2014 Subaru BRZ - Minor and Major Mechanical Changes

[WingsofWar]

Originally Posted by serialk11r

In this case it'd only be 5 though right? Besides, 4 of them would be linked together anyways...You might not even need to vary their position against load, just engine speed.

WoW, 15% seems a little sketch but if it's just the throttle, that could be possible. I am not informed on this by any means but it sounds to me like considering the flow of the entire system rather than just one piece would make that difference look much smaller. With TGVs sitting in a narrow part of the intake tract though, yea I imagine smoothing out the valves and stuff would help. Just throwing ideas out there, but maybe sanding the pivot part a little, and then using some epoxy or foam or something to slightly fill in the small gap, maybe rounding off the edges too (although that could mess up very low load behavior).

i dont really expect 15%...but i had similar ideas...

Also I was joking about it being OEM ITBs in my original post. But since Dim talked about secondary throttle plates...i was just playin around some crazy ideas...lol

what we have currently for TGV in older EJs is this



With secondary actuated throttle plates at idle...the plates would just be partially open for airflow but still have that tumble effect..and with a hollow throttle body.

Then when the throttle plates open for high-speed we don't have that little division along the full length of the lower portion of the TGV bodies with no flow obstruction besides the plate itself.

[Calum]

Guys, why are we getting so bent out of shape over a torque dip that doesn't effect 99% of our driving? Improving it is NOT worth it if it means having any restriction in the air path.

About the throttle body, people laughed at me when I spent an evening with a throttle body a hack saw and a couple of files. And sure, if I did nothing but the throttle body the difference would have been small if anything, but when you do that kind of thing with the whole system that's when real differences are noticed.

Weight redux is the same way, it's not about trying to find one item that's 500 lbs, it's about finding 500 items that weigh 1 lb each.

[ahausheer]

Some members are eqperiencing low and rough idle I wonder if the TGV's are addressing that problem.

[Snoopyalien24]

Originally Posted by WingsofWar

Same can be said about DI itself being anti-enthusiast in nature. TVG may not have been the best solution for WRX owners. But it really makes me question about it in this application.

TVG is mainly used in the past as a primary purpose to restrict air flow, during idle resulting in reduced emissions. But with DI in place and a weak stratified charge injection at idle, the idle emissions and fuel consumption has already made signficant improvements. Making TVG redundant...

TVG was really counter-productive in WRX with already horrible manifold AITs from the factory being turbo and experiencing noticeable heat soak. Does the FA20 also suffer from the same AITs with its phleonic resin compound intake manifold and not experiencing hot intake charges?

Why couldnt subaru use variable intake lengths if they were really targeting smoother TQ charcteristics via intake accoustic tuning? Rather than go TVG..

Besides the engine changes, anything on wheel bolt patterns?

[DubGUy]

Don't know how to post thread but anybody seen this?

[ahausheer]

Originally Posted by DubGUy

Don't know how to post thread but anybody seen this?

Back on topic. So the TVG's just create a better swirl pattern for fuel mixing?

[mike2100]

Originally Posted by WingsofWar

Also I was joking about it being OEM ITBs in my original post. But since Dim talked about secondary throttle plates...i was just playin around some crazy ideas...lol

Originally Posted by FT86club blog post

Other changes may include OEM ITB (individual throttle bodies), watercooled EGR (exhaust gas recirculation) with a collector, Hitachi DI injection drivers ECU and Hitachi injectors with a dual spray pattern.

Dude the blog post totally convinced me they were actual ITBs! I was getting sad for a moment there, thinking I just bought my car and there was a huge upgrade coming in the next model year.

[Dimman]

Originally Posted by ahausheer

Back on topic. So the TVG's just create a better swirl pattern for fuel mixing?

Briefly, yes.

It's actually the shape and 'aim' of the port combined with the velocity of the air. Air velocity is related to piston speed and port cross section. TGVs reduce cross section for more velocity at lower piston speeds (rpm).

[serialk11r]

Originally Posted by ahausheer

Back on topic. So the TVG's just create a better swirl pattern for fuel mixing?

Not swirl, but tumble. Apparently the big thing these days is tumble.

