Safest standard boost ST205

[NZVengeance]

I have a ST205 WRC it runs 12.5psi standard

Whats the max i can take that too for a all day driver without worrying about shit going wrong


Cars done 170k

[barryogen]

what ever the factory boost is... thats what toyotas massive R&D budget is for, working things like this out.

If you upgrade fueling and all the things that go with it, the "safe" boost level will creep up.

[diss7]

st205s have fuel maps all the way to 18psi.

I ran mine at 17psi for years without incident. You'll go thru clutches quicker. But everything else is upto the task.

[NZVengeance]

so it would jsut require what to change it?

an external wastegate? or can the standard one to the job?
a boost controller of some sort tho i believe they are mechanically controlled.

[diss7]

Do the downpipe and high flow panel filter first. Leave the stock airbox, I'm a big fan of it. Exhaust too but not as necessary, and you will get a few psi from that.

Get an EBC after that.

[NZVengeance]

thats the thing tho isnt the boost on the ct20b mechanically controlled so an ebc would not be of any use.

im not sure im just asking

[Mr Revhead]

yeah the turbo is controlled by an actuator....
but what controls actuator

[diss7]

thats the thing tho isnt the boost on the ct20b mechanically controlled so an ebc would not be of any use.

im not sure im just asking

as above, all turbos are controlled mechanically, using a boost controller alters the signal they get.

You can manually bleed air off with a tap, but best to use an EBC.

[NZVengeance]

right so an electrical feed from the ecu tells the actuator how much boost.

so when you hook up an ebc you are effectively bypassing the ecu's signal?

[~SlideWays~]

right so an electrical feed from the ecu tells the actuator how much boost.

so when you hook up an ebc you are effectively bypassing the ecu's signal?

I don't know gt4's but the actuator will have a vacuum hose coming from the pressurised part of the intake (most likely the manifold).

You need to put a bleed valve in that line. Or even better plumb in an EBC and a solenoid can bleed off pressure causing the actuator to 'think' its getting less pressure.

[fivebob]

right so an electrical feed from the ecu tells the actuator how much boost.

No quite correct in the case of the ST205. The ECU controls boost to a certain extent in this manner, mainly to keep the boost low when the engine is cold. However max boost is determined by the size of the bleed hole in the VSV (vacuum Switching Valve), which bleeds off boost from the wastegate actuator. If stock boost control is left in place then you are limited to about 14-15PSI peak boost.

so when you hook up an ebc you are effectively bypassing the ecu's signal?

No, you are replacing the stock boost control completely. You disconnect and block off the VSV output from the wastegate actuator, and replace it with an EBC between the turbo and the wastegate actuator.

[NZVengeance]

hmmm this seems complicated lol. perhaps when the time comes i will seek assistance from a TS member in auckland who has done this.

[fivebob]

This might help (or confuse the situation even more)

Vacuum diagram for a ST215 (not quite the same but close enough)

[NZVengeance]

can you take that pic to photoshop and add pictorial comments to it. showing how to fit a ebc. and assuming it has an external wastegate.

[Bling]

if you actually go and buy an ebc it will have instructions.... amazingly enough

[NZVengeance]

yea probably in 6 languages but non of them english

[flygt4]

essentially, the turbo vsv hose in the middle bottom of the pic gets unplugged and blocked up. thats easy to find as its one of the two hoses that comes offthe wastegate actuator in the bottom left of the pic. its the one that snakes off around behind the block.
doing that will remove the warm/cold boost limiting (at least it did on my 185). its just a safety so munters dont run everywhere at full boost on a cold engine.

then you intercept the other hose coming off the wastegate actuator with your boost controller.
as the wastegate actuator is just a diaphragm that is opened and closed by the boost pressure from the turbo (easy to see by following the picture), by intercepting that line and bleeding a bit off you will trick it into thinking it hasnt reached maximum pressure and allow you to run higher boost. how much you bleed off will adjust your boost pressure.
ie if wastegate opens at 12.5psi, and you bleed off 2psi, then it will make 14.5psi before it opens and stops the turbo making more boost.

[fivebob]

[sergei]

one thing to watch out with aftermarket downpipes, a lot of them create over boost problem. The sizes of the wastegate valves on standard ST205 turbo are pretty small, even boring them out to the max in my case did not resolve overboost (saying that I had 3" exhaust with virtually no mufflers). Boost control on ST205 is very poor and tends to fluctuate (the fluctuation is even audible between 3.4 to 4.5krpm), if you achieve 17psi one day, in another it will be 19psi, even with EBC. I would say set it to 15psi and it should provide you with a safe margin. Do not use mechanical bleed valves to achieve that, other wise it would be boost cutting a lot.

[sergei]

double post