Early proposal: FA20 with a FB25 shortblock, .5l more displacement anyone?

[Kostamojen]

Originally Posted by Dimman

Last is something I'm not certain on, and that is I think the DI/D4-S engines have different shaped pistons, due to the nature how the direct fuel injection spray works. So another wrench in the machine there.

I'm curious about this too. The only photo we saw of internals was stolen from FB motor diagrams from when those motors were released.

[Kostamojen]

Just made a quick comparo photo using that small brochure picture we have of the FA20 heads from the FRS/BRZ, comparing it too the FB20 heads:

[coyote]

Even if the pistons are different in the direct injection cars, there will be a direct injected FB25 engine very soon. The way Subaru works, it will mirror the setup in the FA20.

My bet is that will occur before the ecu rom file is available.

I hope people do build Frankenmotors, as that will create a market for me to sell my FA20. It's also the only way you'll get a significant power increase while staying NA.

[Dimman]

Originally Posted by coyote

Even if the pistons are different in the direct injection cars, there will be a direct injected FB25 engine very soon. The way Subaru works, it will mirror the setup in the FA20.

My bet is that will occur before the ecu rom file is available.

I hope people do build Frankenmotors, as that will create a market for me to sell my FA20. It's also the only way you'll get a significant power increase while staying NA.

The way Subaru worked with the EJ, it will be a decade before they decide to but DI on it. (joke...)

Am I seeing vertically stacked dual runners on that FA20 schematic? As in a TVIS-type system?

[Kostamojen]

Not sure what you mean, but the FB's have a little metal dispersion plate in the intake port that slides into slots on each side of the port, which is probably what you are seeing in terms of that diagram:

[coyote]

Originally Posted by Dimman

Am I seeing vertically stacked dual runners on that FA20 schematic? As in a TVIS-type system?

I think I know what you are talking about.

Google Subaru, risers, tgv.

[Dimman]

Originally Posted by coyote

I think I know what you are talking about.

Google Subaru, risers, tgv.

I know what TGV's are, but if you look at that pic, the blown-up FA pic looks like it has a more definite split down its intake runner.

[arghx7]

Originally Posted by Kostamojen

I'm curious about this too. The only photo we saw of internals was stolen from FB motor diagrams from when those motors were released.

Time will tell, but most of the methods and knowledge from the old ways of doing things are going to be thrown out. The thing that makes the D-4S system (as applied in the Lexus 2GR-FSE engine) different than the typical port-injected design is that

The piston, the intake ports, and the injectors are all engineered together in a way that changing any of the parts could create a lot of problems to overcome.

The intake port is high flow but also has significant tumble flow that is critical for mixture formation. The piston has a "shell shape" and the direct injector uses a dual "fan" spray pattern. To my knowledge only Toyota is using that combination of production engines.

[Kostamojen]

Ya, if the pistons are like that this idea probably won't work at all without custom pistons...

[coyote]

Originally Posted by Dimman

I know what TGV's are, but if you look at that pic, the blown-up FA pic looks like it has a more definite split down its intake runner.

Yep, but after the tgvs, the factory riser has a vane which separates the flow into two.

I have spoken to an engineer who specialises in flow dynamics and he has suggested it might be to assist flow at low velocity.

Regardless, it doesn't seem to make any tangible difference whether it is there or removed.

[coyote]

Originally Posted by Kostamojen

Ya, if the pistons are like that this idea probably won't work at all without custom pistons...

Subaru have stated there is an FB25 with direct injection on the immediate horizon.

You seem to know how they work, they won't be reinventing the wheel (so to speak).

Yet another reason to just pull it out and go with an EJ

[Kostamojen]

As far as I can see, I don't see any TGV's on the FA20, and I don't expect there to be (especially with the location of those injectors). Although I don't think there is any argument about that, just whether or not the intake port is split.

[Homemade WRX]

yup, long time bump. Stumbled upon this since I'm already several steps ahead of this thread.

Originally Posted by Dimman

I know what TGV's are, but if you look at that pic, the blown-up FA pic looks like it has a more definite split down its intake runner.

You may be seeing in the intake port itself where there is a sheetmetal divided that slides in. It has these round dowel like pieces that hold the sheet and retain it in the port...when the dowels are inserted into the head.

Originally Posted by Kostamojen

Ya, if the pistons are like that this idea probably won't work at all without custom pistons...

Nope
I'm just waiting on the the 'shell'/chamber geometry from the FA20 for a starting point.

[Levi]

Can't wait for the first FA20 rebuilds, whether frankenstein engines or kits. But I don't know if I'd prefere a 9.000 RPM FA20 or a 270 Nm FA25.