What's the reason for Torque dip in BRZ Dyno ?

[Dimman]

Originally Posted by Jordo!

Here's how you minimize or eliminate that torque dip once and for all: Lysholm blower

Fixed.

[MANDALAY]

Nah Rotrex SC and ECU and a great tune

[jedibow]

Factory tune retards timing in that area, most likely to increase emissions.

[Subaruwrxfan]

Has anyone posed the idea yet that they deliberately tuned the car that way just for driving excitement? When I was driving around today, I realized that once I get out of the mid-range "valley" the car takes off, almost in VTEC fashion, but not quite. Honestly I think it adds to the driving excitement because the car doesn't feel like it hits a brick wall during the valley, but once it starts cooking over 5k again, it really scoots. It's just playing a mind game on us.

I just think a dip that huge in the dyno graph has to be deliberate. If it was a performance issue or plumbing problem with the intake or exhaust or whatever, they would have fixed it. Subaru has dyno'd this car far more times than any tuner has I'm sure.

[arghx7]

Just to be clear guys, unless the vehicle is for some reason tested with extremely high road load force, There are no WOT pulls in any emissions test cycle. None. The torque curve at WOT does not directly affect the emissions certification. The heaviest acceleration is under the US06 drive cycle, but it's still not going to be a WOT pull.

[industrial]

Originally Posted by Subaruwrxfan

Has anyone posed the idea yet that they deliberately tuned the car that way just for driving excitement? When I was driving around today, I realized that once I get out of the mid-range "valley" the car takes off, almost in VTEC fashion, but not quite. Honestly I think it adds to the driving excitement because the car doesn't feel like it hits a brick wall during the valley, but once it starts cooking over 5k again, it really scoots. It's just playing a mind game on us.

I just think a dip that huge in the dyno graph has to be deliberate. If it was a performance issue or plumbing problem with the intake or exhaust or whatever, they would have fixed it. Subaru has dyno'd this car far more times than any tuner has I'm sure.

The GR STI came with a terrible tune from the factory. Tuners were easily able to increase the low end torque by massive amounts and smooth out the power curve while making the car's engine run safer. Theory has it that it came with a crappy tune because of emissions and efficiency targets (like cafe). It really wouldn't surprise me if that is the case here with the brz/ft86 as well.

[arghx7]

The GR STi ran longer in closed loop (longer delay until entering open loop) to keep CO emissions down, that's all.

[Razz]

There's a link on this or the BRZ forum to an inside site that say's for 2014 the manifold will be re-designed to take this dip away.

[industrial]

Originally Posted by Razz

There's a link on this or the BRZ forum to an inside site that say's for 2014 the manifold will be re-designed to take this dip away.

Yeah, by adding seemingly restrictive tumbler valves. I wonder if they will make the dip go away by just lowering the low end torque...

[blu_]

Originally Posted by Dimman

Anyways, not so much a drop as a lowend boost. But people are still either feeling it as a dip, or imagining they feel it. Or not feeling it at all. Depending on the driver.

Agreed. It seems pretty obvious to me that this is what is going on with resonance. I for one would gladly sacrifice some of that bump for increased tq in the rest of the powerband.

[ahausheer]

I thought the new tumbler valves are basically non restrictive and were going to be used for low rpm emissions, not to get rid of the torque dip. There is another thread on this site that suggests the torque dip is due to cam timing and not intake pressures. Apparently the MAP is steady through the rev range but the engine pulls timing at the torque dip. I think it is looking more and more like the dip is programmed on purpose for MPG and emissions tests or for knock control.

[serialk11r]

Originally Posted by ahausheer

I thought the new tumbler valves are basically non restrictive and were going to be used for low rpm emissions, not to get rid of the torque dip. There is another thread on this site that suggests the torque dip is due to cam timing and not intake pressures. Apparently the MAP is steady through the rev range but the engine pulls timing at the torque dip. I think it is looking more and more like the dip is programmed on purpose for MPG and emissions tests or for knock control.

Um sorry could you link me to said thread? MPG and emissions tests aren't going to run in that rpm range and will certainly not hit max load, and knock control is not called "programmed on purpose". The old tumbler valves were supposed to be for cold start emissions, the new ones are for low speed combustion stability, I think.

[arghx7]

Originally Posted by industrial

Yeah, by adding seemingly restrictive tumbler valves. I wonder if they will make the dip go away by just lowering the low end torque...

Link?

That's to meet upcoming California LEV III and Euro VI emissions I bet.

[Snoopyalien24]

Why don't people add a supercharger and thats it? Or how Gazoo did, and dual charged it?

Oh yeah cuz its expensive as hell. I think it is DI, but for up coming years it will be fixed