature is found on the Hondata s300 and Hondata Kpro systems. Gear based boost is an excellent way to control boost for road racing, auto-x, daily drivers and drag racing. The major advantages with gear based boost are that it’s not solely based on time, or vehicle speed. You can vary the amount of boost for each gear, aiding in traction on any type of tire. Hondata allows for the ability to have two separate “boost by gear” tables, so that you can have table for street tires and another for slicks. The disadvantages of gear based boost in traction limited applications is that only one boost setting is achieved for a particular gear. In order to gain maximum traction, less boost should be run at lower rpm and increased, as rpm increases for each gear. Hondata cannot currently do this. This is the simplest boost control method to dial in.


Speed Based Boost: Speed based boost is found on the AEM EMS system. Vehicle speed based boost control has several advantages and disadvantages. It’s perhaps the hardest boost control method to dial in, as wheel spin gives a higher vehicle speed reading to the EMS (vehicle speed is read from the transmission), and typically with increased vehicle speed the boost is increased as well. It’s unfortunately a vicious cycle in which wheel spin leads to over shooting of the target boost. Once dialed in so that excessive wheel spin does not occur, it has the advantage of being able to increase boost for each gear with engine rpm. This is a progressive control of boost that can ultimately lead to better control of traction in comparison to gear based boost.


Time Based Boost: Time based boost is excellent for drag racing, but does not work well for any other application since there are far too many conditions to predict (up shifting, down shifting, stop/go driving, varying throttle ranges, etc). Time based boost only works if the driver is consistent on shift points, and activating the timer on launch. It is by far the most effective and consistent way to control boost for drag racing, as gear change or wheel spin does not affect target boost control. The NLR AMS 500 and 1000, as well as the Turbo XS Quad Stage controllers all work excellent with the time based boost feature.


Multiple Boost Levels: On the simplistic end of boost controller features for a daily driver, or a mild power level drag car (under 600whp) there is a multiple level boost control. With boost controllers like the Turbo XS dual stage, Greddy Profec B, NLR AMS-500, and AEM EMS Tru-Boost you can have two boost levels. For a daily driver, this gives you the ability to have a “low” and “high” boost level, and for a drag racing application gives you a “launch” boost level and “high” boost level for a top gear at the track. For high horsepower cars (600whp+) the Turbo XS quad stage boost controller gives you the ability to have four separate boost levels. You can stage the boost by time, gear or speed depending on how you trigger each stage (whether by timer, or engine management system (gear or speed methods)).


Boost Ramp Rate Control: Ramp rate control is primarily a drag racing feature. This feature is found on the NLR AMS 500 and 1000 controllers. Ramp rate control is found on either gear based or time based mode. This allows you to increase the boost with a target amount per second, allowing for the ultimate in control. For example, on launch if you want the boost to come in slower you would have a lower ramp rate over a specified amount of time. Then, as the vehicle speed increases you increase the amount of boost over specified time. This can be the difference of putting 800whp down to the ground, or spinning the tires the entire way down the track. The AMS 500 controller allows for only one stage of ramp rate control. The AMS 1000 controller allows for up to 6 stages of ramp rate control.


Boost Override: Boost override allows you to “on the fly” switch to a lower amount of boost. This is helpful in excessive wheel spin conditions, or if you simply don’t want to run as much boost.


Co2 Boost Control: In order to understand why Co2 boost control is needed in some applications, basic knowledge of how a wastegate and boost controller works is needed.

An external wastegate has a diaphragm which creates a seal, and a spring which holds the wastegate closed. Spring rates vary depending on the amount of boost you want to run. Typically they are given in a "bar" value. For example, 1 bar would be 14.7psi. This would mean that in order to open the wastegate you would need to exert a greater pressure than the 14.7 psi spring holding the wastegate closed. In order for the wastegate to work you must have the boost reference port hooked up to the compressor side of the turbo or intake manifold. If you don't have this vacuum line attached then the boost pressure will not be limited to the set spring pressure; it will build unlimited boost pressure until your engine is destroyed (“bottom” wastegate port). Normally, exhaust manifold pressure pushes against the valve and diaphragm (through the vacuum line attached to the compressor reference port) which in turn pushes against the wastegate spring. When the exhaust manifold pressure exceeds the spring pressure the wastegate’s plunger opens releasing the excess pressure through the wastegate outlet (typically via a dumptube).