If you notice the diagrams, the TGV is sorta encouraging air to travel on the side of the valve closer to the center of the cylinder, but the end of that guide vane thing is pretty far from the port itself so I wonder what it actually does. Assuming that picture is from Subaru, then we can probably infer from the little swirly arrows drawn everywhere that the tumble flow is perhaps induced in the intake tract right before the port?

If it makes more torque at low rpm without them, then you know it's just there for idle or emissions or something. However this time they're messing with direct injectors, so it could be different, but not sure. Hopefully someone who knows about this stuff can chime in.

[Dimman]

Originally Posted by serialk11r

Not swirl, but tumble. Apparently the big thing these days is tumble.

If you notice the diagrams, the TGV is sorta encouraging air to travel on the side of the valve closer to the center of the cylinder, but the end of that guide vane thing is pretty far from the port itself so I wonder what it actually does. Assuming that picture is from Subaru, then we can probably infer from the little swirly arrows drawn everywhere that the tumble flow is perhaps induced in the intake tract right before the port?

If it makes more torque at low rpm without them, then you know it's just there for idle or emissions or something. However this time they're messing with direct injectors, so it could be different, but not sure. Hopefully someone who knows about this stuff can chime in.

That's not tumble. Just turbulence. We shouldn't focus so much on tumble vs swirl as it's the same thing just spinning around a different axis within the combustion chamber. Charge motion.

The turbulence in the port isn't 'tumble' in the traditional sense but it is doing the same thing, mixing fuel from the port injector with air.

Tumble has become the current motion form because of the switch to 4 valve heads. Swirl in the 2 valve days was generated by aiming the port to the side of the cylinder so air would kind of meet it at a tangent then follow the cylinder wall in a circle and create a swirly vortex.

With pent-roof 4v heads they can't aim both valves' flow off to the side very well so they tried the same thing by aiming for it to hit the back at a tangent and circle vertically instead.

The angles of the ports affects this as does their aim and how fast the air comes in. A secondary concern is maintaing the motion as compression reduce the space. This is why F1 engines were less than the FA20 with 12:1 CR.

I think Toyota calls the Swirl Control because it looks like the segregate the port for each intake valve in the 3GRFSE and may only have the valve in one to favour flow to one side of the chamber. This may create a tilted pattern between tumble and swirl and is also pure speculation on my part...

[ahausheer]

Are those things vacuum controlled (thus on or off) or are they continuously variable and controlled by an electric motor via the ECU?

[phillip]

Originally Posted by WingsofWar

+Water-cooled EGR with a collector..might also be adopted into the FA201. Although I don't really see how this is a benefit for greater emissions.

Externally cooled Exhaust Gas Recirculation lowers cylinder temperatures pre- (and therefore post-) combustion. It is used primarily to reduce nitrogen oxide (NOx) emissions, which are created when Nitrogen and Oxygen (main components of air) interact at high temperatures. Because it's replacing air/fuel to be combusted, it can result in lower power efficiencies if applied incorrectly, but the cooling effect can sometimes be significant enough to cancel that out (less heat absorbed by the engine = more work produced by the piston).

[bimmerboy]

Originally Posted by OrbitalEllipses

TGVs are not OEM ITBs...

Feel like this needs to be re-iterated

[serialk11r]

Originally Posted by phillip

Externally cooled Exhaust Gas Recirculation lowers cylinder temperatures pre- (and therefore post-) combustion. It is used primarily to reduce nitrogen oxide (NOx) emissions, which are created when Nitrogen and Oxygen (main components of air) interact at high temperatures. Because it's replacing air/fuel to be combusted, it can result in lower power efficiencies if applied incorrectly, but the cooling effect can sometimes be significant enough to cancel that out (less heat absorbed by the engine = more work produced by the piston).

Errr the point of EGR is to reduce emissions and pumping loss by putting mostly inert spent gas back into the intake, and this should only be happening at part load. Under full load you need all the air you can get. The reason you want cooled EGR is because uncooled EGR will raise cylinder temperature and reduce efficiency (by lower heat capacity ratio). Lean burn is better for fuel economy because recirculated exhaust slows down combustion much more than fresh air does, but lean burn causes a major NOx problem.