Turbo spooling waaaaaay high!, need boost to come down......how?????? Options

[injection]

Thank-you everyone, for all of your ideas, I believe Smaay is right, our ST205 engines are prone to boost creep,I was trying to figure out what would be the best to go about it, and didn't want to do any fabricating, or downsize my DP, basically put out money I didn't half too....then it dawned on me, I have a tuned muffler, which I took the silencer out of, and have never ran it on the car I'n the first place, my theory behind this is, this will add some restriction to my fulll 3" system, and make my wastegate vent properly.....i was scared how it would sound with the silencer in, but when i turned key and started her up, i actually like it better then open cannon, it sounds deeper and a throatier pitch, my Blitzz DD BOV is more of a high pitched whistle, and believe it or not, but when you rev it the RPMs raise quicker then before.......want to take it for a rip to see if my wastegate can keep up now, and if my boost has leveled off to a power making stable level. Insurance is off of it right now, and for another 4 months ( Damn Canadian Winters! ) but the roads are dry right now, if nice tomorrow will go down the street n back, see if there is a difference, am very excited, if this works, Smaay, you da man, then Rav Race, I will have to buy a boost controller to up the boost, depending how much I've come down, u have an APEXI right'?
I don't know if I would get electronic, little to much right now, I know they fine tune better then the Manuel ones, but a Manuel will have to suffice, if, the silencer idea works....

[Rav4Race]

if u need any help to tune your avc-r, im here:) well we r all here!:)

[Smaay]

i run a manual boost controller in all my cars. i think they are more reliable.

[injection]

cool guys, went down the street, actually, went down a backroad highway, and i couldnt really open it up to much, only because of the no insurance thing, the fine is $560.00 for not having insurance, and they tow your ride as well, not to mention, if i went by a cop, definetly would be an excessive as well, but i did take it all the way up in second, was around 6200rpm and @ 16psi, didnt want to push much more, only because the rpms were rocketing very quickly...inbetween looking at boost rateing and rpm guage, i didnt want to blow a shift! so, i tried this 4 times on a stretch of road, and my #s were consistent, so far looking good!! no hesitation, or exhaust popping! very smooth and powerful! i know im right on that fine line though, when i reached about 4800rpm i was at 16psi, it just passed 16 but not quite 17 @ 6200rpm, this tells me, it seems to be holding now.....where as before, i would be at 18psi @ 5500rpm and going higher, would have to let off so i didnt hit fuel cut. the exhaust sounds awesome @ 6200rpm with that silencer in there...very deep, angry tone! it feels like i gained power by adding some restriction... it was never this smooth before, i like it!!!
just curious fellas, what is 16-17psi in bar form, everyone rates they'r boost in bar form.....this is something i never took the time to understand, please enlighten me, ( sorry if this is a stupid Q. ) i honestly don know, thanx-a-lot!
will have to test it in third gear on a load next time.....hope all is cured, all this from adding a simple silencer, craziness

[Rav4Race]

i run a manual boost controller in all my cars. i think they are more reliable.

u said earlier u had avc-r?! ??

[evo_lucian]

Divide psi by 14.7 to get boost in BAR.
10 psi ÷ 14.7 = 0.68 BAR
14.7 psi ÷ 14.7 = 1 BAR

Manual boost controller will work just fine for you.

[injection]

Sweet, thanx Evo for the formula, wont forget that, and yeah will be looking into a manuel boost controller,

[celica95-95]

I had same with my st205 , with a 3" down-pipe and intake , the turbo is spooling faster which means it will make more boost because for the better air flow

[delusionz]

a cheap fix would be to have a restrictor gasket made from thin steel and placed in your exhaust line, this will bring down power quite a bit,

otherwise the best option is external wastegate...

[3WayStunna]

Wow zombie thread. Lol might as well as add my .02. Just wanted to add to the debate on how (and to be specific) an AVCR can lower and control boost pressure when experiencing boost creep. Just to note this is just me speaking from my experience. Not trying to stomp on ideas or promote APEXi's products.

I think the problem can be solved with an ELECTRONIC boost controller. And here is why i think that. The stock boost controller is the VSV. Basically a bleed valve. When the BCS (Boost Control Solenoid) senses an overboost problem, the ECU sends a signal to the VSV ( Vacuum sensing Valve) basically putting the turbo in the mode we all know best (boost cut/fuel cut etc.).

How this works is once the BCS sends the signal to the ECU, the ECU de-engergizes the VSV allowing bleed air to leak from the waste-gate. This works well on the stock setup but as we start to add more and more then we would likewise have to upgrade our controls to the stock system as well. How an electronic boost controller (specifically the AVCR) works is by getting rid of the stock boost controller system all together, in a manner that a manual controller cant do.

