Normally Aspirated?? why tune?

BigT · 02-17-2012, 09:48 AM

Quote:

Originally Posted by Evil Sports

But wont the on board ECM deal with this, or at least warn if its an unsafe condition

Yes and no. During cruise and idle, when the ECU is in closed loop, Fuel Trims are used to keep the AFR "stoich". These fuel trims can vary from positive to negative up to a certain percentage. (I'm not sure what the max percentages are for the Z.) This is mostly affected by changes to the intake tract ie different size MAF housings, new throttlebodies, intake manifolds, etc. However, when getting out of closed loop and into open loop (WOT), Fuel trims are usually NOT used. The ECU is pre-programmed to provide a certain amount of fuel based off TPS and RPM. These are the tables that are greatly affected when more airflow can get in and out of the engine. (mods) This causes a lean issue that cannot self fix and must be taken care of with a tune.

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