VSV question

[GT4-Addict]

Hey everyone.
I am just wondering, if i Disable my VSV, will it permenantly run at the lower or higher boost level?

My car is having a boost problem where while cruising along it suddenly drops from normal high boost to the pressure it runs at when cold (Which is dertmined by the vsv right?) and i think its a faulty VSV.

I dont have a boost controlller or tap at the moment but i am looking at putting one in within the next month or so. I know you have to disable the VSV to correctly use a boost controller anyway.

Thanks for any help!

[Boosted_162]

Low boost. The VSV allows higher boost when all conditions are met (engine temp etc).

So if you run say 7psi in 1st/2nd, and 10psi in 3rd up, you are going to run 7psi permanently.

[sergei]

Hey everyone.
I am just wondering, if i Disable my VSV, will it permenantly run at the lower or higher boost level?

My car is having a boost problem where while cruising along it suddenly drops from normal high boost to the pressure it runs at when cold (Which is dertmined by the vsv right?) and i think its a faulty VSV.

I dont have a boost controlller or tap at the moment but i am looking at putting one in within the next month or so. I know you have to disable the VSV to correctly use a boost controller anyway.

Thanks for any help!

I would suspect faulty thermostat (jammed open).
What happens is coolant temperature goes below certain threshold and ECU disabling VSV. That will happen under cruising as the engine does not produce a lot of heat while there is plenty of cooling.

[GT4-Addict]

Hmm thats a good thing to check, however the only thing is that very rarely, it overheats, which i would not expect from a jammed open thermostat. I think i will replace it though.

I went out and had a look down the back of the turbo yesterday, and noticed some oil had leaked out, which makes me now think it has a blown seal, could this be the cause of the problem?

[sergei]

I believe you have a bigger problem than non working VSV.
You could wire in a small test light on the VSV plug and see if it switches off to confirm that the ECU switches it of.
Back to you bigger problem: if car occasionally overheats, you either have a blown head gasket, or some fault with the cooling system (gunk in the radiator, sticking thermostat, rusted water pump impeller etc.) or all of the above.
Leaky seal will not cause drop in boost.

[GT4-Addict]

I dont think its a blown head gasket, im not losing any noticble amounts of water. I think it might indeed be the thermostat.

As for the boost, i thought prehaps it was going into limp mode, but then figured it cant be, because after about 5-10 mins of just cruising slowly, i get full boost back again, without having to reset the ecu, turn off the car or anything like that. This is what made me think its something up with the VSV, Prehaps i will try wiring up a test light.

Is the VSV itself easy to get to?

And if it is the vsv, disconnecting it and instaliing a boost tap (which i will set to 10psi) should solve the problem right?

[sergei]

I dont think its a blown head gasket, im not losing any noticble amounts of water. I think it might indeed be the thermostat.

As for the boost, i thought prehaps it was going into limp mode, but then figured it cant be, because after about 5-10 mins of just cruising slowly, i get full boost back again, without having to reset the ecu, turn off the car or anything like that. This is what made me think its something up with the VSV, Prehaps i will try wiring up a test light.

Is the VSV itself easy to get to?

And if it is the vsv, disconnecting it and instaliing a boost tap (which i will set to 10psi) should solve the problem right?

Boost taps are horrible. You will get boost spikes occasionally, sometimes hitting boost cut and bringing CEL. Invest into a proper electronic boost controler (and not a electrically switch-able boost tap).
As for low boost mode it is not limp mode it is just cold mode that ECU goes into when the coolant temp is below certain limit.

[Heylin]

Sounds like air in the cooling system if its overheating randomly, check your radiator cap seal (new cap is only $16). A proper cooling system flush wont hurt either. Also the thermostat stuck open is a common issue if youre getting stuck on low boost, check to see your temp gauge comes upto 1/2 way if it never gets there then your thermostat could be stuck.

Boost taps are horrible. You will get boost spikes occasionally, sometimes hitting boost cut and bringing CEL. Invest into a proper electronic boost controler (and not a electrically switch-able boost tap).
As for low boost mode it is not limp mode it is just cold mode that ECU goes into when the coolant temp is below certain limit.

Sorry but this is crap, I use a GFB Atomic manual boost controller and run 16PSI on my Turbo. No spikes whatsoever. 10PSI will be a non issue.

As for boost cut, pull the sensor hose, been done plenty of times on hundreds of MR2s with no issue.

[sergei]

Sounds like air in the cooling system if its overheating randomly, check your radiator cap seal (new cap is only $16). A proper cooling system flush wont hurt either. Also the thermostat stuck open is a common issue if youre getting stuck on low boost, check to see your temp gauge comes upto 1/2 way if it never gets there then your thermostat could be stuck.

Boost taps are horrible. You will get boost spikes occasionally, sometimes hitting boost cut and bringing CEL. Invest into a proper electronic boost controler (and not a electrically switch-able boost tap).
As for low boost mode it is not limp mode it is just cold mode that ECU goes into when the coolant temp is below certain limit.

Sorry but this is crap, I use a GFB Atomic manual boost controller and run 16PSI on my Turbo. No spikes whatsoever. 10PSI will be a non issue.

As for boost cut, pull the sensor hose, been done plenty of times on hundreds of MR2s with no issue.

I guess you are lucky . Or perhaps you don't know that it is spiking, especially after you pulled off the hose.

[Heylin]

I guess you are lucky . Or perhaps you don't know that it is spiking, especially after you pulled off the hose.

Not that the factory gauge would tell you about spiking anyway, its a POS.

But my HKS Gauge is very sensitive and tells the truth - ZERO SPIKING. Possible that the spiking ones utilise the the ball spring setup as opposed to GFB which is a bleed valve type.

