Engine technology thread.

[Nurburgring]

The BEAMS is seriously overrated from factory. On a very happy reading dyno (where my stock AP1 S2000 put down 210whp) a Redtop BEAMS with full exhaust and intake put down 149whp@6800rpms.

I was surprised by the low numbers, but 150whp seems to be about average for that engine stock:
http://www.mr2.com/forums/beams-owne...-registry.html

Also, the BEAMS uses a lot of valve lift to get those bumbers: 10.5mm IN / 9.2mm EX, I can assure you the FA20 is nowhere near that aggresive given emissions fuel efficiency considerations.

[Sully]

20v 4a-ge are also tend to be overrated a bit too.

[Dimman]

Originally Posted by Sully

20v 4a-ge are also tend to be overrated a bit too.

Not really, 5 valve heads just kind of suck (see page 1 of this thread, the 4 vs 5 vpc started this whole thing...)

Edit:

Originally Posted by Nurburgring

The BEAMS is seriously overrated from factory. On a very happy reading dyno (where my stock AP1 S2000 put down 210whp) a Redtop BEAMS with full exhaust and intake put down 149whp@6800rpms.

I was surprised by the low numbers, but 150whp seems to be about average for that engine stock:
http://www.mr2.com/forums/beams-owne...-registry.html

Also, the BEAMS uses a lot of valve lift to get those bumbers: 10.5mm IN / 9.2mm EX, I can assure you the FA20 is nowhere near that aggresive given emissions fuel efficiency considerations.

A bunch of numbers from nameless chassis dynos don't really offer a lot of evidence. There are some in the 170ish whp range with essentially stock motors which would put them on par with the losses of the S2k.

There is also this quote, (which is what my focus is on):

It's quite interesting to see, that between the lowest and highest HP cars, they are all making between 150 and 160 ft lbs of torque.... the only difference being, where on the curve that they made the power.

The key to NA power isnt making more torque, it's pushing the torque further up the rev range.

http://www.mr2.com/forums/beams-owne...html#post97104

Whatever the case, I feel that there is some missing torque potential in the FA20. And 197 hp @ 7000 isn't exactly astronomical...

[serialk11r]

Another thought Dimman. The other thread people were discussing Subaru motors, and well I think we all know Subaru motors aren't really quite as efficient as their competitors. Sure this motor was completely reworked and all but in the end maybe it really is just a Subaru motor that Toyota attempted to "cure" with some direct injection. Worst case scenario :/

[Ryephile]

Dimman, you already know this, but the FA20 lives in a different era. Fuel economy and emissions are significantly more strict, and that changes design priorities. If like what old greg figured out regarding port sizing tuned for a boosted setup, that may allow for a slightly aggressive cam profile without much gain in VE, giving a balance of fuel economy and torque. It's all a compromise these days.

[Dimman]

Originally Posted by Ryephile

Dimman, you already know this, but the FA20 lives in a different era. Fuel economy and emissions are significantly more strict, and that changes design priorities. If like what old greg figured out regarding port sizing tuned for a boosted setup, that may allow for a slightly aggressive cam profile without much gain in VE, giving a balance of fuel economy and torque. It's all a compromise these days.

The over-porting is something I've thought about as well. (he actually quoted me when he brought up this point )

But the reviews don't seem to indicate that it has shitty low end. But maybe the response is covering for that a bit? This is not helping me... Just give me a damn torque curve. Or a test drive.

Over-porting is liveable if that means we un-cork the breathing, cam it, and bump up the rev limit, so long as fueling can support it and the rods/bearings can handle the extra rpm.

[bambbrose]

I think, or I'm hoping, that the motor is overbuilt and strong.

Just going by piston speed, 8500 RPM should be a reasonable limit for street/track use without needing repeated tear down.

I hope the bottom end is tough. If we can just upgrade the valvetrain and tune to 8000-8500 RPM this car is going to be awesome.

[madfast]

from the insideline BRZ test:

A firm yank of the shifter into 2nd gear and the BRZ lays a small stripe with a chirp. There may only be a 2.0-liter, four-cylinder under the aluminum hood, but it definitely has some kick. In fact, the all-new flat-4, or "FA" engine as Subaru calls it, can deliver nearly all of its 150 pound-feet of torque at just 2,800 rpm.


It's only a momentary burst of torque, though, as it falls off a bit before rising again at 4,800 rpm. It then peaks at 6,300 rpm and stays flat right through 7,000 rpm. That's where the 200-horsepower peak sits, too, and the redline is another 400 rpm after that.

[serialk11r]

Originally Posted by bambbrose

I think, or I'm hoping, that the motor is overbuilt and strong.

Just going by piston speed, 8500 RPM should be a reasonable limit for street/track use without needing repeated tear down.

I hope the bottom end is tough. If we can just upgrade the valvetrain and tune to 8000-8500 RPM this car is going to be awesome.

