A short summary is this:
The turbo takes exhaust to spin a turbine which pressurizes the intake air. If left unchecked the boost pressure could grow to dangerously high levels. A wastegate lets exhaust bypass the turbo so the boost pressure does not rise too high. On 3000GT/Stealth twin turbos the wastegate is set for approximately 6 psi.
That means that if you plumb the intake boost pressure directly to the wastegate the boost pressure will
not go higher than 6 psi. The stock boost controller bleeds off the boost signal to the wastegate so that the wastegate only sees a 6psi signal when the boost pressure is around 10-12 PSI.
Aftermarket boost controllers usually stop the boost signal completely until desired pressure is reached. By completely stopping signal from reaching turbos, the turbos should spool up at maximum speed
Sport Compact Car Magazine did a great boost controller comparison in the July 2002 issue.
I will quote them several times below.
You want to change the boost pressure so you have to modify the signal going to the waste gate.
There are 3 common ways of doing this that I will compare.
Bleeder valve
Ball and Spring check valve
Electronic boost controller
1. Bleeder Valve:
The bleeder valve works by putting a controlled leak in the boost signal going to the waste gate.
This is used with a stock boost controller solenoid.
Pros:
- Cheap! you can make one for only a few dollars.
- You can increase your stock boost by few PSI easily. Cons:
- Inconsistent, may be difficult to set accurately and my come out of adjustment. If not carefull boost will spike a few PSI over the pressure you set it at.
- Turbo spool times not as fast as possible. Since pressure is going to waste gate then bleed off the wastegate opens a little at first and turbo does not spool as fast as possible.
- No warning signal
- Need aftermarket boost gauge
- Not really adjustable from inside of car
2: Ball and Spring Check valve.
The ball and spring Boost valve works by completely blocking the boost signal until the boost pressure gets high enough to bypass the check valve and reach the wastgate. The boost pressure is blocked by a ball that is held in place with a spring thats tension is set by a screw. When the boost pressure is high enough it overcomes
the spring force and the boost pressure reaches the wastgate.
Pros:
- Cheap $40 at http://www.boostvalve.com/
- Minimum turbo spool times. Since no boost single reaches the wastegate the turbo spool at maximum speed until the desired pressure is reached. Cons:
- Not adjustable from inside the car.
- No warning signal
- Need aftermarket boost gauge
- Sometimes hard to set and may not be reliable. Mine was perfect for 1 year and then I had to adjust it constantly I finally gave up and bought a Blitz DSBC and I love it.
Below is a copy of graph that Sport Compact car did showing the spool up of the boost valve on a single turbo DSM. Notice that the boost does spike fairly high.
3. Electronic Boost controllers.
A electronic boost controller works by monitoring the boost pressure and only allows boost signal to reach
the wastegate when needed to control boost. Electronic boost controller are the best option in my opinion.
I used to think that electronic boost controllers were a waste of money until a got a datalogger. Now I can monitor if the engine is knocking or not. So I can keep safely keep pushing the boost level as high as possible then backing off as soon as I see engine knock. Since the maximum safe boost level will vary from
day to day I want to modify my boost levels all of the time. An electronic boost controller would allow me
to do that So I will probably buy one as soon as I can afford one.
Pros:
- In cab adjustment, available overboost buttons allow quick boost jumps
- Fuzzy logic learns boost curve of engine and learns how to optimize boost.
- Built in boost gauge. Please note they are usually hard to see when driving
- Programmable boost warning to alert you if you are overboosting for some reason (like a disconnected signal line to boost solenoid!)
- Looks Cool!
- When set right, allow for quick turbo spool and can almost eliminate boost spikes
- Some controllers allow you to program boost level based on RPM and even gear selection. This is an excellent feature for FWD cars that have traction problems, the boost can be lower until the car hooks up the boost increases. For a AWD car this is not really necessary.
Cons:
- Expensive $400-$600!
- Can be difficult to program correctly (depends on model)
- Takes up room in dash that you may not have.
Examples of some boost controllers:
Ball and Spring type Manual boost controller:
Boostvalve.com
Ric Gillis makes a very affordable and accurate control valve. I use it on my car
and highly recommend it if you can not afford an electronic boost controller.
$39 for universal kit and $45 for a 3000GT/Stealth specific kit see.
Price List
He also has directions for using stock boost solenoid for a low boost setting
6psi. I tried this and the boost was so low I hated it but it is a great idea
if you want a valet switch for when you loan your car to others. See directions
for standard install and
Standard install or
Dual Level install
DijonTool.com
DijonTool.com: Also makes manual boost controllers. They make 1,2 and 3 setting
manual boost controllers (ball and spring) I have not tried them but DSM guys have
had good luck from what I have heard. The boost levels are controlled from a toggle
switch in the interior of the car, very cool.
1 boost level $50
2 boost levels $90
3 boost levels $180
Hallman Boost Controllers: $50 to $165
They have a new manual boost controller connected to a cable that lets you adjust boost from inside the car!
I saw one at the DSM shootout and it was very well made. It is also larger than the boostvalve.com
boost controller. This means that the ball is bigger which requires a bigger spring. A bigger spring
Is going to be less prone to fatigue and theoretically should not vary as much as smaller spring controllers
JoeP boost Controller:
A DSM favorite with a great reputation. It places the spring between 2 balls
so the spring doesn't bind up and if control knob is lost the EXTRA ball will
plug the hole. $45
Electronic Boost Controllers:
1. HKS EVC-EZ:
Definitely NOT Recommended for 3000GT It spikes horribly, see chart below
2. HKS IV:
Great reputation, but Sport Compact car seemed to have a bad unit so they had no good test results
3. Greddy Profec A:
Not really recommended for 3000GT it spikes too much, see chart below
4. Greddy Profect B:
Recommended for 3000GT it hold boost very well, see chart below
5. A'pexi AVC-R B:
Sport Compact car Recommended this boost controller because it held boost very well, see chart below
Please note that many 3000GT and Stealth owners have had spiking problems with this boost controller after upgrading turbos. The programming is too complicated for some people too. Some owners LOVE this boost
Controller but I personally would not recommend this. I have never heard any issues like this with Blitz DSBC.
6. Blitz SBD-ID:
Note: The Blitz DSBC is shown below (Not the SBD-ID)
The picture below is the DSBC mounted in the center console.
I call this the Millenium Falcon Mod because the white plastic cover is an extra piece in a Millenium Falcon Model kit I had.
Recommended for 3000GT it holds boost very well, see chart below for SPC-IDR
The older model DSBC type R uses the same solenoid so performance should be the same
