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

[serialk11r]

Originally Posted by Matador

...... -__-

Honest question, what are you thinking? I'm confused

[Matador]

Originally Posted by serialk11r

Honest question, what are you thinking? I'm confused

Just giving you a ribbing for panning me in perrin's thread mate :happy0180:

[Motordyne]

As so many others have mentioned above, there are so many different possible reasons for the hump its hard to say without a whole lot of experimentation.

I get the impression its related to resonance tuning of either the intake manifold or the headers. It looks like an out of phase portion of the resonance tuning.

Its not completely unusual though. Here are 2 different intake manifolds on the Nissan 350Z. One with shorter intake runners, the other with longer intake runners.

None of these are completely flat and both have different dips due to their respective manifold resonance characteristics.

[serialk11r]

Originally Posted by Matador

Just giving you a ribbing for panning me in perrin's thread mate :happy0180:

I could tell But what's wrong with my post?

[arghx7]

I spoke to an industry person who is an expert on such matters as this, a person I greatly respect whose knowledge exceeds my own. He in essence agrees with Dimman:

Originally Posted by Dimman

It isn't so much that there is a horrible dip, but that the motor manages to create a LOT of torque in the 2500-3200 rpm range. (Name another 2.0L NA motor that makes ~150 lb-ft @ 3000 rpm...)

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.



it would take, at minimum, changes in the intake and exhaust system to add torque around 4000rpm. Like any other resonance tuning, when you improve one area there's a chance you will hurt another.

It seems unlikely that you could just reflash the ECU on a stock car with merely a catback and "get rid of" that dip without lowering torque somewhere else. There are a lot of engines with conventional port injection and cam phasers that have a similar dip.

[Dimman]

Originally Posted by arghx7

I spoke to an industry person who is an expert on such matters as this, a person I greatly respect whose knowledge exceeds my own. He in essence agrees with Dimman:



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.



it would take, at minimum, changes in the intake and exhaust system to add torque around 4000rpm. Like any other resonance tuning, when you improve one area there's a chance you will hurt another.

It seems unlikely that you could just reflash the ECU on a stock car with merely a catback and "get rid of" that dip without lowering torque somewhere else. There are a lot of engines with conventional port injection and cam phasers that have a similar dip.

The boost range looks like it is timed to the length of the primaries (at 14-16" via my eyeball) and an effective cam duration of ~200ish degrees. Haven't looked to see if there is something that corresponds on the intake side, but I think the 'sound tube' may actually be playing a role with this too...

[ahausheer]

Wonder if this resonance theory has anything to do with the fact that there are 5 intake resonators (including sound tube as branch resonator)

[MANDALAY]

Originally Posted by Dimman

There doesn't sound like there is any actual 'switching' of port and DI. There is continuous changing fueling of both from the sounds of it. Like they have 2 simultaneous, continuously changing fuel maps that run together.

The other thing to keep in mind is from the dyno graphs, that 'dip' is ~ 85% of peak torque. The low rpm peak and the high rpm peak are very close to BOTH making peak torque.

It isn't so much that there is a horrible dip, but that the motor manages to create a LOT of torque in the 2500-3200 rpm range. (Name another 2.0L NA motor that makes ~150 lb-ft @ 3000 rpm...)

A TOYOTA ENGINE thats 15 years ago

[arghx7]

Dude that's in Newton meters.

[AlmostMDD]

Originally Posted by MANDALAY

A TOYOTA ENGINE thats 15 years ago

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?

[czar07]

Originally Posted by arghx7

Dude that's in Newton meters.

190NM = 140 lb-ft

[arghx7]

Originally Posted by czar07

190NM = 140 lb-ft

Yes. Notice how 140 isn't 150.

[Dimman]

And at 3000 rpm it's just a touch over 160 Nm ~120 lb ft.

And 120 isn't even close to 150.

[old greg]

Originally Posted by Dimman

And at 3000 rpm it's just a touch over 160 Nm ~120 lb ft.

And 120 isn't even close to 150.

You're reading it wrong.