Report: BRZ STI Model Already in the Works, No Turbocharger

[86fanatic]

For me it's not whether a turbo will fit, a huge inter cooler would fit, or a bigger engine would fit. It's the fact that the car already has a front weight bias and adding any mechanical bits or heavier engine pieces will just further throw that off.

The car was engineered to have a very small engine in the front. Make that engine more powerful with revised cams, or tweaking the DI system, but if they bring up a more powerful version which adds 50+ pounds to the engine bay I will be disappointed.

[DoogenBurns]

Originally Posted by Levi

Even 300 PS on FA20 without FI is possible.

As a diesel mechanic, I see a lot of potential out of common rail fuel injection systems. The ability to add fuel after flame propagation, the ability to control the amount of direct injection events, and how long they last, not to mention the ability to increase compression ratio for a more complete burn are all positives in my opinion. I think I'm going to have a lot of fun messing with the DFI settings. (Assuming Toyota's DFI system is anything like diesel common rail )

EDIT: I think if subaru's engineers are creative they will be able to get a lot of power out of their current set-up.

[Allch Chcar]

Originally Posted by cyde01

does that mean 250 hp n/a!? dayum how would they do that? they'd have to increase displacement!!!

No, that is journalistic license. I think 225 is a far more reasonable expectation but there is no basis for anything right now.

Originally Posted by Leeky

Rubbish, i spent a lot of time under the bonnet of the BRZ taking pictures of the space in front of the engine.

You could easily fit a massive intercooler in there.

Personally i believe the engine bay could comfortably take a 6-cylinder engine (V6 Mind, not inline of course).

So i call BS on the AutoExpress artile

Hey Leeky. You don't post as much as you used to. Don't be a stranger.

Originally Posted by 86fanatic

For me it's not whether a turbo will fit, a huge inter cooler would fit, or a bigger engine would fit. It's the fact that the car already has a front weight bias and adding any mechanical bits or heavier engine pieces will just further throw that off.

The car was engineered to have a very small engine in the front. Make that engine more powerful with revised cams, or tweaking the DI system, but if they bring up a more powerful version which adds 50+ pounds to the engine bay I will be disappointed.

I have to agree with you. Surely people who want more power will be willing to make this sacrifice, or they might reduce some of the weight upfront to compensate. But , seems unnecessary to me.

[BMWDavid]

Take a look at the Porsche 4.0L GT3-RS, 500 HP. That's 125 HP per liter. Engine revs to 8500 rpm. Has many costly bits inside; Ti rods, ported heads, fancy valve springs and etc. Don't forget that Porsche has variable valve timing as well as a different valve lift at a higher rpm.

So the FA20 @ 2L would be at 250 HP if Subaru went this way. Surely would be a pricey engine. Now if they took it to 2.5L, about the same cc per cylinder as the Porsche 4.0L, then we are talking 312 HP.

I agree that it should not be a turbo with weight penalty over the front end. Plus a NA engine has a better feel as it revs. Not that a torquey turbo engine is a bad thing, but I think it would be out of charactor for the BRZ.

[serialk11r]

The Porsche hits power peak at 8250 which is quite high. Porsche can afford to do that since their 2 cam profile setup lets them not sacrifice low end torque, just as Honda was able to push the power peak to 8300 or something on the F20C. On the FA20, they only have one set of cam lobes, so the higher they push the power peak the less low end torque they have. I'm not familiar with how much duration you add to the intake for more rpm, but I imagine that you won't be seeing 200Nm until something like 3500rpm, where you can get 200Nm at 3000rpm on the current FA20.

You don't need titanium bits to hit 8500, it just makes it easier but more costly. However making a 7400rpm engine go to 8500 probably requires a lot of changes.

Of course the 1LR-GUE manages slightly better low end torque despite its sky high 9500rpm rev limit, but they have a 3 stage variable intake to help patch the torque.

A lot of people won't like this idea but a mild hybrid system could boost the low end torque an incredible amount, perhaps even have the max torque peak in the 1000s.

[Redback]

Originally Posted by 86fanatic

For me it's not whether a turbo will fit, a huge inter cooler would fit, or a bigger engine would fit. It's the fact that the car already has a front weight bias and adding any mechanical bits or heavier engine pieces will just further throw that off.

The car was engineered to have a very small engine in the front. Make that engine more powerful with revised cams, or tweaking the DI system, but if they bring up a more powerful version which adds 50+ pounds to the engine bay I will be disappointed.

Not sure that increasing the engine capacity within the existing block would add much additional weight.

If they only adjust the bore dimensions of the FA20 (to say, 94mm) the pistons may heavier (though not necessarily) and you may need a slightly larger radiator, but the increase in weight would be very small.

[MtnDrvr86]

Originally Posted by serialk11r

The Porsche hits power peak at 8250 which is quite high. Porsche can afford to do that since their 2 cam profile setup lets them not sacrifice low end torque, just as Honda was able to push the power peak to 8300 or something on the F20C. On the FA20, they only have one set of cam lobes, so the higher they push the power peak the less low end torque they have. I'm not familiar with how much duration you add to the intake for more rpm, but I imagine that you won't be seeing 200Nm until something like 3500rpm, where you can get 200Nm at 3000rpm on the current FA20.

You don't need titanium bits to hit 8500, it just makes it easier but more costly. However making a 7400rpm engine go to 8500 probably requires a lot of changes.

Of course the 1LR-GUE manages slightly better low end torque despite its sky high 9500rpm rev limit, but they have a 3 stage variable intake to help patch the torque.

