boost spikes---weird

[EuroGSTSpyder]

Ok I have been reading threads about this and i checked most things so I need to turn here:

I installed a 18G w internal wastegate on a friends GST 1998. Every other mod is there as well..660's 255 pump, 3# exhaust, intake pipe, open air filter. HallmanPro MBC,gauges, SAFC II etc..
Stock O2 and manifold still.

Now the weird thing is that I get huge boost spikes on this sucker. When I step on it it flips up to 1,6bar and then drops to desired 1bar. It is a little different on different gears and this is buggin me!! I tested the IC system to hold 2bar and only leak is a very very tiny one at the seals on the TB..nothing else.
MBC is hooked up correctly....one from intake hose and one from wastegate-correctly installed on the MBC.

So what else to look for and why can this happen??

 

[DSM90AWD]

Boost spikes are generally a result of boost pressure not reaching the WG solunoid quickly enough. This can be mitigated by using a shorter run of tubing (i.e. a nearer boost source) and/or larger diameter tubing.

Also look for kinks in the lines and/or leaks

 

[EuroGSTSpyder]

Well I cannot run it any shorter since the MBC is mounted on the top of the radiator just in front of the turbo IE the line is no more then ten inch long and its the lines supplied by Hallman them selves.
The other line comes from the BOV vacuum line.Routed right across to the MBC so its not long either..same line provided by Hallman.
I checked everyhose regarding this and its no leaks no holes no nothing. THats whY I had to ask since I cannot think of anymore to check for**

 

[DSM90AWD]

Have you tried to run a straight vac line to the W/G to see if it is the WG itself that is the problem?

Also was the turbine housing ported?

 

[EuroGSTSpyder]

I have the line from the wg actuator nipple directly hooked up to the MBC and that line is not ten inch long.
The other one that goes to the MBC ( cannot come up with the name right now but you know wich one) is t-ed into the BOV vacuumline. (There is no niple on the turbo to hook it up to if you were to suggest that)


Turbo is not ported. Dont know the size of the WG flapper either.
EDIT: Its a brand new Greddy 20G.

I have hooked up my own car in exakt same way and I have no problems like this whats so ever.

 

[DSM90AWD]

(There is no niple on the turbo to hook it up to if you were to suggest that)

I meant cutting the MBC out completely by connecting a line from the BOV "Tee" to the WG actuator to see if it still spiked.

Is your W/G actuator adjustable? If so did you pre-load it? Preloading can limit the WG's movement and ability to react quickly.

Porting of the WG passage is always a good idea to optimise flow (especially bad stock location/size on Mitubishi turbos).

It's really all about the WG itself being able to bypass enough exhaust in all situations and reacting to sudden changes in boost.

 

[EuroGSTSpyder]

I meant cutting the MBC out completely by connecting a line from the BOV "Tee" to the WG actuator to see if it still spiked.

Is your W/G actuator adjustable? If so did you pre-load it? Preloading can limit the WG's movement and ability to react quickly.

Porting of the WG passage is always a good idea to optimise flow (especially bad stock location/size on Mitubishi turbos).

It's really all about the WG itself being able to bypass enough exhaust in all situations and reacting to sudden changes in boost.

Ok will try to see if it helps then.Should be quick to do and see if it will work.

No its not adjustable WG on the turbo.

Yeah porting is good but he bought the turbo like this and I was just to install it.

 

[sumenlo]

You also might wanna consider switching to an electric boost controller. Manual boost controllers don't control the response of boost levels very well which is probably why you're getting the spikes. You can set the electric one to hold at your desired boost level and avoid any spikes or creeping. They are more responsive that way.

 

[oldman]

DSM90AWD is right on the money which is weird because he's usually wrong. There's a delay of the pressure signal reaching the actuator which can be caused by either hose being too long, leaky hose, defective mbc or all of the above. Bypass the mbc first, if that doesn't work replace the hose and perform a boost leak test if you have not already done so, it's a must after a turbo install.

 

[EuroGSTSpyder]

I tested the IC system to hold 2bar and only leak is a very very tiny one at the seals on the TB..nothing else.

This leak is very very very tiny(shaft seals) and should not in any way affect the boost in this way.
I will try to by pass the MBC and see what happens when I get time to.Working now :-(
Will also go over all the conenctions of the hoses to see that they are tight and sealed properly.

 

[oldman]

Will also go over all the conenctions of the hoses to see that they are tight and sealed properly.

I was mainly referring to hoses to and from the mbc.

 

[EuroGSTSpyder]

Me too...Wil check to see they are not leaking at the connection to the MBC and wg nipple and so on. Also check again for leaks in general on any hose.

Thanx for helpin me out Any hints are good at this point so..keep em commin if you got more**

 

[EuroGSTSpyder]

first thing tested. Ran line straight to WG actuator and still spikes.
The turbo is brand new so is the MBC. Cant find any leaks in the IC system or the hose lines to the turbo/MBC.
Can it be that the unported stock O2 is causing this?

 

[oldman]

first thing tested. Ran line straight to WG actuator and still spikes.
The turbo is brand new so is the MBC. Cant find any leaks in the IC system or the hose lines to the turbo/MBC.

No, if removing the mbc made no difference then the mbc is ok. It's more likely that this is actuator/wastegate related, if you're 100% sure the system is leak free.

Can it be that the unported stock O2 is causing this?

Probably not, unported o2 housings usually cause creep not spike.

BTW Where are you taking the pressure source from? Turbo or intake?

 

[EuroGSTSpyder]

I had one hose from WG nipple to MBC..the other one I took from the BOV line,wich come from the intake.Take it from another place? Where?
Have no nipple on the turbo to use.

Since the turbo is brand new I would think that the WG is not faulty but...you never know of course.

 

[oldman]

I had one hose from WG nipple to MBC..the other one I took from the BOV line,wich come from the intake.Take it from another place? Where?
Have no nipple on the turbo to use.

Since the turbo is brand new I would think that the WG is not faulty but...you never know of course.

Well, there are pros and cons whether you take it from the intake manifold or the turbo. In a case of boost spike, taking it from the turbo should help if not cure it. Think about the length of travel for pressure source to get from turbo to manifold and back to turbo vs. from turbo to mbc back to turbo. I suggest tapping the J-pipe with a 1/8 npt and try taking the pressure source from there and see if it makes a difference. If this doesn't solve the problem then it's pretty clear the issue is the actuator/wastegate.

 

[DSM90AWD]

Well, there are pros and cons whether you take it from the intake manifold or the turbo. In a case of boost spike, taking it from the turbo should help if not cure it. Think about the length of travel for pressure source to get from turbo to manifold and back to turbo vs. from turbo to mbc back to turbo. I suggest tapping the J-pipe with a 1/8 npt and try taking the pressure source from there and see if it makes a difference. If this doesn't solve the problem then it's pretty clear the issue is the actuator/wastegate.

Not to mention if the BOV is leaking (definite possibility if a stock 2G BOV) that the boost signal might be further delayed.

One sure bet would be an external WG which could be had for ~$300 (Tial38, flanges and welded to exh manifold).

 

[EuroGSTSpyder]

Greddy Type S bov.
Will try to see if I can fix the nipple on the pipe then..and I have to find the problem definitly so I can tune it in

 

[Grinder]

EDIT: Its a brand new Greddy 20G.

It is a brand new Greddy 18G...

And tnx for helping..

 

[EuroGSTSpyder]

Thanx "Mighty Mike" ( owner of the car). Yes its a 18G and not a 20G as I said. WIll try the hose things first and see if I cen get it better.