The top port on the wastegate is normally open to the atmosphere. This provides no additional resistance to the wastegate “spring”, and the wastegate will operate at the desired spring pressure. In order to increase the amount of boost over the spring pressure inside the wastegate, two methods can be used.

The first method is using a manual boost controller. A manual boost controller works using a spring and check ball. By screwing the adjusting screw into the boost controller you put more pressure on the spring which reduces the amount of airflow through the boost controller and into the boost controller port (“bottom” wastegate port). Less airflow means less pressure will be assisting the spring to keep the wastegate plunger shut. The “top” port is left open to the atmosphere with a manual boost controller.

The second method is using an “electronic” type boost controller. An electronic boost controller uses a solenoid inline of the boost pressure source to the top port on the wastegate. The solenoid is “pulsed” by a PWM (pulse width modulated) output from the boost controller or engine management system. With more opening and closing of the solenoid more pressure is applied to the wastegate. With less opening and closing, less manifold pressure is applied and less boost is achieved. When more boost pressure is applied to the top port of the wastegate, it directly applies more force to the wastegate valve, keeping the valve shut until enough exhaust pressure is applied to open the wastegate. This is essentially like adding a higher rated wastegate spring (stiffer). The bottom port of the wastegate is connected directly to the pressure source (compressor cover or intake manifold), with nothing installed inline.

Exhaust pressure increases as boost pressure increases. The amount of exhaust pressure in the exhaust manifold is affected by the turbo exhaust wheel size, exhaust housing size, exhaust manifold type (equal length or log), displacement, cam profiles, etc. In most situations using a manual boost controller you are not able to increase boost much more than a 2:1 ratio, meaning if you are running a 10psi wastegate spring you are not able to increase the boost much more than 20psi. With an equal length manifold, and large turbo sometimes a 3:1 ratio can be achieved. When using an electronic boost solenoid on the top port of the wastegate, as much as 6:1 ratio can be achieved if an equal length manifold and large turbo are used. For high boost applications, using a small wastegate spring for lower gear traction an electronic boost controller is what is necessary. For most turbo set-ups (probably 95% of what is on the market) achieving a 6:1 ratio is not possible. This is where running a compressed gas that can apply greater than manifold pressure is necessary. For example, a 3psi wastegate spring can be used, and flowing 90psi of co2 pressure to the top port of the wastegate will allow for greater than a 6:1 ratio. This gives the ability to get the boost low enough to aid in traction, and increase boost to pressures in excess of 50psi if needed. The boost solenoid vents the excess Co2 pressure so that target pressure can be reached. This also allows for more boost consistency with elevation change, as you are not relying on less available atmospheric pressure for the turbo compressor to work with. Boost controllers such as the AMS-1000 or AMS-500, and the AEM boost controller solenoid being used with the AEM EMS or Hondata systems are compatible with Co2. It should be noted that Co2 as a pressure source is not practical for a daily driver, and should really only be used for drag racing applications.


So what does Evans Tuning Recommend?
All of the controllers listed are what we sell, recommend, and use on our personal daily drivers, race cars and turbo projects. There are many other controllers on the market, but for the features, cost and performance our selection is top notch. For drag racing the AMS-500 or 1000 is perhaps the ultimate in control, but comes at a higher price. For daily drivers looking to just increase the boost a bit higher than spring pressure the Turbo XS single stage or dual stage, Greddy Profec B, or AEM Tru Boost boost controllers work extremely well. For high power daily drivers, road race and auto-x, gear based and speed based boost control works excellent with the AEM EMS and Hondata systems, but these engine management systems have to be used. There is no single best boost controller, but with this article we hope to educate your decision.

**Please note that the Hondata s300 with boost solenoid and Hondata Kpro with boost solenoid are applications only for Honda/Acura. All other boost controllers are universal.