The IS250 puts out 204HP, which is 204/2.5 = 81.6 HP per liter. With the 3.0 version in the GS it is also 245/3.0 = 81.6 hp per liter. But with the IS350 it is 306/3.5 = 87.4 HP per liter. The 350 should be putting out about 286HP if it was tuned the same as the 2.5 and 3.0 versions. So what did Lexus do to the 3.5 version that gives it the extra 20HP?

 

Displacement.

Having high compression close to 12:1 also helps.

 

IS250 actually has a higher comp ratio than the IS350, he was using hp/liter so displacement doesnt really matter in that kind of measurement

 

Direct Injection helps on the 2GR helps as well.

 

250 and 350 both have direct injection

 

Yes exactly. All three engines are the same. But the 3.5 version has more HP per liter (87.4) versus 81.6 for the smaller 2.5 and 3.0. Where does the 3.5 get the extra HP per liter?

 

-magic-

 

Th 350 has a combination of direct and port injection. The 250 only has direct injection, so that is most likely the difference. There are several past tech articles on the forum about the FSE engine.

 

chuck norris

 

High compression and the direct port injection......

 

Ok then, at 87.4 hp per liter, the IS250 should be putting out 219HP. It only has 204. I don't think the port injection affects the high rpm horsepower as it only operates in low and moderate engine speeds.

 

Cams, air flow, injector size, exhaust flow, timing/ECU tuning, any or all of those.

 

I can't answer the OP's question, but you guys need to check your facts before opening the proverbial mouth. Out of all the responses so far, only SilverBolt's makes the most sense.



1. 2GR-FSE (3.5L) is a mixture of DFI and traditional PFI (port fuel injectors). 4GR-FSE (2.5L) is the only engine which is completely DFI. (Credit to Scotty99 in beating me in posting this while I looked for the sources and links.)

2. The 4GR-FSE runs at 12:1 compression ratio. 2GR-FSE runs at 11.8:1.

Source: Official 2IS Specifications

Cheers,
Kermee

 

Having both direct AND port injection doesn't guarantee more power. It only helps alleviate worries regarding running lean. Running rich would increase the power, but the amount that you're saying (about 6hp/liter) is unlikely to be achieved... plus Toyota wouldn't run something rich to just boost power ratings =P (or at least it's assumed haha).

Having a lower compression ratio obviously wouldn't add power... but the addition of port injection would have leaned toward utilizing a higher CR since fuel distribution wouldn't be an issue.

It must all be in the valve timing. Since it can be manipulated, it can be altered to add or reduce power and a minute difference of 6hp/L would be possible.

But let's just be happy it's rated at 306 peak hp in the US and not 286 like it "should've" been. =P

 

roundhouse kicks are good for at least 20 hp/liter