It does this by

1:) Altering the boost signals to the ecu by having them go to the AVCR first
2:) Getting rid of the VSV system completely in a manner that im sure many manual boost controllers would do
3:) Using a faster acting solenoid than can more quickly handle the amount of boost the AVCR is picking up from the BCS
4:) Fine tuning, fine tuning, fine tuning.
5:) Using an electronically controlled solenoid

You will still experience boost cut though, but you would be able to fine tune out the boost creep or just simply set a lower boost IE: .9-1.0 bar, for example.
Now im not saying that any of the other ideas wouldn't work and hopefully not beating on a dead horse. Its just the the original poster said he isnt in it to add an external waste-gate, which would also work (not sure on how well with the stock ecu), and adding restricter plates etc. IMHO is just too much for a problem with an obviously simple solution.

The only way to get rid of the boost cut btw is either through an after market ECU or FUEL CUT DEFENDER of some sort (make your own or buy one).

Also some reading, in case terms are lost on some folks.

http://www.celicahobby.com/forums/ubbthrea...ite_id/1#import

THE TURBOCHARGER
The turbocharger is a centrifugal compressor driven by the otherwise-wasted energy in the exhaust stream. It is a 2 chambered housing with a shaft through the center extending into both chambers. A turbine wheel is mounted on one end of the shaft and is in the exhaust stream, and an impeller wheel is mounted on the other end. That is the compressor end, and it is connected to tubing that goes to the intercooler, and then to the throttle body. A turbocharger is really a very simple device, and as long is it regularly fed clean , high quality oil from the engine lube system, and allowed to cool down before engine shutdown, will last nearly as long the engine itself.

THE WASTEGATE
There are two alternate paths for the exhaust flow at the turbo. One is across the turbine, and the other is out the wastegate, allowing it to bypass the turbo. Since more energy at the turbo means more air to the engine, which means more energy to the turbo, which in turn means more air to the engine, which means...well, I think you get the point. The wastegate is necessary to limit the airflow output from the turbo.
The wastegate isn't simply open or closed; it modulates to maintain very precise control over the turbo's speed and output.

SOME BASIC PHYSICS
Compressors are pumps, and pumps create flow. When the turbo creates more airflow than the engine is consuming, then the air becomes pressurized. So boost pressure will rise and fall as the turbo output increases and decreases. Thats why the wastegte controls the speed and airflow of the turbo. And pressure and flow are directly related. That means you can not get "more flow at the same pressure..."

THE WASTEGATE ACUTATOR
The wastegate actuator is simply a can with a rubber diaphragm on one end, and 2 ports with hose fittings on the front end. Looking into the engine compartment form the driver's side, it can easily be seen just to the right of the turbo compressor inlet. The hose on the left is connected to the turbo, and the hose on the right is connected to the T/VSV. (more on that later) There is a spring that holds the diaphragm in place that has a yeild value of about 7 psi.. As pressure builds in the turbo, air begins to fill the actuator and pushes against the diaphragm. When the pressure exceeds the spring value, ~ 7 psi, the actuator moves out, pushing a rod, and opening the wastegate.

TVSV
(Turbocharger Vacuum Switching Valve) is a "factory-installed boost controller". It is simply a solenoid-operated valve that, when energized (open) allows air to escape from the actuator, lowering the pressure in the actuator, and allowing the wastegate to modulate closed. This vented air actually flows back into the intake airstream between the airflow meter and the turbo intake so it does not distort the ECU's air/fuel ratio calculations.

The T/VSV is a normally closed-energized open valve. The ECU will energize (open) it whenever you boost IF 1) engine coolant temps are up to normal , and 2) ambient (intake) air temps are above ~ 32 deg F. (There may be some variation with that number). If the T/VSV is open (high boost mode) and the ECU gets a signal from the knock sensor, it will de-energize (close) the T/VSV. Likewise, if there is an over boost signal from the boost pressure sensor, it will de-energize the T/VSV as part of the "fuel-cut" sequence.

NOTE: Unless you have an aftermarket boost controller, disabling the T/VSV will lock you into low-boost mode!! It WILL NOT increase boost.

The normal range of max boost ranges from 7.1 to 11.8 psi, according to the Factory Repair Manual. Low boost problems are almost always a result of some problem in the boost control system and rarely with the turbo itself..

BOOST PRESSURE SENSOR AND FUEL-CUT
The boost pressure sensor is simply a pressure transducer that monitors manifold pressure and reports it to the ECU as a voltage value. If the voltage exceeds about 4.4 volts (~12 psi on '91, 92' and early 93's, ~16 psi on late 93's and up) the ECU initiates the fuel-cut sequence. It de-energizes the T/VSV to lower boost, retards ignition timing, and restricts fuel delivery by limiting the injector cycle. The "check-engine" light will come on for about 20 seconds, and a code 34 will be stored in the diagnostic memory. You will be in "limp mode" and unable to boost again until you shut off the engine and restart it. No other reset is required to return to normal operation. You do not have to pull any fuses or disconnect the battery (Internet legend!)

For a complete schematic diagram of the turbo and boost control system, go here:
http://member.newsguy.com/~gtfour/technicl.htm#Turbo
Click on "Boost Control"

This post has been edited by 3WayStunna: Apr 9, 2012 - 9:30 AM

[delusionz]

in my case, when i had the factory turbo and factory exhaust i got overboost with the tvsv blocked/capped/plugged/etc...