[sergei]

I guess you are lucky . Or perhaps you don't know that it is spiking, especially after you pulled off the hose.

Not that the factory gauge would tell you about spiking anyway, its a POS.

But my HKS Gauge is very sensitive and tells the truth - ZERO SPIKING. Possible that the spiking ones utilise the the ball spring setup as opposed to GFB which is a bleed valve type.

But the question is, given the chance, would you swap it for electronic one?

BTW factory type of boost control is also bleed (VSV bleeds off). Factory boost control can spike by itself as well.
With bleed type of control, you are relying on wastegate spring alone to control the boost, with the feedback being compromised by the bleed.
Depending on valve's geometry and system volume the bleed can have unpredictable results. Even the length of hoses will affect the performance.

The reason why bleed is bad because instead of static pressure difference at any given point, there dynamic factor involved of air flow through the bleed valve, thus making the pressure in the waste-gate control chamber non linearly dependant on the pressure in the reference (outlet of the turbine).

[Heylin]

Well my seems to work fine, so I wouldnt swap it for electronic unit. Perhaps different results on different cars ?, but I know of 3 MR2s that use the GFB to run higher boost on CT26 and CT20b turbo and those owners also reported rock solid readings with no spikes.

So its safe to say if youre running a Ct26 or Ct20b on a 3SGTE and aimaing for stable boost at 10 - 18PSI then a GFB atomic is going to do the job.

Dont get me wrong, electronic is great to, especially if you want high and low settings at the push of a button. and the nice glowing lights for more eBling.

But for what GT4-Addict is looking at 10PSI on stock turbo (could even go for 12). THe $$ saved on a GFB could be better spent on a 3" dump pipe.

[GT4-Addict]

As for boost cut, pull the sensor hose, been done plenty of times on hundreds of MR2s with no issue.

Where abouts is the sensor hose located? is that the hose from the wastegate that runs to the VSV itself? Or is it a Different hose?

As for running an electronic boost controller, i looked into it but i cant really afford it, being a uni student and all!

Im lookiing at a turbosmart gated boost tap, its not the bleed type, info is here: http://www.turbosmartonline.com/index.php?id=43 im looking at either the boost tee or the single stage controller. anyone have any expericence/opinions on these?

[Heylin]

Not sure in the GT4, but for MR2 its a little black box at drivers side rear of engine bay with a small diameter black hose going into the bottom of it.

http://mr2.gordaen.com/mods/11/03b.jpg

Just a matter of pulling it and plug the end with a screw and a small hose clamp to hold it in place.

Your factory boost gauge wont work after this, either way you need to get an aftermarket gauge so you can safely set the boost level and monitor.

Not sure on the turbo smart ones but the GFB is cheaper and is proven to work on the 3SGTE with stock turbo. Ive been running mine for 3 years now and its worked flawlessly.

Personally I think the whole turbo spool speed for gated vs bleed is a marketing ploy, if youre ever in Hamilton I'll take you for a drive in the MR2 and you can tell me if theres any noticible lag... between yelling oh shit oh shit oh shit.

http://www.trademe.co.nz/Trade-Me-Motors/Car-parts-accessories/Performance/Turbos/auction-230477469.htm

Parts wise at most youre looking at

$90 for the GFB
$30 worth of 8mm Diameter rubber hose to hook GFB and boost gauge up.
$30-50 for a 2" mechanical boost gauge
Mabey $10 for a gauge pod \ mount

Still cheaper than an electronic boost controller.

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[GT4-Addict]

i already got a boost gauge. who owns a turbo car and dosent have one, pshhhhh.

ill definitly look at the GFB instead, its far cheaper, and im not really too worried about any micro differences between bleed type and gated type.

ill try locate that sensor, and pull the pipe. sounds like a good cheap plan to me, would it be hanging around the diagnostics box by any chance?

Also, when i put the boost tap in, is it difficult to set it to my required level? Ive never installed/used one before but i know what im doing around engines so im not worried about the work involved, just worried about being able to set it accuratley without a Dyno

[Heylin]

Factory gauge (in MR2, assume Gt4 the same) takes an electronic signal from the boost pressure sensor, pulling the hose tricks the ECU but also stops your factory gauge from working.

+ your factory boost gauge would need to have actual measurements in PSI or BAR and measure in 1 PSI or 0.1 BAR increments.

Not sure havent seen a GT4 gauge so cant comment, but assume same engine same setup with sensor and gauge.

To set basically you start out with the GFB fully open and adjust the screw down in increments unti lbost starts to go up, as it goes up use smaller increments to fine tune.

Initially youll be turning it 5 or 6 times times from fully open before you start to get factory PSI. Up around the 14PSI mark 1/2 a turn equates to about 1 PSI.

[sergei]

i already got a boost gauge. who owns a turbo car and dosent have one, pshhhhh.

I don't . I have a boost gauge but it sit on my project, my daily ST205 does not have any of that crap, it is stock standard and this is the way I like it.

[GT4-Addict]

My gauge is an HKS one, came installed in the car when i got it. The muppet who hooked it up hadnt even bothered hooking it up to the lights etc WTF.

Im not worried about losing the stock one, its damn unclear about whats going on anyway, all it tells me is that the turbo is busy doing something.

Sounds pretty easy to set up the boost tap, so ill definitly do that as soon as i can afford it!

hopefully pulling the sensor pipe will fix my boost problem too, as this is just plain annoying when it happens!!!!

[GT4-Addict]

I think i have found the turbo bppst pressure sensor, it says Sensor Assy. Turbo on it. it has a vacum hose running from the sensor to what i think is the intake? can anyone confirm this for me?

[Heylin]

If its a black box with a small black 6mm rubber hose going into bottom of it the yep thats the one.