Boost leak [Archive] - SaabCentral Forums

: Boost leak


mastayoda24
31st May 2007, 03:20 AM
hi,

I am having some trouble here. i have some nice mods I want to do, but i want my car running good before i do them.

I have changed all of my vacuum hoses and changed my cuplers for the intercool piping turbo and all of that. I am still having boost leaks. It drops from max 10 psi to 5 psi.:x it was droping to 3 psi.

Any ideas what it is or just how i could find out what is causing such a huge drop in psi.
should i go ahead and do the mods and see what happens or what. im going to get a fmic, slitly bigger turbo, up boost, test pipe in place of kat, and fuel injectors.

saab boost
31st May 2007, 04:20 AM
sounds silly but it cud be ur exhaust bloked
mine lost boost on sunday and it cud hardly boost so after checkin everything i took exhaust off and had full boost, found out cat had broke up and bloked it slighty so turbo couldnt spin properly.
worth a try

mastayoda24
1st June 2007, 01:56 AM
i tried it. it realy did not help to much. maby 1psi saved.
thanks
a could it be caused from the intercooler getting to hot, and/or the turbo is to small to hold full boost.

Palmer1980
1st June 2007, 02:46 AM
Don't do the mods to fix the problem. It will only get worse.




Are you running 91+ octane gas?

How are the spark plugs, and the sparkplug wires?


What about the dizzy cap, and rotor?


I think it's not a boost leak. I think you are getting knock, and the APC is pulling the boost.

The APC system controlls the turbo, and if the engine is knocking, it will pull boost.


It sounds like you have the turbo side of things figured out, now try a few othetr things I mentioned.

When I was stock, I would hit 12, then drop to 8 by redline.

Now, it's more.

:)

mastayoda24
2nd June 2007, 03:49 AM
Don't do the mods to fix the problem. It will only get worse.




Are you running 91+ octane gas?

How are the spark plugs, and the sparkplug wires?


What about the dizzy cap, and rotor?


I think it's not a boost leak. I think you are getting knock, and the APC is pulling the boost.

The APC system controlls the turbo, and if the engine is knocking, it will pull boost.


It sounds like you have the turbo side of things figured out, now try a few othetr things I mentioned.

When I was stock, I would hit 12, then drop to 8 by redline.

Now, it's more.

:)
91+ octane. cheak
spark plugs. cheak
sparkplug wires. cheak

what should i be looking for with the dizzy cap and rotor.
and what should my spark plugs be spaced to, because im not shure where it is at exactly and where it should be.

Si
2nd June 2007, 07:21 AM
If you have any real boost leak you will hear it, makes a noise very similar to the bypass valve, i had lots of problems on my 8v turbo after installing a FMIC, either blowing the cuff off the TB or connectors leaking, my NG900TS is also leaking boost at the moment, i'm not sure if it's the intercooler piping or my forge BPV sticking open(which is also another cause of boost leak).

allessence
2nd June 2007, 11:19 AM
Sounds like a bad BOV.

Take the hose from where it is on the manifold and put a vacuum on it. If it will maintain 20" of vacuum than it should be okay.

For a quick test you can just wrap you lips on the hose and try to blow thru the hose. If BOV is really bad you will be able to blow thru.

This is with a stock Bosch BOV. If your running an aftermarket one Sometimes they stick and create the same problem but the blowing thru the hose will show you nothing unless its a membrane type.

mastayoda24
2nd June 2007, 03:48 PM
everything seems to be good.

but still what should i be looking for with the dizzy cap, and rotor.
and what should my spark plugs be SPACED to, because im not shure where it is at exactly and where it should be.

and if i am getting knock. what can i do about it, besides lowing boost.

mastayoda24
3rd June 2007, 04:04 PM
to tell if im getting knock, should i get a data logger, and is the LM-1 and LMA-3 the only ones that are out there.

Saab-Daniel
4th June 2007, 03:35 AM
To see if you get knock, connect the ground-side of a LED to pin19 in the APC-box, and the 12v-side to, well, 12v. No need to worry about resistors, you get resistors inline inside the APC. The LED will flicker when you get knock.
Daniel.

c900
4th June 2007, 06:42 AM
everything seems to be good.

but still what should i be looking for with the dizzy cap, and rotor.
and what should my spark plugs be SPACED to, because im not shure where it is at exactly and where it should be.

and if i am getting knock. what can i do about it, besides lowing boost.

Plugs should be gapped to between 0.6 and 0.7 mm I think - been a while since I did plugs on my 900's.

With the distributor cap and rotor, look to make sure there are no arcing paths, and check that the cap isn't cracked. I've had one crack and it caused a bit of a problem that wasn't immediately obvious. Also if the distributor oil seal (where it mounts to the cylinder head cover) is bad you're going to get oil into the distributor cap which can, if it builds up too much, create a leakage path with atmospheric moisture that can sap energy from the coil when it discharges.

If the outside electrode of the rotor is very pitted and doesn't look like a nice even curve, replace it. Also look at the contact points for the spark lead connections - they degrade quickly even with new cap/rotor but with a pitted leading rotor electrode the energy transfer to the spark leads can drop off markedly because the continuity between rotor and spark lead contact is not good.

Engine timing can affect it too - if the timing is off you'll have spark plugs firing at the wrong time(s) and the rotor may not be in the right place inside the cap to give optimal transfer of energy from the coil to the spark lead before the rotor moves away from the spark lead contact it's just passed.

Craig.

mastayoda24
4th June 2007, 03:51 PM
thanks ill check it out.

allessence
5th June 2007, 08:47 AM
Also the engine tune info is on the sticker on the drivers side upper fender. Open the hood, look just past the fuse box and you should see a white sticker.


This has all the engine info, including spark gap.