Simple Boost Control

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Brendan
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Simple Boost Control

Postby Brendan » Sun Jan 11, 2004 11:07 am

Simple Boost Control

All of the following info was written by Glenn (aka BOOSTBOY) even though it has been posted by Brendan.

Introduction

By far the most cost effective power upgrade for any turbo car is simply to raise the level of turbo boost pressure over the standard factory setting. On the Honda City Turbo, the factory level is set at approximately 10-12psi. Even a slight raise in manifold pressure can give you a very noticeable gain in power and doing this can be quite cheap and easy.

Here is one way to do it...

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Brendan
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Re: Simple Boost Control

Postby Brendan » Sun Jan 11, 2004 11:08 am

Construction & Installation

First of all you are going to have to take a trip to your local pneumatics supplier to purchase the following list of components needed to build yourself a simple boost controller.

- ¼" needle valve
- ¼" brass barbed fitting
- ¼" brass 'T' piece
- ¼" vacuum hose
- Small hose clamps x4

With all of these components in hand, you are now ready to build yourself a boost controller.

First job is to modify the 'T' piece. On the top section of the 'T', you have to completely solder up one end. An easy way to do this is to use a small heat torch, heat up one end and solder it up but a simple soldering iron will do the job, it'll just take a little longer. Once the end is sealed with solder, you need to drill a 1.5mm hole through it using a 1.5mm drill bit. This is about the only 'work' you have to do; the rest is simply installing it!

You now need to locate the wastegate signal line. This is located on the intake side of the turbo. It is the rubber hose that runs from the compressor housing to the wastegate actuator can. Once located, you need to cut it directly in half! It is probably best to remove the hose to do this as it then gives you the opportunity to check it for cracks or pinholes. If it has any sign of a crack, replace it as any air leak will effect the reliability and accuracy of your new boost controller. With the hose now cut into two pieces you can install the 'T' piece, remembering to use hose clamps on the joins. At this stage it is important to get the orientation of the 'T' correct. Make sure that the end that you soldered up faces the compressor side of the hose, not the wastegate actuator. With the hose now back together; it can be re-installed onto the turbo, remembering the 'T' piece orientation.

Now is a good time to find a suitable location for your needle bleed valve. Anywhere in the engine bay that is easy to access is ok, preferably as close to the turbo as possible. How you mount the valve is up to you, a few simple cable ties may do the job or you may choose to fabricate a small bracket. Before you mount it up, screw the barbed fitting into the inlet of the valve, preferably with the use of some thread tape to ensure sealing. With the valve mounted up you now just need to connect it to the remaining leg of the 'T' piece with some hose clamps and the job's done!


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Re: Simple Boost Control

Postby Brendan » Sun Jan 11, 2004 11:09 am

How it works

The wastegate on a turbocharger is a simple bypass valve that redirects exhaust gasses around the turbine wheel and out of a small gate valve. Doing this controls the shaft speed of the turbo and in turn its total output. The wastegate valve is controlled by a pneumatic actuator, which consists of a small canister with an internal diaphragm and spring. Air pressure taken from the turbo compressor is fed to one side of the diaphragm by the wastegate signal line where the air pressure works against the mechanical pressure of the spring. When the boost pressure is sufficient enough to overcome the force of the spring, the diaphragm moves, which in turn moves a rod that connects to the wastegate valve and opens it. Once open, gasses can escape from before the turbo, which can then regulate the turbo shaft speed. The boost level is therefore controlled by the stiffness of the wastegate actuator spring. If you were to bleed some of the pressure out of the wastegate signal line before the actuator 'sees' it, you could theoretically 'trick' it into thinking it is not running a high boost level. Essentially this is all that this boost controller, and any other controller for that matter, does.

So, the standard actuator is set to open at 12psi. We want to run 15psi. If you bleed 3psi from the signal line, you are still going to have 15psi manifold pressure but the wastegate still thinks it is running 12psi so it opens as normal, only now it is regulating 15psi manifold pressure.

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Re: Simple Boost Control

Postby Brendan » Sun Jan 11, 2004 11:09 am

Adjustment

Before you adjust anything, you need to have a working boost guage installed in the car. Trying to adjust boost without one is very dangerous and is likely to end up in engine failure.

Making sure that the valve is fully shut, take the car for a drive and bring it on boost. It should drive completely normally and the boost level should be as normal, if anything you may get a small initial boost spike. It there is a greater boost level than standard you have a leak somewhere. If everything is normal, it is now time to start gradually raising the boost level. Gradually open the valve, bit by bit, taking the car for a drive each time. Each time you open the valve a little further you should be getting a higher boost level. Keep doing this until you reach your desire boost level.


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Re: Simple Boost Control

Postby Brendan » Sun Jan 11, 2004 11:10 am

Caution

There is a limit as to how far you can raise your boost level. It will be different with every car's state of tune. If you are looking at raising the boost by a considerable amount you are going to have to get the car on a dyno and monitor air/fuel ratios. If you go much more than 16-17psi with the standard City Turbo fuel system you are running a big risk of lean out, the major contributor to engine killing detonation. Remember, more boost equals more power which means more stress on your engine internals and driveline, not to mention your turbo which with a simple boost change can raise shaft speed by more than 20 000rpm! You have been warned!


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