Official JDM BRZ weight and MPG

[tranzformer]

Originally Posted by serialk11r

I forgot about the lack of underbody panels on the RA. But all you really have to do is buy some corrugated foam board and tape it to the bottom...

No, boxer is not inherently less efficient. Subaru's EJ engines were just really old and inefficient by design.

Foam? What about it getting wet and eventually deteriorating over time?

[Rampage]

Originally Posted by serialk11r

The US one has lower CR because US fuel quality has some issues or something.
It's hard to compare these tests but yea the 86 isn't doing as well in economy as it could be. Hard to say why. I'm curious what this scores on the EPA test because you'd think CAFE standards would prompt them to try to do better, if this only get say 31mpg (for CAFE calculation, I don't remember what that is exactly), then even with its small volume it poses a pretty big threat to the 39mpg small car requirement.

200HP is a lot to get out of a NA 2.0 Liter powered car. It is tuned for performance not MPG. Look at the old S2000. They did not get good mileage either. Can't have everything.

[Dimman]

Originally Posted by Rampage

200HP is a lot to get out of a NA 2.0 Liter powered car. It is tuned for performance not MPG. Look at the old S2000. They did not get good mileage either. Can't have everything.

Actually for its 12.5:1 compression and combined port/direct injection setup, 200 hp and 151 lb-ft of torque are pretty 'meh'. It should have some good economy.

[chulooz]

Originally Posted by Rampage

200HP is a lot to get out of a NA 2.0 Liter powered car. It is tuned for performance not MPG. Look at the old S2000. They did not get good mileage either. Can't have everything.

If there is one thing I am not worried about its MPG's, I sure wont be driving it with fuel economy in mind.

[maxeveland]

theres no way i thought a sports car like this would get 35 mpg. I hdo hope however that the 30 number is at least in the city or combined

[serialk11r]

Originally Posted by Rampage

200HP is a lot to get out of a NA 2.0 Liter powered car. It is tuned for performance not MPG. Look at the old S2000. They did not get good mileage either. Can't have everything.

All the S2000 needed was a non-retarded 6th gear and it would've gotten well over 30mpg. People think "tuning for performance" means you lose a lot of economy, that's not actually true. The friction and cooling losses going from a long stroke low rpm economy engine to a shorter stroke high rpm heavier/stronger internals engine is very small, and when the combustion efficiency is good (as it is on all newer cars) there is no issue with low rpm efficiency.

The beauty of small displacement high rev is if done right, you can have both power and economy. When your engine grows too big you can't gear it down anymore.

[chulooz]

Originally Posted by serialk11r

All the S2000 needed was a non-retarded 6th gear and it would've gotten well over 30mpg. People think "tuning for performance" means you lose a lot of economy, that's not actually true. The friction and cooling losses going from a long stroke low rpm economy engine to a shorter stroke high rpm heavier/stronger internals engine is very small, and when the combustion efficiency is good (as it is on all newer cars) there is no issue with low rpm efficiency.

The beauty of small displacement high rev is if done right, you can have both power and economy. When your engine grows too big you can't gear it down anymore.

No, it actually is true. Find a tuner that will tell you different.

[serialk11r]

It's not true on modern engines. Back when they had fixed cams and port injection? Yea.
Gears have far far more to do with economy than anything else.

[chulooz]

Fuel consumption is performance, this is not even debatable.

[Snoopyalien24]

I like this thread. Reading it makes me smarter. I don't know much mechanically about cars, but this is helping lol.

[DSR2409]

Originally Posted by chulooz

Fuel consumption is performance, this is not even debatable.

Balls out tuning will require more fuel, true, but has anyone ever lost mpg from intake, headers, and/or exhaust? Even a higher compression ratio makes for more efficient combustion...It is when the power band gets moved up to 5-9k rpm that mpgs suffer immensely. Look at Mazda's Skyactiv...they basically built a race engine that makes power in the low rpms in order to achieve better fuel economy...And it worked!!!

The only reason modified street cars lose mpg over stock is because, well, you don't modify a car to drive at the same speeds as a stock car...

[DSR2409]

Originally Posted by Dave-ROR

Isn't the JDM motor quite different from the US on the SkyActiv Mazda 3 though?

I have no idea how JC08 compares to the EPA testing, but that may be a bad example. I recall the compression ratio at least being significantly different but I may be wrong (on the US vs JDM Mazda 3 SkyActiv).

JDM compression ratio is 14:1, while the US gets 13:1. The only reason is because, in Japan, people are willing to use higher octane fuel in an economy car, and, in the U.S, we are barely willing to buy it for a sports car that requires it.

On that note, though, Mazda is incredible!! Developing an engine running 13:1 compression, reliably, on 87 octane fuel! It's just too bad Americans suck...

[Chupacabra]

Originally Posted by DSR2409

It's just too bad Americans suck...

Not ALL Americans!

[serialk11r]

Originally Posted by chulooz

Fuel consumption is performance, this is not even debatable.

Efficiency at low rpm is only compromised with poor design, and low load efficiency is ALWAYS poor. Proper gearing ensures proper load, and direct injection or variable valve timing ensure good combustion at low speed. Tuning an engine for greater max power is not why a 2ZZ-GE gets only 30mpg on the highway while a civic with its 1.8 can cruise along at 45mpg. The variable lift actually makes low rpm combustion quite efficient.

When you throw a turbo on you're changing the equation quite a lot, but many performance oriented designs are not inherently far worse for fuel economy. An engine typically doesn't run well below 1500 rpm (that is, the efficiency starts to go down as you demand more load from it), so there are limits to how high you can go on displacement before you cannot get efficient street driving no matter what, but you don't hit that until you go past 3L.

Also, not all things are a performance/efficiency tradeoff. If you want a mindblowing example, high rpm cams + direct injection like we have on the FA20 give poor low rpm VE, but the direct injection maintains combustion stability and efficiency and increases thermal efficiency. That's right, the high rpm torque bias will give you better mpg around town.