Just saying, piston speed is sorta useless. Piston acceleration and rod/stroke ratio along with mass give the bearing loads. I'm worried about this engine because adding width is necessary for either lift control (secondary rockers/followers, adds about an inch on each side minimum regardless of system) or longer rods (current ratio is 1.54ish assuming we're not being fed total bullcrap about the dimensions being the same as older Subaru motors), and it sounds like adding width is not an option. They could go back to the short stroke from before but that would be undoing a lot of their work.

[madfast]

Subaru tweaked the torque curve to flatten before its peak (at about 3200 rpm you have 90 percent of usable muscle), but the car can also feel a little slow to build passing power at higher vehicle speeds. In short, this engine needs revs to really scoot the car. Mind you, we noticed this issue while driving in excess of 100 mph on the test track. Downshifts instantly fix the problem, but so would a turbo. Sadly, Subaru says that’s not happening, at least not until this car sees a refresh.

from: http://www.popularmechanics.com/cars...drive#fbIndex5

so are they saying subaru intentionally flattened the curve in the middle? Hmmm... Dimman may have just been vindicated...

[serialk11r]

I think I just figured out the mystery behind the slow introduction of continously variable lift/duration...

http://www.sciencedirect.com/science...10218075900644
"While combustion stability at very lean operation is guaranteed, intake air throttling in the part load range is necessary to keep combustion temperature high enough for effective oxidation of CO and HC."

Doh. Stupid emissions s***. Do European cars really stink that much more then?
From this perspective D-4S makes even more sense; At low load they can keep temperatures higher if they use port injectors. This is also probably (IIRC) why BMW uses massive amounts of EGR at part load.

[Ryephile]

Originally Posted by madfast

from the insideline BRZ test:

A rough guess based on adverbs like "nearly" and "a bit":
145 LbFt @ 2800 RPM
140 @ 3800
145 @ 4800
151 from 6300-6950
150 @ 7000

Funky! All without intake tract flaps or variable valve lift.

[Dimman]

Originally Posted by madfast

from: http://www.popularmechanics.com/cars...drive#fbIndex5

so are they saying subaru intentionally flattened the curve in the middle? Hmmm... Dimman may have just been vindicated...

I suppose I could go back and selectively quote a bunch of my posts to look 'internet right'. But I'd still be 'reality wrong'. So no, not really...

I dropped the ball on a couple of things, I think. One of them is 'because race-car' (this car isn't). Here are some more:

A) Lack of understanding on the power of wave,overlap,pulse,acoustic tuning.

The double hump curve I did for my AVLS hypothesis is probably similar to the real one, but for different reasons. What is likely is that they have a traditional somewhat symmetrical torque curve to start with. The BEAMS probably focused the acoustics tuning to coincide with the max inertial effects (@ ~4800 rpm) as well as on the upper side of that to hold BMEP losses down so as to hit the hp target. They also probably let the 'flat-spot' opposite waves occur on the lower side of 4800. The FA20 likely did somewhat the opposite. In race-tuning chopping off your torque peak by putting a flat spot there is un-heard of. But this isn't a race car. Like they said they tuned on either side of the inertial-optimal peak. I also think that certain tuning lengths can cause two torque spikes, but usually a drop between them. And if the results caused a flat-spot and chopped the peak off, so what? Torque can be flaaaaat. But why?

B) The car's intended audience and market position.

This is something I should have thought about earlier, because I posted about it already but in a different context. First off, this car is not intended for car enthusiasts. Say what??? Has Dimman lost is freakin' mind??? No. This car is intended for people who self-identify as car enthusiasts. See the difference? I've made a hypothetical sales comparison between the tC and the FR-S using 'Suzy Secretary' before, trying to justify away a big pricing gap between the two cars based on how fast they 'feel' (low-end torque). Now if the FR-S was a lot more expensive but felt slower maybe Suzy Secretary (who self-identifies as Suzy Speedracer) will 'enthusiastically' pick the 'faster' tC. The issue that Toyota/Subaru will have is that there is a gap in what self-described enthusiasts expect in a sports/sporty car. And this engine tuning would allow them to hit the broadest possible target. I have no problem using all of my rev-happy cars' powerbands (1JZGTE back in the day, 7200rpm no-problem) so 4800 rpm torque peak is no big deal. But given how a lot of people drive, 4800 rpm probably hardly ever gets touched even when they are 'on it' (I hardly hit 4000 in my Legacy in normal driving). So the smarter-than-me engineers worked out a very good compromise. The benefit for 'real' enthusiasts is the flat-ness and probably very linear throttle response, as well as hitting the 200 hp everyone expected.

I made the assumption that they would shoot for ~170 lb-ft in an automotive ****-measuring way. They didn't. They went for a universally driveable performance motor.

TMC/FHI: 1
Dimman: 0

[Ryephile]

Yup I think you've nailed it there. The FT-86 was never supposed to offer performance-metric bragging rights for anyone. It seems that Jack Hollis' speech during the FR-S Concept unveil was more revealing than most of us assumed or hoped; the car is about a balanced approach, not being a one-hit wonder, be it HP/L, BMEP, or outright power. It's not about any of that, it's about reasonable power, reasonable torque, reasonable fuel economy, reasonably light, reasonably affordable. That last bit is still TBD though.