| His post was very long, and this is the revelant part I think you asked about.. He also references a MAF/Dummy MAF intake.. but the results I believe are the same for any TT Z A/F Ratio Balance
In all the time I have been in the Z scene, I have yet to see or hear of anyone testing the A/F difference between the two sides of the engine. THIS IS A CRITICAL TEST! While just about every mildly-modded Z (wastegate actuators according to which side is running rich or lean. The resolution is somewhat of a complicated explanation, but well worth understanding ? it could save you a multi-thousand dollar engine! Since the MAS is only connected to the driver?s side turbocharger, it is the ?reference? side for the air metering system ? the ECU only ?sees? what is going on with this side. However, the driver?s side turbocharger actually feeds air into the passenger bank of cylinders (the intake manifold ?crosses-over?). This means that the passenger side exhaust is the reference side for determining your base A/F ratio ? what you see as the A/F on the passenger side of a dual-pop configuration is the ?actual? A/F that the ECU is generating. Here are the logistics:
Example 1: If the driver?s side exhaust is running leaner than the passenger side, it means that your passenger turbo actuator is tighter than the driver?s side, thereby making the passenger turbo spool more and flow more air into the driver?s side of the engine. Solution1: Since the passenger side actuator is the most difficult to get to, and in this case, it is the stiffer of the two and you should adjust the driver?s turbo actuator to increase the preload on the actuator rod. This will cause the driver?s turbo to spool more like the passenger turbo as well as rise to a shaft speed closer to the passenger side as well. Adjustments should be made ~1/8? at a time and tested with two consecutive pulls to test the A/F results between the sides. If it is still leaner than the passenger side, you need to shorten the actuator rod a little more. Continue doing this until you achieve an A/F balance between the sides of no greater than 0.2 A/F. Example 2: If the driver?s side exhaust is running richer than the passenger side, it means that your passenger turbo actuator is looser than the driver?s side, thereby making the passenger turbo slower to spool and moving less air than the driver?s side turbo. Solution 2: In this case, you are going to have to tackle the passenger side actuator and tighten it up a little. You might want to just go ahead and shorten the rod a full ?? to 3/8? just so you won?t have to do it a second time if it wasn?t enough. You can always tighten (shorten) the driver?s side actuator afterwards if you went a little too far on the passenger side. By no means do you want to loosen an actuator rod to correct either one of the problems shown above. The problem you may face if you loosen them is decreased peak boost ? the turbos simply wont make the peak boost they are supposed to. However, in the case that your lowest boost is <18psi and you cant go any lower, you may need to loosen your actuator rods on both sides to get your base-boost level back down to a manageable level. Only do this after verifying that all of the boost control hoses are properly connected and that they have no holes in them. You will also need to verify that there are no leaks in the actuator diaphragms as well. Loosening the actuator rods is a ?last ditch effort? to curing an over-boost issue as there are a plethora of other causes for this that are much easier to correct. An unfortunate reality of this test and repair is that it pretty much requires the use of a dynamometer to correct as the dyno provides A/F feedback that is vital to this process. Some may believe that simply setting the actuators to open at the same time by applying air pressure to both actuators and adjusting as necessary will correct this, but unfortunately this is not the case. The actuators will be the same between both sides, however, the angle of which the actuator rod connects to the wastegate control arm is slightly different from each side. You can get things ?pretty close? by using this method, but when you really start turning up the boost to higher levels, you will run the risk of one side leaning out and possibly damaging the engine. " It came from this Post.. [ http://www.twinturbo.net/net/viewmsg.aspx?forum=technical&msg_id=898410&forum=technical&dtSearch=1 ] Thanks Ash.. Cj
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