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

[Dimman]

Originally Posted by old greg

You're reading it wrong.

Ack... PS, kW, N•m, kgf•m...

Two different power scales on the left and torque on the right. Oops. Metric is simpler...

And that is the motor that I thought the FA20 would be an even torquier version of anyways thanks to D4-S and more compression, plus reduced friction.

[HunterGreene]

Originally Posted by Dimman

Ack... PS, kW, N•m, kgf•m...

Two different power scales on the left and torque on the right. Oops. Metric is simpler...

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.

[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