is an engine management system needed if i build the internals on my scion tc?

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Old 31 Dec 2013, 10:25 am   #1 (permalink)
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Default is an engine management system needed if i build the internals on my scion tc?

i am preparing to boost and i was going to build the internals on my 2006 scion tc before i do, due to mileage just to be safe, and i was wondering if i got new pistons and such, the pistons would probably be overbored +.5mm, but i am just uninformend as far as the requirements regarding engine management and when it is needed.

this isnt really a boost related question this is only regarding the engine internals being overbored by .5mm and if i need an engine management system for that, i know i will need an engine management system for boost but that was going to be after i built my engine instead of doing it all at once i was going to build the engine and upgrade the transmission, break everything in, then boost.4
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Old 31 Dec 2013, 10:39 am   #2 (permalink)
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The EMS operation consists of the passive part (collecting the readings from various sensors) and the active part (performing the needed calculations and setting the operational parameters for the engine). It doesn't "know" anything about mechanical parts such as pistons, rods, crankshaft etc, they might even not be there as long as the input data flow is within design-set limits.

If you achieve more power, it is likely that one or more parameters will exceed the design limits, making the EMS take corrective action (reduce ignition advance or similar) in order to bring them back. This is where you might expect engine acting strange or going into some kind of limp mode.

So it is likely that you will need some corrective action on the EMS to accommodate a different set of parameters. This requires a specialized, properly equipped shop capable of "chipping" the EMS.
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Old 31 Dec 2013, 10:54 am   #3 (permalink)
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This is a difficult question and I am not familiar enough with the TC on some specifics. There are after market piggy back units that address some issues. For example a stock ECM often has limits on just how big an injector can be used and still have a good idle. Boost either needs to be kept low enough to stay inside those parameters or a solution found. Rising rate fuel regulators, secondary injection systems are alternate solutions. But these can only go so far. The other major problem is the ignition advance curve, now some ECM's have ways to program the curve with out a secondary unit. The one part that will need to be changed for sure is the MAP sensor, the stock one will fault out the ECM.

By far the current best solution is to replace the stock ECM with a Mega Squirt unit and learn how to monitor what is going on with a lap top real time and reprogram it as you go.

At a minimum you are looking at a need for bigger injectors and different MAP sensor.

To make sure you get all the items addressed for big boost- look into a mega squirt unit.


If you stay with in the recommended engine bore oversizing suggested by Toyota no new ECM should be needed. Even mild cam changes and should do all right. On the rebuild- spring to get the crankshaft flash removed and if you can get the engine balanced a little tighter. See if you can find a windage tray if none is being used also. With attention to those details it is often easy to pick up ten or more HP.

Four pounds boost should not tax the system. The problem I had on running light boost was that most aftermarket units can not be tamed down that far with out investing in an additional waste gate actuator.
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