technerd

All of the U.S. specs. that I have seen on the 4GR-FSE (the engine in the IS 250) state that the torque peak occurs at 4800 RPM. But if you look at Lexus's Japanese website it says that the torque peak occurs at 3800 RPM. See the following URL:

http://lexus.jp/models/is/performance/powerunit.html

I wonder if there is an error on either the Japanese website or the U.S. specifications, or if there truly is a difference between the output of this engine in the different markets.

Another thing to notice about the 4GR is that the torque curve is as flat as they come! The graph shows that like 98% of the peak torque (seriously) is available at 2000 RPM, then there is the tiniest blip right before 4000 RPM (which accounts for the peak) then it doesn't tail off until about 5400 RPM.

The torque curve on the 2GR, in contrast, has a pronounced hump starting at 3500 RPM which peaks at 4800 RPM and then starts tailing off almost immediately.

flipside909

You may want to read this:

https://www.clublexus.com/forums/sho...80&postcount=4

technerd

Hmmmm! I understand that SAE's standards for measuring power and torque have changed recently and that Toyota is complying with these standards (at least in the United States).

But it doesn't seem possible to me that changes to the protocol for MEASURING torque would change the SHAPE of the engine's torque curve and move the location of the torque peak from 4800 RPM to 3800 RPM. Moreover, from what I've seen so far, the new standards are reducing horsepower numbers from 3 to 5 % on most Japanese cars, but they aren't effecting torque numbers as much. Look at the changes in the numbers from 2005 to 2006 for the 4 cylinder Camry as an example. The engine was not modified so the differences in the power and torque are due only to the changes in the measuring protocol. HP dropped from 160 at 5700 RPM to 154 at 5600 RPM (about a 4 % reduction). Torque dropped from 163 ft-lbs at 4000 RPM to 160 ft-lbs at 4000 RPM (that's less than a 2% reduction). The key point is that the torque peak still occurs at the SAME RPM.

The peak torque number for the 4GR is 260 NM in Japan that translates to about 192 ft-lbs. The U.S. number is about 3.5% lower at 185 ft-lbs. The magnitude of the difference in the peak torque number plus the SIGNIFICANT change in the location of the torque peak cannot be explained by the difference in measuring standards. There must be different tuning in Japan or these is a mistake somewhere.

IS JOE

I don't know the exact differences in the new SAE standard, but from everything I've read, its not just a correction factor change. It's a test and proceedure change. Using a completely different test methodology and proceedure could move the torque peak around. I can't say for certain though, since i don't know enough about the changes.

Also, it could be that the car is subject to less stringent emissions standards in Japan. They may be able to get away with more aggressive tuning. Maybe they take into account different qualities of gas from around the world?

technerd

These last 2 points about differences in gasoline and emissions standards accounting for the difference in the torque number is a possibility. I was hoping that the U.S. specifications were in error and the torque peak actually occurs at 3800 RPM . I'm intrigued by the IS 250 because of its outstanding fuel economy (at least when mated with the automatic), but I was concerned about some reviewers claiming that it has sluggish performance. A 4800 RPM torque peak would suggest that the performance would be sluggish even though the peak numbers are comparable to a 325. I was pleasantly suprised when I saw how flat the engine's torque curve was. If the U.S. torque curve is the same as the Japanese one, I think the IS 250 should have good PERCEIVED performance because almost all of the engines torque is available from 2000 to 5000 RPM.

flipside909

Don't worry about what it looks like on paper. Wait until you drive it to give it a fair assessment. You really won't get a feel of the IS250 by mathmatical equations and comparisions. That's not a fair assessment of it's actual real world capabilities.

spwolf

All GR engine series have pretty decent torque curve from below 2,000 rpm to the peak... obviously, more displacement will bring more torque from down below...

XeroK00L

Good observation and interesting point, technerd (and welcome to ClubLexus!). But as you said yourself since the 98% of the peak torque is availble from 2000rpm for the 4GR-FSE I wouldn't be worried about at which engine speed the torque peaks at all.

I agree with IS JOE that the difference in the peak torque engine speeds is likely a result of the change in test procedure. In Japan they still use the old measurement methods (and hence the 215ps/212hp horsepower rating).