Frankinaustin

I saw that the 1996 year model of the SC400 generates more HP - 260. What did they improve to make this happen? Thoughts?

Carpe Diem

Hi Frank,

I think this is because of a change in the ECU and also applies to 97. The engine wasn't redesigned until 98.

Whatever happen to the SC wheels you had for sale. What year SC are they from?

George

Lucky Devin

So, theoretically by just changing the ECU in the pre- '96 models of the SC400 would make the same power gains, or at least some improvement?

JBrady

Actually, there were a few changes.

(the following numbers per Mitchell)

The 4.0 liter 1UZ-FE found in the 1990-1994 LS400 and the 1992-1995 SC400 had the following specs.

250hp @ 5600rpm
260tq @ 4400
10.0 : 1 compression ratio

The 4.0 liter 1UZ-FE found in the 1995-1997 LS400 and the 1996-1997 SC400 had the following specs.

260hp @ 5300rpm
270tq @ 4500
10.4 : 1 compression ratio

I am uncertain WHY Lexus didn't upgrade the 95 SC400 with the more powerful engine found in that years LS400.

Now, nearly a half a point more compression is a good start in making more power. Notice peak power happens 300rpm sooner and peak torque 100rpm later.

Also, the cam lift specs are different so apparently the camshafts are not the same.

I am uncertain about the SC400 but on the LS400 the exhaust system and the intake system was changed.

A further word: I personally believe the earlier engines are over-rated by 10-15hp. I gather this from both dyno testing and pictures of the factory engine dyno. Also, the improvement in acceleration on the 95 LS400 is better than you would expect compared to its very modest claimed 10hp increase. All things considered I would say the earlier engine is in reality 235hp and the 95 LS400 / 96 SC400 engine is accurate at 260hp.

Carpe Diem

Wow, that's a great answer. Thanks!

Lex Luthor

Right on the money jbrady. The additional compression seems to be responsible for the bulk of the gain, the change in the ECU and cam profiles I believe are basically to take advantage of the higher CR. As to why Lexus waited a year before changing the SC, i'm told they wanted to debut it on the LS first, don't really see the logic in it either. Devin, don't bother trying to use the newer ECU.