Frage uber restrictor in AMAL valve 224

[kodjo]

Hallo,

I am not so gut a German so I'll try Englisch.

I am trying to diagnose a low boost pressure and I have got a question: My 224v has a restrictor in the R (return to airbox) line from the AMAL valve that is controlling the boost pressure. I think this is strage, I would expect a restrictor in the C (Charge) line.

Were is the restrictor in your car?

[Thorsten Ruge]

For fixing any restriction you just pull off the suspected hose and check on it.
To check on our 3-way pneumatic valve, you disconnect the 3rd hose in the back and drive the car. If the boost is back(carefully now, don't accelerate into the red area of the boost indicator in the dash),- clean the plugs on the valve and all three hoses.
If the boost is not coming back with the back hose disconnected, your waste gates are staying open, the knock sensor faulty, or your turbos are down for some reason.
If your boost is back but not in connected position, your AMAL pneumatic 3 way valve is broken or your vacuum system down by broken hoses.
There are no factory restrictors at all,- take 'em out or show a picture of your suspect!

[kodjo]

Danke Thorsten für diene Antwort!

For fixing any restriction you just pull off the suspected hose and check on it.
To check on our 3-way pneumatic valve, you disconnect the 3rd hose in the back and drive the car. If the boost is back(carefully now, don't accelerate into the red area of the boost indicator in the dash),- clean the plugs on the valve and all three hoses.  

Done that, boost is back then!

If your boost is back but not in connected position, your AMAL pneumatic 3 way valve is broken or your vacuum system down by broken hoses.

The 3 way valve is not broken. It works (C to W open when no power, R<C>W open in energised in position), clicks when putting the key in "RUN" position. Cleaned it (opened it and cleaned the inside also).
Put pressure on the hose going to the wasegates, no leaks and moving wastegates. Connected the Charge hose form turbo with the W (wastegates) hose: Base boost 0,7bar. That pressure is normal I think and the C (charge) hose is now proved working.

There are no factory restrictors at all,- take 'em out or show a picture of your suspect!

Please look at (The restrictor is marked "3"): http://www.eurospares.co.uk/userImages/0..._011_1.gif 

I have that one in place but I think it should be in the middle port on the 3 way valve?

The car is in perfect condition (from new plugs to new fusebox) and everything is in working order.

[V624v]

Hi, Kodjo!

The right position of the valve is in the junction of line "R" by the factory Maserati. So yours is sitting in place.

Regards! Attila

[kodjo]

Thanks Attila for your answer. I like to keep it stock so leave the restrictor in the "R" port. This set-up is different from any other brand using this valve, all have the restrictor in the C port. This makes sense if you study the pneumatic forces and flows. Using the R port to place a restrictor is strange a least.

I still do not get boost, just a bit above baseboost. Checked all of the sensors and actuators, cables going to them, got new plugs, wires, distributer, rotor usw. Inspected the Ignition ECU and the Injection ECU.

Car drives great, just low boost

[veith2224v]

hi kodjo,

Thorsten gave an excellent description of an easy fault diagnosis. I remember that a similar case was discussed earlier in this forum, in the end it turned out to be a somehow faulty valve although it appeared to react like You described (and everybody would guess it would).

As far as I understand the working principle of the valve in a biturbo, there is some backpressure inside the valve created by the restrictor in R-position. This might work "against" the movement of the closing element initiated by the electronics. In fact, in a biturbo the pneumatic valve obviously does not stay closed until a certain pressure level is reached and then open but constantly beeing a little open, depending on the electronic signal and the pressure inside the valve.

Might well be, that either Your restrictor element is too small / too big or electronics imply an opening impulse for some reason.
Easiest way to check is to mount a second valve which is supposed to be working correctly. If not, Your electronic might detect some knocking or at least drives the valve opener as if the engine was knocking. With regards to the latter case, a check is more difficult. If both ECUs work, might be cabling or otherwise caused bad signaling to the valve. Worst case is to detect a faulty knock sensor, which I so far do not have a way to check apart from exchanging with a new one to check as the bloody thing [besides being almost impossible to reach within a running engine compartment] needs ground connection constantly.

cheers,
Veith

[kodjo]

Thanks Veith for your reply. Yes, Thorsten gave nice fault finding tips, thats great. So far I did all the "simple" stuff. As an former owner of a Saab 900 with APC (MABC) I should know all the trics. So far, no improvents made.

I found a perfect discriprion of how the AMAL valve should work:
http://forums.audiworld.com/showthread.php?t=1476692 

You can see the restriction in the C port. Audi, Saab, Ford, all use a restriction in the C port. This makes sense if one would try to understand the pneumatics. I think Maserati made a mistake here but for now I try to keep it stock.

If one could tap on the knock sensor (with a screwdriver or something) with the key in the "run" position then the AMAL valve should klick. Sadly, I can not see the knocksensor, only the cable going to it.

Well, I read the post you mentioned. Thats why I inspected my valve closely and found it in perfect shape. But then again, it goes wrong somewere in the electrics as I get a lot of boost when bypassing the valve.

Tomorrow I will do some test: Messure the boost pressure with a gauge and see the difference between a connected and disconnected AMAL valve.

Does anybody know the boost pressure with a disconnected valve? Should be around 0,7 bar I think.

[Thorsten Ruge]

Ok,- so let's assume it's the knock sensor. The 0,7bar are good to go, those valve bodies can crack some times in a way you cannot track.
Pierce the knock sensor's cable and route it parallel up to its connection point via a volt metre. It is not the the old SAAB 900 arrow head sensor anymore, but can die from water or oil, or grind the pulse cable hull off.

[kodjo]

I have done that allready. Got 1,6mV with a running engine. It changes a bit with the RPM's. The cable is good, no resistance. I can not see any change in boost with or without knock sensor connected.

I'm out of options

[kodjo]

Hi there! Succes is on my side. Today I measured the base boost. This is the level of boost that you get when the MABC or similar is not working, ie disconnect the AMAL valve. I got max 0,4 bar boost. Seems low (saab 900 = 0,5bar) bus sofar I can not find the correct value. Adjusting is a bitch as you need to adjust the wastegate...So, with the restrictor in "R" as per manual, and the connnector in place, the max boost is 0,6 bar. Replaced the restrictor from "R" to the "C" port.

I think it belongs there, not only because of the pneumatic setup as discussed above, but it is realy made to sit in the "C" port! Look at the pictures, the "C" port has a shape the prefents the restrictor from getting deeper into the valve than shown on the picture. Boost is now up to 0,8bar, half in yellow.

Don't know or my new setup is stock, but I like it and I do not get erratic boostlevels. I'll keep it like this and use the "R" port for the winter!

Restrictor in "R"

Restrictor

Restrictor in "C"