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

Hi guys

I have searched for some dyno results(you may have already seen) of FRS/BRZ. Each of them shows that there is a "low output" during about 3000rpm to 5000rpm. Please see the attachment.


Could someone help to explain the reason? Why the torque outputs like that?

When doing dyno, I think they should not shift the gearbox.

DI

I'm sorry i can not understand why direct injection will make such.
could you please explain more or give some url/reference ?

No one is sure for now, but many engines have a dip in the midrange, which is possibly due to intentional tuning for a "dual powerband", low range and high range as a compromise between daily driving and performance driving.

Tuning in the broadest sense of the word.

3k~5k is DI only, that's one of the reason for the drop of tq.
~3k it's dual injection.
3.5k~4.5k is single injection
5k~up dual injection again

Frankly speaking, I don't agree with it .

1. The dip is so big. please refer some other DI engine ( GM, VW/Audi ), yes they also have dip, but much smoother...

2. Dual powerband , i don't agree.. because 205NM for a 2.0NA enigine is not hard, it is a very easy target. Please rever PSA 2.0NA code EW10A which was built in 2006? http://image.xcar.com.cn/attachments...igWFwHzCaU.jpg

or some bmw engines or honda engines. most of them can reach 200NM without DI.



But i don't know the reason ,and it might be a pity... i think.:iono::iono::iono:

I never said DI had anything to do with it, and I don't think it does, although it's possible it does.

What I think is that the cams have peak efficiency at 6000 or whatever, and the intake has peak efficiency at like 2500, so you get 2 peaks. The drop isn't that bad really, as a percentage of peak torque. But these are all guesses.

Also keep in mind that the rev range here is 7500 rpm, so it's natural to see more variation in torque than when the rev range is only 6000.

Pity? What's the difference between GM, VW, Audi, BMW & FRS/BRZ engine?

It's call BOXER ENGINE! Search all the NA 4 cylinder boxer engine dyno

Untill the Ecu gets cracks now one can answer this, honestly I find this thread pointless as its been covered everywhere around this fourm

Easy now... True, we had this debate on several threads before, but it's not pointless ;)

Sorry that came off harsh I didn't mean for it to, I hate reading and typing as you never can tell someone's tone

Just throwing out another possibility, it could caused by intake resonance creating a low pressure in that rpm range.

Also thanks for your typing

You forgot to use the font SARCASTICA BOLD

I think it will be fixed with tuning so nobody needs to worry about it. It has been said by Tada I believe that they could have released it with 220bhp from the factory but had to dial it back because of emissions.

We have already begun to see how corked up this engine is from recent dynos from Perrin and other companies with aftermarket exhausts being manufactured that it is going to be quite easy to get power down the road.

How many NA engines do you see gaining 7whp from a cat back exhaust upgrade alone? Thats not even including the mid pipe as they have not even shown that dyno yet.

There is a dyno supposedly showing a 30hp increase from just an exhaust and what many speculate as a tune.

The point is the engine is being held back more than was first expected and the dip while part of the reason is nothing to worry about as it will be fixed in due time.

Take a look at my avatar....see the HUMP in the map ;)

Our testing showed the same dip

Its possible that it is only tuning, but I would guess that its more likely tuning coupled with some sort of unfavorable harmonic. May be able to affect it with intake manifold and header re-tuning.

Sorry - pic to go with the above post:

http://www.ddperformanceresearch.com...20dyno%202.jpg

here's a better pic

http://i190.photobucket.com/albums/z...RZTRTABLE-.jpg

23 by 17 maps?

What an odd choice.

Long standing discussion, and have many theories.

1. Direction Injection switching
2. Timing retardation to work with DI
3. Intake Acoustics
4. Non-optimized AVCS
5. Combination of 2 or more of the above.

Personally i believe its the result of DI...
The IS350 with similar injection has similar TQ fluctuations when switching to DI for relying on intake pressures and higher cylinder compression to form a homogenous mixture.
http://lexus.jp/models/is/performanc...mg_2gr_001.gif

as well as the GS350
http://lexus.jp/models/gs/performanc...-2gr-fse-1.gif

While just looking at this curve may turn you off, its actually the best way to make this much power while using the least amount of fuel and pumping out the least amount of emissions. While a similar conventional port fuel injected system can make the same power or more...it will also use more fuel and not pass our ever stricken global emissions laws. Even the Civic R FN2 has been discontinued due to not passing emissions in Europe and it makes a similar powerband that of the FA20.

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...)

Yeah, sorry what i meant by switching was the cylinder environment. Direct injection is on all the time...while port fuel supplement is on at 0-3000rpm and around 6800-7400rpm. Making DI the primary source of fuel giving off a consistent weak strat across the revboard. Didn't mean it like a on and off switch...

I think the issue here is how ignition timing is effecting the two fuel maps especially at the "switch" when port comes off. Especially since DI loves lots of retarded timing, and that there are really different cylinder pressure differences between the two maps.

Has anybody hooked up current probes and taken data on the injection timing yet?

I wonder when complete bolt ons from header all the way to cat back, will I fail emissions test? :cry:

While this is true (and impressive), I really am interested in seeing how some tuning can smooth that out. Whether it is handled by bolt-ons or a remap, this would be worth quite a bit to me, as long as it is CARB legal. Fuel mileage isn't as much of a concern to me as feeling uninhibited in my shift points.

exactly what i think too,
im more inclined to say, "toyota/subaru found more low end TQ" rather then "oh they lost some TQ in the middle,

reminds me of the arguments i have about open stack trumpets on quad throttles,
can i have long trumpets = yes but you loose some power at high rpm,
oh then can i have best high hp = yes but you need very short stacks,
can i have high hp but with long trumpets = NO
why = helmholtz resonance....20 minutes later
:suicide:

...... -__-

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

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

:)

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.

http://www.motordyneengineering.com/...-post-dyno.jpg

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

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.

http://www.ft86club.com/forums/attac...1&d=1338842223

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...

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

A TOYOTA ENGINE thats 15 years ago

http://img254.imageshack.us/img254/1021/pin544.png

Dude that's in Newton meters.

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?

190NM = 140 lb-ft

Yes. Notice how 140 isn't 150.