Gt4 Boost Guage

[GT4 BOOSTER]

ok the one on the dash board , how does it supposed to function , its on minus on tick over , does it move up as the speed of the car increases and fills something up untill it hits plus then you let the turbo rip .tia marc.

[daktari]

Ummm. It should be reading 0 at tickover or when there is no strain on the engine. It should start moving as you accelerate but if it`s anything like the one in the gen 5 its best to totally ignore it. It`s totally lazy. I`ve got a ruddy great 80mm GReddy gauge thats hyper sensitive, I`m usually boosting about .5 BAR before the dash one starts to move.

Maximum boost on the dash gauge would appear to be about 6PSI just under .5 BAR.

It`s really better to get an additional gauge.

[GT4 BOOSTER]

is the boost stored somewhere , or is the needle just letting you know the turbo is active?

[djdna2000]

It should read..

.. zero when the ignition is on but the engine not running

.. well into -ve at idle

.. +ve when you are under load (i.e. accelerating)

.. once past 3500 rpm should be off the top of the scale under load

.. well into -ve when moving but off throttle

However, your first mod should be a proper boost gauge so you can tell what the engine is doing. The stock one is almost pointless - it has no scale, and is capacitively damped (made to move slowly) to stop idiots ringing up toyota and claiming one of their gauges is flickering - a real boost gauge moves very quickly.

A TIM or similar can be had for around £30, though for more accuracy and features there are lots of better ones out there.

[djdna2000]

and max boost on your 205 is 0.9 bar, which is just off the top of the stock chocolate fireguard.

[GT4 BOOSTER]

how do you go about adding a guage then and how do you adjust boost pressures?

how would i know a safe limit was reached ?

is 255 bhp not enough that i need to alter boost settings ?

lol i'm gonna end up doing a james dean if im not carefull with this gt4

[daktari]

is the boost stored somewhere , or is the needle just letting you know the turbo is active?

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Most boost gauges work off vacuum/pressure from the inlet manifold. So its a direct input into the gauge. As soon as the turbo starts boosting and producing pressure then this is transmitted to the gauge. if you follow me. Some gauges work off a sender which is in turn activated by vacuum/pressure.

Not sure how the standard guage is activated. And the Gen 6 one appears to be a bit different to the Gen 5, tho i suspect the operating principle is the same.

[daktari]

how do you go about adding a guage then and how do you adjust boost pressures?

how would i know a safe limit was reached ?

is 255 bhp not enough that i need to alter boost settings ?

lol i'm gonna end up doing a james dean if im not carefull with this gt4

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GT4`s are heavy old beast. Plus you lose a lot of the power through transmission. I reckon mines putting out about 250-260 and it`s still not enough IMO.

[djdna2000]

Before you think about upping boost pressures etc I think it's well worth reading around - when I first got mine I knew nothing about turbocharged cars so I researched stuff well before messing around. Please have a read through the tech stuff on my site, particularly the beginner's mod guide ( http://www.st205.net ) and also check out www.howstuffworks.com and look at the turbocharger entry, very useful.

In answer to your questions:

Adding a gauge is easy, or you can get a garage to do it for you pretty cheaply if you don't feel up to it. Should be a half hour job. A cheap one will be mechanical, as Daktari says you have a pipe that goes straight to the gauge. An electronic one will have a sensor that sits in the engine bay and relays info to the gauge electronically.

Safe limits are up to you, but I would say no more than 1.2 bar on the ST205, but get used to the stock performance first - as you say 255 bhp is plenty for now!

The boost is not 'stored' anywhere, it is available at any stage as long as the revs are high enough, check out that howstuffworks link for a proper explanation. Or the turbo page on my site.

[djdna2000]

daktari - the stock gauge works off the MAP (manifold absolute pressure) sensor, this sensor also supplies the ECU with boost info.

[daktari]

daktari - the stock gauge works off the MAP (manifold absolute pressure) sensor, this sensor also supplies the ECU with boost info.

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Gotcha. Hope the ECU aint as lazy as the gauge