Maseratitude

I checked boost pressure with a good gauge at the tube of ignition ECU.
Result was about 0,55 (8 psi) bar with some peaks (but i'm not sure) at 0,6 bar (8,7 psi)
I also tried to change restriction in R tube of amal valve with a 3,8 mm with this pressure was stable at 0,6 bar (8,7 psi) (dashboard gauge inside yellow zone at the beginning)
I think original restriction for my car is 3,4 mm
My car is biturbo Si 1987 223hp with not synchronized throttle body
Engine completely rebuilded
Turbo rebuilded in a turbo shop ( i'm not sure that they checked wastegate )
the car has been like this for many years

Correct boost pressure should be 0,7-0,8 bar ???
How it behaves pressure gauge in your cars ???

I want check wastegate arm preload
Any ideas ???

As many people here use my BTIM they will tell the same as I told you: 0.7-0.8bar on biturbo, 1bar on Ghilbi 2L

It's not complicated to test: disconnect the hose on the W port of the SEM and see what happens. Beware, the injection ECU shuts down if 1.2 bars lasts 16 seconds.

I will try to do this test.
If the pressure will rise what does it mean ???
If the pressure won't go up what does it mean ???
Wastegate problem ???
Amal valve problem ???

I only noticed that Amal valve have a little leak under pressure
With the valve non energized I tried to blow in C pipe plugging W pipe and a very little quantity of air escape from R pipe

If boost raises higher this means the restriction is in the SEM valve.
If it does raise then your engine + turbo are unable to go higher.

Thank you.
Do i must plug C rubber hose and remove Amal sem valve ???
???
Or just leave disconnected W rubber hose ???

Disconnect the W hose. Well, may be disconnect all of them in case they are not connected to the right place.
Also check that the W goes to both wastegates, C goes to one compressor output, and the third (F ?) to the filter (or hanging). You'll find same stamps on the SEM valve. Check there is nothing stuck in the F hose.

I had the same symptoms with my racing after rebuilt. The amal valve was the problem. You can find new ones for less than 100 euros (check at rosepassion.com) same as the porsche 944 for example or saab maybe closer to you. It could be other things, but it could just be that

Hi.
My backpain is disturbing me.
So in these days i'm not performed W hose pipe test.
I have some questions.
With ignition on but engine off i tried to test knock sensor, knock sensor plugged with connector produces some millivolts if tapped with a screwdriver, but Amal sem valve don't click ( amal valve should click and connect C and W???)
I purchased a new amal valve but like the old one it's not hermetic in not energized position (if I blow in R some air escapes from C and W)
In these days I try to replace it to see if improve boost pressure.
In the ignition ecu what can drives amal valve ???
Knock sensor ???
Map sensor inside the ecu ???
Injection ecu don't make nothing to adjust boost pressure ??? Is it Right ???
I ask this because in another systems based on iaw04 the injection ecu drives boost pressure.
A disconnected knock sensor what results it would have on the boost ???
And a defective ignition ecu map sensor ???

Btim from Alpa could help you, with all the data’s you need.

Hi.
Today I checked wastegate
My wastegate initially opens at 0,2 - 0,25 bar and fully opens at 0,5 - 0,55 bar
These turbo wastegate should to initially opens at 0,388 bar ???
Preload on wastegate 2 mm ???
What I can do ???
The problem with these car is the turbo needs to be balanced each other.
With one turbo is more easy.
One of the turbo (passenger side) is in a bad position to work on it.
I don't want to take out my turbo
Could be this my low boost problem ???

Slight wastegate disbalance will not prevent from going to the max boost, the amal will regulate as required. There is no need to go to 0.01 adjustement precision, this is impossible on a spring loaded primitive wastegate system.

Ignition ECU does not really regulate the boost, I'd say it protects from over pressures.

Disconnecting knock sensor has no impact on the ignition. Actually knock system has never worked on these cars.

But if my wastegate open to early (0,2 bar) the engine behaviour change.
Infact my car is quite lethargic
Rhb5 vm8 must initially open at 0,39 bar
I learned about wastegate arm, that preload change maximum boost
Without preload only spring resistance oppose the gate to open and the gate result initially open at a low pressure and also fully open at low pressure.
Today I phoned at one turbo rebuild shop with a lot of experience on Maserati biturbo and they told me that I can try to regulate wastegate with turbo on the car using a dial gauge comparator and a pressure gauge so with this I can know the exact moment in witch wastegate start to open and a what pressure.
And also I can check the travel of the arm and the respective gate opening with new preload value
Do you think that wastegate are not the culprit ???
Wastegate are not disbalanced each other are equally not setted. (I think there are not any preload)

biturbomax a écrit : I learned about wastegate arm, that preload change maximum boost

Yes without SEM.

Do you think that wastegate are not the culprit ???

Yes

New sem valve installed.
Same boost pressure.
Last white line.

When I return in italy i'll try to detach W hose from sem valve to see if pressure go up.

What can i check ???

Hi biturbomax,

Try to link the W hose (wastegates) in the R (air filter return) connection of the SEM and link the R hose in the W connection of the SEM (you put before the reductor which is in R in W)
Don't change the C hose (compressor)
And try to drive with that i have made that on my car successfully
I think my SEM is inverted
I will buy another SEM for check