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Re: Help with tuning issues, turbo swap? new owner of 99T Posted by Gary Stottler [Email] (#1463) [Profile/Gallery] (more from Gary Stottler) on Tue, 27 May 2014 05:09:56 In Reply to: Re: Help with tuning issues, turbo swap? new owner of 99T, pavl, Thu, 22 May 2014 14:51:54 Members do not see ads below this line. - Help Keep This Site Online - Signup |
Pavl,
I agree that rebuilding the Warm Up Regulator/Control Pressure Regulator is a good idea. The Control Pressure should vary with temperature, lower when cold, higher when warm. Also, I suggest that you check that you don't have any restriction in the fuel return line from the fuel distributor back to the tank - a restriction there can make it run lean.
As far as injectors, you might want to consider replacing all 4. They are available from Rock Auto (http://www.rockauto.com) - just search for Saab 1980, 900, Turbocharged, Fuel Injectors (they are same as 99T) and they have them for as little as $10.67 each. If I recall I bought a set of the $10.67 ones and they say "Bosch Germany" on them. The Rock listing shows the Bosch part number ( 0 437 502 004 ) if you want to confirm they are same as the original ones.
With all that done, you need to make sure that the Lambda system (the electronic control part of the Fuel Injection) is working - put a jumper wire in place of the fuel pump relay with the engine not running and make sure that the modulator valve is buzzing. If it is not working, the engine will run very lean. If it is backfiring, check the timing also and make sure that the vacuum advance in the distributor is working. If the Lamda valve is buzzing, you can, as a diagnostic, unplug the Lamda sensor (Oxygen sensor) and the system will run at 50% duty cycle. The engine should run fine that way if all else is good. Also, make sure that the wide-open-throttle microswitch (the throttle lever pushes it closed, it's hanging on the side of the throttle body towards the distributor) is working. With the engine idling if you push that switch closed manually (without moving the throttle) you should hear the idle speed up/smooth out due to extra enrichment. When you are really running at full throttle, you definitely need that enrichment to be there, or bad things can happen!
As a general statement, I am not sure that the stock fuel system can flow enough fuel for the engine to run rich enough above about about 10 psi boost. If you are going to try different turbos or mods once you get the basics straightened out, you may want to install an Air/Fuel ratio sensor to make sure you are staying rich enough (11.0 to 1 at least?) under higher boost. These engines make heat and eat up exhaust valves when run at high boost!
Good luck,
Gary
_______________________________________ Gary Stottler
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