Engine technology thread.

[Dimman]

Originally Posted by serialk11r

Hmmm reading cyde01's comment in another thread about how the D-4S system is the next gen system and how they were apprehensive about sharing it with Subaru...I take back what I said about this engine being disappointing because they didn't have time to make it as good as possible. New theory: the engine sucks because Toyota didn't want to share all of their tech with Subaru, and it is not very likely a revised engine will come out. Well this seems disappointing.

I should clarify. I don't really mean it sucks. It just doesn't seem to meet expectations based on prior motors. Without the BEAMS or 2GRFSE references, it slightly beats the 2.0L volume production standard set by Honda with the K20Z in terms of driveable powerband.

I don't think there is an issue of sharing tech with Subaru, it will be about product placement. Toyota's percentage ownership is indicative of a long-term relationship. (this is VERY different that what happened with Geely) But Toyota is (to a certain degree) or will be (more so in the future) the boss. It doesn't make a lot of sense for them to place an acquisition with a perceived niche market on an equal perceived value level than the parent.

I do think we will see a revised engine. And am hoping that my missing torque may be found there...

Edit: Some of the things I have thought about as to the 'why' are:

A) The previously discussed deliberate 'nerfing' so sell more stuff. There is precedent for this with the Anti-Lag systems in Mitsubishi and Toyota rally homologation specials as well as in bikes involving secondary 'shower-head' injectors. But this would be a purely commercial issue and would piss me off royally. "Buy the TRD Platinum Nurburgring-edition power-tuner for $2000 and unlock MOAR POWAH!"

B) I even thought about if this were a 5 valve engine. I dismissed this quickly due to what I feel would be cost and sheer practicality issues with the direct injection. But looking at the spec sheet they don't actually say it is a 16 valve motor... I don't know enough about 5 valve behaviour to make as confident of a statement regarding power delivery. I do know that the direct injection would fix one of the short comings (balanced fuel/air mixture), and possible two (the divided combustion chamber), if the head gets more radial valve placement and the direct injector nozzle. Valves would have to be TINY though... Long shot, but who knows...

C) They tuned it to act like a high duration/overlap cam'ed engine but with tiny ports to choke power. So it's delivery would feel more like a big-cam S2K's but still run at sensible revs/airflow.

D) Subaru did do it all, and refused help from Yamaha beyond using the D4-S, and they suck...

E) They want to re-create the history of the 4AGE, and have an over-ported (slow intake velocity and high rpm needed for torque) intro head, and the better small port comes later.

Who knows...?

[serialk11r]

Yea I suppose only time will tell, but the motor is just so f***ing suspicious. Something is up.

[Dimman]

Originally Posted by serialk11r

Yea I suppose only time will tell, but the motor is just so f***ing suspicious. Something is up.

I still think my 168 lb-ft at somewhere around 4000 rpm is correct.

Partly also from the early C&D and Motor-Trend butt-dynos placing peak torque around there, and feeling that power tapers off after 6500 rpm. The brochure numbers would probably feel weak low but also feel like power would want to keep coming as revs rise.

Also the 'official' specs from Scion have 'Preliminary' emphasized.

Also the news that this is Gen2 D4-S hopefully means 'better' (more torque, less fuel) as well.

Also keep in mind that the higher the BMEP, the lower BSFC. Although that is fuel consumption at full throttle, some of that must translate to superior economy in normal driving as well. And that was a major target as well.

[bambbrose]

Originally Posted by syldrin

wtf...... why leave it open? seems..... flimsy

To allow for aggressive wheel fitment without running too low of offsets in the front?

That would be a nice benefit in my mind at least.

[Dimman]

Originally Posted by bambbrose

To allow for aggressive wheel fitment without running too low of offsets in the front?

That would be a nice benefit in my mind at least.

I apologize if I seem like a bit of an asshole here, but this is one of the longest, most on-topic threads going in a forum notorious for derailments.

Wheel fitment does not belong. There are other threads about that.

Cheers.

[bambbrose]

Completely understand.

On topic, in this pic


what is the large clump of bulk on the top left cam cap? What bolts to this giant mass?

[Dimman]

Fantastic question. I have no idea... And I can't find it on the other side.

[chulooz]

Can you isolate the part you are talking about?

[bambbrose]

Possibly the injection high pressure pump? I'm not familiar with the pumping methods, but I'm sure it would need a direct drive from either the cam or crank to obtain proper reliable pressure.

[Dimman]

Originally Posted by chulooz

Can you isolate the part you are talking about?

Rear of the head facing us in the pic. Piece that looks like it could attach to the upper/intake cam. In other pics it's not on the other side,

[serialk11r]

Are you sure it's not on the other side? :O
IIRC cam phasing mechanism is significantly wider than the cams themselves, that would explain it, assuming it's not missing from the other side.
EDIT: upon further examination of Kostamojen's pics, nope that has to be the cam phasing mechanism, it's there on the other side...dunno what I'm seeing that you're not.

Oh and Dimman, I don't think specific torque is that reliable of an indicator of how efficient an engine is. Remember for a given displacement, the engine doesn't necessarily pull in that full volume's worth of air. Ferrari with its ridiculously high specific torque is in part because they have the money to ensure that the engines have lower losses in some respects, but the cams are designed to pull in as much air as possible, and this directly reduces efficiency. In addition, at part load, it causes more pumping loss. When manufacturers making normal cars that average people use, they can't have continuous cam profiles, and they need to think about things like fuel efficiency, so even at peak torque they aren't quite as good.

[old greg]

Originally Posted by syldrin

wtf...... why leave it open? seems..... flimsy

Notice the general lack of structure forward of the strut towers. Torsional rigidity is between the wheel hubs (diagonally), so the stiffness of the structure outside the wheelbase doesn't usually contribute much. The only thing the the chassis has to do at the front and rear is hold body panels and absorb impact energy in a crash.

[Ryephile]

If item in question is circled, I have no idea. A mounting bracket for something? It's not the HPFP, because that's visible on the other side of the engine, being driven off the middle of the intake cam and sitting on top of the cylinder head.

[Ryephile]

Based on this picture of the BRZ reveal at the TMS, there's a whole wad of wiring above that bracket in question.





Anyone else have an idea? Perhaps a vacuum pump?