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

[Dimman]

Originally Posted by HunterGreene

Measurements in factors of 10? Craziness!

Seriously, though, good thread. I have been seeing mentions of this "power drop" around the forum, good to see the discussion condensed in one thread.

I'm Canadian so have the odd situation of knowing distances between towns in km, temp in C°, but my height in feet and inches, and my weight in pounds. And my damn power in Horses, and lb-ft...

It's the fact that they hold on to 'metric' horsepower. But change it. PS in Japan and DIN in Germany. Why the hell do they have to change a unit they aren't even supposed to use?

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.

[Ryephile]

Originally Posted by arghx7

It's not so much a "torque dip" as it is a "torque bump" under 3500rpm. This is caused by aggressive scavenging from high overlap--lots of intake and exhaust cam phasing combined with the characteristics of the manifolds.

Good perspective. Essentially, this would mean the engine has a "natural" torque peak at about 6k, but then has some creative acoustic and camshaft specifications to achieve a torque bump at lower RPM.

Originally Posted by AlmostMDD

I think Dimman's point stands, not quite 150 ft lbs at 3000rpm. But isn't the FA20 engine dyno somewhat conservative compared to what people are observing on chassis dynos?

Kinda, but not really. It may have slightly more torque than advertised below 6k RPM, however above that the torque plummets rather quickly and ends up achieving peak power spot-on to advertised power.

[eriktherod]

Just to be sure, this exists on the FR-S also right? I heard (not on here) that the BRZ does it but the FR-S does not, which makes no sense to me.

[old greg]

Originally Posted by Dimman

It's the fact that they hold on to 'metric' horsepower. But change it. PS in Japan and DIN in Germany. Why the hell do they have to change a unit they aren't even supposed to use?

It's not as bad as you think. DIN is just the German Institute for Standardization, and when it's mentioned with power ratings it's akin to "SAE net HP". PS is actually the equivalent German abbreviation for HP, Pferdestärke is the direct German translation of the words "horse strength". The other assorted names for the unit are just local translations as well. Chevaux (horses) in France, hästkraft (horse power) in Sweden, etc.

[ahausheer]

Originally Posted by eriktherod

Just to be sure, this exists on the FR-S also right? I heard (not on here) that the BRZ does it but the FR-S does not, which makes no sense to me.

The FR-S better do it, otherwise those BRZ owners are going to be pisssed.

[Dimman]

Originally Posted by old greg

It's not as bad as you think. DIN is just the German Institute for Standardization, and when it's mentioned with power ratings it's akin to "SAE net HP". PS is actually the equivalent German abbreviation for HP, Pferdestärke is the direct German translation of the words "horse strength". The other assorted names for the unit are just local translations as well. Chevaux (horses) in France, hästkraft (horse power) in Sweden, etc.

But 1 PS = .986 bhp.

Or is this not correct anymore since the SAE made some changes a while back?

[OrbitalEllipses]

Originally Posted by Dimman

But 1 PS = .986 bhp.

Or is this not correct anymore since the SAE made some changes a while back?

I thought this was correct because PS ratings =/= USDM sticker HP ratings.

[Dimman]

Originally Posted by OrbitalEllipses

I thought this was correct because PS ratings =/= USDM sticker HP ratings.

But a while ago I remember ratings changed here, so it might be standardized now?

[OrbitalEllipses]

We should all be metric to avoid this headache.

[Boosted2.0]

Yes, the FR-S has the same dip.

As I stated on the previous thread, my opinion is that it is most likely intake or exhaust resonance. You see smaller versions of the same thing on 1ZZ and 2ZZ motors. Free up the intake and exhaust and retune and it may go away or be reduced.

Link to our FR-S dyno:

http://www.ft86club.com/forums/showthread.php?t=7319

[Coheed]

I am going on a limb here, I think it is tuned this way. Possibly to prevent knock at a highly volumetric part of the map. Or it could be for emissions purposes. If scavenging is improved around 3000rpm, this could be leading to a knock threshold at 3500rpm or so. I think it could be tuned out, but to meet strict emissions standards and lower NOx emissions they probably had to do it...

Again, just my thoughts on absolutely no scientific data at all.

[Jordo!]

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

[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.