A lot of people won't like this idea but a mild hybrid system could boost the low end torque an incredible amount, perhaps even have the max torque peak in the 1000s.

Thats what hybrid tech needs to be used for, at least is sports cars. Isnt that what Porsche is doing in the 918?

[serialk11r]

Originally Posted by MtnDrvr86

Thats what hybrid tech needs to be used for, at least is sports cars. Isnt that what Porsche is doing in the 918?

918 I wouldn't call it just a "low end torque boost", it's more like they're using electric motors to MASSIVELY increase the power to weight ratio. Electric motors have much higher specific output than gasoline engines afterall, and the regeneration is very helpful in racing where you're always on the brakes, so it's basically free energy.

I think a mild hybrid system with a lighter battery pack would be perfect for the BRZ because they'd be able to keep more of the FA20 engine, while providing absolutely monstrous low end torque.

By the way, I just found a website with a lot of rod specs on a lot of engines consolidated, and the lowest rod stroke ratio I can find on an 8000rpm engine is about 1.57, while the FA's rods look like they're in the vicinity of 130mm => 1.50 rod stroke ratio. I wonder if anyone who has engine specs is allowed to release them yet...

[blu_]

I am skeptical about Subaru getting more than maybe 110hp p/l out of an NA engine. They have never really had great volumetric efficiency. I would love to be proved wrong though.

[tachi1247]

Originally Posted by BMWDavid

Take a look at the Porsche 4.0L GT3-RS, 500 HP. That's 125 HP per liter. Engine revs to 8500 rpm. Has many costly bits inside; Ti rods, ported heads, fancy valve springs and etc. Don't forget that Porsche has variable valve timing as well as a different valve lift at a higher rpm.

So the FA20 @ 2L would be at 250 HP if Subaru went this way. Surely would be a pricey engine. Now if they took it to 2.5L, about the same cc per cylinder as the Porsche 4.0L, then we are talking 312 HP.

I agree that it should not be a turbo with weight penalty over the front end. Plus a NA engine has a better feel as it revs. Not that a torquey turbo engine is a bad thing, but I think it would be out of charactor for the BRZ.

That engine costs as much as an entire BRZ. I wouldn't say that is a good one to use when comparing engine stats to what is possible for this car.

If subaru creates a seperate trim line with more power and only finds 25 more hp, I would say that is a total waste. I wouldn't pay more than $1200 extra for that model which doesn't leave much room for suspension or brake upgrades. They need to add at least 50-70 hp along with the other upgrades to get real money out of me . Hell, they should pick up 20hp at the mid cycle refresh just through refining and tuning the engine as is.

[serialk11r]

We still have to see the engine to know what is "limiting" the power so to speak.

Problem is people clamoring for turbo don't seem to see the limitations of a turbo. Turbos make useful boost in a much narrower range than the engine itself, and the response is extremely far from intuitive and predictable near the full load mark (but some people don't care about that). Right now the low end torque on this engine is really really bad, and increasing the top end will likely make it even worse. A turbo that boosts the bottom end won't be increasing peak hp much, and you lose bragging-rights-to-money-ratio and kick-in-the-pants-above-25mph-to-money-ratio, unless they come up with a variable geometry turbo which doesn't seem likely.

[tranzformer]

Originally Posted by serialk11r

We still have to see the engine to know what is "limiting" the power so to speak.

Problem is people clamoring for turbo don't seem to see the limitations of a turbo. Turbos make useful boost in a much narrower range than the engine itself, and the response is extremely far from intuitive and predictable near the full load mark (but some people don't care about that). Right now the low end torque on this engine is really really bad, and increasing the top end will likely make it even worse. A turbo that boosts the bottom end won't be increasing peak hp much, and you lose bragging-rights-to-money-ratio and kick-in-the-pants-above-25mph-to-money-ratio, unless they come up with a variable geometry turbo which doesn't seem likely.

A properly sized twin scroll turbo would fix many of those issues.

[serialk11r]

Not really, a twin scroll turbo separates the cylinder pulses and is thus more efficient but at the end of the day the "total exhaust energy" delivered to the turbine for each given level of constant load (by this I am referring to the desired load given by accelerator pedal position that the ECU tries to interpret) is completely non-linear, and even a slight amount of lag makes it worse.

But response aside (which some people don't care about, and that's fine), a twin scroll turbo doesn't change the fact that the turbo can only be optimized for a narrow range. You need a variable geometry turbo to fix the high end vs. low end tradeoff.

[Dimman]

Originally Posted by serialk11r

We still have to see the engine to know what is "limiting" the power so to speak.

Problem is people clamoring for turbo don't seem to see the limitations of a turbo. Turbos make useful boost in a much narrower range than the engine itself, and the response is extremely far from intuitive and predictable near the full load mark (but some people don't care about that). Right now the low end torque on this engine is really really bad, and increasing the top end will likely make it even worse. A turbo that boosts the bottom end won't be increasing peak hp much, and you lose bragging-rights-to-money-ratio and kick-in-the-pants-above-25mph-to-money-ratio, unless they come up with a variable geometry turbo which doesn't seem likely.

I have, sitting beside me as I type, a Garrett variable geometry turbo. I wanted to see if it (from a VW TDI) could be modded to suit a gas motor as a hybrid with a proper compressor side, and maybe some hot-side porting.

But the damn turbine and manifold are a single unit!!!

No wastegate, but a boost-signal-fed actuator that (probably, as I can't look inside without a bandsaw...) moves the vane(s).

Is it the different EGTs that limit these to being common on diesels but $$$ on gasoline cars?