Interesting EG33 output comparison...
 

It's very hard to compare the SVX to current cars as the EG33 was developed before variable valve timing was common in production vehicles (think only the '91 NSX used it back then).

Decided to compare the specific hp/liter and torque/liter outputs of the EG33 vs the naturally aspirated models offered in the MKIV Supra, Z32 300ZX and 3000GT which were in its price range and performance class. Results are shown below:

300ZX
2960cc
222hp & 198lb-ft
75 hp/l & 66.89 lb-ft/l

Supra
2997cc
220hp & 210lb-ft
73.4 hp/l & 70.07 lb-ft/l

3000GT SL
2972cc
222hp & 201lb-ft
74.69 hp/l & 67.63 lb-ft/l

SVX
3318cc
230hp & 228lb-ft
69.3 hp/l & 68.72 lb-ft/l

While the hp/l output of the EG33 is a little below the others, the lb-ft/l output is right in the mix of things which is probably a testament to the IRIS system Subaru developed. :)

Another observation is that the hp and tq values are almost identical on the SVX, but significantly different on the other engines. Seems like Subaru tuned the EG33 with torque in mind. I'm sure they could have tuned the engine to make ~240hp & 215lb-ft, but probably due to the car's heavy curb weight, 4EAT trans and awd drivetrain, the SVX needed all the torque the engine could muster...

-Chike

the extra tq could also be contributed to the increase of displacement over the other 3.0 engines

And no doubt the manual conversions run more like the other models sticks as well, #'s wise anyways.

Not in this case as I've calculated torque per liter.

If a 3L V6 engine makes 250lb-ft and a 6L V8 makes 500lb-ft, both engines have the same lb-ft/l output of 83.33. Engine size is therefore irrelevant in these calculations...

-Chike

oh right, im retarded.

you realize that an auto is not slower than a manual right?

No you just asked a good question. There might be others who would never have asked the question and draw the wrong conclusion... ;)

-Chike

?? You mean in engine output, no? In reality, there's a decent %age of power absorbed by ATF...:rolleyes:

Chike,

It would be better to make the comparison by dividing HP by both displacement and the rpm at peak HP.

Here's the deal - an auto trans is almost identical to a manual except for the torque converter! The torque converter allows the output shaft from the engine to turn the input shaft that runs through the trans without any physical connection (except for when the lock-up clip engages)...

It does this by a process called hydraulic coupling - liquid is not easily compressed - so when the the output shaft from the engine spins, the hydraulic fluid (i.e. ATF) doesn't compress easily and spins the input shaft that leads to the trans. This torque is multiplied by means of two fan shaped objects found in the torque converter called the impeller and turbine (think of two fans facing each other - if one is off and the other blows air onto it, the blades of the first fan will start to spin as well).

To make a long story short, hydraulic coupling isn't perfect, and causes a loss in the torque being transmitted of around 5-7%.

So that's why drag racers in rwd cars will say as a rule-of-thumb that a manual would typically lose 15% of crank power to the wheels, while automatics lose around 20%.

-Chike

Good point Mychailo.

The EG33 has a very low power peak of just 5400rpms, while the other engines make their peak power in the 6000-6500rpm range. Kinda makes you wonder what kinda power this engine could truly make if tuned differently... ;)

-Chike

I understand how automatics work, of course there's more parasitic loss, You guys are assuming the gear ratios are the same between autos and manuals, they're not.

True, but gearing only does so much.

Let's look at an example. The WRX wagon that comes with 227hp, is offered in 5MT and 4EAT versions. The 5MT has 3.90 gears in front and 3.55 gears in the back. The 4EAT wagon has 4.11 gears both front and back.

The 5MT version has gone 14.8 @ 95mph in the 1/4 mile by Road & Track. However, the same mag got a 15.2 @ 91 mph for the 4EAT version...

-Chike

Mychailo,

I looked up the rpms at which the other cars made their peak hp and got:

300ZX 222hp @ 6400 rpms
3000GT 222hp @ 6000rpms
Supra 220hp @ 6000rpms

Not sure how you wanted to plug them into the equations, so I wanted to give you the values.

-Chike

MEP is found from:

BHP/(rpm*displ)

rpm is in krpm (rpm/1000)
displ is in liters

MEP is a better way to compare the efficiency of different motors because it takes into account the rpms the motor is turning at peak HP. Its important to take rpm into consideration because greater rpm is an easy to create more power (assuming that some amount of torque can be produced).

Here are the results
car-------------disp (cc)----bhp----rpm at peak HP----MEP
300zx----------2960-------222----6400--------------11.72
Supra----------2997-------220-----6000-------------12.23
3000GT SL---2972--------222-----6000-------------12.45
SVX------------3317-------230-----5400--------------12.84

When taking into acct rpm, the SVX motor takes the win in efficiency.

It would be interesting to see what the SVX motor would crank out with longer duration cams, higher lift, and appropriately tuned intake and exhaust. If the MEP of 12.84 could be maintained but peak HP moved to 6500 rpm, the motor would be cranking out 275 HP.