Question about after market parts?

Best place to ask for aftermarket advice is the Supra Forum.

I think your friend is referring to a bypass valve. When the boost gets to high, the valve opens so that you don't overboost the engine.

A boost controller allows the driver to control the maximum amount of boost by changing the amount of boost before the bypass valve opens. Raising boost past factory specs will probably lead to shorter engine life. You really have to know what you are doing when you play with boost.

BOV..

When you step off the gas (will be more obvious with a cone filter rather than a standard airbox) you might get a fluttering noise. It may be the wastegate operating, alternatively it could be the turbo stalling.

It happens because when the throttle butterfly in the throttle body is slammed shut (when you change gear in a stick and step off the gas) any boost pressure is stopped in it's tracks and basically backwashes to the turbo wheel and stalls it. If you seriously increase the boost, it is possible to shatter the turbo wheel.

There are two types of blow off/bypass valve. One vents to atmosphere (atmospheric), and makes the characteristic "Pptttttsh" sound when you change gear. This can cause fueling issues for a car with an Air flow meter. You may get black smoke on gear changes. Supraforums as suggested will be able to help with a good choice if you want an Atmospheric BOV

The other type is in circuit with the intake (recirculating). The vent is plumbed back into the intake to the turbo. It doesn't make such a good noise. But it does solve the fueling issues.

Turbo Timer... Allows the timer to keep the engine running to keep oil circulating through the turbo for a preset time and then stop the engine. After a good fast run, you should let the engine idle between 30 seconds and two minutes depending on how long long since you last gave it boost.

Some interfere with alarm systems, but other can interface, allow the alarm to be set, but disable the immobiliser, until the preset time is up, unless someone tries to drive the car when it is on timer without the key. Depending on what sort of area you live in, you may or may not want to lave the engine running for upto two minutes when you are there.

Easier to take your time shutting windows, taking off shades/glasses, and listening to the next track on the radio/CD before you kill it.

Boost Controller... A boost controller fits between the turbo and the waste gate actuator. They fool the waste gate into not opening and allow more boost over the preset actuator pressure. They can manual, you operate a knob/screw/ dial on the controller under the bonnet, drive to test pressure, adjust, and drive again. Can take time, and can do any compensation for atmospheric pressure, or automatically adjust for any boost spikes.

Electronic boost controllers are a lot more expensive, but can be quite clever. Some offer such goodies as multiple preset boost levels, and a graphical boost gauge, and better protection against boost spikes. Some of them can also be mated to replacement ECU/AEM systems from similar manufacturers to control boost based on what the ECU sees from it's sensors. They use a solenoid to restrict flow to the wastegate and can open and close more acuratley and faster than with a ball and spring that manual boost controllers use.

If you are going to up boost then a BOV is more useful, and an aftermarket boost gauge is essential. If the Supra one is anything like that in the turbo Celicas of the same period, it is an indication of boost at some recent time, rather than an actual display of what the engine is doing.

Again Supraforums can tell you good boost gauges, boost controllers, and what a safe level of boost is for a Supra engine, without having to tear the engine down and uprate the internals.

2 Caveats though.

1) If you go for a manual boost controller, go for the relief valve, ball and spring type, not the bleed valve type. They respond better, and do a better more solid job of controlling boost.

2) If you add more boost, you need to add more fuel. The ECU automatically does this through fuel maps, but above a certain level of boost, it may not have maps to cope, or have sufficient fuel pressure, or big enough injectors to supply the fuel it knows it needs.

I'm about to go with the manual boost controller/CAT replacement pipe/Front mounted intercooler on my UK spec GT4/Alltrac turbo celica.

I already have a Sard R2D2 atmospheric BOV. Once you have decided what parts you want/need have a look at an Ebayer who trades under the name 5400RPM. He is in Malaysia, is very quick at what he delivers, and the goods appear to always be in great condition. He stocks items by most of the recognised jap tuning part companies too.

Very informative, impressive, i do think the original poster may be a bit baffled by it all, since it was just a suggestion given to him by a friend, but i found it interesting, top marks. Steve.

SNIP

No worries. Turbos are very simple. Keeping the rest of the engine working arround them is were everything goes to pot and gets interesting.

Do some googling, and search for the Saab APC system. Saab started fitting this to cars in the mid 80's. Originally it was an addon box to the ECU, but later it got integrated. Very simple electrical (rather than electronic) boost control that actually allowed some tweaking for feel and adjustment, so you could alter max boost and boost climb if you broke the seal on the box. They also produced several "Red box" APCs from the factory for motorsport cars, and later for limited edition road cars. without tweaking, they were good for an extra

10BHP, when tweaked you could be looking at 20-30 brake more. It monitors the boost and operates a solonoid (like a modern boost controller) hold closed the wastegate. They have in the past been retrofitted to Volvos and other european turbo cars to increase boost but keep things safe.

Saab were turboing road cars since the 70's, so they have a lot of knowledge and owners like to share it.

The other stuff's already been covered in depth. But if you have enough power the way it is now, I'd leave it as-is and drive it in good health. When you start doing major engine mods, it's like eating potato chips - Nobody can have just one... ;-)

The only thing I'd add is a turbo oiler of some sort for the turbo, especially if it isn't one of the water-cooled designs. First, you sit there and idle for a few minutes before shutdown, so the turbo cools off some and spins down to a minimum speed.

Then after you turn off the engine, the oiler keeps the oil flowing to the turbo for a few more minutes and makes sure the turbo center bearing doesn't get scored from lack of oil or overheat and coke up before it has had a chance to spin to a full stop and cool some more.

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