Besides the ECU programmed limit, what is the limiting factor that defines our engine's rpm redline?

It is valve float? Crank/piston strength limited? Transmission durability limited?

 

valve float is one issue... can the rods handle the increased rpm? is the motor even efficient at higher rpms? etc...

 

not in our applications, the peak power is below the redline, so raising it is pretty useless unless you have modifications to the valvetrain, motor, and breathing to shift the redline.

 

He's not asking about that though. If that were the limiting factor, you could rev the engine at 12000 RPM all day long. It would be highly inefficient, but still run. We both know, however, that it's not. I'm thinking it's probably the rods and valve float but I really don't know.

 

Perhaps I should ask the question in a different way.

Besides the ECU, if I wanted to raise the redline from the stock 6200 rpm to 6700 rpm, what would I have to change or modify so that engine damage would not occur?

It is likely wrong, but according to MotorTrend, the peak HP occus at 6000 rpm for a 1998.

 

for a car that weighs as much as the LS i dont really see the point of shifting the powerband HIGHER up the rev range....

 

http://www.lextreme.com/1uzfe_info.html
According to this link (at the end), he says the "stock internals" are good to 9000 rpm. Does "stock internals" mean the valves and springs too?

 

Yes. Keep in mind he's referring to the 1UZ-FE found in the 1990-1994 LS400.

 

Probably valve float.. The rods, and crank are pretty strong.. considering how much power CAN be put to them...

To fix the valve float you would have to get heavier valve springs..if they are even available... Also then you may be putting to much pressure on the Cam for the lubrication it has.. causing excessive cam wear. Even then.. it is ulikely you would get more power.. without doing some serious head work.. It would be better totry and increase power in the current RPM window... Supercharger, or Turbo... or even some spray.. if you can live with the limitations that has... Old saying (Bottles are for babies.. REAL men get blown.)

Sorta off topic... BUT....its related to valve float.

I had a 85 Honda VFR 500 Interceptor. Redline was 12,000 RPM... But with no limiter..so I had it to 13.5K+ a couple times while missing a gear... Valve float was a problem on the 500's.. around 20,000 miles and the valve springs would get weak..and BANG!! No more engine... God .. I miss that V4 sound and power sometimes... It was making 68HP from carburated 500cc in 1985!! pretty impressive... same as the current Ninja 650.. thats fuel injected.
Here was my bike... sold it last summer.
[IMG][/IMG]


A few vids, the first one is my bike sorry for the crappy digicam video.. and sound does not do it justice.. it had a much deeper sound than this. Also I was in a hurry.. Only had 50 sec worth of memory for video.


Couple more vids from the net..better sound.
This one is a 750cc bike.. 6 min long. But the sound is very similar.. Just really nice. Not as whining as a inline 4 cyl
http://youtube.com/watch?v=sGGq-yHRjRg

This one is a VFR800... pretty new model... These sound the best of all.. especially with a good pipe on it.. almost sounds like a V8 at low revs.
http://youtube.com/watch?v=06mhHNme71c

Another VFR800.. this one is a Vtec model.. sweet. ride 3 min or actual riding.

http://www.youtube.com/watch?v=G9Q3wFlT9OY&NR=1

Enjoy.
Ken

 

The 2nd generation LS400 is supposed to be weaker on the inside as far as rods and things go. So I think if you managed to rev it into the 8000 RPM range, you might throw a rod.

I know that the car does alot better when shifting at 6100 RPMs than 6350 which is our redline I do believe.

The fastest I ever clocked a 98-00 LS from 0-60 was on a cool night with this digital reader I had. Made the 60MPH in 5.89 seconds. The rest of times ranged from 6-6.2 and with a full load of people 7 seconds flat.