TGV Operation Change

Jon [in CT] · **Posted:** Fri Jun 27, 2008 10:55 pm

When Tumble Generator Valves were first introduced in 2001 on the New Age WRX, they were documented as:

Quote:

The tumble generator valves are controlled by the ECM according to the coolant temperature and the time elapsed after start of the engine. When the engine is started, the butterfly valves are moved to the closing ends. In this state, the intake air flows at very high speeds passing through narrowed passages in the directions determined by the individual intake air ports in the cylinder head. This creates tumbling air motions in the cylinders, which enables lean mixtures to be ignited and thus harmful exhaust emissions to be reduced during engine start. The tumble generator valves are fully open when the engine is operating at an ordinary driving speed, allowing intake air to flow without being changed in direction and velocity.

I believe the coolant temperature necessary to trigger opening of the TGVs is in the vicinity of 140°F (maybe 145°F).

Beginning with the 2007 Legacy, Subaru began adopting a new TGV regime (see below). It's possible that the 2007 Legacy load/rpm TGV table for TGV operation has always been present. If so, this would be useful to those wishing to adopt lean cruise. Or, alternatively, 2007+ Legacy owners might wish to cancel the new extended TGV operation range to improve drive-ability (i.e. surge/bog during cruising).

nsfw · **Joined:** Thu Nov 23, 2006 2:23 am **Posts:** 2565

That's interesting, I wonder if my '05 would run smoother when cold if the TGVs were active until the motor warmed up.

gabedude · **Posted:** Fri Jul 25, 2008 2:30 pm

Seems like the 07 STI has the same TGV system (one unit, sensor is in the actuator). That would explain my odd fuel trims (-15, -10, 0, 0) because I have TGV deletes. I wonder if the TGVs on the 07 STI are closed in the lower RPM, low load. I bet they are.

nsfw · **Joined:** Thu Nov 23, 2006 2:23 am **Posts:** 2565

I don't see any TGV control tables in my 05 ROM, but I'm guessing that they do exist.

Merchgod, have you ever looked for them? If there are tables that will let me keep them active until the car warms up (or exceeds some RPM or load threshold?) I'd like to do some experimenting.

merchgod · **Joined:** Thu Mar 30, 2006 2:38 am **Posts:** 5336

NSFW wrote:

Merchgod, have you ever looked for them? If there are tables that will let me keep them active until the car warms up (or exceeds some RPM or load threshold?) I'd like to do some experimenting.

I don't have time right now to look too much into this (or any further), but I took a quick look at TGV stuff for the 07 LGT. There's at least 2000 lines of code dedicated to it and like everything else, it is not as simple as a few thresholds. The following known inputs are used in one way or another (other than the TGV-related variables): IAT, ECT, RPM, MAF, VEH. SPEED, IDLE SWITCH, BATTERY VOLTAGE, REQUESTED TORQUE, SI-DRIVE MODE. Looking at just RPM, there is one simple threshold (> 3000 RPM or <= 2900 RPM) and a group of 2D tables -> row = RPM, data = Requested Torque (0 - 3200 RPM -> 350 - 70 RQ, 3600+ RPM -> 0 RQ). ECT has some extreme thresholds (< - 40 F, > 248 F) and also a 3D table (row = battery voltage, col = ECT, data = multiplier related to TGV output, higher the BV the lower the multiplier, higher the ECT the lower the multiplier, range 1.99 to 0.85).

RomRaider

TGV Operation Change

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